CSU predicts a very active hurricane season: 16 storms, 9 hurricanes
A very active Atlantic hurricane season is on tap for 2011, according to the seasonal hurricane forecast issued June 1 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 166% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is identical to their April forecast. The forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 61% (42% is average.)
The forecasters cited four main reasons for an active season:
1) Neutral to weak La Niña conditions are expected during the most active portion of this year's hurricane season (August-October). This should lead to average to below average levels of vertical wind shear.
2) Above average May sea surface temperatures in the tropical Atlantic.
3) Below average surface pressures during May in the tropical Atlantic.
4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.
Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to weak La Niña conditions in the equatorial Eastern Pacific, and above-average tropical Atlantic and far north Atlantic SSTs during April - May. Those five years were 2008, which featured Hurricane Ike and Hurricane Gustav; 1996, which had two hurricanes that hit North Carolina, Fran and Bertha; 1989, which featured Category 5 Hurricane Hugo; 1981, a very average year with 12 named storms, 7 hurricanes, and 3 intense hurricanes; and 1951, a year that featured 6 major hurricanes. The mean activity for these five years was 12 named storms, 8 hurricanes, and 4 intense hurricanes.
How accurate are the June forecasts?
The June forecasts by the CSU team between 1998 and 2009 had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes cause 80% - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses a brand new formula never tried before, so there is no way to evaluate its performance. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.41 to 0.62 for their June forecasts made between 1984 and 2010, which is respectable.
Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.
Figure 2. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2001-2010, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2001 - 2010 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.
TSR predicts 25% more activity than normal
Expect the Atlantic hurricane season to be about 25% more active than usual, the British private forecasting firm Tropical Storm Risk, Inc. (TSR) said in their pre-season forecast issued on May 24. TSR calls for 14.2 named storms, 7.6 hurricanes, 3.6 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 124, which is 22% above average. Their May 24 forecast numbers are very close to their previous forecast issued in April. TSR predicts a moderate 55% chance that activity will rank in the top 1/3 of years historically, and a 59% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 16-25% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.
TSR projects that 4.4 named storms will hit the U.S., with 1.9 of these being hurricanes. The averages from the 1950-2010 climatology are 3.1 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 7 - 11% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.3 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.
TSR cites two main factors for their forecast of an active season:
1) Their model predicts that sea surface temperatures will be 0.11°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. They define this as the area between 10°N and 20°N, between the coast of Africa and Lesser Antilles Islands (20°W and 60°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)
2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 0.19 meters per second (about 0.4 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.
FSU predicts a very active hurricane season: 17 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their third annual Atlantic hurricane season forecast today. This year's forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE) of 163. They cite warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation as the major factors influencing their forecast.
Other seasonal forecasts
The UK Met Office's Glosea4 model is predicting a moderately more active season than normal, with 13 named storms and a ACE index of 151. The Cuba Institute of Meteorology is calling for 13 named storms and 7 hurricanes. NOAA predicts 15 named storms, 8 hurricanes, and 4.5 intense hurricanes. Pennsylvania State University predicts 16 named storms.
A surprise tropical disturbance for Florida
The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure and winds have leveled out at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds peaked at 19 mph, gusting to 22 mph, at 10:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. A Windsat pass this morning did not show a closed circulation, and I doubt 93L has enough time to develop into a tropical depression before landfall in Florida. The coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph this afternoon, though.
Figure 3. Afternoon radar image of 93L from the Melbourne, Florida radar.
Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico. The Hurricane Hunters are on call to fly into 93L Thursday afternoon at 2pm EDT, if necessary.
Central Caribbean disturbance
Moisture and heavy thunderstorm activity continues to slowly increase in the region between Central America and Jamaica, and wind shear is falling. With wind shear now 20 - 30 knots, we can expect this disturbance to show increased organization today, and recent satellite images show the beginnings of a surface circulation trying to get going about 100 miles off the coast of Northeast Nicaragua. All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them Thursday through Saturday this week.
Figure 4. Satellite image of the Central Caribbean disturbance.
Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, tomorrow (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. Welcome to the hurricane season of 2011!
Jeff Masters
Reader Comments
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guess not haha
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1115 AM EDT WED 01 JUNE 2011
SUBJECT: TROPICAL STORM STORM PLAN OF THE DAY (TSPOD)
VALID 02/1100Z TO 03/1100Z JUNE 2011
WSPOD NUMBER.....11-001
I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA -- GULF OF MEXICO
FLIGHT ONE -- TEAL 70 FLIGHT TWO -- TEAL 71
A. 02/1800Z A. 03/1200Z
B. AFXXX 01AAA INVEST B. AFXXX 0201A CYCLONE
C. 02/1700Z C. 03/1000Z
D. 28.0N 87.0W D. 28.0N 94.0W
E. 02/1730Z TO 02/2200Z E. 03/1100Z TO 03/1600Z
F. SFC TO 10,000 FT. F. SFC TO 10,000 FT.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
NOTE: THIS IS THE FIRST OF A DAILY MESSAGE WHICH WILL
BE TRANSMITTED THROUGHOUT THE HURRICANE SEASON.
