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 AllBoardedUp:
It's all in how they market the product! How about this, "Nutria Is Nutritious"!


nutria fur coat on sale at amazon.com for $1550.00

i swear

http://www.amazon.com/STUNNING-SHEARED-NUTRIA-COAT-sz12/dp/B001GPKDYQ
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Quoting KEEPEROFTHEGATE:
AOI/XX/XL
MARK
10.23N/30.41W


Boy.. That sure is a ton of convection!!!!
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2109. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting all4hurricanes:
So nobody knows if the 11 has been posted?!? there should be a way to check that


http://www.nhc.noaa.gov/

Front page of that site tells you which systems are active. None are active, so Colin is not back at this time.

Quoting Goldenblack:
Gotta find a closed circulation...they are absolutely determined that that criteria be strictly adhered to this year.

I agree that this is just as dangerous as a tropical storm if you are on the business side (NE)



That's the criteria always. Yes, this is still as dangerous as a tropical storm. This is a problem for strong disturbances without a closed circulation. Even though they are not officially tropical cyclones, they can produce weather of tropical storm intensity.
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Quoting wfyweather:
Hurricane Hunters are currently investigating... correct?


No. Apparently they were doing an Oil Spill mission.
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See y'all tomorrow morning!
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1717 Skyepony "NW passage, almost open [Arctic sea ice map]"

As is the NorthEast Passage, though the sea ice extent has yet to reach the 2003 minimum...

- - - - - - - - - - link to large map - - - - - - - - - - - - - - - - - - - - - - - - - - - link to large chart
...which makes me wonder if the years odd enough to make headlines will soon be the ones in which either the NorthWestPassage or the NorthEastPassage fails to open for regular*shipping from earlyAugust through midOctober.

* Continuously navigable without icebreaker escorts.
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Hurricane Hunters are currently investigating... correct?
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Quoting ho77yw00d:


That was beautiful and very thoughtful..


hello everyone. i'm just logging in. i'm wondering, why the poetry?

also, check this out

http://www.ssd.noaa.gov/eumet/eatl/flash-rb.html
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Quoting alaina1085:
Severe thunderstorm warning for SELA... Got a strong line of tstorms coming with 60 mph wind. Thats more then Bonnie! LOL.
it was a good light show:)
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2098. 7544
there i s no 11pm next one is at 2am est
Member Since: May 6, 2007 Posts: 0 Comments: 6857
2097. Ossqss
click to enlarge





Member Since: June 12, 2005 Posts: 6 Comments: 8186
2096. Relix
Quoting CybrTeddy:


GFS, ECMWF, NOGAPS, CMC develop this.


Most of them show it going WNW then NW
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Not till 2AM, they haven't upgraded Colin, and probably won't without evidence of a closed circulation

Quoting TropicalAnalystwx13:


Can you all not get access to the site or something? I can, and its not there. :\
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OK I'm going to bed who knows maybe we'll see Colin Tomorrow
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Quoting jlp09550:
What happened to 92L?





ir look like it went poof
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
Quoting all4hurricanes:
So nobody knows if the 11 has been posted?!? there should be a way to check that


Can you all not get access to the site or something? I can, and its not there. :\
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Quoting extreme236:


The highest vorticity is associated with the convection, therefore the surface center will likely become dominate there. Colin will probably regenerate.


Too bad we don't have visible loops or recon. Both would help a lot!
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2090. KEEPEROFTHEGATE (Mod)
AOI/XX/XL
MARK
10.23N/30.41W
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2089. amd
Quoting AllStar17:


That is the old center, I believe.

Furthermore, earlier this evening, many people were commenting on a new surface center forming under the convection, which seemed to clearly be the case looking at visible loops.

Now that visible loops are no longer available, it is extremely difficult to make that determination.

Too bad we don't have visible....also too bad we do not have another HH mission.



That could be true, but right near near 20N 65W is the only place that I see any circulation, and if there is a small circulation (which I cannot see at the moment) embedded within the convection, it would be too far away to cause the winds at San Juan to be out of the west or northwest.

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2088. xcool
AllStar17 .1010 mb yea
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Unless there are Advisories on current tropical cyclones, the twos are at 8PM and 2AM...8AM and 2PM...etc.

Quoting all4hurricanes:
So nobody knows if the 11 has been posted?!? there should be a way to check that
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Quoting NCHurricane2009:


Interesting, your obs suggest a broad surface circulation SW of the ball of convection. That seems to coincide with where the surface trough of Colin is analyzed in the NHC surface analysis. I agree with you about if Colin doesn't regenerate a center underneath the ball, this is not going to have a great chance to come back. That's what I am forecasting, that Colin won't come back for that reason.


The highest vorticity is associated with the convection, therefore the surface center will likely become dominate there. Colin will probably regenerate.
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Quoting xcool:


?

Now they have it as a low?
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What happened to 92L?

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what would cause ex-colin to stall? is this stall a possible shift? if so, a shift in what direction? thanks in advance:)
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Quoting alaina1085:
Severe thunderstorm warning for SELA... Got a strong line of tstorms coming with 60 mph wind. Thats more then Bonnie! LOL.


