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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Quoting Tazmanian:
this is a waave you would find the W PAC wow


taz,

the nhc should just put the whole atl under a tropical storm watch the rest of the season
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Quoting CyclonicVoyage:


All the major dynamical models are clustered on a full re-curve so, equally?




what about the stall that I have read about? Could this change the nw movement of the models?
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It seems the models have something coming out of the huge wave..but heads NW and nowhere near any land..
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2259. JLPR2
Quoting Tazmanian:
this is a waave you would find the W PAC wow



There's lots of energy there, soon we should see a fight between vorticity centers.

Well... I hope there is a fight! XD
Member Since: September 4, 2007 Posts: 7 Comments: 8691
With the utmost respect for the professionals, isn't this year a bit strange? I cannot recall a season with such shreaded disturbances. I feel like we are in a very odd pattern and might be due to the MJO. Can someone elaborate? I notice that the forecast for any of these storms is only as good as the next move it makes. Just a laymans take.
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Quoting sarahjola:
oh, i was just talking about how it looks. believe me i am the last person who needs to be schooled on the dangers of a hurricane. been there, done that.:)

which, taking someone house




or a hurricane


jk
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this is a waave you would find the W PAC wow

Member Since: May 21, 2006 Posts: 5091 Comments: 115088
Quoting AlexEmmett:

that is not excelent by anymeans, lol it will be a girl ans she could take your house. btw this one i have a really bad feeling about i just want it to go away
oh, i was just talking about how it looks. believe me i am the last person who needs to be schooled on the dangers of a hurricane. been there, done that.:)
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2253. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15670
2252. JLPR2
Quoting neonlazer:
If it turned into an Alex and came for the gulf coast...hell...ill move to Canada..


The problem wouldn't be it heading to the Gulf, it would be Time, Alex didn't strengthen farther because he had land masses on the way, imagine a storm as big as Alex with that much water ahead of it. O_O
Member Since: September 4, 2007 Posts: 7 Comments: 8691
2251. will45
Quoting txsweetpea:



Can anyone post the link ...I dont even know what the models are saying!Thanks in advance



Link

if you need any help using them just send me an e_mail
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not dead huh?


Member Since: May 21, 2006 Posts: 5091 Comments: 115088
2249. KEEPEROFTHEGATE (Mod)

NMFC Norfolk Tropical Feed
NO Active Tropical Warnings in the Atlantic, Caribbean, or Gulf of Mexico
By Maritime.CDO@navy.mil (NMFC CDO) from Naval Maritime Forecast Center Norfolk Virginia. Published on .

As of Thu 05 Aug 2010 04:00:02Z
2010 Storms
All Active Year

Atlantic
92L.INVEST
04L.COLIN
East Pacific
99E.INVEST (T.C.F.A.)
Central Pacific
NONE
West Pacific
97W.INVEST
96W.INVEST
Indian Ocean
90B.INVEST
Southern Hemisphere
NONE
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Quoting JLPR2:


it kind of reminds me of Alex but instead of the Caribbean it's in the CATL.
I really hope we dont get an Alex type storm in the CATL. :S
If it turned into an Alex and came for the gulf coast...hell...ill move to Canada..
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2247. JLPR2
Quoting neonlazer:
Lol, it is a very large wave, but so far(it is a bit early for too much organization) the vorticities are obviously all over the place..lol


it kind of reminds me of Alex but instead of the Caribbean it's in the CATL.
I really hope we dont get an Alex type storm in the CATL. :S
Member Since: September 4, 2007 Posts: 7 Comments: 8691
Quoting Tazmanian:



92L is dead


Taz you have lost the bubble... 92L is not dead.
Its as dead as Colin is, and its definitely not dead.

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2245. KEEPEROFTHEGATE (Mod)
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Quoting Hurricanes101:
92L is still very much alive, it was not deactivated



hurricane101 look at this wave


Member Since: May 21, 2006 Posts: 5091 Comments: 115088
2243. JLPR2
Quoting HadesGodWyvern:


Tropical Wave category.. O_o


yup o.O I have no idea how Ex-Colin ended up in that category. XD

Quoting NCHurricane2009:


Or, how about the idea that the convection is getting held back from the old open circulation by the ULL, and that Colin is getting increasingly disrupted by wind shear? I think that's a possibility right now.


Nah, if it were the ULL it would be shear and Colin doesn't look sheared, if the circulation were to leave the convection behind it would wane, something needs to be there for the convection to build.
Or maybe its a mid level circulation taking over?
Member Since: September 4, 2007 Posts: 7 Comments: 8691
Quoting Tazmanian:



92L is dead

agreed it looks like that fat lady didnt just sign for it she sat on it
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Quoting Tazmanian:



92L is dead


Taz no its not, it was not deactivated

quit saying things that are not true, people will get confused
Member Since: March 10, 2010 Posts: 1 Comments: 7686
Quoting truecajun:


i haven't seen anyone say which ones were getting it right, but i haven't been on much.



