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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Blog dead all of the sudden :(
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971. HadesGodWyvern (Mod)
well that was uncalled for.. =/
Member Since: May 24, 2006 Posts: 50 Comments: 45301
969. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Warning #13
TROPICAL STORM GONI (T0907)
9:00 AM JST August 5 2009
=========================================

Subject: Category One Typhoon Overland South China

At 0:00 AM UTC, Tropical Storm Goni (994 hPa) located at 21.9N 112.3E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The storm is reported as moving west slowly

RMSC Dvorak Intensity: T2.0

Gale-force Winds
================
120 NM from the center

Forecast and Intensity
=========================
24 HRS: 22.0N 110.7E - Tropical Depression
Member Since: May 24, 2006 Posts: 50 Comments: 45301
LOL..your questions get the answers they deserve sport.
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Heres more on the subject,..

New Saffir-Simpson Scale for 2009
Topic Author: Rodney Harris


The National Hurricane Center (NHC) has announced it will be removing the storm surge and flooding references from the Saffir-Simpson Hurricane Scale -- on an experimental basis -- for the 2009 Tropical Cyclone season.

The modified scale will be called the "Saffir-Simpson Hurricane Wind Scale". I emphasize wind because that's what the NHC will attempt to focus on when defining storms using this scale -- nothing more.

Scientists have found that the storm surge and flooding information included in the current scale can often be inaccurate and lead to a misconception on how strong a storm will be. This was evident when residents admitted they didn't plan on evacuating during Ike, because it was "just a category 2 storm.
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Quoting 19N81W:
amazing how nothing can develop this year even when conditions are favourable...I stand by my bet no named storms making landfall in the US..


So you are saying that we need to watch carefully for the UNNAMED storms instead?
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evening everyone...surfmom..did i hear a swell...lol...lord haven't heard that in a while..
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Out fer "RESCUE me",..my Fav,..Dennis Leary iz da man.
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Quoting nrtiwlnvragn:


Your "new" scale is going to have to take into account where a hurricane strikes. Those hurricanes landfalling in different locations would not have the same impact.


It nots my scale blogger,and Logic would dictate your presumption,..

And of course a Cane landfalling in 2 different areas would have different effects as to coastline and elevation and shape.
Thats a given even with thew SSS.

So I dont know what point yer trying to deliver.
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Quoting Patrap:
The SSS was designed for Wind Loading on Structures and is a Poor Scale for quantifying Impact.Esp as to Surge values.
The SSS dosent take into account a Storms size which is a relative factor in most Hurricanes,. A Small compact CAt-5 dosent have the impact a LARGE Cat2-5 in wind speed as Rita,Ike and Katrina showed us well.
There is a Big Push to replace the SSS with a more Relavent scale,but that is many years away unfortunately.


Your "new" scale is going to have to take into account where a hurricane strikes. Those hurricanes landfalling in different locations would not have the same impact.
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Quoting leftovers:
long rg surf report has a swell hitting north carolina could this be our soon to be invest http://www.stormsurf.com/

hummmmmmmmmmm?
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00z CMC

Visible GIF
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957. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Warning #15
SEVERE TROPICAL STORM MORAKOT (T0908)
9:00 AM JST August 5 2009
=========================================

Subject: Category Two Typhoon In Sea South of Japan

At 0:00 AM UTC, Severe Tropical Storm Morakot (975 hPa) located at 22.6N 133.3E has 10 minute sustained winds of 50 knots with gusts of 70 knots. The storm is reported as west-northwest slowly

RSMC Dvorak Intensity: T3.5

Gale-force Winds
================
475 NM from the center in the southern quadrant
200 NM from the center in the northern quadrant

