Average hurricane season foreseen by CSU, NOAA, and TSR

By: Dr. Jeff Masters , 4:45 PM GMT on June 02, 2009

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A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued June 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 11 named storms, 5 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 88% 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 April forecast, which 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 (28% chance, 31% chance is average) and the Gulf Coast (28% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.

The forecasters cited several reasons for an average season:

1) Sea surface temperature (SST) anomalies in the tropical Atlantic are quite cool. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Substantial cooling began in November 2008 (Figure 1), primarily due to a stronger than average Bermuda-Azores High that drove strong trade winds. These strong winds increased the mixing of cool waters to the surface from below, and caused increased evaporational cooling.

2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. This occurs because El Niño conditions bring higher wind shear over the tropical Atlantic. The CSU team expects the current neutral conditions may transition to El Niño conditions (70% chance) by this year's hurricane season. I discussed the possibility of a El Niño conditions developing this year in a blog posted Friday.


Figure 1. Change in Sea Surface Temperature anomaly between November 2008 and 2009. Most of the Atlantic has cooled significantly, relative to normal, over the past 7 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to slightly warm ENSO conditions, slightly below-average tropical Atlantic SSTs, and above-average far North Atlantic SSTs during April-May. Those five years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1965, which had Category 3 Betsy that hit New Orleans; 1960, which had two Category 5 hurricanes, Ethyl and Donna; and 1959, which had Category 3 Hurricane Gracie, which hit South Carolina. The mean activity for these five years was 10 named storms, 6 hurricanes, and 2 intense hurricanes, almost the same as the 2009 CSU forecast.

How accurate are the June forecasts?
The June forecasts by the CSU team have historically offered a skill of 20 - 30% higher than a "no-skill" forecast using climatology (Figure 2). This is a decent amount of skill for a seasonal forecast, and these June 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 June forecast uses the same formula as last year's June forecast, which did quite well predicting the 2008 hurricane season (prediction: 15 named storms, 8 hurricanes, 4 intense hurricanes; observed: 16 named storms, 8 hurricanes, 5 intense hurricanes). An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.44 to 0.58 for their June forecasts, which is respectable.


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.

NOAA's 2009 hurricane season forecast
The National Oceanic and Atmospheric Administration (NOAA), issued its 2009 Atlantic hurricane season forecast on May 21. NOAA anticipates that an average season it most likely, giving a 50% chance of a near-normal season, 25% chance of an above-normal season, and a 25% chance of a below-normal season. They give a 70% chance that there will be 9 - 14 named storms, 4 - 7 hurricanes, 1 - 3 major hurricanes, and an Accumulated Cyclone Energy (ACE) in the 65% - 130% of normal range. The forecasters cited the following main factors that will influence the coming season:

1) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO).

2) There will either be an El Niño event or neutral conditions in the Equatorial Eastern Pacific. An El Niño event should act to reduce Atlantic hurricane activity. However, our skill at predicting an Niño in late May/early June is poor, so there is high uncertainty about how active the coming hurricane season will be.

3) Cooler-than-average SSTs are currently present in the eastern tropical Atlantic. These cool SSTs are forecast to persist through into August-September-October (ASO). ASO SSTs in the eastern tropical Atlantic have not been below average since 1997. Cooler SSTs in that region are typically associated with a reduction in Atlantic hurricane activity.

Thus, they expect that even though we are in an active hurricane period, the presence of an El Niño or cool SSTs in the eastern Atlantic could easily suppress activity, making a near-average season the most likely possibility. They note that two promising computer models, the NOAA CFS model and the European Center for Medium-Range Weather Forecasts (ECMWF) Global Climate Model System 3, both forecast the possibility of a below-average hurricane season.

2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) has joined the ranks of NOAA and Colorado State University in calling for near-average activity. The latest TSR forecast issued June 4 calls 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 close to the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes, and are sharp reduction from their April forecast of 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 50% chance that this season will be in the bottom 1/3 of years historically, and a 40% chance that U.S. landfalling activity will be in the lowest 1/3 of years historically. TSR gives a 32% chance of a near-normal season, and a 17% chance of a below normal season. TSR rates their skill level as 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.2 named storms will hit the U.S., with 1.3 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 April forecasts for U.S. landfalls is 7 - 18% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 0.9 named storms, 0.4 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their reduced forecast: a large and unexpected cooling of sea surface temperatures in the tropical Atlantic, and warmer SSTs in the Equatorial Eastern Pacific (which might lead to an El Niño event that will bring high wind shear to the Atlantic). TSR expects faster than than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.83 meters per second (about 1.7 mph) faster than average in this region, which would 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. TSR forecasts that SSTs will cool an additional 0.3°C compared to average over the MDR during hurricane season.

