CSU and TSR continue to predict a near-average hurricane season

By: Dr. Jeff Masters , 3:18 PM GMT on August 04, 2009

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A tropical disturbance embedded in the Intertropical Convergence Zone (ITCZ), near 9N 35W, is moving west at about 15 mph. The heavy thunderstorm activity associated with this tropical wave has changed little over the past 24 hours, and remains disorganized. This morning's QuikSCAT pass showed a moderate wind shift, but nothing resembling an organized surface circulation. Top winds were in the 20 - 30 mph range. Strong easterly winds are creating about 20 knots of wind shear over the wave, which is marginally conducive for development. The disturbance is about 300 miles south of the Saharan Air Layer (SAL), so dust and dry air should not hinder development over the next few days.

Given the disturbance's current lack of organization, combined with the presence of 20 knots of wind shear, any development should be slow to occur. The forecast wind shear along the storm's path over the next five days is predicted to remain at or below 20 knots, which should allow some slow development. Sea surface temperatures (SSTs) will warm from about 28°C to 29°C as the storm progresses westward. The GFS model has been indicating some development is possible in several of its runs over the past few days, but has not been consistent with this prediction. None of the other models show any development of the system. NHC is giving the disturbance a low (less than 30% chance) of developing into a tropical depression over the next two days, which is a good forecast. The GFS and ECMWF models predict the system will be approaching the northern Lesser Antilles Islands by Sunday. Both models forecast the development of a band of very high wind shear just to the north of the islands at that time, so the long-range survival of anything that might manage to develop is in doubt.

CSU forecast team continues to predict an average hurricane season
A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued August 4 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 10 named storms, 4 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 83% of average. 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 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their June forecast, which called for 11 named storms, 5 hurricanes, and 2 intense hurricanes. Their April forecast called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (27% chance, 31% chance is average) and the Gulf Coast (26% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane (37%; 42% is average).

The forecasters noted that while sea surface temperature anomalies have increased in the tropical Atlantic and surface pressures have fallen in recent weeks, which normally would favor higher hurricane activity, the presence of El Niño conditions in the Eastern Pacific should counteract these influences. They forecast that the current weak El Niño event will strengthen to a moderate event by September:

El Niño events tend to be associated with increased levels of vertical wind shear and decreased levels of Atlantic hurricane activity. Tropical Atlantic sea surface temperatures anomalies have warmed somewhat since our early June prediction and surface pressures have fallen somewhat. But, the negative influences of El Niño-induced strong Caribbean Basin and Main Development Region vertical wind shear typically dominate over surface pressure and sea surface temperature in the tropical Atlantic.



Figure 1. Change in Sea Surface Temperature anomaly (in °C) between July 2009 and May 2009. Most of the tropical Atlantic has warmed, relative to normal, over the past 2 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: weak to moderate El Niño conditions, and average tropical Atlantic and far northern Atlantic SSTs. Those four years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 1965, which had Category 3 Betsy that hit New Orleans; 1963, which had Category 4 Hurricane Flora that devastated Cuba; and 1957, which didn't have any hurricanes that hit hit land during the peak part of hurricane season. The mean activity for these four years was 9 named storms, 4 hurricanes, and 2 intense hurricanes--almost the same as the 2009 CSU forecast.

How accurate are the August forecasts?
The August forecasts by the CSU team have historically offered a skill of 45 -62% higher than a "no-skill" forecast using climatology (Figure 2). However, they are using a new forecast scheme this year, so it is difficult to judge how skillful this year's forecast might be.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

August 2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) also issued a new forecast today, and have increased their numbers by 20% from their June and July forecasts. TSR is also calling for a near-average season, predicting 12.6 named storms, 6.5 hurricanes, 2.8 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 103% of average. Their June forecast called for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are slightly above the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TSR predicts a 40% chance of an above-average season, 44% chance of a near-average season, and a 19% chance of a below-average season, as defined by ACE index. TSR rates their skill level as 51% above chance at forecasting the number of named storms, 60% skill for hurricanes, and 44% skill for intense hurricanes. These are far higher skill numbers than the June ones: 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.8 named storms will hit the U.S., with 1.6 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these August forecasts for U.S. landfalls is 25% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.1 named storms, 0.5 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites one main factor for their increased forecast: higher sea surface temperatures than expected over the tropical Atlantic, due to the fact that the trade winds over the Atlantic should be slower than originally anticipated. Faster than average trade winds create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling.

The CSU and TSR groups are done making forecasts for the coming hurricane season, but NOAA is still due to put out an August update.

