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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thanks will check out!!
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2461. xcool
i'm out
Member Since: September 26, 2009 Posts: 2 Comments: 15670
2460. xcool
traumaboyy club
Member Since: September 26, 2009 Posts: 2 Comments: 15670
night xcool
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2458. xcool
bye all
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Xcool what is Razzoo??
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good night/morning chicotman
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Jason was/is awesome, and Dr. Shane and Tom on the radio was just a Godsend. Felt like friends on the radio.
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2454. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15670
I used to be excited about a hurricane hitting, never again since Ivan. A tornado cut from Blountstown to AL line....it was amazing and terrifying.
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Im out,thanks xcool.Night all
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I miss Jason Kelly. While he might have been "over the top" for some, it was clear he really loved what he did.
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Quoting traumaboyy:
We are about an hour north of Panama city so I was all excited about being ready but Ivan the terrible actually scared the sKit out of us. We had Jason Kelly telling us the tornadoes was coming at us the whole time.....power was off two hours...and the tornadoes was very close!!


Ivan was a bad boy. I was going crazy trying to find Mom. All the phones were out so she couldn't call me. I had heard that tornadoes had touched down and people were killed but had no way of knowing if she was OK or not. I was a basket case by day five when she finally called me at work.
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2449. HadesGodWyvern (Mod)
India Meteorological Department
Tropical Cyclone Outlook
11:30 AM IST August 05 2010
=================================

A low pressure area lies over northwest Bay of Bengal and adjoining coastal Orissa. The low is likely to become more marked and move west northwestward.


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We are about an hour north of Panama city so I was all excited about being ready but Ivan the terrible actually scared the sKit out of us. We had Jason Kelly telling us the tornadoes was coming at us the whole time.....power was off two hours...and the tornadoes was very close!!
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NHC doesnt update sat images soon enough.
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Quoting traumaboyy:
I bought the diesel because that was the only one I could find with Ivan bearing down on us. when Opal came through we were without power for 4 days, so I was by God going to have a generator....and so lesson learned


Mom lost her power for 5 days after Ivan. She had no generator and the heat nearly killed her. She had a stroke a few months later which is how I ended up here in Panama City. We bought the generator because she had an air bed and difficulty breathing without a/c. The other great thing we bought was one of those A/C units on wheels that has the sliding exhaust that fits any window. We bought ours when Katrina was forecast to come this way.
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2445. xcool
ha
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Tell me more xcool,I like 000%
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2443. xcool
ECMWF shows 000%
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Power goes out here in rural LA all the time.I keep battery backups for short term.Gas gens wont start when I need them.
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sounds like a john deere tractor without a muffler very loud, weighs about 600 pounds....I like our small gas gensets better, barely hear them run and the last one I bought only cost me 300 dollars.
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2440. xcool
diesel better
Member Since: September 26, 2009 Posts: 2 Comments: 15670
I bought the diesel because that was the only one I could find with Ivan bearing down on us. when Opal came through we were without power for 4 days, so I was by God going to have a generator....and so lesson learned
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Quoting traumaboyy:
bought a big diesel generator three days before Ivan hit, electricity has not been off total of ten hours since then. LESSON: PAY TEN THOUSAND FOR A GENERATOR, POWER NEVER GOES OFF!!

We bought a generator (not a monster like yours but a decent sized one) and haven't lost power for more than a couple hours ever since. That was in 2005.
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No jokes, my map skills need work though.I hope all is well
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2436. xcool





850 mb 5,000 feet
Member Since: September 26, 2009 Posts: 2 Comments: 15670
2435. JLPR2
Quoting chicotman:
JLPR your not in that blob,yet right?


Either I didn't understand what you meant or the joke wasn't that good. XD
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bought a big diesel generator three days before Ivan hit, electricity has not been off total of ten hours since then. LESSON: PAY TEN THOUSAND FOR A GENERATOR, POWER NEVER GOES OFF!!
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2433. xcool
ITCZ...
ITCZ AXIS IS ANALYZED ALONG 12N16W 13N21W 10N33W 7N48W 11N59W.
SCATTERED/NUMEROUS STRONG CONVECTION IS WITHIN 75 NM N OF THE
ITCZ BETWEEN 20.5W-22.5W AND WITHIN 180/200 NM N OF THE ITCZ
BETWEEN 31W-41W. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN
150 NM ALONG THE COAST OF W AFRICA BETWEEN 8N-11N...WITHIN
120/150 NM S OF THE ITCZ BETWEEN 20W-23W...AND WITHIN 200 NM N
OF THE ITCZ BETWEEN 41W-46W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 120 NM BOTH SIDES OF THE ITCZ BETWEEN
49W-52W.
Member Since: September 26, 2009 Posts: 2 Comments: 15670
JLPR your not in that blob,yet right?
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2431. xcool
:0
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Hell tomorrow is today
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2429. JLPR2
In the western side of the blob


Broad circulation:
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Got mine serviced today.Im freezing the water bottles tomorrow.
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2427. xcool
HA
Member Since: September 26, 2009 Posts: 2 Comments: 15670
time to kick the tires and light the fires on those generators!!
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Sometimes I think they wait just to keep us guessing
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2424. JLPR2
Quoting traumaboyy:
is it still a bit soon for cape verde?? and why did they not even mention that monster flairup in the 0200??


I'm actually in awe they didn't XD
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2423. xcool
traumaboyy .Never Too Early FOR CV
Member Since: September 26, 2009 Posts: 2 Comments: 15670
I dont predict but to far out might be it
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is it still a bit soon for cape verde?? and why did they not even mention that monster flairup in the 0200??
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I think 92L gonna wake up.Your take on colin needing pullups was good,nice laugh
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2419. xcool
T storms POP ON 92L
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Morning might bring big the goods.Tonight they bloom.
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2417. xcool
I'M WAIT ON ECMWF,
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Im still watching the carribean,It may head west though
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I see that monster in catl.Gfs got me nervous.
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2414. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Im novice,but Im not rip this yet.
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2412. xcool
chicotman 92L ?
Member Since: September 26, 2009 Posts: 2 Comments: 15670

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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.