Dr. Jeff Masters' WunderBlog

African tropical wave 99L slowly organizing

By: JeffMasters, 13:26 GMT le 31 juillet 2012

A tropical wave (Invest 99L) near 9°N 41°W, halfway between the Lesser Antilles Islands and the coast of Africa, has the potential to develop into a tropical depression later this week as it moves westward at 10 - 15 mph. Visible satellite loops show that the disturbance now has a moderate amount of poorly-organized heavy thunderstorms that continue to slowly increase in intensity and areal coverage. There is no surface circulation, but some counter-clockwise rotation of the large-scale cloud pattern is evident. Water vapor satellite loops show that 99L has a reasonably moist environment. The latest Saharan air layer analysis shows that the dry air from the Sahara lies to the north of 99L and is currently not affecting the storm. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light through Friday, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. However, a band of high wind shear of 20 - 40 knots associated with the subtropical jet stream lies just to the north of 99L, and it would not be a surprise to see 99L experience some higher shear conditions than are currently forecast. The farther north 99L gets, the higher the shear it will experience, and the SHIPS model is predicting shear in the moderate range, 10 - 20 knots, for Saturday - Sunday, as the storm works its way to 15°N. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L. There are some major differences in the predicted forward speed of 99L, with the ECMWF and UKMET models predicting the storm will reach the Lesser Antilles on Friday, and the GFS predicting a later arrival, on Saturday. At 8 am Tuesday, NHC gave 99L a 20% chance of developing into a tropical depression by Thursday morning. I expect the storm will begin having trouble with tendrils of dry air reaching down from the north at times this week, but give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday morning. The long-range fate of 99L next week is uncertain. A track west to west-northwest through the Caribbean, or to the northwest towards the U.S. East Coast are both possible. The storm is less likely to survive if it heads northwest towards the U.S.

Extreme heat in the Central U.S.
The withering heat in America's heartland continued on Monday, with high temperatures of 112° recorded in Winfield, Kansas and Searcy, Arkansas. Little Rock, Arkansas hit 111°, their 3rd hottest temperature ever record, behind the all time record of 114° set just last year on August 3, and the 112° reading of 7/31/1986. Wichita and Coffeyville in Kansas both hit 111° Monday, and in Oklahoma, Enid, Tulsa Jones Airport, and Chandler all topped out at 111°. Carr Creek, Missouri hit 110°, the hottest temperature measured in the state so far this year. Highs temperatures Tuesday and Wednesday in this region could reach 110° again, as the most extreme heat this week will stay focused over Oklahoma and surrounding states.

Jeff Masters

Hurricane

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African tropical wave 99L has potential to develop

By: JeffMasters, 15:10 GMT le 30 juillet 2012

The first African tropical wave of 2012 with a potential to develop is Invest 99L, located in the Eastern Atlantic near 9°N 36°W, midway between the Lesser Antilles Islands and the coast of Africa. Visible satellite loops show a large area of the surrounding atmosphere has a pronounced counter-clockwise spin, though there is no surface circulation. The disturbance's heavy thunderstorm activity is pretty sparse, but appears to be slowly increasing. Water vapor satellite loops show that 99L has a reasonably moist environment, and the latest Saharan air layer analysis shows that the dry air from the Sahara lies well to the north of 99L. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light for the next five days, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L, with the storm reaching the Lesser Antilles Islands on Saturday, August 3. NHC gave 99L a 20% chance of developing into a tropical depression by Wednesday morning. I expect the storm will have trouble with dry air at times this week as it crosses the Atlantic, but I give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday night. The long-range fate of 99L is uncertain, but a trough of low pressure is expected to be present over the Eastern U.S. early next week, which would be capable of turning 99L more to the northwest.

Hot in the Central U.S.
The heat in America's heartland continued on Sunday, with Wichita, KS hitting 111°F, just 3° short of their all-time hottest temperature of 114° set on 8/12/1936. Other notable highs on Sunday:

111° Coffeyville, KS
111° Winfield, KS
110° Chanute, KS
110° Parsons, KS
109° Joplin, MO (all-time record is 115° on July 14, 1954)

The low temperature in Tulsa, Oklahoma this Monday morning dropped to only 88°F. This is the all-time warmest low temperature in the city since record keeping began in 1905. The previous record warmest minimum temperature was 87°F set on August 2, 2011 and July 16, 1980. The high in Tulsa Monday - Wednesday is expected to reach 110° - 111°, close to the city's all-time hottest temperature of 115° set on August 10, 1936.

Jeff Masters

Hurricane

Updated: 15:28 GMT le 30 juillet 2012

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Oil industry-funded "BEST" study finds global warming is real, manmade

By: angelafritz , 00:21 GMT le 30 juillet 2012

The Berkeley Earth Surface Temperature (BEST) group is in the news again, surprising climate change skeptics with results from a new study that shows the earth has warmed 2.5 °F over the past 250 years, and 1.5 °F over the past fifty years, and that "essentially all of this increase results from the human emission of greenhouse gases." Dr. Richard Muller, who heads the BEST team, now considers himself a "converted skeptic," which he wrote about in a New York Times op-ed on Saturday:

"Call me a converted skeptic. Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I'm now going a step further: Humans are almost entirely the cause."

Not only is the lead scientist of the project a former climate change skeptic, BEST itself is funded by the Charles G. Koch Charitable Foundation, an organization that is rooted deep in the oil industry and the manufactured doubt industry. Two years ago a report found that the Koch brothers outspent Exxon Mobile in science disinformation at a whopping $48.5 million since 1997. Despite the special interest of their funders, BEST has made it clear, both on their website and in the results they've come to, that funding sources will not play a role in the results of their research, and that they "will be presented with full transparency."

Figure 1. The BEST surface temperature reconstruction (black) with a 95% confidence interval (grey). The overlying curve (red) is a curve fit to the temperature reconstruction based on atmospheric carbon dioxide concentration and volcanic activity.

Muller's research comes to essentially the same conclusion as similar well-known studies on the topic of global temperature rise. It attempts to address the question of attribution—how much has the globe warmed, and what is to blame? They found that solar activity relates very little to the fluctuations in temperature over the past 250 years, and that the warming is "almost entirely" due to greenhouse gas emissions, combined with some variability from volcanic eruptions. It's important to note that while Muller and his team found warming of 2.5 °F over the past 250 years, and 1.5 °F over the past fifty years, the IPCC did not find quite that much warming in their AR4 assessment.

BEST was in the news in October when they released results from their first independent study of surface temperature, which set out to address some common skeptic concerns about previous temperature reconstructions (e.g. NASA, NOAA, and HadCRU), including the urban heat island effect and the potential "cherry picking" of data. Both of these concerns were found to be non-issues. BEST concluded that the urban heat island effect does not contribute significantly to the land temperature rise. In fact, in their new study, they were able to reproduce the warming trend using nothing but rural stations.

BEST Part II doesn't necessarily bring anything new to the science as it currently exists; we've known for decades that the planet is warming and the cause is manmade. But in this case the scientific process played out the way it should: a skeptic of a certain scientific result took on the project, and was open and willing to accept whatever result the science gave him. We now have another batch of results in the group of well-known temperature reconstructions, funded by big-oil-interests, that tells us the planet is warming and that the cause is fossil fuel emissions.

Angela

Climate Change

Updated: 00:23 GMT le 30 juillet 2012

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Severe thunderstorms erupt along a swath 1,500 miles long, killing 2

By: JeffMasters, 14:48 GMT le 27 juillet 2012

A huge outbreak of severe thunderstorms hit the nation on Thursday, causing damage in fifteen states and knocking out power to over 250,000 customers. Two people were killed, one by a falling tree in Pennsylvania, and one due to a lightning strike in New York. Two possible tornadoes touched down: one in Elmira, New York and another in Brookville, PA. The severe storms covered an unusually large area, erupting along a 1,500-mile long swath of the country from Texas to Connecticut. The intensity of the thunderstorms was increased by a very hot and moist airmass; temperatures in the mid to upper 90s were common across the region Thursday. A number of record highs for the date were set, including a 98° reading at Washington D.C.'s Dulles Airport. The threat of severe weather continues for Friday afternoon over portions of the Ohio Valley and mid-Atlantic, as NOAA's Storm Prediction Center has placed these regions in their "Slight Risk" area for severe thunderstorms.


Figure 1. A rare sight: at 7 pm EDT on July 26, 2012, severe thunderstorm warnings were in effect for 132 counties in 15 states along a swath 1,500 miles long.


Figure 2. Visible satellite image taken at 7:02 pm EDT July 26, 2012, of the line of severe thunderstorms that extended from Texas to Connecticut. Image credit: NASA/GSFC.


Figure 3. An imposing sight: A squall line of severe thunderstorms with two bowing segments takes aim at New York, Connecticut, and New Jersey on July 26, 2012. The tip of a bow echo typically has the most violent winds in a severe thunderstorm.

Was Thursday's outbreak a derecho?
Thursday's outbreak of severe thunderstorms was not nearly as violent as the June 29 - 30 Mid-Atlantic and Midwest derecho, since the atmosphere wasn't as unstable. The June 29 storm was one of the most destructive and deadly severe thunderstorm complexes in North American history. It killed 22 people, knocked out power to at least 3.7 million customers, and did hundreds of millions in damage. There were 871 reports of damaging winds logged by the next day, and 36 of the thunderstorms had wind gusts in excess of hurricane force--74 mph. In contrast, yesterday's event had only two thunderstorms with wind gusts in excess of 74 mph, and 383 reports of damaging winds. We can probably classify yesterday's severe thunderstorm event as a weak derecho, since it met the main criteria, as defined by NOAA's Storm Prediction Center: "A derecho is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to that of tornadoes, the damage typically is directed in one direction along a relatively straight swath. As a result, the term "straight-line wind damage" sometimes is used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho."


Figure 4. NOAA's Storm Prediction Center logged 374 reports of damaging winds from Thursday's severe thunderstorms. Two of these thunderstorms had winds in excess of hurricane force (65 knots, or 74 mph.)


Figure 5. The climatology of derecho events over the U.S. Image credit: NOAA Storm Prediction Center.

Quiet in the Atlantic
There are no tropical cyclone threat areas to discuss in the Atlantic. A strong tropical wave is expected to bring heavy rains to the Lesser Antilles Islands and Puerto Rico on Monday and Tuesday, but none of the models are developing the wave. The NOGAPS computer model is suggesting development of a second tropical wave between Africa and the Lesser Antilles Islands August 2 - 3.

