Average hurricane season foreseen by CSU, NOAA, and TSR

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

Share this Blog
2
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 562 - 512

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27Blog Index

Quoting SomeRandomTexan:


I'm wanting to think that I have seen her on during the past month but don't hold me to it...



Hope she is ok , she used to be on here constantly .
Member Since: Posts: Comments:
man there is a lot of unstable air in the GOM... if shear keeps relexing something could form given the variable of time
Member Since: Posts: Comments:
Quoting PELLSPROG:
Anyone know what happened to Conchy Girl ? I don't see her on here anymore !!!!!!


I'm wanting to think that I have seen her on during the past month but don't hold me to it...
Member Since: Posts: Comments:
Anyone know what happened to Conchy Girl ? I don't see her on here anymore !!!!!!
Member Since: Posts: Comments:
Goodmorning Ev1!!!

kinda got a late start on checking everything out but everything looks about the same
Member Since: Posts: Comments:
Member Since: July 3, 2005 Posts: 424 Comments: 128269
High Resolution imagen for the 92L, today. Two vortexes can be seen inside the center:



92L hasn't died yet.............. ;)
Member Since: Posts: Comments:
Also of interest, is the very low SAL content, and the relatively moist air over most of the equqtorial and tropical Atlantic.
No waves in sight, but it would be fun to watch one now, to see what it does in the prevailing conditions.
Good Morning.
After 4 days of cloud, with intermittent showers and some thunder, the Dry Season has returned with a vengeance today.@ 11n 61w.
Hot, windy, hazy.
SPECIAL MARINE WARNING
GMZ650-655-031545-
/O.NEW.KMOB.MA.W.0092.090603T1409Z-090603T1545Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE MOBILE AL
909 AM CDT WED JUN 3 2009

THE NATIONAL WEATHER SERVICE IN MOBILE HAS ISSUED A

* SPECIAL MARINE WARNING FOR...
COASTAL WATERS FROM DESTIN TO PENSACOLA FL OUT 20 NM...
COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA MS OUT 20 NM...
INCLUDING LILLIAN BRIDGE...EAST BAY...ADMIRAL FETTERMAN REEF...
DAVID BOGAN REEF...GARCON POINT BRIDGE...J BROWN LIBERTY SHIP
REEF...NAVARRE BEACH...OKALOOSA MILLENNIUM REEF...ORISKANY REEF...
PENSACOLA BAY BRIDGE...PENSACOLA BEACH PIER...PENSACOLA PASS AND
RUSSIAN FREIGHTER REEF...

* UNTIL 1045 AM CDT

* AT 907 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF THUNDERSTORMS...PRODUCING WATERSPOUTS FROM PENSACOLA BAY
BRIDGE TO DAVID BOGAN REEF...MOVING EAST AT 5 KNOTS.

* THESE WATERSPOUTS WILL BE NEAR
OVER PENSACOLA BEACH PIER BY 955 AM CDT
3 NM SOUTH OF GARCON POINT BRIDGE BY 1000 AM CDT
OVER RUSSIAN FREIGHTER REEF BY 1020 AM CDT
3 NM NORTHWEST OF ADMIRAL FETTERMAN REEF...5 NM SOUTH OF EAST BAY
AND 8 NM WEST OF NAVARRE BEACH BY 1045 AM CDT

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THUNDERSTORMS CAN PRODUCE SUDDEN WATERSPOUTS. WATERSPOUTS CAN EASILY
OVERTURN BOATS AND CREATE LOCALLY HAZARDOUS SEAS. SEEK SAFE HARBOR
IMMEDIATELY.

&&

LAT...LON 3045 8686 3037 8713 3042 8679 3006 8680
2996 8753 3038 8744 3044 8738 3047 8741
3047 8736 3043 8734 3040 8741 3030 8745
3037 8727 3037 8732 3037 8733 3042 8720
3049 8715 3045 8709
TIME...MOT...LOC 1408Z 270DEG 4KT 3038 8716 3009 8739
Member Since: Posts: Comments:
Storm,thanks,thats great stuff,always fascinated with information on the MJO and its effects.
Member Since: Posts: Comments:


latest GOM vis
Member Since: Posts: Comments:
Nice synopsis, StormW. Thanks. I'm going to Key West on Monday and it's the last place I want to be if something does pop up!
Member Since: Posts: Comments:
good day see we got a weak AOI in gom
Member Since: Posts: Comments:
STORMW do you expect this low in the GOM to come ashore in LA like the models indicate, or do you think it sits in the Gulf...Thanks
Member Since: Posts: Comments:
Good morning to all my favorite people! Looking at the GOM blob, I think it will just make some good rain for the folks along the NE gulf coast. With shear as high as it is and the low not forecast to get much lower, I don't think we'll see some organization.

