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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Ex-Colin still holding out to the 40mph winds, however the pressure has decreased by 1mb to 1008mb. Interestingly enough it remains as a "wave".

AL, 04, 2010080512, , BEST, 0, 230N, 650W, 35, 1008, WV,
Member Since: September 2, 2009 Posts: 130 Comments: 21032
GFS more than recurves the CATL wave, it pretty much sends it NW and then to the N shortly after development. Keeps it well away from the Caribbean islands.
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2660. breald
Morning. NOAA will come out with their new predictions today at 11am. Do you think they will lower their numbers?
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Despite the large amount of SAL/Dry air to the north the sheer size of PGI24L will be helping it fight it off, basically the opposite of what we saw with Colin.


Member Since: September 2, 2009 Posts: 130 Comments: 21032
2656. Squid28
morning all...

Is wunderground broken or has all of the caffeine from my java not set in yet? I do not see ex-colin on the tropical/hurricane page
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Not to much going on out there right now... but the CATL wave looks like its getting ready to surf :)



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26493
Quoting CyclonicVoyage:
Danielle in the making, seems like.



Where does this image come from?
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Quoting Jeff9641:
I would watch this area in the C ATL as it looks like this area will pose a threat to the Antilles early next week.
I doubt it, this one will likely recurve as an intense cyclone as depicted by the 06z GFS.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
2651. help4u
Overall pattern is for alot of fish storms next couple of weeks.Models take everything out to sea.
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Quoting CyclonicVoyage:


Looks to be attached to the ITCZ still. No real 850 vort to speak of ATM either.

Really? I see plenty of 850mb vorticity up near 12N 31W.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
I think COLIN has recovered a Low Level Circulation Center, despite of the shear...

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When recon goes to investigate ex-Colin later today I think we'll have a TS again. I also think that we'll see 93L out of the large and vigorous tropical wave in the CATL in the next 48 hours.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Jeff9641:


Very impressive convection in the C ATL. I'm surprised that the NHC doesn't mention this area in there discussion.


Looks to be attached to the ITCZ still. No real 850 vort to speak of ATM either.

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Morning all.

Interesting set up on Monday for Colin according to OPC.

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Quoting Jeff9641:
Good Morning Guys! Big Things Poppin I see!

http://www.youtube.com/watch?v=uVMYFfBo3g8

LOL, mah dog posted da T.I. up, lmao!
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2643. smuldy
Quoting hurricanejunky:


Our beaches here in Ft. Myers/Sanibel/Captiva are pristine and waiting for folks to come enjoy them...
But you have no waves on that side...like ever, except for when people cant safely go in the water
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I'm not sure either, strong model support.
Member Since: July 8, 2005 Posts: 259 Comments: 23012
Quoting CyclonicVoyage:
Danielle in the making, seems like.


Seems like it.
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2639. IKE
I see we're going into a negative NAO, according to this map, but I don't see any threats to the USA, or closer to the USA, for at least the next 10 days. And I'm not including tropical waves...1012mb lows. I'm talking hurricane threats. Maybe it changes on future model runs...

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2637. IKE
Quoting Neapolitan:


I agree. This photo was taken near Naples, Florida, as Ivan's remnants were making their way westward across the tip of Florida. (Note: no filters were used and no post-processing was done on this; the colors are from the dust and humidity Ivan was dragging along with him. 'Twas incredible.)

Ivan sunset


Nice picture. Even with the waves it's rather peaceful looking.
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Quoting gulfcoastdweller:


ok, I can so picture EDF on the daughter's first date. Boy knocks on door, enters the house, sees EDF cleaning his shotgun...."Have a nice time kids".......LOL


oh yea... One more thing... Keep your hands to your self and being on time would be a very good thing for you .... LOL
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Danielle in the making, seems like.

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Quoting severstorm:

Dfly they say the best place for lighning pictures is Tarpon Springs just thought you might want to know. I have seen some great shots of lightning and they all came from that area.


I will have to look that place up as a AOI.. Thanks
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting biff4ugo:
Thanks for the link Earthly!
And good luck with the pics.


Thanks Biff
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting IKE:
Ivan was no slouch...at all...and meant business.


I agree. This photo was taken near Naples, Florida, as Ivan's remnants were making their way westward across the tip of Florida. (Note: no filters were used and no post-processing was done on this; the colors are from the dust and humidity Ivan was dragging along with him. 'Twas incredible.)

