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 Tazmanian:



it would be 11pm


Sometimes they name it in-between advisories.
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Quoting AstroHurricane001:


NOGAPS brings the Tehuantepec low back into Mexico.


NOGAPS FTW!
Member Since: August 26, 2006 Posts: 16 Comments: 4766
funny how everyone trys to find out every possible scenario for something, the unthinkable.

The bottom-line is Colin will be going for a swim out to sea, keep Bermuda in your prayers.
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Quoting BahaHurican:
aquua, link, pls..... ta.


Baha- I posted them in YOUR blog! :)

Keeper, thank you..

Ya'll dayshift crew are way too uptight. I'll see ya'll after shift change.
Member Since: August 13, 2005 Posts: 166 Comments: 26047
Quoting hurricanehunter27:
Looks like Colin is coming back stronger than ever and it now has a closed COC i think it maybe restored to TS stat soon mabye by 8PM advisory.



Storm, Miami, Levi, your thoughts?
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Quoting stormpetrol:
If Colin remnants regenerates being it lost its closed low, will it retain the name Colin or become get the next name on the list, I can't remember how that goes , could someone help me out?


It will be Karen...LOL
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Quoting hurricanehunter27:
Looks like Colin is coming back stronger than ever and it now has a closed COC i think it maybe restored to TS stat soon mabye by 8PM advisory.




it would be 11pm
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Anyone else having trouble w/the NHC site?
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904. 7544
yeap same name but many a dif track tho
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903. srada
From the NWS Wilm, NC

the surfers will have a great weekend

SEAS WILL DEPEND ON WHAT IF ANYTHING DEVELOPS OUT OF THE REMNANTS OF
COLIN. GFS ADVERTISES A CLOSED CIRCULATION RE-DEVELOPING...THUS
DRIVING ENOUGH SE SWELL TO PUSH SEAS TO 5 FT ON SATURDAY AND SUNDAY.
CURRENT FORECAST IS ABOUT A FOOT LOWER...AND WITH NHC NOT EXPECTING
MUCH OUT OF THAT SYSTEM...WE WILL STICK WITH THAT UNLESS AND UNTIL
WE START TO SEE ACTUAL DEVELOPMENT.
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Looks like Colin is coming back stronger than ever and it now has a closed COC i think it maybe restored to TS stat soon mabye by 11PM advisory.

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Quoting nolacane2009:


Thank you. I told you it was a stupid question. I appreciate all the knowledge you all share without getting frustrated at the guys like me that really don't know any thing.
no problem
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Quoting stormpetrol:
If Colin remnants regenerates being it lost its closed low, will it retain the name Colin or become get the next name on the list, I can't remember how that goes , could someone help me out?


Since it is identifiable as the same circulation, it will keep the same name.
Member Since: August 26, 2006 Posts: 16 Comments: 4766


NOGAPS brings the Tehuantepec low back into Mexico.
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same system same name
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They might raise to 30% for Colin.
Member Since: July 8, 2005 Posts: 259 Comments: 24167
Quoting 7544:
orange taz lol



same ch of that yes
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swirl, lay off, alright? I asked first if anyone wanted to see'm. I WOULD HAVE REMOVED them within five minutes. The girls said yeah, so I posted them.
and it's not like we got recon heading into a cat4 undergoing RI, ok?

Member Since: August 13, 2005 Posts: 166 Comments: 26047
894. 7544
na yellow just look again
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Some really cold tops are forming over ex-Colin. Notice the yellow dots??

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Quoting stormpetrol:
If Colin remnants regenerates being it lost its closed low, will it retain the name Colin or become get the next name on the list, I can't remember how that goes , could someone help me out?



it will still be the same storm i think
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Ex-Colin appearance is asymmetric, likely due the upper level confluent axis near 63W created by the upper level low northwest of the system and the upper level high ESE of the system. Regardless, the system if firing deep convection which should help it form a better defined center.
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890. xcool
Tazmanian yep yellow
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889. 7544
orange taz lol
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888. xcool



update
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If Colin remnants regenerates being it lost its closed low, will it retain the name Colin or become get the next name on the list, I can't remember how that goes , could someone help me out?
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Quoting xcool:
Tazmanian .how about red ?



no red tonight yellow more likey
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885. 7544
ok hes moving but w or wnw or n lol tia looking better by the min.
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Quoting aquak9:


glad you got to see, it, POOF they removed it. Ah well.

Thanks for the minuses, you guys, I did ask for a certain amount of leniancy.

P'EHhhh on all of you.


I don't see why you'r ticked off by it. Nearly all comments involving off topic pictures get removed because they do violate the rules of the road. I don't see what makes your case so special.

Anyway, 21Z CIMSS should be out soon. I'm curious to see how this:



and this:


change, mainly curious about 92L. Ex-Colin is already decent in both.
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who can forget this discussion? August....seems to breed the bad ones...

000
WTNT42 KNHC 281454
TCDAT2
HURRICANE KATRINA DISCUSSION NUMBER 23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT SUN AUG 28 2005