Can anyone post the link ...I dont even know what the models are saying!Thanks in advance
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Quoting angiest:


I'm talking more about things like GFDL, HWRF, and such.


All the major dynamical models are clustered on a full re-curve so, equally?

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2238. xcool
:)))
Member Since: September 26, 2009 Posts: 2 Comments: 15670
2237. KEEPEROFTHEGATE (Mod)

ALERT ATCF MIL 99X XXX 100804180000
2010080418
14.9 264.7
15.4 259.7
160
14.8 264.4
050000
1008042351
1
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
WTPN21 PHNC 050000
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
160 NM EITHER SIDE OF A LINE FROM 14.9N 95.3W TO 15.4N 100.3W
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 17 TO 22 KNOTS. METSAT IM-
AGERY AT 042330Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 14.8N 95.6W. THE SYSTEM IS MOVING WESTWARD AT 07 KNOTS.
2. REMARKS:
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 060000Z.
//
9910080312 158N 933W 15
9910080318 155N 936W 15
9910080400 153N 939W 20
9910080406 151N 943W 20
9910080412 149N 949W 20
9910080418 148N 956W 25
NNNN

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Quoting HadesGodWyvern:
B. A POSSIBLE LOW LEVEL INVEST AT 06/1500Z
NEAR 16.5N 84.5W.

---
developing low or 92L for this Friday's investigation?



92L is dead
Member Since: May 21, 2006 Posts: 5091 Comments: 115088
92L is still very much alive, it was not deactivated
Member Since: March 10, 2010 Posts: 1 Comments: 7686
2234. HadesGodWyvern (Mod)
B. A POSSIBLE LOW LEVEL INVEST AT 06/1500Z
NEAR 16.5N 84.5W.

---
developing low or 92L for this Friday's investigation?
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Quoting AlexEmmett:

MAN YOUR BATTLE STATIONS the blog could become highly unstable in the few coming days but so could the atl
Lol, it is a very large wave, but so far(it is a bit early for too much organization) the vorticities are obviously all over the place..lol
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Quoting sarahjola:
excellent

that is not excelent by anymeans, lol it will be a girl ans she could take your house. btw this one i have a really bad feeling about i just want it to go away
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2231. Ossqss
Quoting truecajun:


don't bother arguing with him. no matter what you tell him, he tells you your source is not credible. however, his always are according to him. it's what he does. he's the czar of discrediting


I hear ya, the sources in question are the official sources of the info, that is the funny part :) L8R all
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Quoting Tazmanian:
holy we crap




what a wave
excellent
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Quoting truecajun:
well good night all. tomorrow is another day.


Night Cajun :-)
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Quoting Tazmanian:
holy we crap




what a wave

MAN YOUR BATTLE STATIONS the blog could become highly unstable in the few coming days but so could the atl
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we are here too day too say some words too are be loveing 92L wish has pass a way
Member Since: May 21, 2006 Posts: 5091 Comments: 115088
2226. angiest
Quoting CyclonicVoyage:


Last I checked the CMC was doing the best actually.


I'm talking more about things like GFDL, HWRF, and such.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting JLPR2:


yep I noticed that, maybe ex Colin is ditching its old open circulation and forming a new one?
Hence the convection is stalled over the new LLC


Or, how about the idea that the convection is getting held back from the old open circulation by the ULL, and that Colin is getting increasingly disrupted by wind shear? I think that's a possibility right now.
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ex-colin will fool all of us and curve west or do a little loop:) j/k, or am i.....:)
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well good night all. tomorrow is another day.
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2222. HadesGodWyvern (Mod)


CMC model
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holy we crap




what a wave
Member Since: May 21, 2006 Posts: 5091 Comments: 115088
Quoting truecajun:


sure does. 30 has been a rude awakening in so many ways. lol


34 here.
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Looks like they are sending a plane out tomorrow
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.

ow?
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Quoting angiest:


Has anyone done a model verification for the dynamic models on Colin? They still seem unbelievable.


Last I checked the CMC was doing the best actually.
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Quoting AlexEmmett:

oh boy and i thought the blog was insane tonight


Yeah, this could make it a little more Interesting :)
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Ala Scarlet - I will deal with all of this tomorrow! Good night for now...
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Quoting angiest:


Has anyone done a model verification for the dynamic models on Colin? They still seem unbelievable.


i haven't seen anyone say which ones were getting it right, but i haven't been on much.
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Quoting Orcasystems:
Man your battle stations... Model Shift left on Colin... Florida & the Carols are back in play


Not what I wanted to hear - but what I have been suspecting all day - the trough may not be enough to curve Colin... looks like the models show intensification also...
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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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