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 all4hurricanes:
Does anyone know if Colin has been upgraded? can't they tell with satellite imagery?


It has not been upgraded yet.
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LOL, so true Keeper

Quoting KEEPEROFTHEGATE:
return your chairs to the upright position and strap yourself in things may get a little bumpy for a bit as we begin
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Currents are very weak where Colin is at right now. Almost looks like it built a little mini ridge to sit under.

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Quoting NCHurricane2009:


I saw that too, but I see the center more west than your mark. But, spin in animation looks weak like this is still an open wave, but a sharp one at that.

yeah i saw that too, that mark wasn't me,,, by CMISS
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thats the way it looks to me to
thanks
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Quoting KEEPEROFTHEGATE:
pottery my brother from another mother i sent to you something to take the pain from another

No More Tears
The time has come for the tears to end
for you to be happy and cheerful again.
I am safe in God's home above
cradled in His arms; covered with His love.


We run and play by the Bridge all day
waiting for the day when you'll be here to stay.
You've been crying so much I feel bad
I want you to be happy and not so sad.


Remember the time when I was so small
I couldn't even pickup the rubber ball.
I fought that ball from morning to night
it made you laugh, I was quite a sight.


Remember teaching me sit and stay
we had such fun since I didn't really obey.
but you kept at it with test after test.


Remember the great times we had in the past
like when we walked to the park we had a blast.
We'd run and play all through the park
until the sun went down and it got dark.


Remember the times we went for a ride
I was so excited I'd jump right inside.
Away we went to who knows where
but you and I we didn't really care.


I'll always love you, you're my best friend
I'll be right with you even to the end.
Always remember the great times we had
and there will be no reason to ever be sad.

Written by John Quealy



That was beautiful and very thoughtful..
Member Since: July 3, 2010 Posts: 0 Comments: 427
Does anyone know if Colin has been upgraded? can't they tell with satellite imagery?
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Thanks for posting, keeps me from having to go find. This is really interesting, considering there is an ULL out there

Quoting AllStar17:
Shear decreasing rapidly over ex-Colin:
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Quoting AllStar17:
I have NEVER seen this much convection in the Central Atlantic before!


Are you sure? Look at the LEFT satellite image of Invest 92L (Invest 92L of June, not the Invest 92L we have today) in an earlier blog post I made. 92L had that much convective expanse early this season.
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2053. KEEPEROFTHEGATE (Mod)
return your chairs to the upright position and strap yourself in things may get a little bumpy for a bit as we begin
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No problem, same here, always learning

Quoting druseljic:
Thanks Goldenblack for the response. Been around for years and still learning.
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Shear decreasing rapidly over ex-Colin:
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Thanks Goldenblack for the response. Been around for years and still learning.
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Quoting KoritheMan:
Just did a blog on 92L, ex-Colin, and the 30W wave.


Nice update. Seems I am a Colin downcaster tonight. I don't believe the models about regneration right now, the ULL is too expansive (200 mb westerlies all the way to the Bahamas) and affecting Colin now, and sometimes models weaken ULLs too fast. I know Colin looks organized, but that's the upper portion of the storm. The lower portion is to the west of the organized clouds in the latest surface analysis, westerly shear from ULL in effect right now.
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I don't think the NHC anticipated Colin moving so quickly before, and I don't think they planned on a stop now, so this may be screwing up all the models...

i wish we could get that recon info
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2046. KEEPEROFTHEGATE (Mod)
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2045. gator23
Quoting AllStar17:


Does not seem like that is the case looking at shortwave IR loops.

thank you I was hoping someone who had more knowledge then me could shed some light. I appreciate it allstar.
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BahaHurican
Sorry, seem to be having some sort of quoting malfunction, anyway i would be watching closely
if i was their might not get to you though kinda looking more like between bahamas and US.
by looking at steering currents hope this storm doesnt get stupid!
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Quoting gator23:
It looks like Colin is stationary however it could be possible the LLC is moving away from the convection.


Does not seem like that is the case looking at shortwave IR loops.
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Not out of the question, but not likely. Again, slow movement and the timing of the high building back in would cause that. I still cannot believe that we are dealing with that strong a trough in early August.

Quoting druseljic:
Someone at work who follows the tropics mentioned that Colin's behavior might be setting up for a loop ... didn't suggest it would head for land ... was just wondering what the possibility of this was?
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2041. 7544
same here colin has stalled out imo
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2040. gator23
It looks like Colin is stationary however it could be possible the LLC is moving away from the convection.
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I do know the BAMM suite shifted father westward for ex-Colin.....it will be interesting to see if the other models show the same.
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Quoting gator23:

the CMC track wise has been pretty good with these trop storms granted my sample size is bonnie and colin but still


I'm pretty sure it was good with Alex, too, but that was soooooo long ago, haha!
But Bermuda gets the right front quad from "colin" in that run, too... no good.
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2037. angiest
Quoting BreadandCircuses:


Many top line chefs like John Folse have been coming uo with nutria rat recipes to try and create a market for the rodents to get them out of the wetlands, they haven't had much luck getting a lot of people to try it, though. I've eaten nutria a couple times, it's not bad, kind of like squirrel, the meat is stringy, though.

