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 xcool:





hmmm if am looking at that right it looks like its forcasting 3 name storms
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2361. will45
Quoting TexasHurricane:


huh? I was just wondering if the gfs or others are developing it.....


did you not see the language he used?
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Quoting KerryInNOLA:
Alex, your being a bad boy tonight. Too much candy again. Do you want mama to wash your mouth out with soap again?

lol um nope
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Quoting will45:
2349. TexasHurricane 12:54 AM EDT on August 05, 2010

if you quote comments like that it will get ya in trouble


huh? I was just wondering if the gfs or others are developing it.....
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Quoting TexasHurricane:


any models picking up on this?

yes
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That convection is really bubbling.

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2354. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
2353. will45
2349. TexasHurricane 12:54 AM EDT on August 05, 2010

if you quote comments like that it will get ya in trouble
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2352. JLPR2
Quoting KEEPEROFTHEGATE:
anyway iam off to catch some zzzz later bloggers
be back around by 7 730


night!
Member Since: September 4, 2007 Posts: 7 Comments: 8732
I was reading through the discussion archive for Hurricane Jeanne in 04, man what a mess, lol.

What I did notice in reading history is that the discussions were MUCH more detailed back then, I miss that. You could sense the forecasters passion for his forecast.
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Quoting Hurricanes101:
92L is not dead, it was not deactivated

just because it doesn't have a pinhole eye does not mean it is dead



ture but


but they did not any update this

File:invest_al922010.invest
2 KB
8/4/2010
6:21:00 PM
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Quoting AlexEmmett:
who was the f-er that pissed mother nature off
wow that is a freaken scary possible homewreaker


any models picking up on this?
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Someone tell me what is the spin at 72w 12n coming off the coast heading for convection around 92l?
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Quoting jlp09550:
RIP 2329.

im still hear and lets get bakc to the tropics we actually have things to talk about
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2346. KEEPEROFTHEGATE (Mod)
anyway iam off to catch some zzzz later bloggers
be back around by 7 730
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RIP 2329.
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Quoting HadesGodWyvern:




that map only shows invests that has a higher chance to becoming a cyclone in the next 48 hours and active tropical cyclone tracks.

yah but look at vort, sat and the nhc lack of interest in it shows me its a nothing
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92L is not dead, it was not deactivated

just because it doesn't have a pinhole eye does not mean it is dead
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Quoting txsweetpea:



what about the stall that I have read about? Could this change the nw movement of the models?


There is another trough forecast to come of the US in 5 or 6 days. If the current one doesn't get the job done, a stall would more than likely assure the second to take care of it.

Timing Timing Timing.

Of course that can change as I finish typing this message.
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2340. HadesGodWyvern (Mod)
2321. AlexEmmett 4:42 AM GMT on August 05, 2010

taz was right 92L is deader than king tutt




that map only shows invests that has a higher chance to becoming a cyclone in the next 48 hours and active tropical cyclone tracks.
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2339. xcool
;)
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2337. KEEPEROFTHEGATE (Mod)
Quoting StSimonsIslandGAGuy:
Meh. Whenever someone posts from a nonsense source, I'll reveal it as I see fit.
that is your right but to tell someone they have no right is not right i don't think you understand
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2334. will45
let me rephrase that they going today i didnt notice the clock lol
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Enough arguing guys!!! Get back on track..
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Quoting txsweetpea:
Is the HH (recon) out investigating?



nop
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2331. will45
Quoting txsweetpea:
Is the HH (recon) out investigating?


they are going tomorrow if it doesnt get canceled
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Quoting jlp09550:


Good evening, sir or madam.

sir it is
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Is the HH (recon) out investigating?
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Quoting jlp09550:


Looks can be deceiving.

last time i checked its heading into some very hot water it can only get scaryer
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2324. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting TexasHoosier:
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!


Here's the NHC site that has some really nice imagery: Link.
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Quoting xcool:


he back haha

taz was right 92L is deader than king tutt
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2319. xcool
AlexEmmett .lmao
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2316. xcool


he back haha
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting neonlazer:
You must mean SE louisiana..its bone dry here in central LA..wish that line would have made it here...


Y'all might get some sprinkles tonight. I know we sure will down here in Vermilion parish.
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Quoting neonlazer:
You must mean SE louisiana..its bone dry here in central LA..wish that line would have made it here...


yep your right!
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Quoting will45:


its on the Navy site. But they never took it down when it was downgraded.

and now its gonna get upgraded its looks too good right now
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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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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.