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 MiamiHurricanes09:
looks good Miami lets see if the NHC will mention it on the next TWO Does it have any model support
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Quoting aquak9:


A'course, we could always have Hurricane Hollywood- the media would be all over it! :)


LMAO!
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760. xcool



HMMM
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GETTING NAILED IN FORT MYERS/SANIBEL AREA...AGAIIIIN....!!!!
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Good afternoon, What direction is XColins remnants heading?
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756. xcool


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Quoting angiest:


Viewing base velocity in grlevel3. If, and I do mean if, there is some sort of llc it appears very poorly defined. There is now sharp line between winds to and from the radar.


that is the poorly defined center that has up to this point been preventing Colin from closing off by the convection. The fact that it is becoming ill-defined increases the chances that Colin will be able to get his own circulation better organized
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unf- that's a little good news. Even the cayenne pepper plants are complaining about the heat and dry weather.
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Quoting Drakoen:
Something might be trying to get going just west of 30W above 10N in the Tropical Atlantic. The overshooting tops are becoming concentrated in that region and the cimss 850mb depicts a maxima around the aforementioned coordinates.
looks impressive !!
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739- eyewall- thanks. Man I like that link. Keep it handy for me, wouldja? And hey, that don't really look so bad. Not looking for coastal flooding and beach erosion, hey Sunday might just be a great day up here.
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question for storm if you are out there, that massive tropical wave off the cape verde islands, what are your thoughts ???? has an extensive amount of convection
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Quoting CybrTeddy:


Well, there already have been similarities to this years naming list and 2004's naming list.

Alex was the first named storm, and first Hurricane of the 2004 and 2010 season.

Bonnie hit Florida in 2004 as a TS, and hit Florida in 2010 as a TS.

Colin's going to recurve under a unseasonable trough, similar to Charley re-curving into Florida under a unseasonable trough (Although, Colin's going out to sea and won't be strong like Charley)

Similarities end there though


That is interesting. Let's hope that the similarities do end there as 2004 was an icredibly devastating and ruinous year.
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748. unf97
Quoting aquak9:
thanks unf.

All I wanted was some rain, and some high rough waves. Ah well. Maybe next time. :(


Actually, Aquak, our rain chances here in Jax will get better during the weekend as an upper level trough will swing through the U.S. East Coast, and a frontal boundary will sink southward into North Florida as the weekend progresses. GFS stalls that front, so hopefully that will provide the needed lift and mechanism to finally provide some much needed rain in the next few days.
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Quoting 757weather:
anyone else see a possible llc just north of St. Thomas, if not check PR radar and wind obs.


Viewing base velocity in grlevel3. If, and I do mean if, there is some sort of llc it appears very poorly defined. There is now sharp line between winds to and from the radar.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Massive tropical wave that appears to be consolidating near 30W 10 N like Drak just said looks impressive
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Shear's been lessening around Colin.
Member Since: July 8, 2005 Posts: 259 Comments: 23012
743. xcool
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Quoting ho77yw00d:


I can live with that my name can just move on out to sea lol


A'course, we could always have Hurricane Hollywood- the media would be all over it! :)
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Quoting jeffs713:

'tis the season.


Yup. As the weather channel would say: "the tropics are waking up"
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Quoting aquak9:
Jedkins- nice new avatar, can't hardly see the snakes tho cause of the t-shirt. Sigh...i can't believe you're all grown-up now.

ok, I read back, gotta coupla questions:

1. I don't see any rain coming for NE Fla from Colin. What am I missing?

2. Will I get any wave/ocean churning by Sunday from Colin on the NE Fla coast?

Thanks ya'll. :)


Waves don't look as good as yesterday, but there is always tomorrow....
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Quoting sky1989:

1998's Danielle


2004's Danielle

If that wave off of Africa does develop into Danielle, it may seem ironic but it has a good chance of taking a track similar to these two.


I can live with that my name can just move on out to sea lol
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thanks unf.

All I wanted was some rain, and some high rough waves. Ah well. Maybe next time. :(
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The TUTT has certainly taken it's toll on ex-Colin in terms of W-SW sheer but I'll give him an A+ for hanging in there.......Per some of the literature, the Atlantic TUTT is at it's stongest in July and August and starts to dissipate around September and October. My point is that with La Nina conditions forecast by the peak of the season, the TUTT will not be as much of an issue for storms near the Antilles during the peak in mid-September going into October.
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735. xcool


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Quoting Drakoen:
Something might be trying to get going just west of 30W above 10N in the Tropical Atlantic. The overshooting tops are becoming concentrated in that region and the cimss 850mb depicts a maxima around the aforementioned coordinates.