I think there is still a $5 a tail bounty on nutria in LA, which is helping control their numbers. Some have even suggested trying to create a market for nutria fur, I couln't see that ever taking off, can't picture people wanting to don nutria rat fur coats.


If I remember correctly Nutria were brought to LA to breed for their fur.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
BTW, I'm still not seeing any recon via google earth KML....
Member Since: October 25, 2005 Posts: 19 Comments: 22322
2034. KEEPEROFTHEGATE (Mod)
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Quoting sammywammybamy:
Did Recon find a Closed LLC?


No one has any data.

Probably an oil spill mission. I don't know.
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Someone at work who follows the tropics mentioned that Colin's behavior might be setting up for a loop ... didn't suggest it would head for land ... was just wondering what the possibility of this was?
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2029. gator23
Quoting BaltOCane:
Link

The CMC picked up on the CATL wave this morning and takes it north for a bit, before pushing it back W-WSW.

But that was the 12z and it's the CMC, so take that for what you will.

the CMC track wise has been pretty good with these trop storms granted my sample size is bonnie and colin but still
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Quoting CyclonicVoyage:


Record breaking SST's bring record amounts of convection :-)
When the conditions are right, the record breaking SST's could easily develop a few very strong hurricanes.
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2027. 7544
Quoting weatherman12345:
quick question:
since the nhc already found winds of 60 mph would that be the intesnsity when they find a LLC.


popcorn time hes going to ssurpise eveyone lol at dmax
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I can say one thing for sure. Colin is NOT moving 20-25 mph ATM.
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Link

The CMC picked up on the CATL wave this morning and takes it north for a bit, before pushing it back W-WSW.

But that was the 12z and it's the CMC, so take that for what you will.
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There's a pretty well-worn track of storms recurving in between the CONUS and Bermuda, never making any landfall. I wouldn't rule that out w/ Colin. I'm in reed's camp on not buying the Bermuda landfall just yet. A lot depends on speed, strength and location of that trough.
Member Since: October 25, 2005 Posts: 19 Comments: 22322
Quoting AllStar17:
I have NEVER seen this much convection in the Central Atlantic before!


Record breaking SST's bring record amounts of convection :-)
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2021. KEEPEROFTHEGATE (Mod)
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I have NEVER seen this much convection in the Central Atlantic before!
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I agree that is more likely

Quoting Twinkster:


the trough is going to be a dominant feature through the weekend and unless the nao become negative quicker than expected the trough will take this northwest and north. It is possible that it gets far north and then rishon begins building back in and it heads back west, however I am 95% certain that this will recurve and the other 5% is that it will hit am area from the Carolina northwards
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Quoting weatherman12345:

Why?
sry just tryin to learn here


The 60 mph TS readings where probably glitches. Flight level winds support a 40 mph TS.
Member Since: July 8, 2005 Posts: 259 Comments: 24181
Quoting Goldenblack:
That is possible. I am just saying what weather12345 and others are saying...he could miss the trough, or he could center relocate, or he could begin moving north.



the trough is going to be a dominant feature through the weekend and unless the nao become negative quicker than expected the trough will take this northwest and north. It is possible that it gets far north and then rishon begins building back in and it heads back west, however I am 95% certain that this will recurve and the other 5% is that it will hit am area from the Carolina northwards
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Quoting JavPR:
where can i see the models that develop that central atl wave?
No model runs on it yet... not designated an invest as yet.
Member Since: October 25, 2005 Posts: 19 Comments: 22322
Quoting Relix:
Our CATL wave is destined to be a fish storm it seems.


To early to tell atm.
Member Since: July 8, 2005 Posts: 259 Comments: 24181
Quoting Relix:
Our CATL wave is destined to be a fish storm it seems.


Too early to say. It will be slow to develop....which may allow it to get further west. It is still very much up in the air as to where it goes.
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Quoting blsealevel:
I think this is what Reedzone was looking at eirler, I know I saw it, dosn't weaker storms tend to not be affected by Northerly Trough's as stronger ones do? but it still modeled to go NW this will change and start the widow washer effect soon though i think anyway.
That's why he was saying he thought this would get closer to the US coast than models are portraying before it's all over. Just so long as it doesn't get far enough west to negatively impact the Bahamas I'm ok...
Member Since: October 25, 2005 Posts: 19 Comments: 22322

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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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