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 KEEPEROFTHEGATE:
thanks doc

i bet a lot are surprized by no change in numbers


i reckon wanting to stick to your guns...
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Quoting CybrTeddy:
the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday, and 92L probably does not have enough time over water to develop into a tropical depression

None of the models bring this into Nicaragua. It has 72 hours or so before a landfall in the Yucatan to develop. SHIPS brings this just below hurricane status. Great blog btw Doc!

I was wondering about that myself.
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Quoting AllStar17:
Does anyone have a good loop of the African wave?
Link
Member Since: June 17, 2006 Posts: 44 Comments: 5010
So storm should refer to Orca as "Big Mammal".
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Quoting CybrTeddy:
The blowup of convection is TUTT enhanced but could be enough to help Colin survive the shear.


92L has a better chance of developing to me, low shear, anti-cyclone, high TCHP and SSTs.


Don't sleep on the African wave.
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Quoting Orcasystems:


Oh sure.. take the conservative track like the NHC... right down the centre :)



+1 lol
Member Since: June 17, 2006 Posts: 44 Comments: 5010
Does anyone have a good loop of the African wave?
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The blowup of convection is TUTT enhanced but could be enough to help Colin survive the shear.


92L has a better chance of developing to me, low shear, anti-cyclone, high TCHP and SSTs.
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I am tracking three areas of interest, all of which have a shot at (re)development:

1. Remnants of Colin
2. Invest 92L
3. African Wave
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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
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Quoting SeniorPoppy:
Quoting sammywammybamy:

Let me Get your Crow Ready.

Do you Want it Well Done or Medium Rare?

If it comes to that... medium please. Right in between lol.



Oh sure.. take the conservative track like the NHC... right down the centre :)

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Quoting Orcasystems:


No, I am talking about this one that is sneaking in under the radar, just like 92 did.


Okay, i see
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Quoting StormW:


I was referring to Orca as Big Fish

sorry, lol, i thought it was a fish storm.
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Quoting PRweathercenter:

Are we talking about the same fish? I'm looking off the west coast of Africa, there seems to be a mid level spin forming over that Strong wave!


No, I am talking about this one that is sneaking in under the radar, just like 92 did.

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Quoting StormW:


I was referring to Orca as Big Fish


Isn't Orca a whale? LOL
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the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday, and 92L probably does not have enough time over water to develop into a tropical depression

None of the models bring this into Nicaragua. It has 72 hours or so before a landfall in the Yucatan to develop. SHIPS brings this just below hurricane status. Great blog btw Doc!

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Quoting Hardcoreweather2010:
The CSU numbers didn't remain the same . They lowered them

CO State Lowers forecast a Tad.. Named from 18-16 Hurricanes 10 to 9


Huh? In June, they called for 18/10/5; today's update calls for the same. I think you're looking at the post-7/31 forecast. That is, for what's left of the season as of that date.
Member Since: November 8, 2009 Posts: 4 Comments: 13597
Member Since: June 17, 2006 Posts: 44 Comments: 5010
Quoting sammywammybamy:

Let me Get your Crow Ready.

Do you Want it Well Done or Medium Rare?

If it comes to that... medium please. Right in between lol.

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Quoting StormW:


Been watching that Big Fish...waiting to get some better satellite analysis, but I'm watching it close. Gonna take a good look at it later.

Are we talking about the same fish? I'm looking off the west coast of Africa, there seems to be a mid level spin forming over that Strong wave!
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Good Morning Everyone..Oh what a heatwave we are having here in the south..

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

so colin is in unfavorable area for development but yet he is still intensifying..what would he do when actually gets in favorable area..explode into another Bill?? I just hope this does recurve..anyone know what the ships calling for intensity?
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Quoting Jeff9641:
No vacations now as we are in this for the long hawl buddy!
LOL...no vacations will be approved until after Nov. 30th! Unless you are Greek, you can go after Dec. 31st!
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Quoting SeniorPoppy:
I'm calling for 13 storms. I think that is reasonable. 18 seems a little far fetched IMO.


Let me Get your Crow Ready.

Do you Want it Well Done or Medium Rare?
Member Since: June 17, 2006 Posts: 44 Comments: 5010
Quoting StormW:


Been watching that Big Fish...waiting to get some better satellite analysis, but I'm watching it close. Gonna take a good look at it later.


Poor pottery... he has been measuring his rainfall in multiple inches per day, pretty soon he is going to convert to feet per week.
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The CSU numbers didn't remain the same . They lowered them

CO State Lowers forecast a Tad.. Named from 18-16 Hurricanes 10 to 9
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Quoting PRweathercenter:
Tropical Weather Forecast for Eastern Puerto Rico
Link
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Thanks Dr. Masters.

Dr. Masters said at the beginning of the season that things would start late, due to shear left over from El Nino. I am not smart on all the tools you guys look at, to know if that has really been the case, but so far he is looking pretty good on his forecast.

I enjoy everyone's play-by-play analysis here. So much better than trying catch the 2-3 minutes highlights on TV. And way more info that the NWS gives. Call this ESPN / Sport Talks of tropical weather!

Back to lurking.
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Pat just said quit counting numbers.
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did the nhc jump the gun on downgrading it however i still do not see a llc on satelite
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Thanks, Dr. Masters! So the real start of the season, begins.
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Quoting StormW:
StormW's forecast from June 01, 2010

Total Named Storms: 17-19
Hurricanes: 9-11
Intense Hurricanes: 4-5


So Far:

Named Storms: 3

Hurricanes : 1

Major Hurricanes : 0

Member Since: June 17, 2006 Posts: 44 Comments: 5010
"Tropical Storm Colin was ripped apart by wind shear yesterday,..." Last Friday, some of the models projected that it would be a Hurricane by now, or at least a strong TS! Do they factor in any possible future areas of wind shear when they make their forecast?! I guess not!

This is why you can't trust any model 100%.
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I'm calling for 13 storms. I think that is reasonable. 18 seems a little far fetched IMO.
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Thanks Jeff...interesting numbers
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Quoting Jeff9641:


CSU predicts 18 and that it is.


Yeah, 18 is enough.
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Thank You Dr. M; I know you have been very busy this year but are you expecting to post a Blog on the anticipated position of the A-B high and the implications on potential tracks this year as you have done in the past?.........Thank You.
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Quoting StormW:
Thanks Dr. Masters! You're not going on another vacation anytime soon...are you?


That last little Blob that passed over Pottery turned into 92, what do you think of this other little Blog heading at him now Storm, its bigger and better defined then the last one?
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Quoting StormW:
Thanks Dr. Masters! You're not going on another vacation anytime soon...are you?


+1
Member Since: June 17, 2006 Posts: 44 Comments: 5010
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Quoting KEEPEROFTHEGATE:
but the doc also stated i quote

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.



CSU predicts 18 and that it is.
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Member Since: June 17, 2006 Posts: 44 Comments: 5010
Wow. Scary season indeed. September must be on tap for an explosion of storms. Probabilities for US landfall is scary stuff.
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No vacations now as we are in this for the long hawl buddy!
Member Since: November 4, 2009 Posts: 0 Comments: 6577
TSR August Forecast

17.8/9.7/4.5
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AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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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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