Have a great Olympic weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

Severe Weather

Updated: 15:00 GMT le 27 juillet 2012

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Major severe thunderstorm outbreak expected; U.S. drought intensifies

By: JeffMasters, 14:16 GMT le 26 juillet 2012

A dangerous outbreak of organized severe thunderstorms with strong, damaging winds is expected this afternoon from Ohio eastwards through Pennsylvania and into New England, says NOAA's Storm Prediction Center (SPC). They have put the region, which includes Columbus, Pittsburgh, Philadelphia, and New York City, in their "Moderate Risk" area for severe weather, just one notch below the highest level of alert. Much of the region is also under advisories for extreme heat, with temperatures in the upper 90s expected. This extreme heat will help energize the thunderstorms by making the atmosphere very unstable. A cold front passing through the region will trigger the severe weather episode beginning around 2 pm EDT this afternoon, near the Indiana/Ohio border. This front already triggered a round of severe thunderstorms early this morning across Michigan, which knocked out power to 16,000 customers. This afternoon, severe thunderstorms may organize into a complex that features a bow-shaped echo. If such a complex brings violent straight-line winds in excess of 58 mph (93 km/hr) over a swath of at least 240 miles (about 400 km), it will be called a derecho (from the Spanish phrase for "straight ahead".) The atmosphere is not as unstable as was the case for the June 29 - 30 Mid-Atlantic and Midwest derecho, however. That storm was one of the most destructive and deadly fast-moving severe thunderstorm complexes in North American history. It killed 22 people, knocked out power to at least 3.7 million customers, and did hundreds of millions in damage.


Figure 1. Severe weather risk for Thursday, July 26, 2012, from NOAA's Storm Prediction Center (SPC).

U.S. drought intensifies
The great U.S. drought of 2012 held constant in size but grew more intense over the past week, said NOAA in their weekly U.S. Drought Monitor report issued Thursday, July 26. The area of the contiguous U.S. covered by drought stayed constant at 64% , but the area covered by severe or greater drought jumped from 42% to 46%. These are truly historic levels of drought, exceeded only during the great Dust Bowl drought of the 1930s and a severe drought in the mid-1950s. The July 2012 drought is second only to the great Dust Bowl drought of July 1934 in terms of the area of the contiguous U.S. covered by moderate or greater drought (if we assume the drought conditions measured in mid-July are representative of the entire month of July, which is a reasonable approximation given the lastest drought forecast.) The five months with the greatest percent area in moderate or greater drought, since 1895, now look like this:

1) Jul 1934, 80%
2) Jul 2012, 64%
3) Dec 1939, 60%
4) Jul 1954, 60%
5) Dec 1956, 58%

If we consider the area of the contiguous U.S. covered by severe or greater drought, drought conditions as of July 24, 2012 now rank in 3rd place:

1) Jul 1934, 63%
2) Sep 1954, 50%
3) Jul 2012, 46%
4) Dec 1956, 43%
5) Aug 1936, 43%


Figure 2. July 24, 2012 drought conditions showed historic levels of drought across the U.S., with 64% of the contiguous U.S. experiencing moderate or greater drought, and 46% of the county experiencing severe or greater drought. Image credit: U.S. Drought Monitor.

Extreme heat continues in the Heartland
St. Louis, Missouri's summer of extreme heat reached record levels on Wednesday, when the city hit 108°F. This marked the 11th day this summer in St. Louis with temperatures of at least 105°F, beating the old record of ten such days in 1934. The minimum temperature in the city fell to just 86°F, tying with July 24, 1901, as the warmest minimum temperature ever recorded in the city. St. Louis has seen just 0.53" inches of rain this month, far below the normal 3.35" it usually records by this point in July.

Jeff Masters

Severe Weather Drought

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Greenland experiences melting over 97% of its area in mid-July

By: JeffMasters, 12:58 GMT le 25 juillet 2012

Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, CA, was analyzing radar data from the Indian Space Research Organization's Oceansat-2 satellite last week when he noticed that 97% of Greenland appeared to have undergone surface melting on July 12--an event completely unprecedented in 30 years of satellite measurements. In a July 24 press release from NASA, Nghiem said, "This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?" Multiple satellite data sets confirmed the remarkable event, though. Melt maps derived from three different satellites showed that on July 8, about 40 percent of the ice sheet's surface had melted, as a strong ridge of high pressure set up over Greenland. By July 12, the melting had expanded to cover 97% of Greenland. As I blogged about last week, temperatures at at the top of the Greenland Ice Sheet, 10,551 feet (3216 meters) above sea level, and 415 miles (670 km) north of the Arctic Circle, had risen above the freezing mark four times in the 12-year span 2000 - 2011. But in mid-July 2012, temperatures eclipsed the freezing mark on five days, including four days in a row from July 11 - 14. Interestingly, ice core records show that in 1889, a similar pronounced melt event occurred at the top of the Greenland Ice Sheet, and such events occur naturally about every 150 years. "But if we continue to observe melting events like this in upcoming years, it will be worrisome," said Lora Koenig, a NASA/Goddard glaciologist and a member of the research team analyzing the satellite data. Such an event could occur as early as this weekend: the latest wunderground forecast for the Greenland Summit calls for above-freezing temperatures to return again by Saturday through Tuesday, with a high of 36°F (2°C) on Tuesday. This would come close to the record warm temperature at Summit of 3.6°C set just two weeks ago. Exceptionally warm temperatures in Greenland this July have been made more likely by the fact that Arctic sea ice area has been at record low levels so far this month. Furthermore, the Greenland Ice Sheet has become darker this July than at any point since satellite measurements began (Figure 2), allowing Greenland to absorb more solar energy and heat up.


Figure 1. Extent of surface melt over Greenland's ice sheet on July 8 (left) and July 12 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12. Image credit: NASA.



Figure 2. The albedo (reflectivity) of the Greenland Ice Sheet at its highest elevations (2,500 - 3,200 meters, or 8,200 - 10,500 feet) has steadily decreased in recent years as the ice has darkened due to increased melting and dark soot being deposited on the ice from air pollution. This July, the high elevations of Greenland were the darkest on record, which helped contribute to the record warm temperatures observed at the Greenland Summit. Image credit: Dr. Jason Box, Ohio State University.


Video 1. Melt water from the record July temperatures in Greenland fed the raging Watson River, which smashed two bridges connecting the north and south of Kangerlussuaq (Sønder Strømfjord), a small settlement in southwestern Greenland. The flow rate of 3.5 million liters/sec was almost double the previous record flow rate.

Greenland's Petermann Glacier
Greenland's glaciers have seen significant changes in recent years, as they respond to warmer air and water temperatures. Northwest Greenland's Petermann Glacier has seen two massive calving events in the past two years, though it is uncertain if these events were caused by the warming climate. The most recent event came on July 16, 2012, when the glacier calved a 46 square-mile iceberg two times the size of Manhattan. The same glacier calved an iceberg twice as big back on August 4, 2010--the largest iceberg observed in the Arctic since 1962. The freshwater stored in that ice island could have kept the Delaware or Hudson rivers flowing for more than two years, or kept all U.S. public tap water flowing for 120 days. According to a university press release by Andreas Muenchow, associate professor of physical ocean science and engineering at the University of Delaware's College of Earth, Ocean, and Environment, “While the size is not as spectacular as it was in 2010, the fact that it follows so closely to the 2010 event brings the glacier’s terminus to a location where it has not been for at least 150 years. Northwest Greenland and northeast Canada are warming more than five times faster than the rest of the world, but the observed warming is not proof that the diminishing ice shelf is caused by this, because air temperatures have little effect on this glacier; ocean temperatures do, and our ocean temperature time series are only five to eight years long — too short to establish a robust warming signal.”


Figure 3. The massive 46 square-mile iceberg two times the size of Manhattan that calved from Greenland's Petermann Glacier on July 16, 2012, as seen on July 21, 2012, using MODIS satellite imagery. Image credit: NASA.

Related posts
Record warmth at the top of the Greenland Ice Sheet (July 18, 2012)
Unprecedented May heat in Greenland; update on 2011 Greenland ice melt
Greenland update for 2010: record melting and a massive calving event

Jeff Masters

Glaciers Heat Climate Change

Updated: 19:48 GMT le 15 août 2012

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Category 4 Typhoon Vicente hits China

By: JeffMasters, 13:40 GMT le 24 juillet 2012

Typhoon Vicente powered ashore about 60 miles (100 km) southwest of Macao, China Monday at 19:30 UTC as a dangerous Category 4 typhoon with 135 mph winds. The typhoon brought sustained winds of 58 mph with a peak wind gust of 83 mph to Hong Kong, and sustained winds of 55 mph with a peak wind gust of 76 mph to Macao. No deaths are being blamed on the typhoon, but 118 were injured, and the storm is dumping very heavy rains over Southeast China that will cause serious flooding.


Figure 1. Radar image of Vicente at landfall 60 miles (100 km) southwest of Hong Kong, China. Image credit: Hong Kong Observatory.


Figure 2. Firemen investigate the collapsed scaffolding caused by typhoon Vicente at a residential building in Hong Kong Tuesday, July 24, 2012. The strongest typhoon to hit Hong Kong in 13 years swirled into southern China as a tropical storm Tuesday, still potent enough for mainland authorities to order the evacuation of tens of thousands of people and warn residents of possible flooding. (AP Photo/Kin Cheung)

A hurricane forecasters' nightmare
Vicente was an example of a hurricane forecaster's nightmare. In six hours, Vicente strengthened from a Category 1 typhoon with 80 mph winds to a Category 4 storm with 135 mph winds. Even twelve hours before this remarkable burst of intensification, there was little indication that Vicente would undergo rapid intensification. It is very fortunate the the typhoon missed a direct hit on the heavily populated areas of Hong Kong and Macao, because there was no time to evacuate all the people who would have needed to leave for the impact of a Category 4 storm--particularly since the storm hit at night. If a similar type of storm were to affect a vulnerable area of the U.S. coast such as the Florida Keys, New Orleans, Houston/Galveston, or Tampa Bay, the death toll could easily be in the thousands. I have great hopes that the Hurricane Forecast Improvement Program (HFIP), currently in year three of a ten-year effort aimed at improving hurricane intensity forecasts by 50%, will be able to give us tools to be able to predict rapid intensification events like Vicente's several days in advance. However, we are still many years from being able to predict such events, and the hurricane forecasters' nightmare storm is still a very real possibility.

Atlantic to get more active?
NHC is giving a disturbance along a frontal boundary 600 miles east-northeast of Bermuda a 10% chance of developing into a tropical depression, but this system is not a threat to any land areas. Recent runs of both the GFS and NOGAPS models have predicted that tropical waves coming off the coast of Africa late this week and early next week could show some development. These predictions have not been consistent, but we are getting towards the time of year when we need to start watching the tropical waves coming off of Africa.