Forecast and Intensity
=========================
24 HRS: 23.9N 129.0E - 65 knots (CAT 3/Typhoon)
48 HRS: 25.3N 124.8E - 75 knots (CAT 3/Typhoon)
72 HRS: 26.3N 121.7E - 75 knots (CAT 3/Typhoon)
Member Since: May 24, 2006 Posts: 50 Comments: 45301
The SSS was designed for Wind Loading on Structures and is a Poor Scale for quantifying Impact.Esp as to Surge values.
The SSS dosent take into account a Storms size which is a relative factor in most Hurricanes,. A Small compact CAt-5 dosent have the impact a LARGE Cat2-5 in wind speed as Rita,Ike and Katrina showed us well.
There is a Big Push to replace the SSS with a more Relavent scale,but that is many years away unfortunately.
Member Since: July 3, 2005 Posts: 424 Comments: 128275
NAO positive=troughiness=shear
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954. flsky
Does the fact that the two storms on either side of the Pacific signify that they have formed b/c of the shallowness of the water close to shore?
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Quoting Drakoen:


Shear looks to drop over the MDR region in about a week or soLink


Unless you find a giant broom to sweep all this dry air and saharan dust of the atl it will be tough.
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Quoting stormpetrol:
Let me tell you all something about Gilbert, Gilbert passed basically nearly as close as Hurricane Ivan to Grand Cayman 2004, Gilbert was in 1988, Gilbert had wind gusts at 158mph in Grand Cayman if I remeber correctly and to me Gilbert was just a Summer squall compared to Ivan of 2004, electricity was out at the most 48 hours for most in Gilbert , for me in Ivan it was 5 weeks , some nearly 3 months. I personally think they need review the scale on which hurricanes are graded, some are way underrated and some are way overrated , just my personal opinion from experiencing 2 of the 10 most intense Atlantic Hurricanes on record.


This just goes to show you that intensity does not always indicate the amount of damage. Another good example of this is Mitch.
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NAO forecast

Member Since: March 19, 2009 Posts: 0 Comments: 1421
Quoting hurricane23:


Hey Koritheman!

ITCZ has somewhat picked up over the past week or so, only small issue along with dry/stable air is 30-40kt shear blowing the caribbean and south western atlantic.


Shear looks to drop over the MDR region in about a week or soLink
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Quoting KoritheMan:


TUTT has been a dominant feature across the Caribbean this year.


Thats indeed correct.
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amazing how nothing can develop this year even when conditions are favourable...I stand by my bet no named storms making landfall in the US..
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Atlantic, King TUTT
Member Since: July 3, 2005 Posts: 424 Comments: 128275
.
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Quoting KoritheMan:


Listen to my voice. Relax. Listen to my voice.


Hey Koritheman!

ITCZ has somewhat picked up over the past week or so, only small issue along with dry/stable air is 30-40kt shear blowing the caribbean and south western atlantic.
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Quoting hurricane23:
Dry/stable air has really been the dominant feature thus far this hurricane season.Fast westerlies continue along most of the caribbean which again is very typical of el nino years.Only thing worth mentioning tonight if its even worth a mention is the current wave across the central altantic which at this time remains disorganized with no signs of imminent development.

Adrian


TUTT has been a dominant feature across the Caribbean this year.
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Its coming!

Member Since: March 19, 2009 Posts: 0 Comments: 1421
941. JRRP
Quoting KoritheMan:


Listen to my voice. Relax. Listen to my voice.

jejejeje
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Quoting FLWeatherFreak91:
Although the wave is currently losing a lot of its convection and may not develop at all, you can easily see how it is moistening up the tropical atlantic very well. It is plowing very moist are westward and pushing the dry air out of the way to the north and the south. Any wave exiting the coast of Africa behind this wave will find a much improved atmosphere for development. Plus, MJO will increase in the Atlantic later next week, increasing more the chances of development.
Looks like it is absorbing the energy from the wave behind it..
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Let me tell you all something about Gilbert, Gilbert passed basically nearly as close as Hurricane Ivan to Grand Cayman 2004, Gilbert was in 1988, Gilbert had wind gusts at 158mph in Grand Cayman if I remeber correctly and to me Gilbert was just a Summer squall compared to Ivan of 2004, electricity was out at the most 48 hours for most in Gilbert , for me in Ivan it was 5 weeks , some nearly 3 months. I personally think they need review the scale on which hurricanes are graded, some are way underrated and some are way overrated , just my personal opinion from experiencing 2 of the 10 most intense Atlantic Hurricanes on record.
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Dry/stable air has really been the dominant feature thus far this hurricane season.Fast westerlies continue along most of the caribbean which again is very typical of el nino years.Only thing worth mentioning tonight if its even worth a mention is the current wave across the central altantic which at this time remains disorganized with no signs of imminent development.