I'll have an update on Wednesday.
Jeff Masters

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672. HadesGodWyvern (Mod)
oh no! rickrolling on a weather blog >.<
Member Since: Posts: Comments:
I stand by my woman geaux tigers lol...now back to tropics.....Hurricane Felicia is looking very impressive i feel it could reach major hurricane status pretty soon....I wonder if there is any relationship between the explosive activity in the Eastern pacific and the null activity in the Atlantic....
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Gee Whiz,
This is no fun at all,
teasing doesn't work here at all.
Must be a lot of serious Weather
Observer Scientist types on today.

I am amazed that nobody has come back
with a retort to my obvious baiting
with the "Charlotte important" comment.
Savannah, Charleston, Raleigh, folks,
you can't take that stuff lying down...??

C'mon folks fire away.
Charlotte has collapsed since the banks
there have failed anyhow...
Like the fall of Rome, haha.
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I am fascinated by the two areas of interest around our disturbance. We have the area of high low-level vorticity at 10N30W and the area of high upper-level vorticity ("the" blob) at 9N36W. It may be the result of the easterly shearing that has taken place today, but I'm not sure that 20-25kts could account for such a distance between the two areas of circulation. I am more inclined to think it is an artifact of how the original African wave came off the coast, with the robust (then) mid-level circulation trailing and coming off farther north than the main convective area.

If you look back at the old runs of the GFS, this is exactly what it predicted for this time today. It furthermore predicts that the 10N 30W blob, the one that is gaining convection right now, will become dominant, pulling the blob we've been watching all day into it, and THAT is what will develop.

It's an interesting scenario, and it seems like it would make for a potent system, between the low-level vorticity of the 30W system and the vast moisture envelope of the 36W one. Development farther north than expected also would give the system an edge in lifting out of the ITCZ.

I think a lot hinges on how well the two areas do this evening. If either of them develops, it basically has to pull in the energy of the other one. This evening we will probably get a good idea as to which one will win.
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Where is everyone
Member Since: May 16, 2009 Posts: 1 Comments: 1231


TS ENRIQUE
~780mi. SW of Cabo San Lucas
~15.0N
~118.4W
~60mph
~WNW@16mph
~998mb.

FELICIA
~1315mi. WSW of Cabo San Lucas
~12.4N
~126.6W
~80mph
~W@14mph
~985mb.
Member Since: July 14, 2009 Posts: 51 Comments: 1731
TXPN29 KNES 042117
SIMWIR

A. 09W (MORAKOT)

B. 04/2030Z

C. 22.5N

D. 134.0E

E. FIVE/MTSAT

F. T3.5/3.5/D1.5/24HRS

G. IR/EIR/SWIR/AMSU

H. REMARKS...DT=3.5 BASED ON .7 BANDING ON LOG10 SPIRAL. PT=3.5. MET=3.5
FOR RAPID DEVELOPMENT. FT BASED ON DT.

I. ADDL POSITIONS

04/1704Z 22.4N 134.2E AMSU


...SCHWARTZ

Member Since: July 21, 2009 Posts: 0 Comments: 552
Quoting kmanislander:
Sorry,couldn't resist it. LOL

lol it crossed my mind too...
Member Since: Posts: Comments:
Quoting gator23:

I rue hearing that pun
Sorry,couldn't resist it. LOL
Member Since: August 19, 2006 Posts: 0 Comments: 15816
Quoting AllStar17:


Woah! Calm down. -1

i was kidding to make a point
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Quoting futuremet:
-1

Fraudulent link


+1 for Rickroll

Quoting archer312:
OK then,
(this was supposed to be a Weather Blog, wasn't it?)

to add to this silliness on North-South states etc,
A Question-
why then is there no East Virginia?

(please don't answer, I know the reason,
it's a joke question)

As for the Carolina situation,
let me be clear, having been born and raised
in Charlotte NC (but live in FL now),
I can tell you all that Charlotte is the only
important and worthy place between Richmond and and Atlanta, or if you prefer, DC and NOLA.

So Charlotte clearly is the natural place to
locate the Panthers.
That's just obvious, folks... (haha)

So, back to the Wx,
will we or won't we have TS Ana
by the end of the week?


Ouch.
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Quoting gator23:

Tiny URL link of Rick Astley for the comedic purposes of Rick Rolling other users after they click the link thinking that it is an article on DR. Lyons beign fired
http://tiny.cc/nytimelyonsfiredLink


There sour puss


Woah! Calm down. -1
Member Since: June 29, 2009 Posts: 13 Comments: 5313
There is a reason I always show and link the URL...like this: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1269#commenttop
Member Since: Posts: Comments:
OK then,
(this was supposed to be a Weather Blog, wasn't it?)

to add to this silliness on North-South states etc,
A Question-
why then is there no East Virginia?

