CSU leaves their hurricane forecast unchanged; 92L and Colin's remains worth watching
Tropical Storm Colin was ripped apart by wind shear yesterday, and the storm's remnants are passing just north of the northernmost Lesser Antilles Islands today. Most of the heaviest thunderstorms are passing north of the islands, as seen on Guadeloupe radar. Long range radar out of Puerto Rico also shows this. Colin's remains are in a rather unfavorable environment for re-development, since the disturbance is passing beneath an upper-level low pressure system with dry air and high wind shear. Wind shear is a high 20 - 25 knots over Colin's remains this morning. Recent satellite imagery shows that heavy thunderstorm activity has increased in intensity and areal coverage over the past few hours, though, and Colin's remnants will need to be monitored for re-development.
Forecast for Colin's remains
The latest SHIPS model forecast predicts that wind shear will drop from 15 - 25 knots today to a moderate 15 - 20 knots on Thursday. Wind shear will continue to decline over the weekend, and this relaxation of shear prompts most of the major models to predict re-development of Colin sometime in the next four days. NHC is giving Colin's remain a 20% chance of developing into a tropical depression by Friday morning. A major trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough will pull Colin to the northwest and cause it to slow down. By Friday, Colin will be moving at half of its current speed. All of the major forecast models are predicting that the trough of low pressure will be strong enough to fully recurve Colin out to sea early next week. Colin's remains may pass close to Bermuda on Saturday, with the latest 06Z (2am EDT) run of the GFDL model predicting that Bermuda will experience tropical storm force winds on Saturday as Colin passes to the west of the island. The Hurricane Hunters are scheduled to investigate Colin's remains at 8pm EDT tonight. It currently appears that Colin will only be a threat to Bermuda and Canada.
Figure 1. Morning satellite image of Colin's remains and Invest 92L.
92L
A tropical wave (Invest 92) in the south-central Caribbean is moving west at 15 - 20 mph. This wave is over warm water and is experiencing low wind shear of 5 - 10 knots, and could show some development over the next two days. However, the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday, or the Yucatan Peninsula on Saturday, and 92L probably does not have enough time over water to develop into a tropical depression. NHC is giving a 20% chance of this disturbance developing into a tropical depression by Friday morning. This storm was being tagged as 98L yesterday; I'm not sure why it is being called 92L today.
CSU's forecast numbers for the coming hurricane season remain unchanged
A very active Atlantic hurricane season is on tap for 2010, according to the seasonal hurricane forecast issued today, August 4, by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team continues to call for 18 named storms, 10 hurricanes, 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) index 185% of average. These are the same numbers as their June 2 forecast. 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 continues to call for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (50% chance, 31% chance is average) and the Gulf Coast (49% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 64% (42% is average.)
The forecasters cited four main reasons for an active season:
1) Moderate La Niña conditions should be present during the most active portion of this year's hurricane season (August - October). This should lead to reduced levels of vertical wind shear compared with what was witnessed in 2009.
2) Current SST anomalies are running at near-record warm levels. These very warm waters are associated with dynamic and thermodynamic factors that are very conducive for an active Atlantic hurricane season.
3) Very low sea level pressures prevailed during June and July over the tropical Atlantic. Weaker high pressure typically results in weaker trade winds that are commonly associated with more active hurricane seasons.
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 four previous years when atmospheric and oceanic conditions were similar to what we are seeing this summer. Those four years were 2005, the worst hurricane season of all time; 1998, which featured 3 major hurricanes, including Category 5 Hurricane Mitch; 1952, a relatively average year that featured just 7 named storms, but 3 major hurricanes; and 1958, a severe season with 5 major hurricanes. The mean activity for these five years was 17 named storms, 11 hurricanes, and 5 intense hurricanes, almost the same as the 2010 CSU forecast.
How accurate are the August forecasts?
The August forecasts by the CSU team over the past 12 years have had a skill 21% - 44% higher than a "no-skill" climatology forecast for number of named storms, hurricanes, intense hurricanes, and the ACE index (Figure 2). This is a good amount of skill for a seasonal forecast, and these August 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. This year's August forecast uses a new formula, so we don't have any history on how the technique has behaved in the past. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.61 to 0.65 for their previous August forecasts using different techniques, which is respectable.
Figure 2. 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. The British firm Tropical Storm Risk (TSR) will issue their outlook for the 2010 Atlantic hurricane season on June 4. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) is scheduled to release their August forecast later today. NOAA will also be issuing their August forecast sometime in the next week.
This season has had three named storms so far (Alex, Bonnie, and Colin.) It will be difficult to have a season with 19 or more named storms, since the four seasons that had at least 19 named storms all had at least five named storms by this point (August 4.) These four seasons were 1887, 1933, 1995, and 2005.
Next update
I'll have an update on Thursday morning.
Jeff Masters
Reader Comments
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the wave just S of CV
Hey Senior, have you heard NASA is getting into the Hurricane Recon game?
I'm not saying I like Joe B, but you opinionated your details by saying that Jeff Masters was better than Joe B. That's a matter of someone's opinion! Joe B has his own club on Facebook. Over 70,000 people would disagree with your opinion...
