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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1612. Ossqss
Anyone find any more info on this?

Huge Hurricane Study Gears Up

NASA Holds Media Teleconference to Preview Major Hurricane Study

"WASHINGTON, Aug. 2 /PRNewswire-USNewswire/ -- NASA will hold a media teleconference on Thursday, Aug. 5, at 3 p.m. EDT to discuss its upcoming airborne research campaign into hurricane behavior."
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1611. scott39
Colin-- 19.5N 61.5W
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Quoting IKE:


0%. There's only 2 things Colin will bother anymore...

(1)Bermuda.
(2)This blog.


ROFL, Ike. See you on the blog early in the am - too rough in here for me tonight!
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Talk about deep convection. Surprised still the TWO didn't mention the area by 30W, given that the GFS and ECMWF develop this in 48 hours or so. They're the experts, so I have no reason to doubt them.

Member Since: July 8, 2005 Posts: 259 Comments: 24017
1606. Drakoen
Quoting nrtiwlnvragn:
ASCAT pass ~30W does not show much




Cyclonic curvature along an axis of convergence
Member Since: October 28, 2006 Posts: 57 Comments: 30489
Models still have Colin becoming a CAT 1 or bigger.



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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Thanks for answering the south Florida question, people who did. I won't ask stuff like that in the future.
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Quoting JenniferGirl:
How likely is Colin to regenerate into a cat 5 and hit south Florida?


Very Likely!!!!!


(Sarcasm)
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1599. xcool
Tazmanian iknow taz ;)
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Quoting will45:


my thoughts exactly. Some people just dont get it do they?


Well, I guess I just don't get it. I was being serious. I just started taking an interest in the tropics yesterday. I am quite sorry.
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Quoting IKE:


0%. There's only 2 things Colin will bother anymore...

(1)Bermuda.
(2)This blog.


LOL Ike
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Plan of the Day
--------------------------------------------------------------------------------


000
NOUS42 KNHC 041430
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT WED 04 AUGUST 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 05/1100Z TO 06/1100Z AUGUST 2010
TCPOD NUMBER.....10-066

I. ATLANTIC REQUIREMENTS
1. REMNANTS OF TROPICAL STORM COLIN
FLIGHT ONE -- TEAL 71
A. 05/1800Z
B. AFXXX 0204A COLIN
C. 05/1630Z
D. 23.0N 67.0W
E. 05/1730Z TO 05/2130Z
F. SFC TO 15,000 FT

2. SUCCEEDING DAY OUTLOOK:
A. A 06/1800Z FIX ON COLIN IF STILL A VIABLE
SYSTEM NEAR 27.0N 69.0W.
B. A POSSIBLE LOW LEVEL INVEST AT 06/1500Z
NEAR 16.5N 84.5W.



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Quoting JenniferGirl:
How likely is Colin to regenerate into a cat 5 and hit south Florida?
Zero percent chance of Colin being a cat 5, not suppose to become a hurricane according to the experts and it is not suppose to hit Florida.
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Again, look at the steering and then the models. It's not a wild prediction, it's a good observation based on a steering map. Not saying it's gonna hit the East Coast anymore, but I just don't think it comes that far east.
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Quoting nrtiwlnvragn:
ASCAT pass ~30W does not show much




Pretty sharp wind shift however.
Member Since: July 8, 2005 Posts: 259 Comments: 24017
Quoting reedzone:


You're doing the right thing :)


Thank you, and thank you to all the people supporting me. I was only on here to speak of weather, and now I get an accusation of being someone I do not know? I'm very confused.

By the way, I've been looking up some stuff. What are the differences in the BAMM models?
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ASCAT pass ~30W does not show much


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1584. will45
Quoting MiamiHurricanes09:
You aren't being serious are you?


my thoughts exactly. Some people just dont get it do they?
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1568. BDADUDE 12:31 AM GMT on August 05, 2010

last I checked, Bermuda is a landmass
Member Since: March 10, 2010 Posts: 1 Comments: 7684
Quoting bappit:
Colin is still circulating.



Nice pic, but in a bad way.
Thanks
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1579. IKE
Quoting JenniferGirl:
How likely is Colin to regenerate into a cat 5 and hit south Florida?


0%. There's only 2 things Colin will bother anymore...

(1)Bermuda.
(2)This blog.
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Quoting JenniferGirl:


What have I done? I told you I'm trying to stop people from fighting. I'm not encouraging anything by any means. I've been siding on the side of justice for all problems that may occur.


You're doing the right thing :)
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1577. xcool
Colin not move much hmmmm
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sits back and shakes head

this is why this blog would probably never be taken seriously, the drama here is pathetic
Member Since: March 10, 2010 Posts: 1 Comments: 7684
Quoting BDADUDE:

And I can also dude. I just wish you would concider other people when you make these wild predictions. I believe this storm will curl out into the atlantic and not threaten any land as the experts have predicted.


Isnt that what stormw predicted at the onset? Right on!!!
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1573. ackee
so far 2010 seasons to me have all right ingredents for active seasons just seem to me WAVE comeing africa so far as not been that strong enought for devlopment another factor notice Upper level low seem be near by when ever system try to develops
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Quoting JenniferGirl:
How likely is Colin to regenerate into a cat 5 and hit south Florida?
You aren't being serious are you?
Member Since: September 2, 2009 Posts: 130 Comments: 21193
1571. xcool
MiamiHurricane .weather,plz thanks
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1567. bappit
92L looks like this.

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How likely is Colin to regenerate into a cat 5 and hit south Florida?
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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.

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