Air France crash
The Air France Flight 447 A330 aircraft that disappeared over the mid-Atlantic Ocean yesterday definitely crossed through a thunderstorm complex near the Equator, according to a detailed meteorological analysis by Tim Vasquez. He concludes that "the A330 would have been flying through significant turbulence and thunderstorm activity for about 75 miles (125 km), lasting about 12 minutes of flight time" but that "complexes identical to this one have probably been crossed hundreds of times over the years by other flights without serious incident". See also the excellent CIMSS satellite blog for more images and analysis of the weather during the flight.

Invest 92
NHC is tracking a storm near the Azores Islands (Invest 92L) that is probably the remnants of the core of an extratropical cyclone that closed off some warm air at the center. The system has developed some heavy thunderstorm activity near its center, making this a hybrid storm. However, with ocean temperatures near 62°F (16°C), this storm has little chance of becoming a named subtropical storm.

Jeff Masters

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Quoting WPBHurricane05:


Amazing, huh? These extratropical/subtropical systems are pretty complex.


No kidding. I always enjoy watching low pressure systems spin up.
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What if 3 out of the 5 hurricanes forcasted hit land?

Just takes 1 over your community. Have a great evening. Adrian
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Quoting jeffs713:

Its still over 16C water, though.


Amazing, huh? These extratropical/subtropical systems are pretty complex.
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Quoting Drakoen:
92L looks to be getting tropical characteristics. Probably too late though:

Its still over 16C water, though.
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if 92L were to be declared, it would beat Vinces record.
Member Since: July 8, 2005 Posts: 259 Comments: 24164
Quoting OSUWXGUY:


Yeah...hopefully no repeat of Andrew...

Andrew was a Cape Verde storm though...and with the ITCZ so far south this year it will be harder for waves to get going - between interaction with South America and reduced Coriolis Effect


Andrew was technically a cape verde style, but only started getting organized north of Hispaniola...
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Quoting Stormchaser2007:
LOL...


02/1800 UTC 44.0N 24.1W ST3.0 92L


Holy crap.
Member Since: July 8, 2005 Posts: 259 Comments: 24164
92L looks to be getting tropical characteristics. Probably too late though:
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Quoting Squid28:


Some of the guppies are stil in service a second "generation"/refurbed model is loaded with meterologial instruments and a bunch of other stuff studying upper atmosphere related issues. A couple others are still performing their original duties of transportation. I believe all of them are now jet powered though. I see them fly into and out of Ellington Field a few times a year


Ellington is actually a NASA terminal... that is one of their main airports from what I understand and they actually store some of the planes there.
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Big storms are starting to pop up all around Florida.

Link
Member Since: April 26, 2009 Posts: 3 Comments: 3667
That band in SE TX looks more like an outflow boundary pushing out to the GOM, possibly enhanced by a seabreeze front. I'm sure the thing in the GOM stirred up the atmosphere enough to start things off, though.

As for the GOM feature itself, I'm not quite sure to make of it on radar. It is showing some persistence, but the storm cells themselves look to be feeding off each other, rather than feeding off the water's heat content. Looks more baroclinic than tropical.
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Quoting Patrap:
Not sure of the Guppys whereabouts,but I believe some are still in service


Some of the guppies are stil in service a second "generation"/refurbed model is loaded with meterologial instruments and a bunch of other stuff studying upper atmosphere related issues. A couple others are still performing their original duties of transportation. I believe all of them are now jet powered though. I see them fly into and out of Ellington Field a few times a year
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Quoting hurricanemaniac123:
Wait a second, why hasn't 92L become Ana yet? It already has 50 mph winds!


As it is still slightly attached to a frontal low.
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zoomed in SeTX
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Quoting OSUWXGUY:


Yeah...hopefully no repeat of Andrew...

Andrew was a Cape Verde storm though...and with the ITCZ so far south this year it will be harder for waves to get going - between interaction with South America and reduced Coriolis Effect

That is true, but I think more of a concern is that anything that moves into that region will find a favorable environment, and we could be in for some suprises along the east coast this year. in the past couple of years we haven't really seen really strong systems along the southeast us coast. We haven't had a major hurricane in those waters in quite awhile.
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Houston Long Range Radar
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Quoting RitaEvac:


Someone like you would of course believe it...


Believe what?
Member Since: April 26, 2009 Posts: 3 Comments: 3667
All i know it the Gulf is feed ign a band that is on land right now... possibly from the ridge and it is pumulting SeTx...
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GOM IR Image LOOP


Current NOLA Radar
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plz no pot stirring.. the blog has been very civil this afternoon
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Hey everybody I have been looking at the blob in the GOM. Any takers on what could this be in the future?

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Quoting Patrap:
The reason one dosent tailgate a 747 in a Cessna..Notice the wake vortice's that the smoke shows well,...Hong Kong Approach.

Looks familiar eh?



OMG! Lets name it! It has an EYE!

