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 reedzone:


Yeah, re-edited the post because the java image never showed up. I wanted to show how that west-northwest steering hasn't moved much over the past week or so.


I need to look back at some of this, but I do seem to remember noticing that also, just didnt think much of it at the time though.
Thanks
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Quoting Seflhurricane:
whats new taz



not march but you havr mail
Member Since: May 21, 2006 Posts: 5091 Comments: 114717
Quoting BahaHurican:
Snap. Just posted similar. Wonder if these "weird" orientations are impacting cyclogenesis....
I don't think so, very interesting nonetheless.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting FLdewey:
Who even cares if he did threaten you? you're arguing with a kid who after he's banned tonight will be back tomorrow with a new name. People act like the police are going to start kicking in door because someone said something.

NttyGrtty would be proud... if he wasn't banned.
Yes, NttyGrtty has been permanently banned from Jeff Masters' blog.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Tazmanian:



mail
whats new taz
Member Since: July 14, 2009 Posts: 0 Comments: 2990
1507. ncstorm
If I was a pysch major, I would come to this blog and studied the many schrzophrenia personalities of JFV..would write my thesis and score my PH.D..LOL..
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good night all lets see what colin does tonight
Member Since: July 14, 2009 Posts: 0 Comments: 2990
Quoting Seflhurricane:
thanks



mail
Member Since: May 21, 2006 Posts: 5091 Comments: 114717
Quoting pilotguy1:


I just ignore and push the minus sign. It's the easy button. Never argue with idiots. It doesn't pay if you want to keep your sanity on the net.
Amen this is true outside the Blog also.
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Quoting MiamiHurricanes09:
Aqua Modis image of ex-Colin.

17:30 UTC



Neat picture, do they have a newer one out? Would be more impressive if it showed the newer ex-Colin as that picture was taken at 1:30 PM EDT.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting pilotguy1:


I just ignore and push the minus sign. It's the easy button. Never argue with idiots. It doesn't pay if you want to keep your sanity on the net.
thanks
Member Since: July 14, 2009 Posts: 0 Comments: 2990
Quoting nyhurricaneboy:
I'm going to apologize to the rest of you for arguing with him... I just can't resist. I just feel... upset... about this, and naturally want to put JFV in his place.
understood but like other have said lets just ignore him but i feel ya everyday he has a new name, but lets get back to tropics :):)
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Aqua Modis image of ex-Colin.

17:30 UTC

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Yeah I don't see any norther turn yet plus the current wind currents are pointing towards the east coast.
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Quoting MiamiHurricanes09:
Look at the tropical waves axis orientation (the one near 30W), it seems to be stretched out from the WSW to the ENE.

Snap. Just posted similar. Wonder if these "weird" orientations are impacting cyclogenesis....
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MAP 5.3 2010/08/05 00:04:50 41.800 -112.111 25.4 1 km ( 1 mi) SSE of Fielding, UT
Member Since: August 11, 2008 Posts: 3 Comments: 1570
Quoting blsealevel:

Reedzone is this what your looking at your pic didnt show up. Thanks


Yeah, re-edited the post because the java image never showed up. I wanted to show how that west-northwest steering hasn't moved much over the past week or so.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Ok all the drama aside, anyone have any thoughts on Colin's swell production possibility?

Its a small storm and probably always will be so I think not much. Though all the current winds are point directly at the EC.
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Quoting pilotguy1:


What's wrong with the ignore button? Poof he's gone. Jeez you guys should get by him.
i ignore him all the time but its a different name everyday , but moving on ...............
Member Since: July 14, 2009 Posts: 0 Comments: 2990

Reedzone is this what your looking at your pic didnt show up. Thanks
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Well while you guys have been hopelessly arguing JFV, I have been

1: Laughing

and

2: Reading up on Joe Bastardi's 2010-2011 Winter Forecast, which was just released today - Link. He nailed the last one, and this one looks right on as well.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
09 mail
Member Since: May 21, 2006 Posts: 5091 Comments: 114717
Anybody else notice how this year's Twaves have been tilted like, all over the place? Whatever happened to the simple ( figure on surface maps? Look at the orientation of this latest "mega-wave" - practically lying down in the ITCZ....
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Not what I meant at all......
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I'm thinking Colin will attain TS status once again by 2am. I think 92L will be orange by 8 am tomorrow.
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1473. aquak9
nyhurricaneboy- First the exclamation, to alert Admin. Then after ten minuses, the post gets removed automatically.

I give plenty of plus signs, too, so my karma is good. :)
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Look at the tropical waves axis orientation (the one near 30W), it seems to be stretched out from the WSW to the ENE.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Drakoen:


Drak,

I hate it when you post images with no text...... then I can't endorse or criticize your thinking! LOL

I usually endorse! :D
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1470. xcool
tropical weather, "Please thanks
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Backing up my thinking with this, a reliable steering map.. You can see a bit of a northward jog, but nothing like what models are showing, the BAMMS may have the idea. I will be adding this info on my 3rd forecast run on the storm.

Steering for a Tropical Storm


Steering for a Hurricane (Category 1)


I just don't see a sharp turn to the north based on this..
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Quoting nyhurricaneboy:


I'll take this one to chat. The blog is no place for this.


That won't give him the attention he needs...please JUST IGNORE HIM....
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Quoting stormpetrol:
Honest to GOD, I'm sick and tired of this JFV crap!!!, Frankly those that complain and report him, if it is him, over& over have fed him and made him grow & quitely frankly I find just as aggravating as the so called JFV himself!! Please learn the only beast that thrive is the one you feed!!!
I am so sick of him and his Garbage to not say the other word, he has been harrasing this bog for too long
Member Since: July 14, 2009 Posts: 0 Comments: 2990

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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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