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 pottery:
Good Evening...
First evening in a long time when I can see the Stars in a Clear sky.

Probably a Sign that all is well with Ebony, our Black Lab, who we put down today.
She was a Good Companion for 13 years, and will be truly missed.
Wife is Sad, so I am in Comforting Mode.

Keep well, All.


Condolences on the loss of your pet Pottery - I know the feeling well - lost 2 of my cats in the last two years. But Ebony will be waiting for you and your wife at the Rainbow Bridge!
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Quoting AussieStorm:

That one was eating cows and goats before it was caught and shot. By there is another 1 similar size out and about up in the top end.


I watched a show on one of the nature/outdoor/National Geographic channels where they went search for... get this "22 foot long" Gators... they figure you have some.... 22 FEET LONG?????
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting CyclonicVoyage:
Really, I think it is a TC now. There are plenty of uncontaminated west winds being reported now. This is a change from earlier.

Indeed, I agree. I strong believe that Colin has a closed surface circulation. I would upgrade it at 11PM EDT.
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Quoting IKE:


One of Ringo's best is a theme for the 2010 Atlantic season...




This blog should be a pay only blog. It is about the only way to straighten it out. It's gotten out of hand on here.


agreed completely!!!
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Quoting Orcasystems:


I don't think it was ever really dropped.... they have not missed a single model run on it yet.


Yeah I know that but, drop the remnant tag.
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1855. txjac
Quoting AussieStorm:

It's a croc not a gator That one was eating cows and goats before it was caught and shot. By there is another 1 similar size out and about up in the top end.


And just how big are these? Like length and weight please?
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Quoting Orcasystems:
What would be nice is if we had some function that would allow us to see how long a user has been a member ;)
Not sure how well that would work Orca, I have been here since just after Katrina but couldn't remember my e-mail account last year due to an illness and had to get another account. Good idea though!
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1852. tkeith
Quoting msgambler:
Them small chillins'
Dem gators been eatin high on da hog...
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1851. pottery
Good Evening...
First evening in a long time when I can see the Stars in a Clear sky.

Probably a Sign that all is well with Ebony, our Black Lab, who we put down today.
She was a Good Companion for 13 years, and will be truly missed.
Wife is Sad, so I am in Comforting Mode.

Keep well, All.
Member Since: Posts: Comments:
1850. angiest
Quoting MiamiHurricanes09:
You really don't want to know what he wrote there. Just don't quote him.


I already ignored him. He said something worse than Charlie Oscar Jones?
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1849. BDAwx
hey I admit my seasonal forecast seems a little tougher to meet everyday. I stick to it anyway.
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1848. IKE
Quoting tkeith:
Paul and Ringo?

they're all that's left...


One of Ringo's best is a theme for the 2010 Atlantic season...


Quoting caneswatch:


You sir have been disrupting the blog for a long time. Why?


This blog should be a pay only blog. It is about the only way to straighten it out. It's gotten out of hand on here.
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Really, I think it is a TC now. There are plenty of uncontaminated west winds being reported now. This is a change from earlier.

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Quoting tkeith:
1826. AussieStorm

whatch yall feed dem gators down there Aussie?

It's a croc not a gator That one was eating cows and goats before it was caught and shot. By there is another 1 similar size out and about up in the top end.
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1844. BDADUDE
Quoting Orcasystems:
What would be nice is if we had some function that would allow us to see how long a user has been a member ;)

agreed
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Quoting caneswatch:


You sir have been disrupting the blog for a long time. Why?
You really don't want to know what he wrote there. Just don't quote him.
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Quoting CyclonicVoyage:


Strongest Vorticity in the tropics right now. Should get re-instated tomorrow.


I don't think it was ever really dropped.... they have not missed a single model run on it yet.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting tkeith:
1826. AussieStorm

whatch yall feed dem gators down there Aussie?
Them small chillins'
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Quoting 2010StormNames:
Cojones, admins, COJONES.


You sir have been disrupting the blog for a long time. Why?
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1838. angiest
Quoting WeatherNerdPR:

With winds and pressure like that, you'd think they'll label it at LEAST a disturbance.


It is, it's the remnants of Colin and it has a 40% (I think?) chance of redeveloping.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting RufusBaker:
Well hmmm guess we wont have a hyper active season but we will see alot of junk popping this month and next
Rufus, u realize that none of the well-known forecasters have dialed their forecasts back below 18 NS? and they kept their ACE at or over 185, too. The hyperactive forecast is still out there....

Plus we will likely see the junk.... lol

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Quoting Orcasystems:
Colin looks pretty good right now.



AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI


Strongest Vorticity in the tropics right now. Should get re-instated tomorrow.
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1834. xcool
hmm
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What would be nice is if we had some function that would allow us to see how long a user has been a member ;)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
1831. BDAwx
Quoting BahaHurican:
I'm great, just kicking back and enjoying some unseasonably cool weather here. Hope u guys just get some relieving rains and not much else.


The end of July saw huge amounts of rain over our Cup Match (3-6"). There was some low-lying flooding but it wasn't too bad. The heat is back on now and heat indices are back into the 100*F range.

A good rainstorm from the remnants would be a blessing for some right now: still 9" down on the year.

Do you think that "cool" weather where you are will have any impact on the hurricane season?
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Quoting MiamiHurricanes09:
00z ATCF Best Track has Ex-Colin with winds of 40mph and a pressure of 1009mb. However it still remains a tropical wave.

AL, 04, 2010080500, , BEST, 0, 202N, 628W, 35, 1009, WV,

With winds and pressure like that, you'd think they'll label it at LEAST a disturbance.
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1828. tkeith
1826. AussieStorm

whatch yall feed dem gators down there Aussie?
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1827. sassisu
This is my first and last post. Been a lurker for a couple of years.I have lurked quietly and learned from Patrap,Levi,StormW,Drak and many others that I have a great deal of respect for. Where have you all gone? I guess its time to move on. Its been nice and thanks to all and I am not JFV!
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Quoting tkeith:
2Dat
I'm just calling it a continuation of Part 1.
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Member Since: Posts: Comments:
PGI24L has pretty good vorticity at the 850mb level.

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1822. tkeith
Quoting Patrap:


True Dat.

Part 2-castng

U betcha,,
2Dat
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1821. FLDART1
where do i find the google earth hurricane hunter
application
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1820. Patrap
Quoting tkeith:
we spell it Brees in Nawlins :)



True Dat.

Part 2-castng

U betcha,,
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1816. bappit
Quoting Patrap:
Gust Front just came thru here Uptown,,Gust to 35mph

Mod Lightening


I like the little ones that preceded the biggie.
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Quoting BDAwx:


I'm good - we're just getting out of a drought, at least in the short term. Back to the summer heat from our High pressure for now.

Yeah but we've had worse than whats forecast so I hope we'll be fine.

How're you doing?
I'm great, just kicking back and enjoying some unseasonably cool weather here. Hope u guys just get some relieving rains and not much else.
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Quoting MiamiHurricanes09:
No they have not.

t


it sould have update with the others
Member Since: May 21, 2006 Posts: 5091 Comments: 115080
Must be the night for big storms. Here in Tampa the Rays baseball game was postponed by 20 minutes because of severe storms and lightning shutting down the power systems (and they have an indoor stadium!)


Quoting Patrap:
Gust Front just came thru here Uptown,,Gust to 35mph

Mod Lightening

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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.