Adrian
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Interesting page on the cyclone records, listed are Atlantic stats below. Link way below.

Most intense Atlantic hurricanes
Intensity is measured solely by central pressure Rank Hurricane Season Min. pressure
mbar (hPa)
1 Wilma 2005 882
2 Gilbert 1988 888
3 "Labor Day" 1935 892
4 Rita 2005 895
5 Allen 1980 899
6 Katrina 2005 902
7 Camille 1969 905
Mitch 1998 905
Dean 2007 905
10 "Cuba" 1924 910
Ivan 2004 910
Source: U.S. Department of Commerce

Greatest Travels
Sources: NOAA [8], [9][10]
Distance
(Miles) Name Date
7500 Hurricane Faith 1966
6500 Hurricane Alberto 2000
6000 Hurricane Cleo 1964
Hurricane Chloe 1967
5500 Hurricane Carrie 1957
Hurricane Flora 1963
Hurricane Dora 1964
Atlantic Records

Pacific
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Quoting eye:
RIP wave, it is poofing....


Not really, its expected with weaker systems like that. You and quite a few other people said the same thing about loads of other storms including me for the past years and we always get proven wrong even with systems this year.
Just takes patience, I doubt it will develop before it reaches the Islands. Looking at the GFS shear model shear should be quite low for cyclone genesis by the time it should get there. The conditions are in place, right now we have to see if it will take them. 50/50 for me atm. Its just a guessing game. Its not in a good enviroment right now with the wind shear but it looks to be letting up.
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Quoting JRRP:

Do you try to hypnotize me?


Listen to my voice. Relax. Listen to my voice.
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934. JRRP
Quoting BenBIogger:


Do you try to hypnotize me?
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Member Since: March 19, 2009 Posts: 0 Comments: 1421
Although the wave is currently losing a lot of its convection and may not develop at all, you can easily see how it is moistening up the tropical atlantic very well. It is plowing very moist are westward and pushing the dry air out of the way to the north and the south. Any wave exiting the coast of Africa behind this wave will find a much improved atmosphere for development. Plus, MJO will increase in the Atlantic later next week, increasing more the chances of development.
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Quoting SevereHurricane:


Yea,
In Katrina I had 12 Feet of water in my home for 3 and a half weeks, Then Rita caused a portion of my roof to collapse.


I went through Andrew in 92. No, fun at all...I've been through all the others thats come through the Homestead area.
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Sorry, confused and old :)
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Was that the recess over Bell ringing?
Member Since: July 3, 2005 Posts: 424 Comments: 128275
Quoting Patrap:


Surge from Hurricane Katrina penetrated 6 miles inland in some Hancock and Harrison County areas in Mississippi.


I remember seeing pictures of the water crossing over I-10 in Mississippi. Well inland too.
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927. Skyepony (Mod)
EDITORIAL: Human face of summer of fireBC is burnin up. People are staying. Sounds like some towns are about to get hit..
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Also dont dismiss tropical storms either

I believe those who lived in Houston during Allison and those in Central Florida after Fay would tell you that a tropical storm can be just as bad.
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Quoting hahaguy:


He said to that date.


He also said that it surpassed Gilbert, and it did not.
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Quoting Ossqss:


The strongest ATL basin cane to that date, surpassing Gilbert. 888 mb if memory server me right.


Surprisingly, Mitch's central pressure never went below 905 mb. Its winds weren't even in excess of Gilbert's, either.
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Quoting BurnedAfterPosting:


That was Wilma, not Mitch

Mitch is tied for 7th with Camille and Dean

Most of the deaths attributed to Mitch was due to massive amounts of flooding in Honduras after the storm made landfall there


He said to that date.
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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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