'tis the season.
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Shocker.. I'm not going to get any rain today for the 13th day in a row where everyone else is going to get rain.
Link
Member Since: July 8, 2005 Posts: 259 Comments: 23012
TSR went down 1 named storm on their forecast update.

19.1 to 17.8

I know, whats .8 of a storm.
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730. unf97
Quoting aquak9:
Jedkins- nice new avatar, can't hardly see the snakes tho cause of the t-shirt. Sigh...i can't believe you're all grown-up now.

ok, I read back, gotta coupla questions:

1. I don't see any rain coming for NE Fla from Colin. What am I missing?

2. Will I get any wave/ocean churning by Sunday from Colin on the NE Fla coast?

Thanks ya'll. :)


Hi aquak!

Answers
1. Yes, you are correct in that it is very likely that likely that NE FL will see virtually no effects from Colin as the storm should it re-organize and get designated again will get picked up by the upper level trough moving through off the East Coast this weekend.

2. There may be a slight swell at the beaches, but the system will well off the coast, so don't expect any substantial wave action this weekend Aqauk.
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my goodness- do that many of ya'll have me on iggy?

post 708
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anyone else see a possible llc just north of St. Thomas, if not check PR radar and wind obs.
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Quoting sky1989:

1998's Danielle


2004's Danielle

If that wave off of Africa does develop into Danielle, it may seem ironic but it has a good chance of taking a track similar to these two.


Well, there already have been similarities to this years naming list and 2004's naming list.

Alex was the first named storm, and first Hurricane of the 2004 and 2010 season.

Bonnie hit Florida in 2004 as a TS, and hit Florida in 2010 as a TS.

Colin's going to recurve under a unseasonable trough, similar to Charley re-curving into Florida under a unseasonable trough (Although, Colin's going out to sea and won't be strong like Charley)

Similarities end there though
Member Since: July 8, 2005 Posts: 259 Comments: 23012
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
U know, I keep seeing pple mention the "wave or Twave at 47W..... Am I missing something on the surface analysis map?



I'm not sure what, besides some ITCZ shower activity, u guys are seeing there....
Member Since: October 25, 2005 Posts: 19 Comments: 20729
Looks like Ex-Colin is establishing a convective current which is why we are seeing deep convection forming near the center.
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Quoting TexasHurricane:
Levi, do you think 92L could make its way in the GOM?


Maybe the southern Bay of Campeche, but it would have had to be developing by now to even threaten the US, so I wouldn't worry about it. It's going west and should only be a central America problem, unless it suddenly blows up tonight.
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Quoting Drakoen:
Something might be trying to get going just west of 30W above 10N in the Tropical Atlantic. The overshooting tops are becoming concentrated in that region and the cimss 850mb depicts a maxima around the aforementioned coordinates.
Ahhh, too many things to track (I better get used to it cuz it's gonna be a long August, Septemeber, and October.) I see what you mean about the overshooting tops, plenty of them associated with PGI24L.

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Quoting Snowlover123:


Looks like a tilted version of TS Tammy of '05.


WOW! It really does!
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1998's Danielle


2004's Danielle

If that wave off of Africa does develop into Danielle, it may seem ironic but it has a good chance of taking a track similar to these two.
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Quoting Hurricanes101:


93L soon?


Would be nice to get the BAMM suite on this.
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Quoting Drakoen:
Something might be trying to get going just west of 30W above 10N in the Tropical Atlantic. The overshooting tops are becoming concentrated in that region and the cimss 850mb depicts a maxima around the aforementioned coordinates.




ECMWF has been hinting at developing this.
Member Since: July 8, 2005 Posts: 259 Comments: 23012
Quoting sammywammybamy:


Looks like a tilted version of TS Tammy of '05.

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Quoting MiamiHurricanes09:
Very strong divergence associated with ex-Colin, that should translate into lower surface pressures.



Overshooting top developing with ex-Colin should help with the UVV.
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Quoting Drakoen:
Something might be trying to get going just west of 30W above 10N in the Tropical Atlantic. The overshooting tops are becoming concentrated in that region and the cimss 850mb depicts a maxima around the aforementioned coordinates.


93L soon?
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Quoting sammywammybamy:


And for the second time this season I have had a sat. picture of a poorly "organized" "system" appear under a spec of dirt on my monitor, and nearly made a pin-hole eye joke.
Member Since: August 26, 2006 Posts: 16 Comments: 4766

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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.