Jeff Masters

Hurricane

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June 2012: Earth's 4th warmest June; heavy rains in Beijing kill 37

By: JeffMasters, 12:19 GMT le 23 juillet 2012

June 2012 was the globe's 4th warmest June on record, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). NASA rated May 2012 the 3rd warmest on record. June 2012 global land temperatures were the warmest on record; this makes three months in a row--April, May, and June--in which record-high monthly land temperature records were set. Global ocean temperatures were the 10th warmest on record. June 2012 was the 328th consecutive month with global temperatures warmer than the 20th century average; the last time global temperatures were below average was February 1985. We've now had three consecutive top-five warmest months on record; April 2012 was the 5th warmest April on record, and May 2012 was the 2nd warmest May on record. The increase in global temperatures relative to average, compared to March 2012 (16th warmest March on record) is due, in part, to warming waters in the Eastern Pacific, where a La Niña event ended in April, and borderline El Niño conditions now exist. Global satellite-measured temperatures in June for the lowest 8 km of the atmosphere were 4th or 3rd warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). Northern Hemisphere snow cover extent during June 2012 was the smallest in the 46-year period of record. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of June in his June 2012 Global Weather Extremes Summary. Notably:

- The U.K. suffered through its wettest June since at least 1910, and coolest such since 1991.

- The monsoon season has been especially devastating so far along the banks of the Brahmaputra River in northeast India and Bangladesh. Over 2000 villages have been flooded and at least 190 deaths reported so far. Almost 20 million people in all have been displaced.

- The Korean Peninsula continued to endure its worst drought in at least 105 years.


Figure 1. Departure of temperature from average for June 2012. In the Northern Hemisphere, most areas experienced much higher-than-average monthly temperatures, including most of North America and Eurasia, and northern Africa. Only northern and western Europe, and the northwestern United States were notably cooler than average. Image credit: National Climatic Data Center (NCDC) .

Arctic sea ice has greatest June loss on record
Arctic sea ice saw its greatest-ever decrease during the month of June, and ice extent averaged over the entire month was the 2nd lowest for June in the 35-year satellite record, according to the National Snow and Ice Data Center (NSIDC). The last three Junes (2010 - 2012) have had the three smallest ice extents for the month, with June 2012 being the 21st consecutive June and the 133rd consecutive month with below-average Arctic sea ice extent. During much of June 2012 and extending into the first half of July, the Arctic Dipole pattern set up. This atmospheric circulation pattern features a surface high pressure system in the Arctic north of Alaska, and a low pressure system on the Eurasian side of the Arctic. This results in winds blowing from south to north over Siberia, pushing warm air into the central Arctic Ocean. The Arctic Dipole pattern occurred in all summer months of 2007 and helped support the record 2007 summer reduction in sea ice extent. The Arctic Dipole pattern has broken down over the past few days, and is expected to be absent through early August. This should slow Arctic sea ice loss, and ice extent may no longer be at record low levels by the first week of August.


Figure 2. Arctic sea ice area in 2012 as of July 22 (yellow line) compared to all the other years since satellite observations began in 1979. Ice area in 2012 during most of June and July has been the lowest on record. The previous record low years were 2007 and 2011. Note that sea ice area (as shown here) and sea ice extent (as measured by the National Snow and Ice Data Center) are not the same thing, but one can use either to quantify sea ice, and both show very similar behavior. Image credit: University of Illinois Cryosphere Today.

Three new billion-dollar weather disasters in June
The globe experienced three new billion-dollar weather disasters in June, bringing the total for the year to nine, said insurance broker Aon Benfield in their June Catastrophe Report. The most expensive disaster in June occurred in China, where heavy rains between the between June 20 - 29 affected northern, central, eastern and southern sections of the country. The rains left at least 50 people dead in 17 separate provinces, and caused damage estimated at CNY17.4 billion (USD2.73 billion). The U.S. suffered two billion-dollar severe weather events in June, bringing the total number of such events to six for the year. The record for most billion-dollar disasters in a year in the U.S. is fourteen (according to NOAA/NCDC) or seventeen (according to Aon Benfield.) The most costly event in June 2012 came across portions of Texas and New Mexico, where severe thunderstorms pelted areas (including the Dallas-Fort Worth metropolitan region) with golf ball and baseball-sized hail. The Insurance Council of Texas said that more than 100,000 claims were filed and total insured losses in the state would exceed $1 billion, with total losses near $1.75 billion. A separate hail event in Colorado and Wyoming caused more than $700 million in insured losses, and $1.25 billion in total losses.


Figure 3. Weather disasters costing at least half a billion dollars so far in 2012, according to insurance broker Aon Benfield in their June Catastrophe Report.

Heaviest rains in 60 years deluge Beijing, killing 37
China's latest billion-dollar weather disaster is a torrential rainstorm that hit Beijing Saturday night, dumping the the heaviest rains the city has seen in 60 years, according to Associated Press. The resulting flooding killed 37 people and did $1.6 billion in damage.


Figure 4. A Chinese man uses a signboard to signal motorists driving through flooded street following a heavy rain in Beijing Saturday, July 21, 2012. China's government says the heaviest rains to hit Beijing in six decades. The torrential downpour Saturday night left low-lying streets flooded and knocked down trees. (AP Photo)

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.


Jeff Masters

Climate Summaries Extreme Weather Flood

Updated: 21:14 GMT le 23 juillet 2012

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Historic 2012 U.S. drought continues to expand and intensify

By: JeffMasters, 14:01 GMT le 20 juillet 2012

The great U.S. drought of 2012 continues to accelerate, and grew larger and more intense over the past week, said NOAA in their weekly U.S. Drought Monitor report issued Thursday, July 19. The area of the contiguous U.S. covered by drought expanded from 61% to 64%, and the area covered by severe or greater drought jumped from 37% to 42%. These are truly historic levels of drought, exceeded only during the great Dust Bowl drought of the 1930s and a severe drought in the mid-1950s. If we make the reasonable assumption that the current area covered by drought is representative of what the average for the entire month of July will be (based on the latest drought forecast from NOAA's Climate Prediction Center), the July 2012 drought is second only to the great Dust Bowl drought of July 1934 in terms of the area of the contiguous U.S. covered by moderate or greater drought. The five months with the greatest percent area in moderate or greater drought, since 1895, now look like this:

1) Jul 1934, 80%
2) Jul 2012, 64%
3) Dec 1939, 60%
4) Jul 1954, 60%
5) Dec 1956, 58%

If we consider the area of the contiguous U.S. covered by severe or greater drought, July 2012 ranks in 5th place:

1) Jul 1934, 63%
2) Sep 1954, 50%
3) Dec 1956, 43%
4) Aug 1936, 43%
5) Jul 2012, 42%


Figure 1. The twice-monthly U.S. Drought Outlook, updated on Thursday, July 19, predicts that drought will continue through October over most of the U.S., and expand to the north and northeast. Image credit: NOAA Climate Prediction Center.

The drought forecast: not encouraging
In their twice-monthly drought outlook, released on Thursday, NOAA's Climate Prediction Center had this to say about the drought: The combination of heat and dryness has severely reduced the quality and quantity of the corn and soybean crop, with 38 percent of the corn and 30 percent of the soybeans rated as poor or very poor as of July 15 by NASS/USDA. Some states, such as Kentucky, Missouri, and Indiana, had over 70 percent of their corn adversely rated. Unfortunately, drought is expected to develop, persist, or intensify across these areas, and temperatures are likely to average above normal. Some widely-scattered relief may come in the form of cold front passages or organized thunderstorm clusters (MCSs), but widespread relief for much of the area is not expected. Unfortunately, the self-perpetuation of regional drought conditions, with very dry soils and very limited evapotranspiration, tends to inhibit widespread development of or weaken existing thunderstorm complexes. It would require a dramatic shift in the weather pattern to provide significant relief to this drought, and most tools and models do not forecast this. Unfortunately, all indicators (short and medium-term, August, and August-October) favor above normal temperatures. With much of the Plains already in drought, above normal temperatures expected into the fall, and a dry short-term and 30-day forecast, the drought should persist, with some possible development in the northern Plains.

One bright spot: drought conditions are expected to improve over the Southwest U.S. over the next few weeks, as the annual summer monsoon peaks and brings heavy rains. The Southeast U.S. has seen some improvement over the past week, due to an upper-level low pressure system that has brought heavy rains. The potential for a landfalling tropical storm to bring drought-busting rains during the August - September - October peak of hurricane season led NOAA to predict possible improvement in drought conditions over the Southeast U.S.


Figure 2. The U.S. has seen twelve weather-related disasters costing at least $15 billion since 1980, according to NOAA's National Climatic Data Center. Two of the top three most expensive disasters have been droughts. The drought of 2012 could well make it three out of four. "It might be a $50 billion event for the economy as it blends into everything over the next four quarters," said Michael Swanson, agricultural economist at Wells Fargo & Co. in Minneapolis, the largest commercial agriculture lender. Only three $50 billion weather disasters have hit the U.S. since 1980.

The Atlantic is quiet
There are no tropical cyclone threat areas in the Atlantic to discuss. The models are showing formation of an extratropical cyclone along an old frontal boundary over 1,000 miles off the Northeast U.S. coast on Tuesday, and it is possible such a storm could acquire tropical characteristics and get a name. Such a storm would not be a threat to any land areas. There is an unusual amount of dry, sinking air over the tropical Atlantic and Caribbean that is squashing development of tropical waves coming off the coast of Africa, so it doesn't look too likely that the U.S. will get something it really needs--a big, wet Category 1 hurricane that sloshes ashore over the Gulf Coast, stalling over the Midwest, bringing copious drought-busting rains.


Figure 3. Portlight volunteers unloading supplies at the FBC in Henryville, Indiana on March 10, 2012. Henryville was devastated by an EF-4 tornado on March 2 that killed 11 people along its path.

Helping out with disaster relief
It's been another busy year for natural disasters in the U.S., and the portlight.org disaster-relief charity, founded by members of the wunderground community, has been very active helping out victims of this year's disasters. Portlight responded to the deadly March tornado outbreak in the Midwest, two separate April tornado outbreaks in Texas and Oklahoma, and the June wildfires in Colorado. Paul Timmons of Portlight has put together a year-to-date summary of portlight's efforts in 2012, and has this call for action:

Now we’re in July…things have gotten quiet, but we know they won’t be quiet for long. We’re in the middle of hurricane season and mid-summer is a time of unsettled and dangerous weather that happens when we least expect it. Our work is never really done and new tasks pop up all the time. With your help and the help of our friends like the amazing people at Wunderground.com and our new friends at Team Rubicon, The Mahalia Partnership, and CCDC, we will be ready.

Where do we go from here? That depends on you, our supporters, volunteers and friends. Our purpose hasn’t changed: we will continue providing support, relief and aid for unserved, under-served and forgotten people wherever they may be…


Peace to all this weekend, and I'll be back on Sunday or Monday with a new post.

Jeff Masters

Drought

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Record warmth at the top of the Greenland Ice Sheet

By: JeffMasters, 21:25 GMT le 18 juillet 2012

The coldest place in Greenland, and often the entire Northern Hemisphere, is commonly the Summit Station. Located at the top of the Greenland Ice Sheet, 10,551 feet (3216 meters) above sea level, and 415 miles (670 km) north of the Arctic Circle, Summit rarely sees temperatures that rise above the freezing mark. In the 12-year span 2000 - 2011, Summit temperatures rose above freezing only four times, according to weather records researcher Maximiliano Herrera. But remarkably, over the past week, temperatures at Summit have eclipsed the freezing mark on five days, including four days in a row from July 11 - 14. There are actually three weather stations located at the location--Summit, Summit-US, and Summit AWS. The highest reliable temperature measured at any of the three stations is now the 3.6°C (38.5°F) measured on Monday, July 16, 2012 at Summit-US. A 4.4°C reading at Summit in May, 2010 is bogus, as can be seen by looking at the adjacent station. Similarly, a 3.3°C reading from June 2004 is also bad. Records at Summit began in 1987.


