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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662. 7544
does anyone know if colin in slowing down in spped tia looks like he is here
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Quoting Levi32:


Yes that part of the forecast is over but we forgot about Bermuda. This could nail them.


ok, hopefully it doesn't blow up to much...
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Quoting Hurricanes101:
right now I am seeing 4 areas of potential

Remnants of Colin, 92L, wave by 47W and wave by 30W

the wave at 47W has the least chance of developing due to land, but if it can pull north of SA it may have a shot

the other 3 areas all have good chances of being named or renamed as is the case with Ex-Colin




can you make a map and pont out the one that has the best ch
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Colin is fascinating....a perfect example of why we should never rip anything until the fat lady has sang.
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right now I am seeing 4 areas of potential

Remnants of Colin, 92L, wave by 47W and wave by 30W

the wave at 47W has the least chance of developing due to land, but if it can pull north of SA it may have a shot

the other 3 areas all have good chances of being named or renamed as is the case with Ex-Colin
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Quoting TexasHurricane:


would this still be a fish storm?


Yes that part of the forecast is over but we forgot about Bermuda. This could nail them.
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Wow it looks like Colin is trying really hard to get its act together. In fact it looks like it has an eye.


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Quoting 2010StormNames:


West, but then the model ends, Taz.


ok
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Quoting Levi32:
I just read JB's column....apparently he thinks this will be a hurricane. I actually don't think that's crazy. What I just saw on the 12z GFS and 12z NOGAPS opened my eyes to this possibility....there's enough heat involved to get this ridge to balloon right over Colin as he approaches Bermuda and once he's far enough north, probably 25N and northwards, he could really ramp it up. He's very close to a tropical storm already right now and is stronger than he ever was with or without a fully closed circulation.


would this still be a fish storm?
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that "stuff" coming Africa looks ugly
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Does the fact that Colin is now a remnant low make any difference for model initialization?
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Quoting BiloxiIsle:
HaboobsRsweet--do you really think the high will be leaving soon? Not because I want storm to come in the Gulf, but the rain today has been a nice break from this heat!


Yesterday I saw what looked like a developing thunderstorm over Houston. Don't know if it every got anywhere but it was the first evidence of convection I have personally seen here in most of a week.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting BiloxiIsle:
HaboobsRsweet--do you really think the high will be leaving soon? Not because I want storm to come in the Gulf, but the rain today has been a nice break from this heat!

I wouldnt go crazy and start saying Gulf haha. It may take some time to shift. Just a sign that pattern is changing. We would not have had those storms without a shift. I have not looked at everything yet to figure out what I thing about the overall track yet. Just expect a shift in forecast.
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I just read JB's column....apparently he thinks this will be a hurricane. I actually don't think that's crazy. What I just saw on the 12z GFS and 12z NOGAPS opened my eyes to this possibility....there's enough heat involved to get this ridge to balloon right over Colin as he approaches Bermuda and once he's far enough north, probably 25N and northwards, he could really ramp it up. He's very close to a tropical storm already right now and is stronger than he ever was with or without a fully closed circulation.
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Member Since: June 12, 2005 Posts: 6 Comments: 8183
644. unf97
Quoting Jeff9641:


I am seeing this on the models this afternoon. It looks if finally E C FL and NE FL will see some substantial rain. This could be the start of very wet few months across FL.


If the long range GFS pans out, it would be very welcomed relief for much of the state. At the very least, rain would definitely be on the increase and we would get a respite from the intense heat we have been getting all summer long.
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Quoting MiamiHurricanes09:
Very interesting.



hi 09 what do the short term and long term gfs show
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Levi what do you mean 'blow up'? Back into a tropical cyclone or something else?
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Link to see Colin as of right now?
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Quoting Levi32:
You know what, the 12z GFS just gave us a clue. When it finally figured out the 200mb pattern, it initialized the 200mb ridge over Colin correctly and this could be trouble for Bermuda in 3 days. I had a feeling something about last night's runs wasn't lining up with the water vapor imagery, and this was it. This could blow up near Bermuda between 30N and 40N. Waters are very warm at 28C all the way up to 40N.
Very interesting.
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638. 7544
is he moving slower now
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Quoting StormW:


Thank you Jon, I appreciate that!! Wish I could be back on active duty.


