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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20/20 for both systems.
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361. xcool
llol
Member Since: September 26, 2009 Posts: 2 Comments: 15684
360. Jax82
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xcool, that chart is DestinJeff's area. :)
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358. SLU
351. xcool 1:49 PM AST on August 04, 2010

Tropics Heating up as Peak of Season Nears


WOW .. I see they got the wave count right. The Cape Verde's wave really and truly is the 32nd for the year so far.
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Quoting StormW:


Great stuff.
Can you give us a brief overview about it?
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Quoting Eagle101:
The following is in honor of our very own Senior Chief:

The Coast Guard celebrates 220 years of service to our great country today…

Thank you for your service Senior Chief.

For over two centuries the U.S. Coast Guard has safeguarded our Nation’s maritime interests in the heartland, in the ports, at sea, and around the globe. We protect the maritime economy and the environment, we defend our maritime borders, and we save those in peril. This history has forged our character and purpose as America’s Maritime Guardian — Always Ready for all hazards and all threats.

Today’s U.S. Coast Guard, with nearly 42,000 men and women on active duty, is a unique force that carries out an array of civil and military responsibilities touching almost every facet of the U.S. maritime environment.

The Coast Guard's motto is Semper Paratus, meaning "Always Ready."

ref: US Coast Guard web site.

Very Respectfully,

Jon
+1
Member Since: Posts: Comments:
The following is in honor of our very own Senior Chief:

The Coast Guard celebrates 220 years of service to our great country today…

Thank you for your service Senior Chief.

For over two centuries the U.S. Coast Guard has safeguarded our Nation’s maritime interests in the heartland, in the ports, at sea, and around the globe. We protect the maritime economy and the environment, we defend our maritime borders, and we save those in peril. This history has forged our character and purpose as America’s Maritime Guardian — Always Ready for all hazards and all threats.

Today’s U.S. Coast Guard, with nearly 42,000 men and women on active duty, is a unique force that carries out an array of civil and military responsibilities touching almost every facet of the U.S. maritime environment.

The Coast Guard's motto is Semper Paratus, meaning "Always Ready."

ref: US Coast Guard web site.

Very Respectfully,

Jon
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351. xcool
Tropics Heating up as Peak of Season Nears


August 4th, 2010
As you can see on the frequency diagram below, the first week of August typically marks the real beginning to the hurricane season. About 90-95% of all named storms occur between August 1st and October 15th in a typical season. The chart below actually shows the frequency distribution of tropical depressions, tropical storms, hurricanes and major hurricanes. The very peak of the season is generally considered to be the 10th of September. And like clockwork, the 2010 season seems to be slowly coming alive this week.





Just a few days ago, Tropical Storm Colin formed east of the Caribbean Sea. Although I think that Colin may have been named a little too quickly (later data indicated that Colin lacked a well-defined circulation center), it still indicates that the tropics are becoming more active. But just as quickly as Colin developed, it ran into wind shear associated with an upper-level low which tore the newly-formed storm apart. The same thing happened to Bonnie a few weeks ago, if you recall. This does indicate that there are still some pockets of strong wind shear across the tropics, something that%u2019s not uncommon for early August.

Colin may be down, but I%u2019m not sure he%u2019s %u201Cout%u201D just yet. Surprisingly, many of the models still indicate that Colin will get past the shear zone produced by the upper-level low and regenerate into a tropical storm. The hurricane-specific models even take Colin to hurricane strength in 2-3 days as it passes a few hundred miles off the East U.S. Coast. That%u2019s certainly possible, but it does look like Colin%u2019s strong winds would not impact any land areas.





In the Caribbean, there%u2019s a disturbance we%u2019ve identified as Disturbance 31. It%u2019s actually a tropical wave that we have been tracking since it moved off the west coast of Africa about 12 days ago. Many tropical waves weaken after emerging off the west coast of Africa in the early part of the season, only to strengthen once they reach the Caribbean. Really, it%u2019s just the associated thunderstorms that weaken, not the waves themselves. Disturbance 31 is certainly looking more impressive today as it moves westward at 15-20 mph. There may be a 40% chance that the disturbance will become at least a tropical storm before it reaches the Yucatan Peninsula on Friday night or Saturday morning. Some models even take it to hurricane strength by then, but those models already assume it%u2019s a tropical depression, something it%u2019s not.

The good news for those across the northern Gulf of Mexico is that the same high pressure that%u2019s been producing the above-normal temperatures should remain in place for at least another week. That means any developing storm in the western Caribbean Sea would be driven westward toward Mexico rather than turn toward the northern Gulf of Mexico. Therefore, we think that Disturbance 31 will probably remain to the south of 23N-24N latitude, whether or not it develops.

Finally, out in the far eastern Atlantic is Disturbance 32. The disturbance certainly has a good bit of energy associated with it, though it is somewhat lacking as far as its organization. A number of computer models indicate that this disturbance will develop into a tropical storm in 4-5 days as it passes well north of the eastern Caribbean. Both the American GFS model and the European ECMWF model take the system safely north and east of the Caribbean and out to sea into the open Atlantic next week. As far north as the disturbance is now, I%u2019d say that such a track out to sea is most likely.