THE AIR FORCE HURRICANE HUNTERS JUST MEASURED A 166 KT FLIGHT LEVEL
WIND IN THE NORTHEAST EYEWALL...WHICH REQUIRES AN ADDITIONAL UPWARD
ADJUSTMENT OF THE CURRENT INTENSITY TO 150 KT. A DROP IN THE EYE
GAVE A CENTRAL PRESSURE OF 907 MB. KATRINA IS COMPARABLE IN
INTENSITY TO HURRICANE CAMILLE OF 1969...ONLY LARGER. GPS
DROPSONDE DATA FROM THE NOAA G-IV MISSION EARLIER TODAY SHOWED
KATRINA'S INTENSE CYCLONIC CIRCULATION EXTENDING THROUGH THE 200 MB
LEVEL...WITH THE FLOW SPIRALING ANTICYLONICALLY OUTWARD IN A
WELL-DEVELOPED UPPER-LEVEL OUTFLOW PATTERN BEYOND A COUPLE HUNDRED
N MI FROM THE CENTER. FLUCTUATIONS IN STRENGTH...DUE TO INTERNAL
STRUCTURAL CHANGES...ARE LIKELY PRIOR TO LANDFALL. HURRICANES
RARELY SUSTAIN SUCH EXTREME WINDS FOR MUCH TIME. HOWEVER WE SEE
NO OBVIOUS LARGE-SCALE EFFECTS TO CAUSE A SUBSTANTIAL WEAKENING THE
SYSTEM...AND IT IS EXPECTED THAT THE HURRICANE WILL BE OF CATEGORY
4 OR 5 INTENSITY WHEN IT REACHES THE COAST.

THERE IS NO CHANGE TO THE TRACK FORECAST. KATRINA SHOULD GRADUALLY
TURN TOWARD THE NORTH...INTO A WEAKNESS IN THE SUBTROPICAL RIDGE
ASSOCIATED WITH A LARGE MID-LATITUDE CYCLONE OVER THE NORTHERN
UNITED STATES AND SOUTHERN CANADA. THE OFFICIAL FORECAST TRACK IS
ABOUT IN THE MIDDLE OF THE DYNAMICAL GUIDANCE MODELS...WHICH ARE
RATHER TIGHTLY CLUSTERED. RECALLING THAT THE AVERAGE NHC 24-HOUR
TRACK FORECAST ERROR IS ABOUT 80 N MI...THE ACTUAL LANDFALL POINT
COULD STILL BE ANYWHERE FROM SOUTHEASTERN LOUISIANA TO THE
MISSISSIPPI COAST. ALSO...WE MUST CONTINUE TO STRESS THAT THE
HURRICANE IS NOT JUST A POINT ON THE MAP...BECAUSE DESTRUCTIVE
WINDS...TORRENTIAL RAINS...STORM SURGE...AND DANGEROUS WAVES EXTEND
WELL AWAY FROM THE EYE. IT IS IMPOSSIBLE TO SPECIFY WHICH COUNTY
OR PARISH WILL EXPERIENCE THE WORST WEATHER.

THIS ADVISORY SHOWS AN ADDITIONAL EXPANSION OF THE WIND FIELD OVER
THE EASTERN SEMICIRCLE BASED ON AIRCRAFT AND SURFACE OBSERVATIONS.
HURRICANE FORCE WINDS ARE FORECAST TO SPREAD AT LEAST 150 N MI
INLAND ALONG THE PATH OF KATRINA. CONSULT INLAND WARNINGS ISSUED
BY NATIONAL WEATHER SERVICE FORECAST OFFICES.

FORECASTER PASCH
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Quoting Seflhurricane:
Tropical weather Outlook


Thank you. I told you it was a stupid question. I appreciate all the knowledge you all share without getting frustrated at the guys like me that really don't know any thing.
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7544, yes it is completely possible for that to happen.
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880. xcool
Tazmanian .how about red ?
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Quoting aquak9:


glad you got to see, it, POOF they removed it. Ah well.

Thanks for the minuses, you guys, I did ask for a certain amount of leniancy.

P'EHhhh on all of you.
ITS ok friend i like your pictures of the coon nice and i even gave ya a plus but then it dissappear
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Quoting Tazmanian:
this could be yellow

likely
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this could be yellow

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Quoting nolacane2009:


Very very very stupid question. What does the next TWO mean.
Tropical weather Outlook
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Quoting aquak9:


glad you got to see, it, POOF they removed it. Ah well.

Thanks for the minuses, you guys, I did ask for a certain amount of leniancy.

P'EHhhh on all of you.


It was to be exspected I enjoyed them, nice to take a break for 1 sec and enjoy the pics cause being new to this and learning can make your head spin lol BACK TO TROPICS!!
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aquua, link, pls..... ta.
Member Since: October 25, 2005 Posts: 19 Comments: 22318
Quoting aquak9:


glad you got to see, it, POOF they removed it. Ah well.

Thanks for the minuses, you guys, I did ask for a certain amount of leniancy.

P'EHhhh on all of you.


mod could be reading the blog and just poofed them anyway, without being flagged.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting Seflhurricane:
it looks likely that Colins remnants may go RED on the next TWO


Very very very stupid question. What does the next TWO mean.
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Spiral banding evident in E side of circulation, restricted to the W thanks to shear, cold cloud-tops becoming evident over the COC (-80C).





All we need to have is a closed LLC, and judging by the marked increase in organization the pass few hours that might happen soon.
Member Since: July 8, 2005 Posts: 259 Comments: 24167
870. xcool


kind old
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I didn't minus the pics, I plused 'em :-D
I wish we had some more racoons around here...all we have are opossums (EWWWW)...
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it looks likely that Colins remnants may go RED on the next TWO
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Quoting 7544:
colins getting there peeps could be td right now or at 8pm

but is he moving ?

could it be possible he can stall and miss that trof alltogether ?


He is moving.
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92L 14.8N/75.3W decent circulation there, orange at 8 pm, doubt it!
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865. xcool
I wouldn't be suprised see to cat1 colins
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nolacane- thankyou, glad you got to see them before the crowd here minus'd them to invisibility.
Member Since: August 13, 2005 Posts: 166 Comments: 26047
863. 7544
colins getting there peeps could be td right now or at 8pm

but is he moving ?

could it be possible he can stall and miss that trof alltogether ?
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Quoting wdtcnewsonlinewx:
Is there any chance that the trough will not fully recurve Colin out to sea?
thats exactly what i am thinking
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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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