Video 1. A 20-ton tractor attempting to repair a bridge washed out by the raging Watson River on July 11, 2012 in Kangerlussauaq, Greenland gets washed downstream. The driver escaped unharmed. Image taken from an article, Warm air over the ice sheet provides great drama in Greenland, at the Danish Meteorological Institute's web site.

Record heat leads to major flooding in Greenland
The record heat has triggered significant melting of Greenland's Ice Sheet. According to the Arctic Sea Ice Blog, on July 11, glacier melt water from the Russell Glacier flooded the Watson River, smashing two bridges connecting the north and south of Kangerlussuaq (Sønder Strømfjord), a small settlement in southwestern Greenland. The flow rate of 3.5 million liters/sec was almost double the previous record flow rate. The latest forecast for Summit calls for cooler conditions over the coming week, with no more above-freezing temperatures at Summit.

Another huge iceberg calves off of Greenland's Petermann Glacier
A massive ice island two times the size of Manhattan and half as thick as the Empire State Building calved off of Greenland's Petermann Glacier on Monday, July 16, 2012. According to Andreas Muenchow, associate professor of physical ocean science and engineering at the University of Delaware's College of Earth, Ocean, and Environment in his Icy Seas blog, the break-off point has been visible for at least 8 years in satellite imagery, and has been propagating at 1 km/year towards Nares Strait. The same glacier calved an iceberg twice as big back on August 4, 2010--the largest iceberg observed in the Arctic since 1962. The freshwater stored in that ice island could have kept the Delaware or Hudson rivers flowing for more than two years, or kept all U.S. public tap water flowing for 120 days. “While the size is not as spectacular as it was in 2010, the fact that it follows so closely to the 2010 event brings the glacier’s terminus to a location where it has not been for at least 150 years,” Muenchow said in a university press release. “Northwest Greenland and northeast Canada are warming more than five times faster than the rest of the world, but the observed warming is not proof that the diminishing ice shelf is caused by this, because air temperatures have little effect on this glacier; ocean temperatures do, and our ocean temperature time series are only five to eight years long — too short to establish a robust warming signal.”


Figure 1. The calving of a massive 46 square-mile iceberg two times the size of Manhattan from Greenland's Petermann Glacier on July 14 - 18, 2012, as seen using MODIS satellite imagery. Image credit: NASA.


Figure 2. Look familiar? Two years ago, a 100 square-mile ice island broke off the Petermann Glacier. It was the largest iceberg in the Arctic since 1962. Image taken by NASA's Aqua satellite on August 21, 2010. Image credit: NASA. I've constructed a 7-frame satellite animation available here that shows the calving and break-up of the Petermann Glacier ice island. The animation begins on August 5, 2010, and ends on September 21, with images spaced about 8 days apart. The images were taken by NASA's Aqua and Terra satellites.

Related posts

Unprecedented May heat in Greenland; update on 2011 Greenland ice melt

Greenland update for 2010: record melting and a massive calving event

Jeff Masters

Glaciers Heat Climate Change

Updated: 18:08 GMT le 25 juillet 2012

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Morocco hits 121°F (49.6°C): a national all-time heat record

By: JeffMasters, 02:01 GMT le 18 juillet 2012

The first new all-time national temperature record of 2012 belongs to Morocco, thanks to the 121.3°F (49.6°C) temperature measured at Marrakech on July 17, 2012. According to the Wunderground International Records data base maintained by our weather historian, Christopher C. Burt, the previous record was 120.4°F (49.1°C) at Agadir on July 30, 2009. A hotter temperature of 51.7°C (125.1°F) was reported from Aghadir (Agadir) Souss Massa Dra region on 17 August 1940 during a chergui wind event. However, this reading is considered unreliable by weather records researcher Maximiliano Herrera, since the temperature was 6°C higher than that measured at nearby stations.

Seven nations set all time heat records in 2011. Nineteen nations (plus the the U.K.'s Ascension Island) set all-time extreme heat records in 2010. One nation (Zambia, in 2011) set an all-time cold record during the period 2010 - 2012. With a very hot airmass in place over much of North Africa, the Middle East, and Western Asia the remainder of this week, more all-time national heat records may fall.


Figure 1. A sample image of what the new Fire Risk layer on our wundermap looks like. This is the Keetch-Byram Drought Index, one of several indices that can be used to measure fire risk. Blue and green colors represent lower risks, while yellow and orange colors show higher risk. The highest risk is shown in dark red. The legend for the Fire Risk layer explains that these highest risk areas are often associated with more severe drought with increased wildfire occurrence. Intense, deep burning fires with significant downwind spotting can be expected. Live fuels can also be expected to burn actively at these levels.

Wunderground releases new fire risk layer on its wundermap
Our interactive wundermap, which allows one to overlay multiple meteorological data sets, has a new layer: a Fire Risk layer. Using data from the U.S. Forest Service's Wildland Fire Assessment System, we give you option to plot up U.S. fire danger using a variety of options: Fire Danger Rating, Lower Atmosphere Stability (Haines Index), Keetch-Byram Drought Index, 10-hr Dead Fuel Moisture, 100-hr Dead Fuel Moisture, and 1000-hr Dead Fuel Moisture. According to the National Interagency Fire Center, California currently has the most number of of large fires burning of any state (5), which makes sense, given what the fire risk map above is showing.

Jeff Masters

Heat

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Historic 2012 U.S. drought: 6th greatest on record

By: JeffMasters, 22:59 GMT le 16 juillet 2012

The great drought of 2012 is upon us. The percentage area of the contiguous U.S. covered by moderate or greater drought increased to 56% by the end of June, and ranked as the sixth largest drought since U.S. weather records began in 1895, said NOAA's National Climatic Data Center in their monthly State of the Climate drought report on Monday. The last time more of the U.S. was in drought occurred in December 1956, with 58%. June 2012 ranked as the 10th greatest U.S. drought on record, when considering the percentage area of the U.S. in severe or greater drought (33%.)


Figure 1. June 2012 ranked in sixth place for the greatest percent area of the contiguous U.S. covered by moderate or greater drought, since record keeping began in 1895. Graphic created from data from NOAA's National Climatic Data Center.

The forecast: hot and dry with increasing drought
The great drought of 2012 is going to steadily worsen during the remainder of July. Recent runs of the global computer forecast models predict a continuation through the end of July of the large-scale jet stream patterns that have brought the U.S. its hot, dry summer weather. The most extreme heat will tend to be focused over the center portion of the county. That was certainly the case Monday, with temperatures near or in excess of 100° observed from South Dakota to Michigan. High temperatures near 100°F are expected in Chicago and Detroit on Tuesday, and over much of the Midwest.


Figure 2. Comparison of drought between June 2012 (top) and June 1988 (bottom) shows that drought conditions covered a similar proportion of the contiguous U.S., but the spatial patterns were different. The 2012 drought is especially intense over the Southwest U.S., but in 1988, this region experienced a very active summer monsoon season that kept the region moist. However, in 1988, the Northern Plains were much drier than in 2012. Image credit: NOAA Earth System Research Laboratory.

A multi-billion dollar drought disaster underway
Agronomists and drought experts are comparing the scale and intensity of the 2012 drought to the 1988 drought. With the forecast offering little optimism, the costs of the 2012 drought are certain to be many billions of dollars, and the disaster could be one of the top ten most expensive weather-related disasters in U.S. history. Droughts historically have been some of the costliest U.S. weather disasters. A four-year drought and locust plague from 1874 - 1877 cost $169 billion (2012 dollars), and was arguably the most expensive weather related disaster in U.S. history (see Jeffrey Lockwood's 2004 book, Locust.) The costs of the great Dust Bowl drought of the 1930s, which displaced 2.5 million people, are incalculable. The costs of government financial assistance alone were $13 billion in 2012 dollars (Warrick, 1980.) The 1988 drought cost $78 billion (2012 dollars), the second most expensive weather disaster since 1980, behind Hurricane Katrina.

The associated heat wave of the great drought of 2012 is also a major concern. The heat waves associated with the great droughts of 1980 and 1988 killed between 7,500 - 10,000 people, according to NOAA's National Climatic Data Center. The heat waves of the 1930s are blamed for 5,000 deaths. The death toll from the 2012 heat wave is approaching 100, including 23 in Chicago, up to 19 in Wisconsin, 18 in Maryland, 17 in St. Louis, and 9 in Philadelphia. The toll will undoubtedly grow as more heat-related deaths are discovered, and as the heat continues.


Figure 3. The U.S. has seen twelve weather-related disasters costing at least $15 billion since 1980, according to NOAA's National Climatic Data Center. Two of the top three most expensive disasters have been droughts.

Tornadoes kill one, injure ten in Poland
A series of rare tornadoes hit northern and western Poland over the weekend, killing one and injuring ten. At least 100 homes were destroyed, and one of the twisters measured 1 km (0.6 miles) in diameter. Tornadoes are quite rare in Poland. According to the publication, An updated estimate of tornado occurrence in Europe by Nikolai Dotzek (2003), Poland reports about two tornadoes per year, and probably has two more per year that are unreported. Thanks go to wunderground member beell for posting this link.


Video 1. Raw footage of the weekend tornadoes that hit Poland.

Jeff Masters

Drought Heat

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Death Valley records a low of 107°F (41.7°C): a world record

By: JeffMasters, 01:31 GMT le 16 juillet 2012

On Thursday morning, July 12, 2012 the low temperature at Death Valley, California dropped to just 107°F (41.7°C), after hitting a high of 128° (53.3°C) the previous day. Not only does the morning low temperature tie a record for the world's warmest low temperature ever recorded, the average temperature of 117.5°F is the world's warmest 24-hour temperature on record. According to weather records researcher Maximiliano Herrera, the only other place in the world to record a 107°F low temperature was Khasab Airport in the desert nation of Oman on June 27, 2012. The previous U.S. record high minimum temperature may be a 103°F (39.4°C) observed in Death Valley, California in 1970. The NWS lists a July 5, 1918 low temperature of 110°F as the official highest minimum temperature recorded in Death Valley. This temperature is disputed by Mr. Herrera, who says the temperature that night was not monitored and passed from 60°F to 110°F then to 60°F again.


Figure 1. Badwater, Death Valley, California. Wide open spaces, infinite views. What's not to love about this place? Image credit: Wunderphotographer SonomaCountyRAF.

