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 SLU:


Looks closed but broad.
Member Since: July 8, 2005 Posts: 259 Comments: 24033
Quoting IpswichWeatherCenter:
Will Colin become Colin again if it reforms or will it become TD5/Dannielle?


If it regenerates from the remnants that once was ex-Colin, than they will still call it TD - TS Colin.
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Wow Doc, I've never seen you post so much here.
Member Since: July 8, 2005 Posts: 259 Comments: 24033
Quoting JeffMasters:


I continue to think a repeat of the 1998 season's numbers is reasonable--15 named storms, 10 hurricanes, 3 major hurricanes. I think it is more likely we'll get 4 majors than 3, though.

Jeff


Thank you, Dr. Masters. I don't think anyone wants a repeat of 2005. I'm interested to see if NOAA keeps or changes its forecast.
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Quoting PensacolaDoug:
RE:132

3 named storms yes. Two were weak. Alex, on the other hand, at 947 mb, was the lowest pressure cat2 we've ever seen.


I believe that in post season, Alex will be upgraded to a Major Hurricane. This is just my opinion however.
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156. SLU
Good job Levi
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RE:132

3 named storms yes. Two were weak. Alex, on the other hand, at 947 mb, was the lowest pressure cat2 we've ever seen.
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Quoting JeffMasters:


I continue to think a repeat of the 1998 season's numbers is reasonable--15 named storms, 10 hurricanes, 3 major hurricanes. I think it is more likely we'll get 4 majors than 3, though.

Jeff

Thanks for your imput Dr. Masters, it seems like it's going to get busy very soon!! By the way, i love your info of flying into hurricane Hugo!!!
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Quoting JeffMasters:


Nope, I'll be blogging every day until November...

Jeff


It's good to see you on the blog Doc Masters!
Member Since: July 1, 2005 Posts: 10 Comments: 1683
Will Colin become Colin again if it reforms or will it become TD5/Dannielle?
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I love the MIMIC TPW product for seeing what is going on in and around an area of interest.

This does show that ex-Colin is rounder with some more spin (vorticity) that it was yesterday.

However, the combination of higher shear (than I thought yesterday) and moving into an Anti-Cyclonic environment (rounding the southwest side of the Bermuda High) should slowly wind down the spin over the next couple days.

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Quoting LariAnn:
To me, shouldn't the strength of named storms be taken into consideration, not just the number? Yes, we've had 3 named storms, but they have been weak sauce in terms of wind. My sister in law called to see how well we made it through Bonnie and I told her that if I hadn't seen it on the news, I wouldn't have known a storm was around. Virtually no wind and low to moderate rain is all we got, and the "eye" went just north of us. So three weak named storms by this time should not be the same as three strong named storms, no?


Unfortunately, they do count. They met the criteria at one point or the other. Fodder in the hurricane soothsayers justification cannon even though actual validity to be counted is questionable in other circles.
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149. JeffMasters (Admin)
Quoting Neapolitan:
Thanks as always for the very informative update, Dr. Masters, but you did make one error; you wrote:

The CSU team did decrease their Accumulated Cyclone Energy (ACE) forecast slightly, from 185% of average to 178% of average.

...but that's not entirely correct. The CSU team still calls for a total seasonal ACE of 185%; the 178% is what was left after July 31st, as there was already 7% before that date.


Thanks; I fixed the error.

Jeff
Quoting Skyepony:
Looking at ACE numbers.. Northern Hemisphere 82 so far, overall 61 behind for the year. West Pacific has only produced 14 ACE, it is 67 behind. Central Pacific has produced none. EPAC & Atlantic total is 68 which is slightly higher than the 62 expected. With 259 being total for the 3 basins expected by the end of the year, even with La Nina reducing C & EPAC #'s not sure if we'll reach the projected 178%, even with Atlantic left to make up the difference. ACE overall remains very depressed.
Hi Sky, can you shed some more understanding as to what ACE means? Is there a tutorial on the web for it somewhere?

Thank you
Member Since: July 1, 2005 Posts: 10 Comments: 1683
Quoting Levi32:
Good morning all.

Blog Update:

Tropical Tidbit for Wednesday, August 4th

Thank you Levi 32!!
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Quoting Levi32:
Good morning all.

Blog Update:

Tropical Tidbit for Wednesday, August 4th


Thanks Levi!
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145. JeffMasters (Admin)
Quoting sammywammybamy:


+1


Nope, I'll be blogging every day until November...

Jeff
144. SLU
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143. JeffMasters (Admin)
Quoting Eugeniopr:
Dr. Masters, besides Colorado State University forcast, can you give us your own opinion on how active the season will be? It started very low.

Thank You


I continue to think a repeat of the 1998 season's numbers is reasonable--15 named storms, 10 hurricanes, 3 major hurricanes. I think it is more likely we'll get 4 majors than 3, though.