FSU!!! GAH...LOL j/k
LATCUR = 19.4N LONCUR = 61.2W DIRCUR = 300DEG SPDCUR = 23KT
LATM12 = 17.0N LONM12 = 57.0W DIRM12 = 289DEG SPDM12 = 24KT
LATM24 = 15.4N LONM24 = 52.4W
WNDCUR = 35KT RMAXWD = 30NM WNDM12 = 30KT
CENPRS = 1010MB OUTPRS = 1012MB OUTRAD = 125NM SDEPTH = S
RD34NE = 30NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
C'mon MJO! You can do it! A little more omph and you're in Octant 1!
accuweather pro has a lot more resources than just JB, it is worth the cost imo, especially with all the model data (including the ecmwf now)
I pay here and for accuweather pro...in addition, I think JB is one of the best, simple as that :)
hey! :)
LATCUR = 14.0N LONCUR = 73.9W DIRCUR = 275DEG SPDCUR = 15KT
LATM12 = 13.9N LONM12 = 71.0W DIRM12 = 276DEG SPDM12 = 14KT
LATM24 = 13.4N LONM24 = 68.0W
WNDCUR = 25KT RMAXWD = 45NM WNDM12 = 25KT
CENPRS = 1009MB OUTPRS = 1011MB OUTRAD = 100NM SDEPTH = S
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
I don't have a problem with JB. Just my opinion though...
Different energy sources? Tropical cyclones derive their energy from the evaporation of water from the sea surface, releasing heat. This energy gets pulled into the system's center and ejected into higher levels of the atmosphere (with a small amount sinking back to the surface). Under shear this mechanism is disrupted and the cyclone cannot properly ventilate itself.
For thunderstorms such as those forming over the plains, the energy source is moisture in the atmosphere and heat from the sun. Without shear the convective cell that develops does not form a cyclone (typically) and does not sustain itself. Under shear, the cell starts to rotate, forming a mesocyclone. The shear also tilts the cyclone, moving the downdraft away from the updraft and reducing the ability of the cell to destroy itself by feeding rain cooled air into the updraft. The rotation in a thunderstorm is what makes it a supercell, it is able to keep drawing in warm, moist, unstable air into the cell. The rotating updraft is also what causes the tornado to form, when it does.
These were not meant to be rigid explanations. :)
Here it is at 324 hours emerging off of Africa, as you can tell it already is a potent tropical storm.
By 384 hours it is a strong hurricane with 6 closed isobars and many hurricane force wind isobars. Also notice the tropical cyclone making landfall over the Yucatan.
1009MB? Cool.
You think that will be typical this year?
You can find every resource they offer on the internet for free. Might not be as nice, but same stuff.
Hey! :D
No once we get into a good negative NAO that will allow the A/B high to come further westward pushing tracks further westward.
ok get this. today the are bringing the DC-8 from Drydon flight research center at Edwards AFB to Ft Lauderdale, the WB-57 which is a high altitude very fast recon aircraft similar to the U-2 is going to fly out of Ellington field in Houston and they are going to fly a global hawk drone out of drydon to park over the top of a cyclone at 60.000' for 20 hours or more to gather data. You can go to the nasa web and read about the different experiments they are going to conduct. The DC- 8 alone has about 10 or 11 different experiments. This is all in a effort to improve cyclogenesis and rapid intensification forecasting. and oh by the way. NOAA is furious.
WHXX01 KWBC 041834
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1834 UTC WED AUG 4 2010
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
ATLANTIC OBJECTIVE AIDS FOR
DISTURBANCE COLIN (AL042010) 20100804 1800 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
100804 1800 100805 0600 100805 1800 100806 0600
LAT LON LAT LON LAT LON LAT LON
BAMS 19.4N 61.2W 20.9N 64.3W 22.4N 66.8W 23.5N 68.2W
BAMD 19.4N 61.2W 20.9N 63.2W 22.5N 64.7W 24.1N 65.6W
BAMM 19.4N 61.2W 20.8N 63.6W 22.2N 65.6W 23.4N 66.6W
LBAR 19.4N 61.2W 21.3N 63.8W 23.2N 66.0W 24.7N 67.5W
SHIP 35KTS 42KTS 50KTS 55KTS
DSHP 35KTS 42KTS 50KTS 55KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
100806 1800 100807 1800 100808 1800 100809 1800
LAT LON LAT LON LAT LON LAT LON
BAMS 24.4N 68.9W 25.8N 68.9W 27.4N 69.0W 29.4N 70.7W
BAMD 25.5N 65.9W 28.1N 65.5W 30.3N 65.8W 31.6N 66.8W
BAMM 24.6N 67.3W 26.5N 67.0W 28.2N 67.0W 29.8N 68.7W
LBAR 26.4N 68.2W 28.6N 67.7W 31.6N 66.9W 34.7N 66.8W
SHIP 58KTS 63KTS 74KTS 79KTS
DSHP 58KTS 63KTS 74KTS 79KTS
...INITIAL CONDITIONS...
LATCUR = 19.4N LONCUR = 61.2W DIRCUR = 300DEG SPDCUR = 23KT
LATM12 = 17.0N LONM12 = 57.0W DIRM12 = 289DEG SPDM12 = 24KT
LATM24 = 15.4N LONM24 = 52.4W
WNDCUR = 35KT RMAXWD = 30NM WNDM12 = 30KT
CENPRS = 1010MB OUTPRS = 1012MB OUTRAD = 125NM SDEPTH = S
RD34NE = 30NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
Do you think we will be seeing a definite increase in storms and strength as we move on to the peak season or will things be kinda like they have been - having trouble developing and then when they do, not being able to sustain it? (besides Alex of course)
Yeah Senior all of this is synoptic, no eyewall low level penny at all. What has got NOAA more concerned than anything else is the unmanned drone. The fact that they can keep this thing in the air so long, so cheep scares the crap out of the guys at Macdill.
I said 1009 about 15mins. ago.
LOL...ok,ok. I see..... :)
Thank you. :)
I suspect that this is part of why base reflectivity on all but the most intense tropical cyclones doesn't actually look that impressive. There is a lot of wind but the storms outside the eyewall are not themselves that powerful due to the conditions the cyclone needs in order to sustain them.
Viewing: 451 - 501
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