Wednesday's high of 128°F (53.3°C) was the 10th hottest temperature in U.S. history, and the hottest temperature measured in the U.S. since July 18, 2009, when Death Valley recorded another 128° reading. The only hotter temperatures in U.S. history were all measured at Death Valley, the most recent one being the 129° measured on July 6, 2007. The all-time high for Death Valley is the 134° reading of July 10, 1913.

Temperatures have cooled considerably at Death Valley over the weekend, and the forecast for Monday calls for for a downright chilly high of just 110°. That's sure to be a disappointment for the ultramarathoners in the grueling Badwater Ultramarathon, which begins Monday in Death Valley. Covering 135 miles (217km) non-stop from Death Valley to Mt. Whitney, CA, it is the most demanding and extreme running race offered anywhere on the planet. I'm sure they would have liked to have had the distinction of running their race last Wednesday and Thursday, during the hottest 24-hour period ever recorded on the planet!

Jeff Masters

Heat

Updated: 14:38 GMT le 16 juillet 2012

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July Atlantic hurricane outlook

By: JeffMasters, 12:55 GMT le 13 juillet 2012

It's mid-July, and we have yet to see a named storm form in the Atlantic this month. The computer models are not predicting any development through at least July 20, and if we make it all the way to the end of the month without a named storm forming, it will be the first July since 2009 without a named storm. Since the current active hurricane period began in 1995, 13 of 17 years (76%) have had a named storm form during July. The busiest July occurred in 2005, when five named storms and two major hurricanes formed. These included Hurricane Dennis and Hurricane Emily--the strongest hurricanes ever observed so early in the season. Only eight major hurricanes have formed in July since record keeping began in 1851. As seen in Figure 1, most of the last half of July activity occurs in the Gulf of Mexico and waters off the Southeast U.S. coast. These type of storms form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance (as happened for Alberto, Beryl, Chris, and Debby in 2012.) There will be at least two cold fronts moving off the U.S. Mid-Atlantic coast over the next two weeks. The first of these fronts will push offshore around July 20, and we will need to watch the waters offshore of North Carolina for development then. Formation potential will be aided by ocean temperatures that are about 0.7°C (1°F) above average along the U.S. East Coast.


Figure 1. Tracks of all tropical storms and hurricanes 1851 - 2006 that formed July 16-31. The U.S. coast from North to Texas are the preferred strike locations. Only a few storms have formed in the tropical Atlantic and Caribbean in July. Wind shear is typically too high and SSTs too cool in July to allow African waves in the Caribbean and tropical Atlantic to develop into tropical storms. However, a few long-track "Cape Verdes" hurricanes have occurred in July, spawned by tropical waves that came off the coast of Africa. African tropical waves serve as the instigators of about 85% of all major hurricanes.


Figure 2. The seasonal distribution of Atlantic hurricane activity shows that July typically has low activity. Image credit: NHC.

Sea Surface Temperatures: slightly above average
The departure of Sea Surface Temperatures (SST) from average over the tropical Atlantic between Africa and Central America was about 0.3°C above average during June (Figure 3.) This figure has not changed much over the first two weeks of July. These temperatures are not warm enough to appreciably affect the odds of a July named storm or hurricane. The strength of the Azores-Bermuda high has been near average over the past two weeks, driving near-average trade winds. The latest 2-week run of the GFS model predicts continued average-strength trade winds through late-July, so SSTs should remain about 0.3°C above average during this period, due to average amounts of cold water mixing up from below due to the wind action on the water.


Figure 3. Sea Surface Temperature (SST) departure from average for July 12, 2012. SSTs were 0.3°C above average over the tropical Atlantic's Main Development region for hurricanes, from Africa to Central America between 10° and 20° North Latitude. Note the large region of above average SSTs along the Equatorial Pacific off the coast of South America, the hallmark of a developing El Niño episode. Image credit: NOAA/NESDIS

El Niño on the way?
For two consecutive weeks, ocean temperatures 0.5 - 0.6°C above average have been present in the tropical Eastern Pacific, which is right at the threshold for a weak El Niño episode. NOAA's Climate Prediction Center has issued an El Niño Watch, and gives a 61% chance that El Niño conditions will be present during the August - September - October peak of the Atlantic hurricane season. The likely development of a full-fledged El Niño episode means that Atlantic hurricane activity will probably be suppressed in 2012, due to the strong upper-level winds and high wind shear these events typically bring to the tropical Atlantic.


Figure 4. Sea Surface Temperature (SST) departure from average for the the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region"). El Niño conditions exist when the SST in this region rises 0.5°C above average. As of July 9, 2012, SSTs in the Niño 3.4 region had risen to 0.5°C above average. To be considered an "El Niño episode", El Niño conditions must occur for five consecutive months, using 3-month averages. Image credit: NOAA Climate Prediction Center.

Wind shear: above average
Wind shear is usually defined as the difference in wind between 200 mb (roughly 40,000 foot altitude) and 850 mb (roughly 5,000 foot altitude). In most circumstances, wind shear above 20 knots will act to inhibit tropical storm formation. Wind shear below 12 knots is very conducive for tropical storm formation. High wind shear acts to tear a storm apart. The jet stream has two bands of strong high-altitude winds that are currently bringing high wind shear to the Atlantic. The southern branch (subtropical jet stream) is bringing high wind shear to the Caribbean, and the northern branch (polar jet stream) is bringing high wind shear to the waters offshore of New England. This configuration often leaves a "hole" of low shear between the two branches, off the Southeast U.S. coast and over the Gulf of Mexico. The jet stream is forecast to maintain this two-branch pattern over the coming two weeks. Wind shear has been about 10 - 20% higher than average over the first two weeks of July, and is predicted to be mostly above average for the coming two weeks. This will cut down on the odds of a July storm.


Figure 5. Vertical instability over the Caribbean Sea in 2012 (blue line) compared to average (black line.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Instability has been lower than average, due to an unusual amount of dry air in the atmosphere, reducing the potential for tropical storm formation. Image credit: NOAA/NESDIS/CIRA.

Dry air: above average
As seen in Figure 5, there has been an unusual amount of dry, stable air in the Caribbean this year creating low levels of vertical instability. This has occurred due to a combination of dry air from Africa, and upper-atmosphere dynamics creating large areas of sinking air that dry as they warm and approach the surface. The Gulf of Mexico and tropical Atlantic between the coast of Africa and the Lesser Antilles have also seen low vertical instability this summer. June and July are the peak months for dry air and dust coming off the coast of Africa, and the Saharan dust storms have been quite active over the past two weeks. Expect dry air to be a major deterrent to any storms that try to form in the tropical Atlantic during July.

Steering currents: average
The predicted steering current pattern for the next two weeks is a typical one for July. We have an active jet stream bringing many troughs of low pressure off the East Coast of the U.S. These troughs are frequent enough and strong enough to recurve any tropical storms or hurricanes that might penetrate north of the Caribbean Sea. Steering current patterns are predictable only about 3 - 5 days in the future, although we can make very general forecasts about the pattern as much as two weeks in advance. There is no telling what might happen during the peak months of August, September, and October--we might be in for a repeat of the favorable 2010 and 2011 steering current pattern, which recurved most storms out to sea--or the unfavorable 2008 pattern, which steered Ike and Gustav into the Gulf of Mexico.

Summary: a below average chance of a July tropical storm
Given that none of the computer models are forecasting tropical storm formation in the coming seven days, SSTs are only slightly above average, and wind shear and vertical stability are above average, I'll go with a 30% chance of a named storm forming in the Atlantic during the remainder of July.


Figure 6. Hurricane Emilia over the Eastern Pacific at 20:35 UTC July 10, 2012. At the time, Emilia was a Category 3 hurricane with 125 mph winds. Emilia peaked earlier in the day as a Category 4 storm with 140 mph winds--the strongest hurricane in the East Pacific so far in 2012. Image credit: NASA.

An active Eastern Pacific hurricane season
It's been a very active start to the Eastern Pacific hurricane season, where we've already had six named storms, four hurricanes, and three intense hurricanes. A typical season has 4 named storms, 2 hurricanes, and 0 intense hurricanes by July 14. The formation of Tropical Storm Fabio on July 12 marks the 4th earliest formation of the Eastern Pacific's season's sixth storm. The record is held by the year 1985, when the season's sixth storm formed on July 2. Record keeping began in 1949.

Have a great weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

Hurricane

Updated: 13:27 GMT le 13 juillet 2012

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Russian wildfire smoke reaches Canada, U.S.; Death Valley hits 128°F

By: JeffMasters, 14:29 GMT le 12 juillet 2012

The U.S. isn't the only country suffering from a severe wildfire season. Russian firefighters have been battling huge blazes in Siberia for months. Central Russia experienced record warm temperatures 11 - 12°F (6 - 7°C) above average during June, feeding fires that have burned more area in 2012 than in 2010--the year of the unprecedented heat wave that killed over 55,000 people. Smoke from this summer's Russian fires rose high into the atmosphere last week, and got caught in the jet stream. As University of Washington professor Dr. Cliff Mass explained in this blog, the strong winds of the jet stream carried the smoke to western North America this week, where sinking air associated with a strong area of high pressure brought the smoke to the surface. On Wednesday, CBC reported that the smoke had settled over Vancouver, British Columbia, reducing visibility and increasing air pollution. Meteorologist Eric Taylor of the B.C. Ministry of Environment said he had never seen ozone pollution levels as high in B.C.'s central Interior as occurred over the past few days. The smoke has created colorful sunsets from Oregon to British Columbia, but a low pressure system is expected to flush most of the smoke out by Friday.


Figure 1. Thick smoke from forest fires burning in Siberia on July 5, 2012 (left) and July 9, 2012 (right.) Image credit: NASA.


Figure 2. The view from West Vancouver, British Columbia on Wednesday was obscured by thick smoke from forest fires burning in Siberia. Image credit: ThemeGreen's Webcam.

Colorado's most destructive wildfire in its history finally contained
It's been another severe year for wildfires in the U.S., with the National Interagency Fire Center reporting 4800 square miles of burned acreage thus far in 2012, an area about 87% of the size of Connecticut. This is pretty close to the 10-year average for this point in the year, and ranks as the fourth highest of the past ten years. However, with summer not yet half over, and more than 2/3 of the Western U.S. experiencing moderate to extreme drought, the Western U.S. fire season still has plenty of time to add significant acreage to its burn total. The hardest-hit state at present is Idaho, where one-third of the country's large fires (twelve) are burning. The worst fires of 2012 so far have been in Colorado, which had its hottest and driest June since record keeping began in 1895. Colorado's most destructive wildfire in its history, the 29-square mile Waldo Canyon fire, was finally 100% contained on Wednesday, aided by a week of relatively cool and wet weather. The fire killed two people and destroyed nearly 350 houses when it burned into northwestern Colorado Springs. Colorado's second most destructive and second largest fire in recorded history was the High Park Fire, fifteen miles northwest of Fort Collins. The fire was 100% contained on June 30. According to the Denver Post, the High Park Fire burned in an area where 70% of the trees that have been killed by mountain pine beetles; the insects have devastated forests in western North America in recent years. So did pine beetle damage contribute to this year's devastating Colorado fires? Using Landsat satellite data, a team of scientists led by University of Wisconsin forest ecologist Phil Townsend have discovered that pine beetle damage appears not to have a significant impact in the risk of large fires, and may reduce fire risk in some instances (Video 1.)


