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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1561. xcool
tropical weathertropical weathertropical weather
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1560. bappit
Colin is still circulating.

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Quoting reedzone:


You're pretty much out of the picture, but I wouldnt completely write it off, stranger things have happened in the past.
Hey, I know about the stranger things [Andrew Jeanne Katrina], which is why I'm REALLY looking forward to the trough.... lol Reminds me of my avatar storm (Isobel, la belle) which for a long time was barrelling for the Bahamas as a cat 5 and scared the KNEES off me... lol

Anyway, it makes for an interesting day or two...

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Link

Reedzone you just may be on to somthing with this; I guess it just depends on how strong the storm gets and any trough's that pop up it's going to be a timing thing to say the least.
IMO thanks
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Approximately how much longer until the HH reach Colin?
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Quoting MiamiHurricanes09:
Yes, NttyGrtty has been permanently banned from Jeff Masters' blog.


What he do?
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1549. Vero1
40%

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT WED AUG 4 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

1. SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN ASSOCIATED WITH THE
REMNANTS OF TROPICAL STORM COLIN IS GRADUALLY BECOMING BETTER
ORGANIZED BUT THE SYSTEM LACKS A WELL-DEFINED CENTER. TROPICAL
STORM FORCE WINDS ARE ALREADY OCCURRING OVER WATER WELL TO THE
NORTHEAST OF THE LEEWARD ISLANDS AND ALTHOUGH UPPER LEVEL WINDS ARE
NOT FAVORABLE FOR SIGNIFICANT DEVELOPMENT...THE SYSTEM HAS THE
POTENTIAL TO REGAIN TROPICAL STORM STATUS ON THURSDAY AS IT MOVES
TOWARD THE WEST-NORTHWEST OR NORTHWEST AT 20 TO 25 MPH. THERE IS A
MEDIUM CHANCE...40 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

2. A TROPICAL WAVE IS PRODUCING CLOUDINESS AND THUNDERSTORMS BETWEEN
COLOMBIA AND JAMAICA. ALTHOUGH THIS ACTIVITY HAS NOT BECOME ANY
BETTER ORGANIZED DURING THE PAST SEVERAL HOURS...SOME DEVELOPMENT
IS POSSIBLE DURING THE NEXT DAY OR TWO BEFORE THE WAVE BEGINS TO
INTERACT WITH CENTRAL AMERICA. THERE IS A LOW CHANCE...20
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER AVILA
NNNN


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1547. will45
Quoting thelmores:
HH HUNTER RECON FOR COLIN??????

ANYBODY???


i cant help you thel recon coder site is down and i havent looked at google
Member Since: July 18, 2009 Posts: 1 Comments: 994
1546. Drakoen
Increase in vorticity with the EATL wave:

Member Since: October 28, 2006 Posts: 57 Comments: 29887
Quoting thelmores:
HH HUNTER RECON FOR COLIN??????

ANYBODY???


The only plane sending data is in the GOM. Last approximate position

001000 2806N 08902W

Member Since: September 23, 2005 Posts: 14 Comments: 10876
Quoting fatlady99:


Yeah, Miami, I saw that and edited my post. Sorry to trouble you. As I said, it's been an awfully long day. I'll go back to lurking.
LOL, no worries.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
HH HUNTER RECON FOR COLIN??????

ANYBODY???
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Quoting MiamiHurricanes09:
Just click on the link I provided you...it says "Aqua Modis".


Yeah, Miami, I saw that and edited my post. Sorry to trouble you. As I said, it's been an awfully long day. I'll go back to lurking.
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Quoting zoomiami:


I would bet that you are right about that - the strange orientation makes it more difficult to be vertically stacked.

I miss the regular old storms that would line up like they were suppose to. Getting tired of the LLC's and MLC's taking off everywhere!
That makes sense. No wonder it's taking these guys so long to get their act together; they have to "straighten up and fly right" first! And I agree with u; whatever happened to the "good old days".... lol
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Quoting BahaHurican:
Looking forward to that trough this weekend...


You're pretty much out of the picture, but I wouldnt completely write it off, stranger things have happened in the past.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
1533. scott39
should EXColin be an invest right now? Is the high still expected to weaken?
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.
Member Since: May 21, 2006 Posts: 5091 Comments: 114728
Quoting nyhurricaneboy:


I see you've lied to us about your age. You're obviously studying for your SATs.

Also, a wise man told me that you go to FIU.
just drop it man dnt give him more steam PLEASE
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1526. Engine2
Quoting reedzone:
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..
I'm with you Reed
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Quoting reedzone:


Florida should be safe, and most likely the East Coast as well, steering does change, you can definitely see the weakness, I think this may come close to the Carolinas, then push out to sea. We'll see though...
Looking forward to that trough this weekend...
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So far it seems like a strange year in the tropics. I do not think conditions are great yet for systems developing into Hurricanes and lasting for several days, watch out though because i doubt things will stay like this too much longer.
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Quoting fatlady99:

Miami, that's really beautiful. What's your source?
Just click on the link I provided you...it says "Aqua Modis".
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting 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..


HAHA!
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Quoting HurricaneSwirl:


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.
Not right now, the satellite is currently cruising over the Artic. It'll be taking pictures of the tropics soon.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:
Aqua Modis image of ex-Colin.

17:30 UTC


Miami, that's really beautiful. (sorry just saw the link, must be tired... long day)
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Can anybody confirm the location of Recon in reference to Colin?

And the next person that puts the letters J F V together gets introduced to my ignore list!

Don't feed the trolls, and they will just go away! Don't even mention them..... don't even comment on my post! JUST IGNORE THEM!!!! PLEASE GOD!
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Quoting BahaHurican:
Snap. Just posted similar. Wonder if these "weird" orientations are impacting cyclogenesis....


I would bet that you are right about that - the strange orientation makes it more difficult to be vertically stacked.

I miss the regular old storms that would line up like they were suppose to. Getting tired of the LLC's and MLC's taking off everywhere!
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Quoting weatherman12345:

Reedzone, do you think Florida is out of any impacts from Colin??


Florida should be safe, and most likely the East Coast as well, steering does change, you can definitely see the weakness, I think this may come close to the Carolinas, then push out to sea. We'll see though...
Member Since: July 1, 2008 Posts: 13 Comments: 7340
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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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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