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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I think we could have a few invests this month. I really dont think any tropical storm will form due to the high shear.

The GFS keeps a nice block of high shear in the Caribbean through mid June.

Member Since: June 9, 2007 Posts: 4 Comments: 15889
fair enough, JLPR, you're right about that. If I remember it, I'll remind you of starting one next year. ;-)
This year I've been too busy during April and May so that I totally forgot to check out the blogs regularly, shame on me *lol*
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18Z Multi-Model

Member Since: July 3, 2005 Posts: 423 Comments: 128236
Quoting Stormchaser2007:


From what? Theres nothing out there.


I have a hunch, although my hunches seem to go 50/50 I just have a gut feeling.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Member Since: June 9, 2007 Posts: 4 Comments: 15889

AOI #1

AOI #2

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305. JLPR
Quoting Stormchaser2007:


From what? Theres nothing out there.


who knows
systems pop up anywhere xD
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sorry for the spelling errors, my finger was faster than my brain.
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Quoting 69Viking:


Yeah the rain figures to keep the water in my ditch long enough to hatch a good crop of tadpoles this year just like in 2005, hmmm, another wet spring in Florida and we remember how that turned out!


Bite your tongue!

Sorry, impulse.

OK, back to catching up, which will eventually bring me back to here.
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302. JLPR
Quoting taistelutipu:
Hi JLPR, good to see you around. I wanted to ask if you are going to do another forecasting challenge like you did last year. It was great fun. So if it is not too much bother for you I'd be looking forward to have one this year as well.


I dont think so xD im a little too late for that we are already on Hurricane season =| maybe next year
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Quoting MrstormX:
Well that about closes the book on 92L but would not be suprised if we see a 93L by weeks end.


From what? Theres nothing out there.
Member Since: June 9, 2007 Posts: 4 Comments: 15889
GOM IR Image Loop


18Z NAM
Member Since: July 3, 2005 Posts: 423 Comments: 128236
on a commercial plane, the radar is the only part of the aircraft thatcannot be protected from lightning strikes. so if laightning struck the craft, the rafar would have been fried and then they could not avoid any of the storms.
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Well that about closes the book on 92L but would not be suprised if we see a 93L by weeks end.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Hi JLPR, good to see you around. I wanted to ask if you are going to do another forecasting challenge like you did last year. It was great fun. So if it is not too much bother for you I'd be looking forward to have one this year as well.

As for 92L, wow, didn't expect to see anything at that latitude on cold water like this.
But I don't think it will be named though, we are not in 2005 when hurricanes did what they wanted and defied logic (remember Epsilon). However, it could still bring some rain and stormy conditions to Spain and Portugal as a non-tropical low.
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Good evening everyone,

The Portlight team is preparing to assist with clean up/rebuilding in Holly Hill, Fl. Please learn more about how you may be able to help!
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Quoting extreme236:


Only hope for an upgrade would be a convective increase. Some of that has happened it appears, but not enough.


Yep. Convection is on a slight increase. Just like you said though, too little too late.

Member Since: June 9, 2007 Posts: 4 Comments: 15889
Quoting GeoffreyWPB:
Don't planes have radar where they can divert avoid adverse weather conditions?


The planes are almost always able to fly through the ITCZ without trouble. They probably didnt think much of it at the time.
Member Since: June 9, 2007 Posts: 4 Comments: 15889
92L is on its death bed, its been put on life support a breakthrough now would be a miracle
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting Stormchaser2007:
Just as I thought. No upgrade without convection.

IT IS ACCOMPANIED BY WINDS OF 45-50 MPH CLOSE TO THE
CENTER BUT IS ASSOCIATED WITH ONLY LIMITED THUNDERSTORM ACTIVITY.


And yet why do they let storms keep their names after they have been stripped bare of all clouds greater than 10 feet high?

The whole naming system is completely messed up.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Don't planes have radar where they can avoid adverse weather conditions?
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Quoting Stormchaser2007:
Just as I thought. No upgrade without convection.

IT IS ACCOMPANIED BY WINDS OF 45-50 MPH CLOSE TO THE
CENTER BUT IS ASSOCIATED WITH ONLY LIMITED THUNDERSTORM ACTIVITY.


Only hope for an upgrade would be a convective increase. Some of that has happened it appears, but not enough.
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Just as I thought. No upgrade without convection.

IT IS ACCOMPANIED BY WINDS OF 45-50 MPH CLOSE TO THE
CENTER BUT IS ASSOCIATED WITH ONLY LIMITED THUNDERSTORM ACTIVITY.
Member Since: June 9, 2007 Posts: 4 Comments: 15889
288. JLPR
well with that TWO looks like the chances for 92L are shrinking
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Heres the ITCZ at the time of the crash. Courtesy of CIMSS.

Member Since: June 9, 2007 Posts: 4 Comments: 15889
286. JLPR
I dont like neutral lol (2005)
but water temps are nowhere close to how they were that year

we may have struggling systems this year because of the normal to lower than normal SST =] hurray!! XD
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TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT TUE JUN 2 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

1. THE NON-TROPICAL AREA OF LOW PRESSURE CENTERED ABOUT 400 MILES
NORTH-NORTHEAST OF THE AZORES ISLANDS HAS CHANGED LITTLE IN
STRUCTURE TODAY. THE LOW...WHICH IS OVER WATER TEMPERATURES OF
NEAR 60 DEGREES...IS ACCOMPANIED BY WINDS OF 45-50 MPH CLOSE TO THE
CENTER BUT IS ASSOCIATED WITH ONLY LIMITED THUNDERSTORM ACTIVITY.
THE LOW HAS BEEN MEANDERING OVER THE PAST SEVERAL HOURS BUT IS
EXPECTED TO BEGIN AN EASTWARD MOTION TOMORROW AND GRADUALLY WEAKEN.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL OR SUBTROPICAL CYCLONE DURING THE NEXT 48
HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER FRANKLIN
NNNN
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What would worry me more is anything that crosses over from the BOC into the Gulf or into the Yucatan channel. That area is my greatest concern.
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Here is an interesting item, though sad at the same time.