Video 1. Wildfire and Pine Beetles: NASA explains how recent devastation of forests in the Rocky Mountains by the mountain pine beetle may be affecting wildfire odds.

Links to follow
Our climate change blogger, Dr. Ricky Rood, has a post on mountain pine beetles and climate change.

I have a post on how climate change is expected to increase Western U.S. fires.

Welcome to the Rest of Our Lives, an 8-minute video put together by climate change videographer Peter SInclair, provides a dramatic look at the extreme weather that has hit the U.S. in June and July.

Our climate change blogger, Dr. Ricky Rood, is in Boulder, Colorado this summer, and had this to say in his June 27 post on the wildfires in Colorado: "The past few days have been relentless. Denver has seen temperatures above 100°F for 5 straight days, and it was 105° today. At the weather station closest to where I live, the thunderstorm that started today’s fire stopped the temperature rise at 97.5 F. The dew point was in the high 30s. The ground temperature in the garden was about 110°. Tonight it all smells of smoke again. It is hard to sleep when the house is 88 degrees and the air smells of smoke. You constantly think of fire."

Death Valley hits 128°: 10th hottest temperature in U.S. history
The high temperature in Death Valley, California hit 128°F (53.3°C) on Wednesday, the hottest temperature measured in the U.S. since July 18, 2009, when Death Valley recorded another 128° reading. Yesterday's 128° was the 10th hottest temperature in U.S. history. The only hotter temperatures were all measured at Death Valley, the most recent one being the 129° measured on July 6, 2007. The all-time high for Death Valley is the 134° reading of July 10, 1913. The forecast for Death Valley calls for a slow cool-down over the next few days, with highs reaching "only" 105° on Monday. That's the date of the start of the grueling Badwater Ultramarathon. Covering 135 miles (217km) non-stop from Death Valley to Mt. Whitney, CA, it is the most demanding and extreme running race offered anywhere on the planet. Lace up your running shoes (not!)

Jeff Masters

Fire Heat

Updated: 17:07 GMT le 12 juillet 2012

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Extreme events of 2011: climate change a major factor in some, but not all

By: JeffMasters, 13:54 GMT le 11 juillet 2012

The science of quantifying how climate change changes the odds of extreme weather events like droughts and floods took a major step forward Tuesday with the publication of NOAA's annual summary of the past year's weather. The 2011 State of the Climate report contains a separate peer-reviewed article published in the July issue of the Bulletin of the American Meteorological Society titled, Explaining Extreme Events of 2011 From a Climate Perspective. In the paper, a group of scientists led by Peter Stott of the Met Office Centre in the United Kingdom looked at how climate change may have changed the odds of occurrence of some of 2011's notable weather extremes. These kinds of attribution studies require huge amounts of computer time and take many months to do, but the scientists plan to start making this a regular part of the annual NOAA State of the Climate report. Some of their findings for 2011:

- Determining the causes of extreme events remains difficult. While scientists cannot trace specific events to climate change with absolute certainty, new and continued research help scientists understand how the probability of extreme events change in response to global warming.

- La Niña-related heat waves, like that experienced in Texas in 2011, are now 20 times more likely to occur during La Niña years today than La Niña years fifty years ago.

- The UK experienced a very warm November 2011 and a very cold December 2010. In analyzing these two very different events, UK scientists uncovered interesting changes in the odds. Cold Decembers are now half as likely to occur now versus fifty years ago, whereas warm Novembers are now 62 times more likely.

- The devastating 2011 floods in Thailand caused an estimated $45 billion in damage, making it the world's most expensive river flooding disaster in history. The study found, however, that the amount of rain that fell in the catchment area was not very unusual, and that other factors such as human-caused changes to the flood plain and the movement of more people into flood-prone areas were more important in causing the disaster. "Climate change cannot be shown to have played any role in this event," the study concluded, but warned that climate models predict an increase in the probability of extreme precipitation events in the future in the region.

- The deadly drought in East Africa, which killed tens of thousands of people in 2011, was made more likely by warming waters in the Indian Ocean and Western Pacific. While the scientists did not specifically tie the warming of these waters to human-caused global warming, they noted that climate models predict continued warming of these waters in the coming decades, and this will likely "contribute to more frequent East African droughts during the spring and summer."


Figure 1. An SH-60F Sea Hawk helicopter assigned to Helicopter Anti-Submarine Squadron (HS) 14, flies around the Bangkok area with members of the humanitarian assessment survey team and the Royal Thai Armed Forces to assess the damage caused by the 2011 floods. Image credit: Petty Officer 1st Class Jennifer Villalovos.

Weather on steroids
One interesting aspect of the paper was the scientists' use of the baseball player-steroids analogy to help explain how climate change can increase the odds of extreme weather: "One analogy of the effects of climate change on extreme weather is with a baseball player (or to choose another sport, a cricketer) who starts taking steroids and afterwards hits on average 20% more home runs (or sixes) in a season than he did before (Meehl 2012). For any one of his home runs (sixes) during the years the player was taking steroids, you would not know for sure whether it was caused by steroids or not. But you might be able to attribute his increased number to the steroids. And given that steroids have resulted in a 20% increased chance that any particular swing of the player’s bat results in a home run (or a six), you would be able to make an attribution statement that, all other things being equal, steroid use had increased the probability of that particular occurrence by 20%. The job of the attribution assessment is to distinguish the effects of anthropogenic climate change or some other external factor (steroids in the sporting analogy) from natural variability (e.g., in the baseball analogy, the player’s natural ability to hit home runs or the configuration of a particular stadium)."



Video 1. National Center for Atmospheric Research scientist Dr. Jerry Meehl explains how climate change's impact on extreme weather is like how steroids affect a baseball player.

Jeff Masters

Climate Change Extreme Weather

Updated: 04:00 GMT le 19 juillet 2012

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U.S. experiences warmest 12-month period on record--again

By: JeffMasters, 21:04 GMT le 09 juillet 2012

Thanks in part to the historic heat wave that demolished thousands of high temperature records at the end of June, temperatures in the contiguous U.S. were the warmest on record over the past twelve months and for the year-to-date period of January - June, said NOAA's National Climatic Data Center (NCDC) on Monday. June 2012 was the 14th warmest June on record, so was not as extreme overall as March 2012 (first warmest March on record), April (third warmest April), or May (second warmest May.) However, temperatures were warm enough in June to set a new U.S. record for hottest 12-month period for the third straight month, narrowly eclipsing the record set just the previous month. The past thirteen months have featured America's 2nd warmest summer (in 2011), 4th warmest winter, and warmest spring on record. Twenty-six states were record warm for the 12-month period, and an additional sixteen states were top-ten warm. The year-to-date period of January - June was the warmest on record by an unusually large margin--1.2°F.


Figure 1. This time series shows the five warmest years that the contiguous U.S. has experienced, and how the year-to-date temperature evolved each month throughout those years. The time series also shows the 2012 year-to-date temperature through June, which was the warmest first half of any year on record for the lower 48. The 2012 data are still preliminary. Image credit: NOAA/NCDC.


Figure 2. Four of the top-ten warmest 12-month periods in the contiguous U.S. since 1895 have occurred since April 2011. Image credit: NOAA/NCDC.

Most extreme January - June period on record
NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought, was 44% during the year-to-date January - June period. This is the highest value since CEI record-keeping began in 1910, and more than twice the average value. Remarkably, 83% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically during the first six months of 2012, and 70% of the U.S. of the U.S. had warm minimum temperatures in the top 10%. The percentage area of the U.S. experiencing top-10% drought conditions was 20%, which was the 14th greatest since 1910. Extremes in 1-day spring heavy precipitation events were near average.


Figure 3. NOAA's U.S. Climate Extremes Index (CEI) for January - June shows that 2012 has had the most extreme first six months of the year on record, with 44% of the contiguous U.S. experiencing top-10% extreme weather.

Tuesday Webinar on the future of extreme weather impacts on business
I'm presenting a 12-minute Webinar talk on the future of weather-related disasters at 2 pm EDT Tuesday July 10. If you want to register (it's free) and listen in, visit the propertycasualty360.com web site. The title of the webinar is, "The Year-Round CAT Season: Is Your Business Prepared for Increasingly Frequent Severe Weather?"

"New McCarthyism" targets climate scientists
Bill Blakemore with ABC News has an interesting five-part interview with climate scientist Dr. Michael Mann, where Dr. Mann explains how a "New McCarthyism" is targeting climate scientists. I reviewed Dr. Mann's excellent book, "The Hockey Stick and the Climate Wars", earlier this year.

A 1 in 1.6 million event?
I originally wrote in this post that "Each of the 13 months from June 2011 through June 2012 ranked among the warmest third of their historical distribution for the first time in the 1895 - present record. According to NCDC, the odds of this occurring randomly during any particular month are 1 in 1,594,323. Thus, we should only see one more 13-month period so warm between now and 124,652 AD--assuming the climate is staying the same as it did during the past 118 years."

It has been pointed out to me that the calculation of a 1 in 1.6 million chance of occurrence (based on taking the number 1/3 and raising it to the 13th power) would be true only if each month had no correlation to the next month. Since weather patterns tend to persist, they are not truly random from one month to the next. Thus, the odds of such an event occurring are greater than 1 in 1.6 million--but are still very rare. I appreciate hearing from those of you who wrote to point out a correction was needed.

Jeff Masters

Climate Summaries

Updated: 20:11 GMT le 10 juillet 2012

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Extreme flood in Russia kills 171

By: JeffMasters, 13:14 GMT le 09 juillet 2012

Earth's deadliest flood of 2012 hit the Black Sea area of Russia on Saturday, where 300 mm (11.8") of rain fell in less than 24 hours. The resulting flood waters swept through the town of Krymsk in the Krasnodar region early Saturday, killing at least 171 people. The heavy rains were caused by a low pressure system that tracked just north of the region. The counter-clockwise flow of air around the low brought moisture-laden air from the Black Sea northwards over the mountains bordering the Black Sea. As the air was forced upwards by the mountains, its water vapor cooled and condensed into heavy rains. The rains were increased due to ocean temperatures in the Eastern Black Sea that were more than 2°C (3.6°F) above average. The extra heat in the ocean allowed much more water vapor than usual to evaporate into the air. Rare 1-in-20 year heavy precipitation events like the one that caused the Krasnodar flood are expected to increase in frequency due to climate change, as the waters of the Black Sea warm. According to the 2011 Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX), issued by the United Nations Intergovernmental Panel on Climate Change (IPCC), 1-in-20 year extreme precipitation events are likely to occur with a 1-in-11 to 1-in-15 year frequency by the year 2100 in the Black Sea area of Russia. A warmer atmosphere holds more water vapor, increasing the odds of very heavy precipitation events.


