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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1762. SWMIWX
Quoting nrtiwlnvragn:


Thanks!
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1761. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting Patrap:


Impressive outflow! nice!
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If I have a choice between what passes for humour and lots of banned jokesters, I know which ones I'd take every time.

Humor is NOT attempting to humiliate other bloggers, no matter what passes for it on US sitcoms.

And now.... I give u the two bright spots of the night:



AND......



Wonder if we're going to hear reports of flooding from this in a day or two...

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1757. ncstorm
Quoting caneswatch:
To all, nyhurricaneboy and jennifergirl ARE NOT JFV! I personally know these two people. Thanks to JFV, jennifergirl has left this blog, and she was gaining an interest in weather. Some of you (like ncstorm), have attacked her for no reason. We lost another one who was interested in weather. Thanks a lot JFV. I can't believe he continually harasses us.



My thesis paper is becoming a book..this is getting good!!
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1756. BDADUDE
Quoting muddertracker:
When did you join this blog? Just curious.

3 or 4 years ago I believe
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1755. robj144
Quoting Patrap:


That's a crazy looking radar loop.
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Quoting FLdewey:
It is a hard scene to navigate. I'm sure many lurkers think shower curtains can somehow predict storms. ;-)


I use a match box with two (2) beatle bugs inside it when the both bugs are upside down look out.
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Quoting FLdewey:


It's TOTALLY worth the 24hours. ;-)
Did they get you, too?
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Quoting Patrap:






Not alot of dry air
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BAMM models shifted westward again, if you look at the steering layers map, these models have a point.
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Blog Update!

August 4, 2010 - 9:15 PM EDT - Tropics Getting Active
Member Since: September 2, 2009 Posts: 130 Comments: 21091
00Z BAMM
Link
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#1717: That's awful news Skye. :(
Member Since: July 11, 2006 Posts: 14 Comments: 11173
Quoting Patrap:


same here pat . I am about to see some nasty weather here in richmond VA.
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1744. Patrap
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Quoting rarepearldesign:


Wat? I am in Canadian Maritime's! In Halifax to be exact? I thought it died? Should I be watching again?


Fish storm for USA doesn't mean we are in the clear, here in Halifax!
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The whole East Atlantic is a crap shoot right now. Wave after strong wave comes off the African coast. Eventually one of em is going to hit pay dirt.
Member Since: July 11, 2006 Posts: 14 Comments: 11173
1740. Patrap
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Quoting weatherman410:
00Z BAMM models show Colin moving closer to east coast again.


Link?
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1737. IKE
Quoting sporteguy03:


see ya in the am Ike bring some good weather tunes.


LOL...will do.
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00Z BAMM models show Colin moving closer to east coast again.
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Thank you, I have been saying that he has slowed considerably over the past couple of hours


Quoting FLDART1:
Colin is looking a little healthier tonight, I dont however see the 20 MPH or so wnw movement
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Quoting muddertracker:
Sad, isn't it? You have one blogger on her who is obsessed with JFV and that causes mini "witch-hunts" all the time. I think it would be almost impossible for a new blogger to find his or her place on this blog now. IMHO!


i am a new blogger and i agree that it is impossible to fit in here i have had several emails accusing me of being this jfv person and telling me to prove that i am not i dont have to prove anything to anyone
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1731. IKE
Quoting rarepearldesign:


We could use a good wind/rain storm, blow some stink off the place. Nothing more than a TS though please :)


Good luck with it.
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1730. Patrap
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Quoting Chicklit:

Is that the same thing as (get a) GRIP which Pat posted?


I don't know.
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Quoting BenBIogger:
Very interesting wave at 10W.

Yah, that caught my eye right away, even before reading ur comment.... need to pull IR imagery on that...
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Quoting IKE:


I forgot about them. Sorry.

Corrected to add #2....

(1)Bermuda.
(2)Canadian Maritime.
(3)This blog.




Mellower crowd in the early am!


see ya in the am Ike bring some good weather tunes.
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Only chance the new bloggers have is lurking for a while like I did (for 5 years)before joining back in June. That way they can see what not to ask - and how thick the skin has to be...

Quoting muddertracker:
Sad, isn't it? You have one blogger on her who is obsessed with JFV who causes mini "witch-hunts" all the time. I think it would be almost impossible for a new blogger to find his or her place on this blog now. IMHO!
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1723. FLDART1
Colin is looking a little healthier tonight, I dont however see the 20 MPH or so wnw movement
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Quoting IKE:


If you're lucky maybe it goes east of you.


We could use a good wind/rain storm, blow some stink off the place. Nothing more than a TS though please :)
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1721. BDADUDE
BDAwx is correct. You only get attacked Reedzone because you wishcast. People generally do not like wishcasters as they skew the facts. I have been watching you for years and your wishcasting is wrong 99-100% of the time. Respect comes on this site with good quality forecasts not always saying that storms are turning more left or going to hit the conus. I do think you could be a good forecaster and am hoping your ways will change, this is why I do not have you on ignore.
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1718. breald
Quoting reedzone:


She left the blog, people kept attacking her for NO REASON. She also just got into the weather, now according to her last post, she doesn't wanna have the interest anymore.. Good job blogger, lost another one, way to go!


yeah I read. I just think it is funny how she was treated compared to others, in the same boat.

Oh well, keep up the good work Reed.
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1717. Skyepony (Mod)
NW passage, almost open..
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1715. IKE
Quoting rarepearldesign:


Wat? I am in Canadian Maritime's! In Halifax to be exact? I thought it died? Should I be watching again?


If you're lucky maybe it goes east of you.
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Quoting BDAwx:
ok.
1. This is weather. You should NEVER say that something will or wont do something. There is always the chance that it does something different to what you say. Even if you have all the model support in the world, or observational support in the world. That chance is always there.
2. Can we people please stop being rude? seriously?please?
3. Can we please use grammar that is vaguely understandable?
4. Finally, can we please not state opinions as fact then tack on "imo" or "jmo" on the end?

[+], BDA, and how r u? I see u may be getting some stormy wx this weekend.... if the forecasts are on track....
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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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