(please don't answer, I know the reason,
it's a joke question)

As for the Carolina situation,
let me be clear, having been born and raised
in Charlotte NC (but live in FL now),
I can tell you all that Charlotte is the only
important and worthy place between Richmond and and Atlanta, or if you prefer, DC and NOLA.
So Charlotte clearly is the natural place to
locate the Panthers.
That's just obvious, folks... (haha)

So, back to the Wx,
will we or won't we have TS Ana
by the end of the week?
Member Since: Posts: Comments:
Quoting futuremet:
-1

Fraudulent link

Tiny URL link of Rick Astley for the comedic purposes of Rick Rolling other users after they click the link thinking that it is an article on DR. Lyons beign fired
http://tiny.cc/nytimelyonsfiredLink


There sour puss i fixed it
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456 will you be giving an up date this afternoon on the tropics..
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Member Since: June 29, 2009 Posts: 13 Comments: 5313
655. HadesGodWyvern (Mod)
FKPQ30 RJTD 041800
TC ADVISORY
DTG: 20090804/1800Z
TCAC: TOKYO
TC: MORAKOT
NR: 7
PSN: N2230 E13335
MOV: W 09KT
C: 980HPA
MAX WIND: 50KT
FCST PSN +6HR: 05/0000Z N2235 E13240
FCST MAX WIND +6HR: 55KT
FCST PSN +12HR: 05/0600Z N2255 E13155
FCST MAX WIND +12HR: 55KT
FCST PSN +18HR: 05/1200Z N2310 E13110
FCST MAX WIND +18HR: 55KT
FCST PSN +24HR: 05/1800Z N2330 E13025
FCST MAX WIND +24HR: 55KT
RMK: NIL
NXT MSG: 20090805/0000Z =

---
hmm Claudette, what Japanese report you looking at?
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Quoting atmoaggie:

? Rolf ?
http://www.ucf.edu/athletics/ isn't going to tell me squat about pressure trends.
It will probably tell you how to fold under pressure.
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Ahora mismo, la de perturbacin del Atlntico parece estar cada vez mejor organizada. En el Satelite Tropical RAMSDIS (visible Loop), parece que hay cada vez mejor definido un de centro de circulacin en niveles bajos cerca de centro de formacin de 9N y 36W. Como algunas personas han publicado, el CIMSS 850mb de Vorticidad , tambin apoya esta conclusin, ya que muestra un aumento de nivel inferior de vorticidad con cada vez mejor definidon. Todos estos son indicios de que podramos estar viendo el desarrollo de un sistema.

En cuanto al futuro, es realmente difcil de determinar puesto que todos los pronosticos dependen de la progresin de la TUTT al norte de Puerto Rico. En la adicin; un rpido vistazo a la mayora de los modelos, sugieren que los vienos cortantes se mantendrn muy hostiles para el fin de semana en el norte del Caribe cuando la perturbacin se espera se mueva a las Islas de Sotavento. Pero, como todos sabemos, los modelos de computadora pueden cambiar y probablemente muchas veces antes de llegar a ese momento, por lo que por el momento, voy a observar la perturbacin y esprar a ver que pasa al acercarse a la regin del Caribe.

chsweatherman > blogger wundergound.com

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Hahaha, gator.
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.
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Quoting kmanislander:


"rue": verb. To bitterly regret a past event or action.

Pun intended !

I rue hearing that pun
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Quoting kmanislander:


"rue": verb. To bitterly regret a past event or action.

Pun intended !


Ahh, lol. Nahh he thought it was hilarious..
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Quoting HIEXPRESS:

Not sure what you expected them to say. There is information there. Sorry to waste your time by posting the link. Maybe this will tell us about the general pressure trends in the area, or confirm what QS is telling us about the general surface windfield.

? Rolf ?
http://www.ucf.edu/athletics/ isn't going to tell me squat about pressure trends.
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Quoting gator23:


NY times article on Dr. Lyons being fired
http://tiny.cc/nytimelyonsfiredLink


-1
Member Since: March 19, 2009 Posts: 0 Comments: 1421
Quoting SavannahStorm:




"The wave has obviously developed a LLC. Reports otherwise are obviously downcaster propaganda."



That guy was great! I miss him
Member Since: Posts: Comments:
Quoting alaina1085:


Ever rue? lol.. What does that mean?


"rue": verb. To bitterly regret a past event or action.