JWP
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Reed....congrats on having spotted this baby-cane yesterday. Nice start to the season. Don't let it go to your head. lol
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This thing has traversed half the country already...why should Florida stop it?
93L is under an anticyclone, this is why shear has been favorable and also why convection has sustained itself for over 12 hours. Another reason why this got going was because the Gulf Stream warmed past 80 degrees over the last month. This allowed the MSC to transition into a tropical low/disturbance. I firmly believe strongly, as the satellite indicated, 93L was a Tropical Depression. The banding was evident and there was a closed LLC. The system weakened due to it going over the cooler, shallow waters. Almost every system that makes landfall on the East Coast of Florida weakens a tad due to the shallow water.
Link
Good Point!
I am also concerned that the Climate is so different now, that analogue years going back more than 10 years will be irrelevant as well.
We are in pretty new territory all round, Weather wise.
Historic Data is fine, but not when conditions are changing like they are.
And thunder too!
=)
Pouring here in Oldsmar!!!!!!!!!
+ + + !!!
+ + +
That looks like a really nice blowup of convection on the west coast.
Is it possible that the band, now extending to the GOM could feed 93L and help it to make it across FL easier?
Florida would take it's toll on a Hurricane, but not so much on a system like this one.
Nice start to the Season, I must say!
In terms of MSE in the early May/June range, CSU seems to be the winner in predicting tropical storms and hurricanes, behind NOAA on major hurricanes, and almost identical on ACE.
In the August update, NOAA seems to be winning in almost every measurable category.
Im curious, though, if it's a fair comparison.
For example, is it fair to take the midpoint of the NOAA expressed range to use when comparing vs. the determininstic numbers from CSU and TSR?
Also, NOAA typically releases their forecast for August after CSU and TSR come out. Is it possible that this could introduce a bias if NOAA utilizes any information from the CSU forecast in their outlook?
Not completely sure it's fair to compare these head to head...
MW
Ya Know, that would just frost my cookies. Riding off shore SE FL. 93L just north, Caribb AOI just east and the rain chances hovering around 0%-10% for the next 7 days, blahh.
Storms of recent past have gotten stronger actually over the peninsula (Ernesto). Farther N you go however, the more hilly it gets.
When he uses the word 'skill', I've never been really sure what he means...
Is it a measure of past success? Or some measure of the inherent integrity of the forecast? Or a measure of likely accuracy? Or what?
RGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 411
NWS STORM PREDICTION CENTER NORMAN OK
100 PM EDT WED JUN 1 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
CONNECTICUT
MASSACHUSETTS
WESTERN MAINE
NEW HAMPSHIRE
NEW JERSEY
SOUTHEAST NEW YORK
SOUTHEAST PENNSYLVANIA
RHODE ISLAND
COASTAL WATERS
EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 100 PM UNTIL
800 PM EDT.
TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE
MILES EAST AND WEST OF A LINE FROM 10 MILES SOUTH SOUTHWEST OF
PHILADELPHIA PENNSYLVANIA TO 35 MILES NORTHWEST OF AUGUSTA MAINE.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU1).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.
OTHER WATCH INFORMATION...CONTINUE...WW 410...
DISCUSSION...SCATTERED THUNDERSTORMS WILL CONTINUE TO INTENSIFY OVER
PORTIONS OF VT/NY/PA AND TRACK EASTWARD ACROSS PORTIONS OF NEW
ENGLAND...NY/PA/NJ THROUGH THE AFTERNOON. A VERY UNSTABLE AIR MASS
HAS DEVELOPED ACROSS THIS REGION WITH DEWPOINTS WELL INTO THE 60S
AND MLCAPE VALUES OVER 3500 J/KG. THIS COMBINED WITH STRONG
WESTERLY FLOW ALOFT AND INCREASING SOUTHERLY LOW LEVEL WINDS WILL
POSE A RISK OF SUPERCELL STORMS CAPABLE OF LARGE HAIL...DAMAGING
WINDS...AND ISOLATED TORNADOES.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 28035.
...HART
I think it's a guessed outcome of the previous guesses.
NGP
The climate is changing.
It always used to be that we'd look to the Cape Verde Islands, or maybe the windward Islands as places where cyclones-to-be passed over....this year it's Staten Island.
And was your answer also a guess? =)
... Strong thunderstorms will affect southern Hillsborough...
Pinellas... Manatee... southwestern Polk and western Hardee counties...
National Weather Service Doppler radar indicates a line of
thunderstorms located along a line extending from Dunedin to Bowling
Green... or along a line extending from Dunedin to 7 miles north of
Wauchula... moving south at 30 mph... will affect Tampa...
Clearwater... Saint Petersburg and Riverview... until 145 PM EDT.
Gusty winds 35 to 45 mph will occur. Frequent lightning is expected.
To be safe go indoors immediately. If caught outside... find a low
spot... and stay away from tall objects. Torrential rains will reduce
visibility to near zero and will cause ponding of water on roadways.
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