All in all, the various computer models which extend out to 10-15 days are showing an increase in development over the coming weeks, something that I%u2019d expect to see in early August. Over the last 15 years, we%u2019ve witnessed about 1 named storm per week forming in the month of August, and I don%u2019t think that this August will be much different. Look for activity to gradually ramp up over the next week or two as wind shear slowly declines. Longer range signals are pointing to a very active September, but that%u2019s the subject of my next update here.

Posted in Uncategorized

Chris Hebert
by
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Here's what JB says this afternoon.
Let the bashing begin.

WEDNESDAY 1 PM
GASP!!!CFS GOES ROIDIAN ON LA NINA.

http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/images3/nino34SSTSe a.gif


Some of the runs are hitting -3. While I dont believe that, the La Nina should be as strong as the one in the early 50s or mid 50s. Keep in mind, the response to global temps lags a bit, but get out the crash gear.

meanwhile look at this:

http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/images3/usT2mMon.gif

The August now cast has Little Rock below normal. They are having their hottest summer ever. August is breaking records left and right and just like all the months where the change is evolving, the model is clueless on the front month here in the states. It is taking IDIOT pills in Alaska with its warmth in Dec and Jan. Look at this:

http://www.jamstec.go.jp/frsgc/research/d1/iod/

use the menu to scroll down to sfc temp, dec-feb


You wanna bet on which one wins?

Both of them show the major global crash in temp for the coming winter season (against the normals) but how the CFS is going to take a cold PDO and make Alaska warm is beyond me.


And dont get your hopes up on its idea of a cold eastern winter, north south up and down the east coast. That looks bogus. While December may be cold, I seriously doubt that the NOv-Dec period is as this model portrays ( CFS)

I wonder if funding has been cut off for this or something. I have never seen it this bad.

ciao for now ****

WEDNESDAY NOON

COLIN TO THREATEN BERMUDA, PROBABLY AS A HURRICANE.

The system will break the shear zone and should be a tropical storm by Friday morning, if not sooner. Recon is finding 45 kt winds on the northeast side, and this system should intensify quite quickly once to 30 north and beyond. The storm is finding the western side of the ridge to move along, and we will be no more than a surfers storm for the US. But this should become our 2cnd hurricane of the season before it runs to its fate in the north atlantic

ciao for now ****
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349. Bonz
Hmmm....CSU kept the numbers the same. I figured they'd drop them a bit lower.
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Quoting MiamiHurricanes09:
At 2PM EDT I would put both 92L and the remnants of Colin at a 30% chance.


because of the strong MLC that recon has found maybe they will up the chances to red within the next 48 hours like 60%
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Will be curious to see what the TWO says.
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At 2PM EDT I would put both 92L and the remnants of Colin at a 30% chance.
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344. xcool
jasoncoolman2010xx huh 30%?
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343. xcool
Floodman yep lol
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Quoting xcool:
1900hurricane .maybe 93L ?

That's kinda what I'm thinking.
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337. xcool
http://www.tropicalstormrisk.com/


August
17.8/9.7/4.5
ACE:183
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336. xcool
1900hurricane .maybe 93L ?
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335. xcool
StormW hey.go take look at joe b video
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Quoting StormW:


If the shear forecast holds true, I would look for some slow organization to begin around 8:00 p.m.
I see what you mean, looking at the 12z GFS is shows the TUTT lifting ever so slightly towards the north giving the remnants less than 10 knots of shear to work with. We shall see what happens.
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Quoting MiamiHurricanes09:
Very large tropical wave with model support.

....and going to bring MORE rains here.
This is shaping up to be a really rainy one.
Now, having said that, it is quite possible that when (if) there are strong Low Pressure systems passing north of here, they tend to suck the moisture north with them, leaving us gasping in the hot humidity and hoping for rain for 10 days at a time.
We shall see.........
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Thanks for the decoder links!!!
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Quoting MiamiHurricanes09:
Looks to be around 19.1N 61.1W where the pressure was at its lowest.


Anyone care to estimate speed and direction?
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Quoting DestinJeff:
What in the Wide Wide World of Sports is going on over there in the far eatern Atlantic?


Meet PGI24L:

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Quoting StormW:


Have a good center fix?
Looks to be around 19.1N 61.1W where the pressure was at its lowest.
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Quoting DestinJeff:
What in the Wide Wide World of Sports is going on over there in the far eatern Atlantic?



It looks creepy from my viewpoint. Looks like something is reaching over the Atlantic. :o

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324. xcool
Colin is soldier.hello.
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting StormW:


On ex-Colin?
Yup.
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Quoting StormW:
Back!
Hey Storm! To fill ya' in, Recon found a non-contaminated 52 knot SFMR wind reading along with many 40 knot SFMR readings. The circulation at the surface however remains open.
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Good Afternoon. I'm finally back from school.
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wb StormW
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Quoting StormW:
Back!
Welcome back storm!
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314. SLU
Quoting CybrTeddy:
Winds are constant out of the E-SE. No west winds.


Same thing I said earlier. The circulation isn't very well defined. The plane will be there for several more hours so maybe it can close off the circulation before the plane leaves.
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Colin does have a vigorous MLC it seems though. Could be trying to work to the surface.
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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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