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 WaterWitch11:
looks as though sw louisiana is having some intense weather. on another note it amazes me how vulnerable new york is to water. god help them if they ever have a hurricane hit them.
You must mean SE louisiana..its bone dry here in central LA..wish that line would have made it here...
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ilp09550, I need some brushing up on my editing and linking skills to be productive on this blog. Can you post the METEOSAT-9 Color IR AVN image that can be gotten to from the NOAA website? That wave at 12N, between 30W to nearly 40 West is really looking like the real deal. Been watching this stuff for years and this one can beat the SAL, things may be rocking in the GOM next week....Thanks!
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2308. will45
Quoting HadesGodWyvern:
04L is not even on the CIMSS page either.


its on the Navy site. But they never took it down when it was downgraded.
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looks as though sw louisiana is having some intense weather. on another note it amazes me how vulnerable new york is to water. god help them if they ever have a hurricane hit them.
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Quoting HadesGodWyvern:
04L is not even on the CIMSS page either.

its on the navy site and thats all that matters
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2304. KEEPEROFTHEGATE (Mod)
Quoting JFLORIDA:



No I just think posting what a amateur website says with nop real scientific background, and under the mane of a person that doesn't exist REALLY DOESN'T COUNT AS CLIMATE SCIENCE>

Now you need to tell me how it does.
no you are right it does not but you must let the indiviual decide for themselves and not under the control of you to decide for them
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2303. HadesGodWyvern (Mod)
04L is not even on the CIMSS page either.
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Quoting TexasHoosier:
Sorry, accidently hit the wrong key before posting the METEOSAT-8 link where you can view the streaming Color IR Loop of the stuff coming off Africa - this looks like the for real tropical waves that will cause major problems - check it out:

http://www.ssd.noaa.gov/eumet/eatl/loop-avn.html

That one at 12N/30W is a Cape Verde system, big and very intense.....


WHOA!!
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Quoting flightweatherfan:
good evenig everyone


Good evening, sir or madam.
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Looks like the big african wave is going to recurve if it developes also.So far this season can put in these words recurve/ULL/mexico/wind shear. But still a good way to go so we will see!
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2298. will45
Quoting txsweetpea:


Thank you !!!!!


u r welcome
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good evenig everyone
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Quoting HadesGodWyvern:
SSD ADT page

hmm they took off 04L as an active cyclone.

that is pretty dumb all things considered
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Quoting will45:



Link

if you need any help using them just send me an e_mail


Thank you !!!!!
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Kerry, since the NHC posted around the same numbers as Dr. Gray, are they wrong?
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2289. HadesGodWyvern (Mod)
SSD ADT page

hmm they took off 04L as an active cyclone.
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Quoting sammywammybamy:
Collin looks like and could be a TS,


yup it has winds of 50(disregarded the reports of 60mph becuase it didnt make sense)
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2285. HadesGodWyvern (Mod)
2281. Tazmanian 4:26 AM GMT on August 05, 2010



thanks but that site is a little hard too me too under stan


oh okay.
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Quoting TexasHoosier:
All-Star 17, here is the link to the METEOSAT-8 Color IR image for the African Wave(s) and it is impressive!!!!!!

http://www.ssd.noaa.gov/eumet/eatl/loop-avn.html

Here is the image:

Holy mackerony
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Quoting TexasHoosier:
All-Star 17, here is the link to the METEOSAT-8 Color IR image for the African Wave(s) and it is impressive!!!!!!

http://www.ssd.noaa.gov/eumet/eatl/loop-avn.html

Here is the image:



You can't use a page as an image. You must link a true image.
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Quoting HadesGodWyvern:
Link

Taz, there is a website that keeps all tropical weather statements for the entire day.



thanks but that site is a little hard too me too under stan
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All-Star 17, here is the link to the METEOSAT-8 Color IR image for the African Wave(s) and it is impressive!!!!!!

http://www.ssd.noaa.gov/eumet/eatl/loop-avn.html

Here is the image:

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Quoting Orcasystems:


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



I think he meant dead to us, in the ATL.

I had some hope for it, also the little blob trailing it that you pointed out this morning.
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2278. HadesGodWyvern (Mod)
Link

Taz, there is a website that keeps all tropical weather statements for the entire day.
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Quoting neonlazer:
I know, that is why i read and not post so much on forcasting..cause it's so iffy sometimes lol

meanwhile colin has a t# of 3.0

Tropical Depression 04L




--------------------------------------------------------------------------------
UW-CIMSS Automated Satellite-Based
Advanced Dvorak Technique (ADT)
Version 8.1.1
Tropical Cyclone Intensity Estimation Algorithm


Current Intensity Analysis




UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 04 AUG 2010 Time : 164500 UTC
Lat : 18:12:45 N Lon : 60:27:05 W


CI# /Pressure/ Vmax
3.1 / 998.8mb/ 47.0kt


Final T# Adj T# Raw T#
3.0 2.8 2.8

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -41.3C Cloud Region Temp : -51.5C

Scene Type : CURVED BAND with 0.46 ARC in LT GRAY

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF
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Quoting AlexEmmett:

that is a nono your taking the data from models that are forcasting a storm with no true center yet the truth is until the models have a true center to start from the data is unrelialbe
I know, that is why i read and not post so much on forcasting..cause it's so iffy sometimes lol
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2275. xcool
maybe Danielle imo
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2273. smuldy
Quoting will45:



Link

if you need any help using them just send me an e_mail
sorry for the ignorance but that says 12z 04aug2010 wouldn't that be the models from 24hrs ago then? isn't it 12z20 05aug2010 now? does that site have old runs or are those the most current runs? sorry again for the q and tia
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Quoting CybrTeddy:


Strong model support.



can you WU e mail me the 2am two plz when it comes out i may not be on in the AM can you WU me the 8am two
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Quoting neonlazer:
It seems the models have something coming out of the huge wave..but heads NW and nowhere near any land..

that is a nono your taking the data from models that are forcasting a storm with no true center yet the truth is until the models have a true center to start from the data is unrelialbe
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Quoting CybrTeddy:


Strong model support.



93L by AM
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2267. will45
Quoting FTLSTRMCHSR:
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.


The season is just getting started good. July is usually a month with high wind shear. Watch things now and i think you will see a change.
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have not seen any thing like this in a long time

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2265. JLPR2
Quoting neonlazer:
It seems the models have something coming out of the huge wave..but heads NW and nowhere near any land..


but that's good :D
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting Tazmanian:
this is a waave you would find the W PAC wow



Strong model support.
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Sorry, accidently hit the wrong key before posting the METEOSAT-8 link where you can view the streaming Color IR Loop of the stuff coming off Africa - this looks like the for real tropical waves that will cause major problems - check it out:

http://www.ssd.noaa.gov/eumet/eatl/loop-avn.html

That one at 12N/30W is a Cape Verde system, big and very intense.....
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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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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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