Pun intended !
Member Since: August 19, 2006 Posts: 0 Comments: 15816
WP092009 - Tropical Storm MORAKOT



Member Since: July 3, 2005 Posts: 424 Comments: 128259
Quoting kmanislander:


Does your friend ever rue having done the documentary ??.


Ever rue? lol.. What does that mean?
Member Since: Posts: Comments:
Quoting Patrap:
..."It does have a CDO !!,..It does have a CDO"!!..






"The wave has obviously developed a LLC. Reports otherwise are obviously downcaster propaganda."

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The Typhoon MORAKOT will pass very close to U.S. Interest in Okinawa.
Member Since: July 3, 2005 Posts: 424 Comments: 128259
Quoting Patrap:
..."It does have a CDO !!,..It does have a CDO"!!..


ur crackin me up patrap
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Quoting alaina1085:


Saweeeeet!! I have a friend who did a documentary on his life and he has this kangaroo for a pet and the roo flipped out on my friend and attacked him! LOL...

and now, back to the tropics... ahm.


Does your friend ever rue having done the documentary ??.
Member Since: August 19, 2006 Posts: 0 Comments: 15816
this wave could be 90E soon all so this could be are 1st big storm of the season,

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Quoting gator23:


Heck for that matter they thought Hugo would effect Miami and Andrew would disappate



...and that Ivan would hit Tampa.
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Quoting IKE:


I'll watch it at the next :50.


OK....but Dr. Lyons will probably change his mind again......he contradicted himself last night also.
Member Since: June 29, 2009 Posts: 13 Comments: 5313
Last Japanese report MORAKOT will be hurrican in 6h and CAT2 hurrican Landing in China south of Shanghai at 100mph or more.
Member Since: July 21, 2009 Posts: 0 Comments: 552
..."It does have a CDO !!,..It does have a CDO"!!..


Member Since: July 3, 2005 Posts: 424 Comments: 128259
Quoting AllStar17:


No problem! I usually just watch TWC for laughs, unless a storm is really coming. I like their hurricane coverage.

I have always found ther Hurricane coverage to suck. Wilma was approaching Naples and they were in Tampa "The storm really isnt that bad" duh you are in the wrong place."
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631. IKE
Quoting AllStar17:


No problem! I usually just watch TWC for laughs, unless a storm is really coming. I like their hurricane coverage.


I'll watch it at the next :50.
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too funny
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Quoting IKE:


Jeez...even Dr. Lyons said it needed to spin up.

Thanks for that information.


No problem! I usually just watch TWC for laughs, unless a storm is really coming. I like their hurricane coverage.
Member Since: June 29, 2009 Posts: 13 Comments: 5313
Quoting Patrap:
"So, since this storm would remain a week from becoming a real threat, just remain calm and just keep an eye on things".



"all is well there is nothing to see here"
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Quoting atmoaggie:


Youngest is more than 2 hours old at NDBC and over 100 miles away. (Didn't show squat 3 hours ago, either.)

Not sure what you expected them to say. There is information there. Sorry to waste your time by posting the link. Maybe this will tell us about the general pressure trends in the area, or confirm what QS is telling us about the general surface windfield.
Member Since: October 13, 2005 Posts: 4 Comments: 2156
"So, since this storm would remain a week from becoming a real threat, just remain calm and just keep an eye on things".


Member Since: July 3, 2005 Posts: 424 Comments: 128259
Quoting cg2916:

When is sunset?

It's happened already not sure of the time.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
623. IKE
Quoting AllStar17:
Dr. Lyons just said Felicia will continue west and remain a Cat. 1 over the next 3 or 4 days. Uh....hello Dr. Lyons.....the NHC forecast takes it to major hurricane status. He also said he is watching our distubance, but if it does not spin up now it will head W / WNW into the west winds that will "kill" it. The shear forecast 456 posted a bit ago showed lessening shear in the Caribbean. Steve also said if it were to spin up now, it may fight against those west winds. Earlier in the blog, someone stated the presence of an anticyclone...is that true that there is one near?


Jeez...even Dr. Lyons said it needed to spin up.

Thanks for that information.
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Quoting cchsweatherman:
In regards to Hurricane Felicia, even though the computer models remain in remarkable consensus bringing the storm in the general direction of the Hawaiian Islands, its very important to remember to remain vigilant yet objective. Just remember Hurricane Ike last season when it appeared that it would smash into South Florida but would make landfall in Texas. Computer models and projected paths will change in time, so now is not the time to panic or become excited (depending upon how you feel about storms). So, since this storm would remain a week from becoming a real threat, just remain calm and just keep an eye on things.


Heck for that matter they thought Hugo would effect Miami and Andrew would disappate
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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.