CSU leaves their hurricane forecast unchanged; 92L and Colin's remains worth watching

By: Dr. Jeff Masters , 2:38 PM GMT on August 04, 2010

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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

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2412. xcool
chicotman 92L ?
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Ya Man?
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2410. xcool
chicotman ?
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Nhc rainbow floater shows good coc just getting to the water.Heading nw to convection.
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2408. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15626
2407. xcool
traumaboyy .oh yeah hit Razzoo frist
Member Since: September 26, 2009 Posts: 2 Comments: 15626
French quarter, hit it every couple of months I love the damn place.
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2405. xcool


wave at 35w
Member Since: September 26, 2009 Posts: 2 Comments: 15626
2404. xcool
92l Not DO GOOD Right Now.
Member Since: September 26, 2009 Posts: 2 Comments: 15626
2403. xcool
traumaboyy ..where you coming to NOLA ?
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Hey xcool, and the gang.I think 92l may be just getting wound up.
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I was afraid of that, is here in NW Florida too, guess I am gonna be sweatin and drinkin in NOLA!!
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2400. xcool
traumaboyy .dam hothot
Member Since: September 26, 2009 Posts: 2 Comments: 15626
2399. will45
they kept x colin at 40% but did say it could be a tropical storm sometime today or friday
Member Since: July 18, 2009 Posts: 1 Comments: 994
xcool how is the heat over there?? headed to NOLA next week for some R/R am I going to be in the pool the whole time or is it tolerable in the evenings?
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000
ABNT20 KNHC 050530
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT THU AUG 5 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE REMNANT OF TROPICAL STORM COLIN...A BROAD AREA OF LOW
PRESSURE...IS LOCATED A COUPLE HUNDRED MILES NORTH OF THE
NORTHERNMOST LEEWARD ISLANDS AND IS MOVING TOWARD THE NORTHWEST AT
20 TO 25 MPH. SATELLITE IMAGES INDICATE THAT THE ASSOCIATED CLOUD
PATTERN CONTINUES TO SHOW SIGNS OF ORGANIZATION...BUT SURFACE
OBSERVATIONS SUGGEST THAT IT LACKS A WELL-DEFINED CIRCULATION.
TROPICAL STORM FORCE WINDS ARE LIKELY OCCURRING OVER WATER WELL TO
THE NORTH-NORTHEAST OF THE LEEWARD ISLANDS AND ALTHOUGH UPPER-LEVEL
WINDS ARE NOT FAVORABLE FOR SIGNIFICANT DEVELOPMENT...THE SYSTEM
HAS THE POTENTIAL TO REGAIN TROPICAL STORM STATUS LATER TODAY OR ON
FRIDAY. AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS
SCHEDULED TO INVESTIGATE THE AREA LATER TODAY IF NECESSARY. THERE
IS A MEDIUM CHANCE...40 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

A TROPICAL WAVE OVER THE WESTERN CARIBBEAN SEA CONTINUES TO PRODUCE
DISORGANIZED CLOUDINESS AND THUNDERSTORMS. SOME DEVELOPMENT OF
THIS DISTURBANCE IS POSSIBLE DURING THE NEXT DAY OR TWO BEFORE IT
MOVES OVER CENTRAL AMERICA. THERE IS A LOW CHANCE...20 PERCENT...
OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH


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That makes perfect sense to me. Then its a race against time, for this system to get past the ridge (to the west) before it breaks down and lets this system move to the NW and eventually to the north. This may be REAL close if the ridge does not break down quickly....although from what is going on in the Esstern part of the US, the LP system there looks to be pretty strong....again, the classic time and distance problem. But if this system is kept to the South below the 20N line before it gets to the 60-70W Longitude line, watch out, cause it could up from below Hispanolia.....good night folks, need to go home and sleep before building more fighter planes tomorrow!!!
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2395. xcool
na
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Dead chat.
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Quoting TexasHoosier:


Hmm, that would be some quick turn to the north. What do you base that on? I live in Fort Worth and the forecast here is for massive heat to continue but for the Mexican High Pressure System to move to the West a bit, which might open things up in the GOM. Is there a big HP system still located over the SE USA or just off the coast that could keep this system south or push it north (like you said) - have not looked at barometric chart here today.....


It's mainly due to the weakness in the subtropical ridge currently over the central ATL...the trough across the NE U.S. is expected to push into the W-ern ATL in the next couple of days, which would erode the subtropical ridge further and allow any developing tropical systems to move N-ward into the weakness around the W-ern portion of the ridge.
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2392. JRRP
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2391. xcool
neonlazer .that very good point ;)
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting atmosweather:


If the system develops it should head WNW around the S side of the subtropical ridge and then turn NW and N-ward as it reaches the W-ern periphery of the ridge. It's unlikely to affect any land areas.