Figure 1. Flood damage in Krymsk, Russia, from Saturday's deadly flood. Image credit: Associated Press.


Figure 1. True-color satellite image of Russia's Krasnodar region along the northeast coast of the Black Sea, taken at 09:30 UTC Friday, July 6, 2012. The counter-clockwise flow of air around a spiraling low pressure system centered just north of the region was bringing a flow or moisture-laden air from the Black Sea over the city of Krymsk. Image credit: NASA.

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

I'll be back this afternoon with a full wrap-up on the remarkable heat wave of 2012.

Jeff Masters

Flood

Updated: 13:20 GMT le 09 juillet 2012

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Heat wave breaks more all-time records in Midwest; relief coming Sunday

By: JeffMasters, 12:50 GMT le 07 juillet 2012

The extraordinary heat wave of late June/early July 2012 toppled more Dust Bowl-era records on Friday, with three cities in Michigan hitting their hottest temperatures ever recorded. Lansing hit 103°, the hottest day in Michigan's capital city since record keeping began in 1863. Lansing has hit 102° four times, most recently on July 24, 1934. Muskegon, MI hit 99°, matching that city's record for all-time hottest temperature set on August 3, 1964. Records go back to 1896 in Muskegon, which has never hit 100°, due to the cooling effect of nearby Lake Michigan. Holland, MI hit 102° Friday, tied for hottest temperature in city history. Grand Rapids, MI hit 104° Friday, the third hottest temperature in city history. Only two readings during the great Dust Bowl summer of 1936 were warmer: 108° on July 13, 1936, and 106° on July 12, 1936.


Figure 1. Water temperatures averaged over Lake Michigan are running 11°F (6°C) above average so far in 2012. Image credit: NOAA/GLERL.

Chicago's third consecutive 100°+ day ties record for longest such streak
Chicago, IL hit 103° Friday, which was just 2° shy of their official all-time high of 105° set on July 24, 1934 (the unofficial Midway Airport site recorded 109° on July 23, 1934, though.) Friday was the third consecutive day with a temperature of 100° or hotter in Chicago, tying the record for most consecutive 100° days (set on July 3 - 5, 1911 and Aug 4 - 6, 1947.) Historically, Chicago has 15 days per summer over 90° and 1 day every 2.3 years over 100°. Under a higher-emissions scenario, climate change models predict that Chicago could experience over 70 days above 90° by 2100 and 30 days over 100°. With summer less than half over, Chicago has seen 18 days over 90° and 4 over 100° in 2012. The record number of 100° days in Chicago is 8, set in 1988. The heat wave in Chicago comes at the end of a nine-month period of record warmth in the city, including the warmest March on record. As a result, Lake Michigan has heated up to the warmest levels ever seen this early in the year. Temperatures of 80°--fifteen degrees above average--were measured at the South Buoy on Lake Michigan on Friday.


Figure 2. Climate models predict many more hot summers like 2012 ahead for Chicago. Image credit: Union of Concerned Scientists.

Historic heat wave in Indiana
"The Indianapolis area is nearing the end of an historic heat wave, the likes the area has not seen in 76 years," said the Indianapolis National Weather Service on Friday. To make matters worse, current drought conditions are worse than during the Dust Bowl of the 1930s. The only times less rain fell from May 1 - July 5 were 1988 and 1895. Indianapolis hit 105° Friday, which was just 1° shy of their official all-time high of 106° set at the official downtown site on July 14, 1936 and July 25, 1934. (The unofficial airport site recorded 107° on July 25, 1934.) Historically, Indianapolis has 17 days per summer over 90° and less than 1 day over 100. Under a higher-emissions scenario, climate change models predict that Indianapolis could experience over 80 days above 90° by 2100, and 28 days over 100°. With summer less than half over, Indianapolis has seen 20 days over 90° and 5 over 100° so far in 2012. Only the years 1936 and 1934 had more 100 degrees days: 1936 with 12, and 1934 with 9.


Figure 2. The severe weather map for Saturday, July 7, 2012, had advisories for extreme heat (pink colors) for portions of 26 states.

The forecast: more record heat Saturday, then relief
More record-breaking triple-digit heat is expected Saturday across much of the Midwest and Tennessee Valley. All-time highs in Washington D.C. (106°), Pittsburgh (103°), Indianapolis (106°), and Louisville (107°) may be threatened. However, sweet relief is in sight. A cold front will move southwards out of Canada on Saturday and Sunday, putting an end to this phase of the great heat wave of 2012. By Monday, temperatures will be near average for most of the eastern 2/3 of the U.S., and will remain near average for the entire week.

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

I'll be back Monday with a full wrap-up on the remarkable heat wave of 2012. Have a great weekend, everyone!

Jeff Masters

Heat

Updated: 12:54 GMT le 07 juillet 2012

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Chicago and Milwaukee hit 103°; relief coming by Sunday

By: JeffMasters, 14:34 GMT le 06 juillet 2012

It was another day of triple-digit heat across the Midwest Thursday, as the nation continued to bake in the intense heat of the record-breaking summer of 2012. Chicago hit 103° on Thursday, just 2° below the city's all-time hottest temperature of 105°, set on July 24, 1934. The Windy City might have exceeded their all-time heat record, but for the fortuitous formation of a small but intense thunderstorm that hit the airport at 2:45 pm. The storm brought a wind gust of 52 mph to the airport and cooled the temperature by 20°. A wind gust of 92 mph was recorded 4 miles offshore over Lake Michigan. Thursday was the hottest day in Chicago since a 104° reading on July 13, 1995. Milwaukee, WI also hit 103° Thursday, which tied for the 3rd hottest temperature in city history. Madison's 104° was their hottest day since 1988, and also tied for the 3rd warmest temperature ever measured in the city. Madison's all-time high is 107°, set July 14, 1936. St. Louis hit 105°, the eighth consecutive day the city has hit triple digits. This streak is now the 3rd longest such streak in city history; the only longer streaks occurred during the Dust Bowl summer of 1936 (streaks of 13 and 9 days.) The current forecast for St. Louis calls for highs of 107 - 108° Friday and Saturday, which will likely bring the city's streak of 100°+ days to ten by week's end. St. Louis' all-time hottest temperature is 115°, set in 1954.


Figure 1. The severe weather map for Friday, July 6, 2012, showed that advisories for extreme heat (pink colors) were posted for portions of 25 states.

The forecast: record heat Friday and Saturday, then relief
More record-breaking triple-digit heat is expected Friday and Saturday across much of the Midwest and Tennessee Valley, but a cold front will move southwards out of Canada on Saturday and Sunday, putting an end to this phase of the great heat wave of 2012. By early next week, temperatures will be near average for most of the eastern 2/3 of the U.S.

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

Jeff Masters

Heat

Updated: 16:16 GMT le 06 juillet 2012

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Borderline El Nino conditions arrive; Chicago, Detroit, and Milwaukee hit 102°

By: JeffMasters, 15:13 GMT le 05 juillet 2012

The odds of an El Niño event developing in time for the August - September - October peak of hurricane season have grown to 61%, said NOAA's Climate Prediction Center in their latest El Niño/Southern Oscillation (ENSO) diagnostic discussion, released on July 5. Ocean temperatures in the equatorial Pacific have increased to 0.6°C above average this week, which is just above the 0.5°C above-average threshold used to define a weak El Niño event. These temperatures must remain 0.5° or more above average for three consecutive months to qualify as an official El Niño. CPC advised that current conditions show a weakening of the east-to-west trade winds over the east-central equatorial Pacific, along with a reduction in heavy thunderstorm activity over Papua New Guinea, which "reflect a likely progression towards El Niño." However, the upper atmospheric winds and circulation patterns don't resemble what we expect of an El Niño yet. For example, in June over the North Pacific Ocean, there was an overall ridge of high pressure (more characteristic of La Niña) rather than a trough of low pressure (more typical during an El Niño). Thus, any development of El Niño during July is likely to be slow. El Niño events tend to suppress Atlantic hurricane activity by increasing the upper-level winds that create high wind shear capable of tearing storms apart.


Figure 1. Departure of sea surface temperature (SST) from average for July 5, 2012. In the equatorial Pacific, waters had warmed to 0.6°C above average, denoting the possible onset of an El Niño event. Image credit: NOAA/NESDIS.

Chicago, Detroit, Milwaukee, and Madison all hit 102° on July 4
The summer of 2012 continued its onslaught of record extreme heat on Wednesday, with the Midwest the focus of the most intense heat. Chicago hit 102°, just 3° below the city's all-time hottest temperature of 105°, set on July 24, 1934. Chicago hits 102° or more an average of once every 7.4 years, and last hit that mark on July 24, 2005. Detroit's high of 102° yesterday was its hottest day since 1988. Detroit's all-time hottest temperature is also 105°, set on July 24, 1934. Milwaukee, WI also hit 102° yesterday, which tied for the 4th hottest temperature in city history. Madison's 102° was their hottest day since 1988, and tied for the 6th warmest temperature ever measured in the city. Madison's all-time high is 107°, set July 14, 1936, and the forecast for today calls for a high of 104°. Other notable extremes from the 4th of July:

St. Louis hit 105°, the seventh consecutive day the city has hit triple digits. This streak is now the 4th longest such streak in city history; the only longer streaks occurred during the Dust Bowl summer of 1936 (streaks of 13 and 9 days) and the Dust Bowl summer of 1934 (an 8-day streak.) The current forecast for St. Louis calls for highs of 102 - 106° Thursday, Friday, and Saturday, which will likely bring the city's streak of 100°+ days to ten by week's end. St. Louis' all-time hottest temperature is 115°, set in 1954.

The high temperature in Pueblo Colorado reached 101 degrees on July 4th, bringing the number of consecutive days with high temperatures of 100 degrees or higher to a record thirteen. The previous record was 9 consecutive days, set in 1990. Record keeping began in 1888.

The low temperature in La Crosse, WI dropped to just 81° Wednesday. This tied July 21 1901 and July 13 1995 for the warmest low ever recorded. Temperature records date back to 1872.

Minneapolis, MN hit 101°, which is 7° below their all-time record high of 108° set 7/14/1936.

Highs of 100°+ are predicted to occur again on Thursday and Friday in Chicago, Detroit, Milwaukee, and Madison. A cold front will bring welcome relief on Saturday to the region, and the region of highest extreme heat will shift southeastwards to the Tennessee Valley. The models have backed off on their prediction of a strong ridge of high pressure bringing extreme heat to the Western U.S. next week, and more typical hot weather can be expected over most of the U.S. next week. Nevertheless, the extreme Midwest heat is causing havoc to the nation's corn crop, and multi-billion dollar drought disaster is taking shape. Today's New York Times details the drought concerns. I did a live interview Tuesday for Democracy Now discussing the recent extreme weather and how we can expect to see more weather like this in the future due to climate change.