If they are able to locate the data recorders from the Air France plane, as they have located the crash site. Any information that they are able to take from them, will that help in understanding the formation of storms in the ITCZ?
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282. JLPR
Quoting plywoodstatenative:
JL, something tells me that after this season you are going to wish that we were able to keep that record going. Something tells me this is going to be one of those seasons not about the amount of storms, but about how many make landfall in the CONUS and at what strength. Like many have said before, I agree with them also, that we will have a less active CV season and instead will see a season with storm forming out of former CV waves in the Caribbean basin based on how the temperatures are at this point in the year. The other item, is I want to see where the Bermuda High winds up being as well as what influence we see from our Jet Stream/Tropical Jet Stream.


yep =S a less active CV season is good news for me but Jeanne was a not so active wave until reaching closer to the virgin islands so that type of storms I don't like xD
it also depends on the steering this year which still hasn't set up
im hoping for a lot of fish and a lots of shear xD
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Quoting plywoodstatenative:
Hurri, do not slam 23 for what he writes in here. Whether or not he wrote it is not for discussion. He is one of the reliable regulars in here.

I am not "slamming" him. I am just asking a reasonable question. :) I was trying to make it sound as respectful as possible so I wouldn't come off as aggressive or demanding; hence the "sorry if I am mistaken" part. I am just very observant and I notice these little things, lol.
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92L:
Link


Member Since: June 9, 2007 Posts: 4 Comments: 15889
Transition from a near neutral La Nina to the El Nino even that everyone is talking about. Whats the chance of seeing EL nino remain neutral this year?
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JL, something tells me that after this season you are going to wish that we were able to keep that record going. Something tells me this is going to be one of those seasons not about the amount of storms, but about how many make landfall in the CONUS and at what strength. Like many have said before, I agree with them also, that we will have a less active CV season and instead will see a season with storm forming out of former CV waves in the Caribbean basin based on how the temperatures are at this point in the year. The other item, is I want to see where the Bermuda High winds up being as well as what influence we see from our Jet Stream/Tropical Jet Stream.
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277. JLPR
Quoting MrstormX:
I am guessing 2004 style season


Mmm possible considering an El ni%uFFFDo event is probably developing

and 2004 was an el nio year

Wouldn't like another Jeanne passing by =S
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Quoting plywoodstatenative:
Mrs, I am from Florida hence the name, and would rather not see a repeat of that season.


I don't think anyone would, Charlie devestated my folks place on Sanibel. But 2004 was an el Nino year and an active one.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
I don't know that "less" activity in a more active period is anything to cheer about. Compared to some years before 03-04, even a quiet year now is much more activity than would have been seen in the past.

Watching the formation of the storms is very interesting. I find events like 92L fascinating because they are so different. Doesn't need a name to be interesting.
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I said nothing will develop in the next couple of weeks, meaning something named. I didn't say the blog will be blob watching and predicting something to form.
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Mrs, I am from Florida hence the name, and would rather not see a repeat of that season.
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272. JLPR
I just hope for another Hurricane free season
this would be the 11th year without one =D
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I am guessing 2004 style season
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Hurri, do not slam 23 for what he writes in here. Whether or not he wrote it is not for discussion. He is one of the reliable regulars in here.
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Pixely image courtesy of Accuweather....

Member Since: June 9, 2007 Posts: 4 Comments: 15889
I for one am worried about this season, got that little tick that tells me that this will be a weird season and not along the lines of the forecasts that we see.

One thing I do want to get across to members in here, please, when any forecast tracks are posted. Do not focus on that black line that speaks about the track that the storm could take. All of us that were in here during last year learned that, and learned how devastating it can be when people focus on that line. Lets blog about the storms, but not allow people to become wary based on what we see or hear on the track
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Plywood, shear is 40kts over the GOM, but expected to relax a little.
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Quoting hurricane23:



As far as long range forecasts are concerned, in my mind the biggest factor by far is the presence of an El Nino or not. The next most important factor is plain luck which can be just as important when a strong EL Nino is in effect: which it isn't yet for this year as the recent warming indicates might be coming.

The way I look at it every season is that one has to just be patient. Some years you have a lot of storms and they all recurve. Some years few storms and two or more hit land. 1 1/2 hurricanes hit land per year on the average. It's like fishing for big fish; if you get one good game fish on a full trip it is a successful trip,. If you get 15 bites, but land no fish, the trip was poor. Or its like a defensive football matchup. You might get one touchdown all game: sometimes in the first quarter, sometimes you don't score until the fourth quarter. It's mostly just plain chance.

Not trying to make a scene, but did you really write that? Your grammar in that post is much different from your other posts...and if I am mistaken, then I am sorry.
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We will know the outcome of 92L in about a half hour, my guess is that it will not be upgraded but the probability will increase to moderate range.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Interesting question per what WPB said:

The discussion last year when it was quiet in here was centered on QuickScat. What is the latest information on that and will we be able to rely on data from that satellite when looking at formation of storms?
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263. JLPR
Quoting plywoodstatenative:
JL, nice to see ya back in here


Nice to be back =D
it has been awhile
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Quoting Stormchaser2007:


If the NHC doesnt increase it potential to at least moderate by 2am tomorrow then I think chances will be slim for this to get named at all. The GFS has the wind field becoming elongated and messy at around 30hours so it better organize quick.


Agreed
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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.