Some of us who are still on active duty remember you Tom...should I start telling sea stories....
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636. Skyepony (Mod)
Levi~ I could see Colin affecting Bermuda. I think he'll be the one that parallels way off shore..Like the one I went on about before season, the one climatology from years of similar ENSO demands~ one of these by the D storm.
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Quoting 7544:
hes looking good now



oh
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Quoting Kristina40:


It has been extremely hot along the Gulf Coast. Abnormally hot which I'm sure is contributing to the very high Gulf temps. My pool water hit 94 degrees last weekend. Thankfully it has cooled off a bit here and we had a few thunderstorms. My pool is now a "refreshing" 92 degrees. I think the Gulf near shore is 88 right now.
my pool is 95 and the swim zone at the GOM is 91+, not even refreshing anymore. And with a dp of 83', I want refreshing dang it.
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To many tutts around....
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630. 7544
hes looking good now
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00
NOUS42 KNHC 041430
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT WED 04 AUGUST 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 05/1100Z TO 06/1100Z AUGUST 2010
TCPOD NUMBER.....10-066

I. ATLANTIC REQUIREMENTS
1. REMNANTS OF TROPICAL STORM COLIN
FLIGHT ONE -- TEAL 71
A. 05/1800Z
B. AFXXX 0204A COLIN
C. 05/1630Z
D. 23.0N 67.0W
E. 05/1730Z TO 05/2130Z
F. SFC TO 15,000 FT

2. SUCCEEDING DAY OUTLOOK:
A. A 06/1800Z FIX ON COLIN IF STILL A VIABLE
SYSTEM NEAR 27.0N 69.0W.
B. A POSSIBLE LOW LEVEL INVEST AT 06/1500Z

NEAR 16.5N 84.5W.

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You know what, the 12z GFS just gave us a clue. When it finally figured out the 200mb pattern, it initialized the 200mb ridge over Colin correctly and this could be trouble for Bermuda in 3 days. I had a feeling something about last night's runs wasn't lining up with the water vapor imagery, and this was it. This could blow up near Bermuda between 30N and 40N. Waters are very warm at 28C all the way up to 40N.
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Quoting Drakoen:
Winds out of the SW and WSW south of Colin:

Hey Drak, could that be a "pouch" way down to the S.E. of Ex-Colin?
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626. Jax82
When is the MJO expected to be in the upward phase in Octants 1/2?
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625. unf97
Long range discussion from JAX NWS forecasters:


LONG TERM...SUNDAY THROUGH WEDNESDAY

WEAK FRONT TO SLOWLY SAG SOUTH ACROSS THE JAX CWA SUNDAY AND
MONDAY. UPPER TROUGH IS PROGGED BY THE GFS TO CLOSE OFF JUST
NORTH OF THE BAHAMAS AS UPPER RIDGE STRENGTHENS OVER THE PLAINS.
THE CANADIAN GEM ACTUALLY CUTS THE UPPER LOW OFF OVER NORTHERN
FLORIDA...WHICH WOULD RESULT IN A RATHER SOGGY SCENARIO FOR
THE LOCAL FORECAST AREA SUNDAY AND MONDAY. BOTH MODELS STALL THE
FRONT SOMEWHERE OVER NORTHEAST FLORIDA WITH A WEAK CIRCULATION
DEVELOPING AT THE SURFACE.



The upper level ridge may get displaced from the SE US and build over the Plains starting next week. Frontal boundary may stall over North FL and form a Low pressure area. This is something possibly to be watched early next week. If anything, this change would bring welcomed relief in the form of increased moisture for NE FL and a respite from the intense heat we have had seemingly all summer long.
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so what do the short tram mode runs of the gfs show
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Quoting Drakoen:


AL, 04, 2010080418, , BEST, 0, 194N, 612W, 35, 1010, WV


that works too lol
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HaboobsRsweet--do you really think the high will be leaving soon? Not because I want storm to come in the Gulf, but the rain today has been a nice break from this heat!
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Quoting NOSinger:
Haboob....BTW...just sounded out your name....LMAO!!

Haha it sounds funny but it is a real weather event. Google haboobs and you will see. Awesome weather event.
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Quoting Hurricanes101:


seems like this center is just forming now, close to the convection around 19.2 61.2


AL, 04, 2010080418, , BEST, 0, 194N, 612W, 35, 1010, WV
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AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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Quoting Drakoen:
Winds out of the SW and WSW south of Colin:



seems like this center is just forming now, close to the convection around 19.2 61.2
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Quoting wayfaringstranger:
Im guessing ex Colins coc would be around 22N, 63W ish?


I see it around 61W/20N. Nice little flareup on the west side of the CoC, by the way:

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Winds out of the SW and WSW south of Colin:

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Quoting NOSinger:
Haboob...makes alot of sense...thx

No problem...I like to look at the big picture and then compare that to the models vs just taking the models for what they are. I expect the models to adjust in the next 24 hours. You already see forecasts up and down the coast increasing chances for precip over the next few days because the cap will be gone and the atmosphere will be very unstable with all the heat and moisture.
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Haboob....BTW...just sounded out your name....LMAO!!
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Link Significant increase in vorticity with 92L. Convection has diminished some what over the past few hours but this will likely be temporary, and should refire.
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Im guessing ex Colins coc would be around 22N, 63W ish?
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.