Ivan sunset
Member Since: November 8, 2009 Posts: 4 Comments: 13268
Thanks for the link Earthly!
And good luck with the pics.
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2630. soloco
Quoting tkeith:
?


Maybe he had a birthday, lol.??
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Good morning WU bloggers.
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Oh, almost forgot! Good morning all!
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Models shifted way east overnight...except, oddly enough, the NHC model. Hmmmm....
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Quoting StormW:
Just a little tidbit to think on...I don't have time to go through all the data (archived), but to touch on the NAO versus storm tracks. When the NAO goes negative (weaker A/B ridge / weaker Icelandic low), this DOES NOT imply storms are just going to automatically re-curve out to sea. The "weaker" high so to speak, with the combination of the Icelandic low, also weakens the "mean" trof that helps to recurve storms, as well as not letting the axis as far south. I mean, think about it, if you weaken the A/B high and Icelandic low, how are you going to strengthen the "mean" trof? Remember, anytime you have a strong ride, you're going to pump a stronger trof east of it. Weaker high...weaker trof to the east.

Here's is a comparison per se, as I said, I don't have time to research every year, but the maps show that, all tracks closer to the U.S. were in a NEGATIVE NAO phase, or transitioning from a moderate/strong negative toward postive, or at a weak positive (almost neutral).

1990 was a predominately positive NAO during the heart of the season, and 2005, 2008 were of what I had just mentioned.







Thanks so much Storm!
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Quoting earthlydragonfly:


You guys have awesome beaches and community.. I love it up there!


Our beaches here in Ft. Myers/Sanibel/Captiva are pristine and waiting for folks to come enjoy them...
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2623. MahFL
Colins center is exposed, moving WNW.
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Quoting KoritheMan:


I can imagine. Opal was horrific. That one, along with 2000's Gordon, should be decent reminders that just because tropical cyclones develop over the Yucatan Peninsula, does not mean that they will be destroyed and unable to intensify when they hit water.

The Yucatan isn't a very mountainous or rugged area.


i think camille was from there wasnt it?
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Quoting tkeith:
I love the Emerald Coast...tryin to make enough money to retire there.
LOVE living here !
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2619. tkeith
Quoting weather457:
Good Morning to All!!!
?
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2618. IKE
Quoting RipplinH2O:
15 trees hit the house and fence. A very long day... Defuniak now has 9 traffic lights? I need to get up there more often...


It may take a few weeks to get both set up.

Quoting divdog:
that storm kicked our butts in FWB. That storm had some serious punch. I had to dig 3 feet of crap out of our pool


And she intensified before landfall. Formidable storm.
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Gooooood Morning folks! :)
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Quoting MiamiHurricanes09:
If the entire run of the 06z GFS would verify we would be by the "G" storm in 16 days. That obviously means nothing since it is very highly unlikely that it will, but as you can tell we are getting to that time of the season that storms start forming left and right.

06z GFS still calls for Danielle to form within the next 3 days.


I am personally ready to track a REAL storm lol. Most seem to have been challenged this year with the exception of Alex at the end.
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2615. NASA101
Quoting hcubed:


Is he still on that?

He STILL hasn't provided his source of the "busting" of Watts.

His arguement of Watts and "no peer-reviewed articles" is questionable, too.

And as far as the "Goddard" issue, is he saying that if a person posts anonomously, we can't believe them?

That would knock out a few warmist web sites as well.


Reported for discussion of non-tropical nature!
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2614. divdog
Quoting IKE:
I've give an honorable mention to this bad girl.....well respected by IKE/the downcaster.....

that storm kicked our butts in FWB. That storm had some serious punch. I had to dig 3 feet of crap out of our pool
Member Since: August 22, 2008 Posts: 0 Comments: 755
Good Morning!
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2612. hcubed
Quoting Ossqss:


Do you know how foolish that comment is? This is about two different (official) sources for the same info. Not your perception of such. Quite telling for sure. Does your opinion change it? No, realize that and grow up. Gheeze,

I am outta here! Consider the source is all I will say, the data and the opinion are two different things.


Is he still on that?

He STILL hasn't provided his source of the "busting" of Watts.

His arguement of Watts and "no peer-reviewed articles" is questionable, too.

And as far as the "Goddard" issue, is he saying that if a person posts anonomously, we can't believe them?

That would knock out a few warmist web sites as well.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.