Honestly though, I like the idea of Extratropical Storm Isnot.
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A pinhole eye !!
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Quoting hurricane23:
Southeast florida has seen some big storms come through here in really slow seasons 1929 hurricane, Betsy, and Andrew all struck SE Fl.during below average activity .The 1935 cane also hit in a slow season.Something to think about hoepfully all the slow predictions wont put folks to sleep with hurricane preps.


When people here "slow season" they tend to let their guard down.
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Quoting CatastrophicDL:
Pat, does the guppy have a technical name or is it not on that list?


Super Guppy Info
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Southeast florida has seen some big storms come through here in really slow seasons 1929 hurricane, Betsy, and Andrew all struck SE Fl.during below average activity .The 1935 cane also hit in a slow season.Something to think about hoepfully all the slow predictions wont put folks to sleep with hurricane preps.
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Thats kewl CATDL
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The reason one dosent tailgate a 747 in a Cessna..Notice the wake vortice's that the smoke shows well,...Hong Kong Approach.

Looks familiar eh?

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Not sure of the Guppys whereabouts,but I believe some are still in service
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Pat, does the guppy have a technical name or is it not on that list?
Member Since: September 3, 2007 Posts: 3 Comments: 1519
I dont yet know how to link. but if you want to see something funny, look at wilmington nc radar. We have one tiny lone thunderstorm that looks like it came from nowhere putting out some heavy thunder to my west
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Everytime I read someone else's Hurrican forecast the news just gets better and better. Even though it is typically slow for us in South Fla for hurricanes lately anyway, it looks to be over early for us here this year. Most likely July! I will take that good new anyday. Sucks for Home Depot and Lowe's though!!! LOL
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Quoting CatastrophicDL:

Only if it is tomorrow so I'm on track to win Ossqss contest. :o)


I'll name anything that looks interesting on the 14th lol.
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Isso or Isnot would be my top picks
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Hill AFB 2009 Open House/Air Show Website


STATIC DISPLAY AIRCRAFT

B-1B Bomber Ellsworth AFB, SD




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Not a bad idea, Jeff-A what-would-you name-it contest.

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Quoting jeffs713:


5 bucks says people still want it named.

Only if it is tomorrow so I'm on track to win Ossqss contest. :o)
Member Since: September 3, 2007 Posts: 3 Comments: 1519
Quoting SomeRandomTexan:
which show are u going to CDL?

The big one for National Air Force Week at Hill AFB in Utah.
Member Since: September 3, 2007 Posts: 3 Comments: 1519
Send me 5$
I'll name it!
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Quoting beell:
...A warm seclusion is the mature phase of the extratropical cyclone lifecycle. This was conceptualized after the ERICA field experiment of the late 1980s, which produced observations of intense marine cyclones that indicated an anomalously warm low-level thermal structure, secluded (or surrounded) by a bent-back warm front and a coincident chevron-shaped band of intense surface winds...

Warm seclusions may have cloud-free, eye-like features at their center (reminiscent of tropical cyclones), significant pressure falls, hurricane force winds, and moderate to strong convection. The most intense warm seclusions often attain pressures less than 950 millibars (28.05 inHg) with a definitive lower to mid-level warm core structure.[27] A warm seclusion, the result of a baroclinic lifecycle, occurs at latitudes well poleward of the tropics.
Link


5 bucks says people still want it named.
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Multiplatform Tropical Cyclone Kinetic Energy and Intensity



Digital Dvorak 92L
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...A warm seclusion is the mature phase of the extratropical cyclone lifecycle. This was conceptualized after the ERICA field experiment of the late 1980s, which produced observations of intense marine cyclones that indicated an anomalously warm low-level thermal structure, secluded (or surrounded) by a bent-back warm front and a coincident chevron-shaped band of intense surface winds...

Warm seclusions may have cloud-free, eye-like features at their center (reminiscent of tropical cyclones), significant pressure falls, hurricane force winds, and moderate to strong convection. The most intense warm seclusions often attain pressures less than 950 millibars (28.05 inHg) with a definitive lower to mid-level warm core structure.[27] A warm seclusion, the result of a baroclinic lifecycle, occurs at latitudes well poleward of the tropics.
Link
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Interesting..BD Image.
Looking a Lil on the STS Side now.

Time of Latest Image: 200906021830
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Quoting hurricanemaniac123:


I mean why isn't it a STS or TS?


Extra-tropical.
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92L Time of Latest Image: 200906021845

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Quoting hurricanemaniac123:


I mean why isn't it a STS or TS?


It's extra tropical
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Quoting StSimonsIslandGAGuy:
The director of the Australian meteorological bureau at the turn of the 19th/20th centuries used to name tropical cyclones after political figures he did not like...giving him the chance to describe them as "causing great distress" or "wandering aimlessly across the Pacific"


Now that's funny! wandering aimlessly ha ha
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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.