Hmm, that would be some quick turn to the north. What do you base that on? I live in Fort Worth and the forecast here is for massive heat to continue but for the Mexican High Pressure System to move to the West a bit, which might open things up in the GOM. Is there a big HP system still located over the SE USA or just off the coast that could keep this system south or push it north (like you said) - have not looked at barometric chart here today.....
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Quoting xcool:
i hope NHC put yellow on wave at 35w-11n anyway.
Probably waiting to make sure it keeps pumpin as, from what ive seen, the waves love to explode and die..but so far the explosions are persisting.
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2387. xcool
i hope NHC put yellow on wave at 35w-11n anyway.
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Thanks Neon, that does look impressive.
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Quoting Tazmanian:



hmmm if am looking at that right it looks like its forcasting 3 name storms


How could any models even initialize on that megatrain of convection? Is that one wave, or three?
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Quoting TexasHoosier:
Thanks to C-Teddy, X-Cool, Alex-E and ilp09550 for the shots of whatever is going on out at 12N/30W. The lineup of systems coming off of Africa is starting to remind me of 2005 when we had pandemonium in the Aug-Oct timeframe in the Atlantic. Somewhere, I have an image of four hurricanes or TS going on at once, lined up heading for US. Does anyone have any scientific thoughts on where this system is headed and what are its chances of really becoming something awful in the next week - I am not looking at our problems, but what of the Tent-City people on Haiti.....


It's still too early to tell on this system. We should have a better idea by this weekend/early next week on where it should be going.
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Quoting TexasHoosier:
Thanks to C-Teddy, X-Cool, Alex-E and ilp09550 for the shots of whatever is going on out at 12N/30W. The lineup of systems coming off of Africa is starting to remind me of 2005 when we had pandemonium in the Aug-Oct timeframe in the Atlantic. Somewhere, I have an image of four hurricanes or TS going on at once, lined up heading for US. Does anyone have any scientific thoughts on where this system is headed and what are its chances of really becoming something awful in the next week - I am not looking at our problems, but what of the Tent-City people on Haiti.....


If the system develops it should head WNW around the S side of the subtropical ridge and then turn NW and N-ward as it reaches the W-ern periphery of the ridge. It's unlikely to affect any land areas.
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Looks to be just coming off the coast.Some say its rip?
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Quoting traumaboyy:
What the heck is that thing between 30 and 45 if anyone is still talkin weather that is?
A very large tropical wave to watch in the next few days
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2379. xcool
TexasHoosier welcome
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Thanks to C-Teddy, X-Cool, Alex-E and ilp09550 for the shots of whatever is going on out at 12N/30W. The lineup of systems coming off of Africa is starting to remind me of 2005 when we had pandemonium in the Aug-Oct timeframe in the Atlantic. Somewhere, I have an image of four hurricanes or TS going on at once, lined up heading for US. Does anyone have any scientific thoughts on where this system is headed and what are its chances of really becoming something awful in the next week - I am not looking at our problems, but what of the Tent-City people on Haiti.....
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Quoting chicotman:
Nice spin at 73w 12n heading nw


that is 92L
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2376. will45
Quoting TexasHurricane:


I guess not.....wasn't paying that much detailed attention....


well his comment has alredy been removed by Admin
Member Since: July 18, 2009 Posts: 1 Comments: 994
...Significant weather advisory for Vermilion and St. Mary parishes
until 1230 am CDT...

At 1201 am CDT...National Weather Service meteorologists detected a
line of strong thunderstorms...along a line extending from Franklin
to 9 miles southeast of Burns Point...moving west at 20 mph.

* The line of strong thunderstorms will be near...
sorrel and Ellerslie by 1210 am...
Burns Point by 1215 am...
Glencoe by 1225 am...
Cote Blanche Island by 1230 am...

The primary threats from these storms are frequent lightning and wind
gusts 35 to 45 mph...which could down tree limbs and blow around
unsecured small objects. Seek shelter in a safe home or building
until these storms have passed.


Sweet!
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What the heck is that thing between 30 and 45 if anyone is still talkin weather that is?
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2373. xcool
3 storms maybe.
Member Since: September 26, 2009 Posts: 2 Comments: 15626
Quoting TexasHurricane:


I guess not.....wasn't paying that much detailed attention....

it really was a big deal if the languge was as bad a he said it was the admin would have deleted the coment and baned me
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Nice spin at 73w 12n heading nw
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2130 melwerle "Hey kids - may be weather related- hope i don't get "banned" Long time here and just wanted to say - it's sunny out, hot, great outdoor weather.
Please wear your sun block.
I know it seems stupid when you're younger and I thought it was too. Not So stupid today. I sailed for 20 years wore sunblock intermittently. Today all hell broke loose with docs thinking it was melanoma and had surgery immediately. Military medicine is amazing. Looking at 4 - 5 more reconstructive surgeries -
- wear your friggin sunblock. It's not that much of a hassle. DO it.
"

Never to early to Wear Sunscreen or too late.
Thanks. It's admirable that you are using your troubles to sound a wakeup call for others.
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Quoting will45:
2363. AlexEmmett 1:01 AM EDT on August 05, 2010


welcome to ignore

im glad ignore me because you have no sense of humur at all
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Quoting will45:


did you not see the language he used?


I guess not.....wasn't paying that much detailed attention....
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Quoting Hurricanes101:


so? that happens from time to time, no big deal



oh ok then
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2366. will45
2363. AlexEmmett 1:01 AM EDT on August 05, 2010


welcome to ignore
Member Since: July 18, 2009 Posts: 1 Comments: 994
Quoting Tazmanian:



ture but


but they did not any update this

File:invest_al922010.invest
2 KB
8/4/2010
6:21:00 PM


so? that happens from time to time, no big deal
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Might get a mention of this by the 8 am TWO.
Member Since: July 8, 2005 Posts: 259 Comments: 23619
Quoting xcool:





hmmm if am looking at that right it looks like its forcasting 3 name storms
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.