Hope the rain parks itself over my house for the night, but it's going to be muggy in the morning though.
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2080. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
So nobody knows if the 11 has been posted?!? there should be a way to check that
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Gotta find a closed circulation...they are absolutely determined that that criteria be strictly adhered to this year.

I agree that this is just as dangerous as a tropical storm if you are on the business side (NE)

Quoting wfyweather:
You know... Ex colin is really looking nice.. they should upgrade it soon.
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Quoting JLPR2:
O_O


Looks a little intimidating XD
That TW is activating the ITCZ nicely.


GFS, ECMWF, NOGAPS, CMC develop this.
Member Since: July 8, 2005 Posts: 259 Comments: 24185
Quoting amd:


Allstar, I agree with gator23 in this case. If you zoom in the ir2 loop around 20N 65W, you will see the lower level center. If you look to the NE from that point, you will see clouds moving from se to nw, and just follow the clouds around the point.

That is where the low level center (possibly surface center) is. It also jives with the wind reports from san juan, that shows w to nw winds.

Also, the low level center is moving slowly west while the convection has come to a halt. If a new low level center does not form near the convection, it is possible to see detachment of the low level center from the convection, and Colin's regeneration potential will drop substantially in that case.

All of this is JMHO.


Interesting, your obs suggest a broad surface circulation SW of the ball of convection. That seems to coincide with where the surface trough of Colin is analyzed in the NHC surface analysis. I agree with you about if Colin doesn't regenerate a center underneath the ball, this is not going to have a great chance to come back. That's what I am forecasting, that Colin won't come back for that reason.
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Quoting FLdewey:


By about 40MPH. ;-)

Ha! Everytime I see your avatar I die laughing!! Thats good stuff.
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2074. JLPR2
O_O


Looks a little intimidating XD
That TW is activating the ITCZ nicely.
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Quoting all4hurricanes:

As in it's 11 and the NHC says Colin still is a wave or the 11 hasn't been posted


It has not been posted here.
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hee hee, I think that 30 MPH would be more than Bonnie...didn't feel a thing when she came through FL.

Quoting alaina1085:
Severe thunderstorm warning for SELA... Got a strong line of tstorms coming with 60 mph wind. Thats more then Bonnie! LOL.
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Quoting amd:


Allstar, I agree with gator23 in this case. If you zoom in the ir2 loop around 20N 65W, you will see the lower level center. If you look to the NE from that point, you will see clouds moving from se to nw, and just follow the clouds around the point.

That is where the low level center (possibly surface center) is. It also jives with the wind reports from san juan, that shows w to nw winds.

Also, the low level center is moving slowly west while the convection has come to a halt. If a new low level center does not form near the convection, it is possible to see detachment of the low level center from the convection, and Colin's regeneration potential will drop substantially in that case.

All of this is JMHO.


That is the old center, I believe.

Furthermore, earlier this evening, many people were commenting on a new surface center forming under the convection, which seemed to clearly be the case looking at visible loops.

Now that visible loops are no longer available, it is extremely difficult to make that determination.

Too bad we don't have visible....also too bad we do not have another HH mission.

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Refreshing isn't it? To talk about 92L, ex-Colin and the CATL disturbances....instead of drama.


Quoting Greyelf:
I'm confused. I'm not sure how to react reading nothing but actual weather related posts. What a refreshing change a few pages make. And just so mine is weather related too - it's clear here in Nebraska. :)
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Quoting AllStar17:


It has not been upgraded yet.

As in it's 11 and the NHC says Colin still is a wave or the 11 hasn't been posted
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You know... Ex colin is really looking nice.. they should upgrade it soon.
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Severe thunderstorm warning for SELA... Got a strong line of tstorms coming with 60 mph wind. Thats more then Bonnie! LOL.
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2065. Greyelf
I'm confused. I'm not sure how to react reading nothing but actual weather related posts. What a refreshing change a few pages make. And just so mine is weather related too - it's clear here in Nebraska. :)
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2064. amd
Quoting AllStar17:


Does not seem like that is the case looking at shortwave IR loops.


Allstar, I agree with gator23 in this case. If you zoom in the ir2 loop around 20N 65W, you will see the lower level center. If you look to the NE from that point, you will see clouds moving from se to nw, and just follow the clouds around the point.

That is where the low level center (possibly surface center) is. It also jives with the wind reports from san juan, that shows w to nw winds.

Also, the low level center is moving slowly west while the convection has come to a halt. If a new low level center does not form near the convection, it is possible to see detachment of the low level center from the convection, and Colin's regeneration potential will drop substantially in that case.

All of this is JMHO.
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Quoting BreadandCircuses:


Many top line chefs like John Folse have been coming up with nutria rat recipes to try and create a market for the rodents to get them out of the wetlands, they haven't had much luck getting a lot of people to try it, though. I've eaten nutria a couple times, it's not bad, kind of like squirrel, the meat is stringy, though.

I think there is still a $5 a tail bounty on nutria in LA, which is helping control their numbers because they are destroying the vegetation in the swamps. Some have even suggested trying to create a market for nutria fur, I couln't see that ever taking off, can't picture people wanting to don nutria rat fur coats.
It's all in how they market the product! How about this, "Nutria Is Nutritious"!
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Quoting all4hurricanes:
Does anyone know if Colin has been upgraded? can't they tell with satellite imagery?


It has not been upgraded yet.
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About

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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