Jeff
142. SLU
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Good morning all.

Blog Update:

Tropical Tidbit for Wednesday, August 4th
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Quoting sky1989:

Looks like the MJO is stuck in gear...
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Thanks Doc.

Mornin' all.
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136. SLU
Link

Recon now south of the center but no west winds so far.
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The BIG picture:

Lining them up...

Source
Member Since: November 8, 2009 Posts: 4 Comments: 13537
134. Relix
Quoting serialteg:


relix = susan soltero


Lol =P
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Quoting CybrTeddy:
Recons on its way!
Link
Yep, this should be interesting even though I doubt that there is a low level circulation, let alone a closed one. However the remnants of Colin have rather strong divergence aloft, that should in turn translate to lower surface pressures.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting Orcasystems:


I have to admit.. it was hilarious... but I had to remove it... you had one foot over that imaginary line.

If you had just posted a link to it... that would have been OK.


Sorry Orcafans, problem corrected at Post #331.
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Interestly enough, the name Colin means "dark". Another meaning is "Victorious poeple"...maybe it will survive after all!
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Quoting ShenValleyFlyFish:
Most common last words of a Red Neck: "Hey y'all, look at me!"

2nd most common: "Git me a stick and I'll poke it."


THAT IS ONE OF THE FUNNIEST THINGS I HAVE EVER HEARD!!!!!

Thank you!!!

ROTFLMBO!!!!
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Quoting LariAnn:
To me, shouldn't the strength of named storms be taken into consideration, not just the number? Yes, we've had 3 named storms, but they have been weak sauce in terms of wind. My sister in law called to see how well we made it through Bonnie and I told her that if I hadn't seen it on the news, I wouldn't have known a storm was around. Virtually no wind and low to moderate rain is all we got, and the "eye" went just north of us. So three weak named storms by this time should not be the same as three strong named storms, no?


I agree 100%! Also, the lifespan of those weak storms was very short!
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Quoting 1celia70:
long range ....gfs model ...has storm on the middle to upper texas coast around august friday 19th....


Link?
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126. Skyepony (Mod)
Looking at ACE numbers.. Northern Hemisphere 82 so far, overall 61 behind for the year. West Pacific has only produced 14 ACE, it is 67 behind. Central Pacific has produced none. EPAC & Atlantic total is 68 which is slightly higher than the 62 expected. With 259 being total for the 3 basins expected by the end of the year, even with La Nina reducing C & EPAC #'s not sure if we'll reach the projected 178%, even with Atlantic left to make up the difference. ACE overall remains very depressed.
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remember,Ana of last year,it formed,died,and then reformed.
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Quoting mikatnight:
See post #329 in Orcasystems Blog for inovative new product from Eva Mendes.


I have to admit.. it was hilarious... but I had to remove it... you had one foot over that imaginary line.

If you had just posted a link to it... that would have been OK.
Member Since: Posts: Comments:
To me, shouldn't the strength of named storms be taken into consideration, not just the number? Yes, we've had 3 named storms, but they have been weak sauce in terms of wind. My sister in law called to see how well we made it through Bonnie and I told her that if I hadn't seen it on the news, I wouldn't have known a storm was around. Virtually no wind and low to moderate rain is all we got, and the "eye" went just north of us. So three weak named storms by this time should not be the same as three strong named storms, no?
Member Since: Posts: Comments:
Recons on its way!
Link
Member Since: July 8, 2005 Posts: 259 Comments: 24033
Surface observations suggest that pressures near 92L remain relatively high (lowest found is 1012mb) however, winds appear to be pretty gusty ranging to above 30 knots.
Member Since: September 2, 2009 Posts: 130 Comments: 21193


The GFS and CFS are in pretty good agreement...
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long range ....gfs model ...has storm on the middle to upper texas coast around august friday 19th....
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118. SLU
Station 41044

21.7n 58.7w

Time (ADT) - 11:37 am

WSPD - 34.2 kts

WDIR - SE ( 139 deg true )

1-minute 39mph winds. If the recon finds a close low then it's back to Colin.
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also what I find is that 92L= the Tropical wave at 72W well according to the 06Z and the v12Z surface maps it has either not moved or not moved very much at all
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Quoting Floodman:


Just keep your shower curtain handy...you'll be fine


Flood, Morning, so what cha think about 92L?
sheri
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Quoting Hardcoreweather2010:


99L went into Mexico


98L went into mexico was deactivated, and then was tagged 99L days later.
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My prediction for the 2010 Hurricane Season:

20 Named Storms

3 Hurricanes, 1 Major Hurricane
16 Tropical Storms
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How come we haven't seen more model runs for 92L ?
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Quoting divdog:
98l tag was a mistake it was for a system that went into mexico a couple of weeks ago


98L went into mexico and 99L formed over Mexico
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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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