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

Jeff Masters

Heat Climate Summaries

Updated: 16:54 GMT le 05 juillet 2012

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The June 2012 U.S. heat wave: one of the greatest in recorded history

By: JeffMasters, 19:34 GMT le 03 juillet 2012

Intense heat continues to bake a large portion of the U.S. this Tuesday, with portions of 17 states under heat advisories for dangerously high temperatures. The heat is particularly dangerous for the 1.4 million people still without power and air conditioning due to Friday's incredible derecho event, which is now being blamed for 23 deaths. The ongoing heat wave is one of the most intense and widespread in U.S. history, according to wunderground's weather historian, Christopher C. Burt. In his Sunday post, The Amazing June Heat Wave of 2012 Part 2: The Midwest and Southeast June 28-30, Mr. Burt documents that eighteen of the 298 locations (6%) that he follows closely because of their long period of record and representation of U.S. climate broke or tied their all-time heat records during the past week, and that "this is especially extraordinary since they have occurred in June rather than July or August when 95% of the previous all-time heat records have been set for this part of the country." The only year with more all-time heat records than 2012 is 1936, when 61 cities of the 298 locations (20%) set all-time heat records. The summer of 1936 was the hottest summer in U.S. history, and July 1936 was the hottest month in U.S. history.

According to wunderground analysis of the National Climatic Data Center (NCDC) extremes database, during June 2012, 11% of the country's 777 weather stations with a period of record of a century or more broke or tied all-time heat records for the month of June. Only 1936 (13% of June records broken or tied) and 1988 (12.5%) had a greater number of all-time monthly June records. I expect when NCDC releases their analysis of the June 2012 weather next week, they will rank the month as one of the top five hottest Junes in U.S. history.


Figure 1. Across the entire Continental U.S., 72% of the land area was classified as being in dry or drought conditions as of June 26, 2012. Conditions are not expected to improve much over the summer: the NOAA Climate Prediction Center’s latest drought outlook shows much of the U.S. in persistent drought conditions, with very few areas improving. The rains brought by Tropical Storm Debby did help out Florida and Georgia, however. Image credit: NOAA Environmental Visualization Laboratory.

The forecast: hot and dry
July is traditionally the hottest month of the year, and July 2012 is likely to set more all-time heat records. The latest predictions from the GFS and ECMWF models show that a ridge of high pressure and dry conditions will dominate the weather over about 80 - 90% of the country during the next two weeks, except for the Pacific Northwest and New England. This will bring wicked hot conditions to most of the nation, but no all-time heat records are likely to fall. However, around July 11, a sharp ridge of high pressure is expected to build in over the Western U.S., bringing the potential for crazy-hot conditions capable of toppling all-time heat records in many western states.

The intense heat and lack of rain, combined with soils that dried out early in the year due to lack of snowfall, have led to widespread areas of moderate to extreme drought over much of the nation's grain growing regions, from Kansas to Indiana. The USDA is reporting steadily deteriorating crop conditions for corn and soybeans, and it is likely that a multi-billion dollar drought disaster is underway in the Midwest.

The wunderground Extremes page has an interactive map that allows one to look at the records for the 298 U.S. cities that Mr. Burt tracks. Click on the "Wunderground U.S. Records" button to see them.

Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

Have a great 4th of July holiday, everyone, and I'll be back Thursday with a new post.

Jeff Masters

Heat Drought

Updated: 19:41 GMT le 03 juillet 2012

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Wunderground.com sold to The Weather Channel Companies

By: JeffMasters, 18:30 GMT le 02 juillet 2012

It's true. After 17 years as an independent company, Weather Underground has been sold, and will now be part of The Weather Channel Companies (TWCC.) As one of the founders of Weather Underground, I am excited about embarking upon this new chapter in our company's history. Having the infrastructure, resources, and content of The Weather Channel Companies will enable wunderground to create some great new products, and improve the quality and reliability of our existing content. We will now be called Weather Underground, LLC, and will maintain the wunderground.com web site as it is.


Figure 1. The original seven founders of wunderground.com, plus our first employee, circa 1998. In front, from left to right: Chris Schwerzler, Jeff Masters, Jeff Ferguson. In back: Dave Brooks, Alan Steremberg, Perry Samson, Chuck Prewitt, and Mike MacDonald.

The wild ride that began in 1995
Back in 1995, when the newly created commercial Internet put up for sale domains with a ".com" designation, and Weather Underground, Inc. became the world's first commercial weather web site, I could not have anticipated the wild ride that brought us to where we are at today. We registered the 2,000th domain ever taken, "wunderground.com", in 1995, missing registering "weather.com " by a month. Later that year, a group of executives from The Weather Channel visited us in Ann Arbor, inquiring on how we might work together. No sale resulted, but over the years, The Weather Channel and Weather Underground have had a number of meetings to discuss a possible merger. Many other companies have inquired about buying us, but we have always opted to stay independent, in order to nurture our creative, alternative weather web site and keep breaking new ground. The company's growth was slow at first, since we never took venture capital money. We grew from 6 employees in 1999 to 20 in 2009. But in the past three years, Weather Underground entered into a rapid period of growth that saw our staff more than double to 57 people. With a swelling user base around the globe, and with demands for our services to be made available across so many new digital platforms like mobile phones and tablets, the board recognized the need for an even greater injection of resources, and the decision was made to merge with The Weather Channel Companies.

How will the merger with The Weather Channel improve wunderground?
The Weather Channel is committed to keeping the Weather Underground brand and the web site in its current form. Weather Underground CEO Alan Steremberg will remain in charge, and our meteorologists and developers will continue to create the ground-breaking weather products that we're renowned for. The plan is to make both wunderground.com and weather.com stronger, by sharing content and infrastructure. Many Weather Underground features, such as our Personal Weather Station data, WunderMap, and my blog, are scheduled to also appear on the weather.com web site in the coming months. My blog's main home will continue to be wunderground.com, and I have been asked to continue to write the same variety of science-based posts on hurricanes, extreme weather, and climate change that I've provided since 2005. I enjoy communicating weather science, and am pleased I will be able to do this for both wunderground and The Weather Channel, which has an audience about three times as large as wunderground's.



Figure 2. One my favorite wunderphotos: a rainbow in Cyprus. With over 1.5 million wunderphotos uploaded, the wunderground community has helped make the web site far better than the employees could have done on their own.

For more information, see our press release, and WU meteorologist Shaun Tanner's blog.

Jeff Masters

Updated: 15:05 GMT le 03 juillet 2012

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Violent thunderstorms kill 3 in North Carolina; extreme heat continues in Southeast

By: JeffMasters, 11:48 GMT le 02 juillet 2012

Violent severe thunderstorms swept through Eastern North Carolina Sunday afternoon and evening, killing three people--one in a collapsed building, and two due to a falling tree. The deadly thunderstorms were fueled by the extreme heat affecting the Southeast, coupled with unusually high levels of moisture. The extraordinary heat and moisture caused high levels of atmospheric instability rarely seen. For those of you familiar with atmospheric stability indicies, the Convective Available Potential Energy (CAPE) in Eastern North Carolina and South Carolina at 2 pm EDT Sunday was 5000 - 6000, with a lifted index of -14. The Morehead City NWS office analyzed CAPE levels in excess of 7000 in the region, which is a truly rare occurrence. Fortunately, there was very little wind shear Sunday, so the upper-level winds were not able to induce the kind of twisting force needed to generate tornadoes. Sunday's powerful storms brought more power outages and damage to a region still suffering the impacts of Friday's rare derecho event, which killed 14 people and left power outages that still affect at least 2 million people. According to insurance broker Aon Benfield, the storm initially knocked out power to 2.5 million people in Virginia, the largest non-hurricane related power outage in state history. A derecho is a fast-moving, long-lived, violent thunderstorm complex that usually develops along the northern edge of a very hot air mass, in conjunction with an active jet stream. Friday's derecho was one of the largest and most destructive in U.S. history, and compares to the May 8, 2009 derecho that swept across the nation from Kansas to Kentucky, killing six and causing $500 million in damage.


Figure 1. Radar image of Sunday's violent thunderstorms that killed three people in North Carolina.

Dangerous extreme heat continues in the Southeast
Temperatures near all-time record levels continued for much of the Southeast on Sunday. The temperature in Atlanta, GA hit 105°F, which would have been the hottest temperature in city history, had the mercury not hit 106° the day before. On Sunday, Columbia, South Carolina hit 106°, the 5th highest temperature ever recorded there. Columbia hit 109° on Friday and 108° on Saturday, the two hottest days since record keeping began in 1887.

People in the Southeast and Mid-Atlantic without power must endure more extreme heat the next few days, with temperatures in the 100s and upper 90s expected over much of the region. While the temperatures are generally expected to be a few degrees cooler than what was seen Friday and Saturday, it is not the extremity of the temperatures in a heat wave that result in the highest heat stress to vulnerable people, but rather the length of time very high temperatures last. A multi-day period of exceptionally hot weather often causes high mortality. Yesterday's airmass was exceptionally humid, which greatly increases heat stress, since the body cools less efficiently in humid conditions. Aberdeen, Mississippi recorded a temperature of 104° with a dewpoint of 84° at 3 pm EDT Sunday, resulting in ridiculously high heat index of 136. Goldsboro, NC had a dewpoint of 87° at 11 am Sunday, the highest dewpoint I can recall seeing in the U.S., and something more typical of what is seen in Saudi Arabia along the shores of the Red Sea. According to wunderground's weather historian, Christopher C. Burt, the highest dew point temperature in world history is probably the 95°F (35°C) recorded at Dhahran, Saudi Arabia at 3 p.m. on July 8, 2003. The dry bulb temperature stood at 108°F at the time, so theoretically the heat index was 176°F. Sharjah in the United Arab Emirates (UAE) apparently once recorded a dew point of 93.2° (date unknown) according to ‘Weather Climate Extremes’ Army Corps of Engineers TEC-0099 report.

Mr. Burt has a new post called The Amazing June Heat Wave of 2012 Part 2: The Midwest and Southeast June 28-30 summarizing the later portion of the historic heat wave currently affecting the U.S. He comments:

What was truly astonishing was the number of all-time any month records that were broken or tied. This is especially extraordinary since they have occurred in June rather than July or August when 95% of the previous all-time heat records have been set for this part of the country (unlike the Southwest where June is often the month that all-time heat extremes are recorded). Eighteen of the 298 locations I follow closely (because of their long Period of Record and representation of U.S. climate) have already broken or tied their all-time heat records. The only year with more all-time heat records is 1936, when 61 cities set all-time heat records.

It is just July the 1st and the summer has just begun.


Quiet in the Atlantic
There are no threat areas to discuss in the Atlantic, and none of the reliable computer models are developing a tropical cyclone over the next seven days.

You won't want to miss my next post, scheduled for 2:30 pm EDT Monday.

Jeff Masters

Extreme Weather Heat

Updated: 11:54 GMT le 02 juillet 2012

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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