I must say that I think the tropical wave at 37W 7N is the healthiest wave we have seen yet this year. It has a little low level vorticity, has been moving WNW steadily and it is building some nice convection with low shear overhead. I think this is the first wave we have had that may have the potential to get a little something going once it hits the Carribean.
Member Since: Posts: Comments:
mid level swirl making landfall on SE LA coast
Member Since: July 14, 2008 Posts: 1 Comments: 9630
Ok. Those warm 1980 ssts made me look at the hurricane season of that year.

Only 11 named storms.
1 U.S. landfalling hurricane and he was a monster! Hurricane Allen, max winds 190 mph. Thats the fastest windspeed I've seen yet. Wow.
It hit Brownsville as a category 3.

The only other landfalling U.S. storm was TS Danielle which hit here (TX/LA Border) in early September. Had to do some thinking if I was here for that 1??? Beat it out of town by 1 month. LOL. Put a lot of miles under my feet that year. No wonder I'm so tired now. :)

1980 also gave rise to many future monsters. It was the first year of Charley, Frances, Georges, Ivan and Jeanne.

Member Since: Posts: Comments:
From the 8 a.m. Discussion:
GULF OF MEXICO...
SCATTERED SHOWERS AND TSTMS PERSIST ACROSS THE CENTRAL GULF N OF 23N BETWEEN 85W-91W. THIS UNSETTLED WEATHER IS ASSOCIATED WITH UPPER DIFFLUENCE E OF A SHORTWAVE TROUGH AND ENHANCED BY LOW-LEVEL CONVERGENCE ALONG A WEAKENING SFC TROUGH. THE REMAINDER OF THE GULF IS IN A MOIST ENVIRONMENT SUPPORTED BY STRONG SW TO W FLOW ALOFT...WITH ISOLATED SHOWERS AND TSTMS OCCURRING ELSEWHERE ACROSS THE SE GULF. SE AND S WINDS OF 10 KT OR LESS ARE AFFECTING MUCH OF THE GULF BASED ON THE LATEST QUIKSCAT PASS...THOUGH BUOYS REPORTS INDICATE THAT GUSTS OVER 20 KT ARE OCCURRING NEAR THE SHOWERS AND THUNDERSTORMS. THE SFC TROUGH IS EXPECTED TO MOVE N AND WEAKEN AS A COLD FRONT ENTERS THE NW GULF THU.
Member Since: Posts: Comments:
540. 7544
Quoting Chicklit:
Shear has relaxed in the Gulf.
And there is a low. Link


yeap we just might see 93l in the gom somewhere soon stay tuned
Member Since: Posts: Comments:
Shear has relaxed in the Gulf.
And there is a low. Link
Member Since: Posts: Comments:
Quoting nrtiwlnvragn:




From Monthly/Seasonal Climate Composites


That will help ! Thank you very much!
Member Since: Posts: Comments:

rather healthy looking wave in the far eastern atlantic



Link
Member Since: Posts: Comments:
GM all,I see 92L still spinning in place,quite a block in the northern stream.
Member Since: Posts: Comments:
Quoting sporteguy03:



Ike are you ready to stick your 51 year old neck and say you think there will be a weak T.D. or T.S. out there? :)


ROFL, Ike has never been afraid to stick his neck anywhere :) Mind you. I keep forgetting he is so old and frail :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting Cazatormentas:
Morning from Spain !

Do you know if it is possible to obtain a map with the North Atlantic SST for 1st october 1980?

Thanks.




From Monthly/Seasonal Climate Composites
Member Since: Posts: Comments:
Quoting IKE:


More coffee?

Now watch it drop it on the 12Z run.

Either way, looks like an increase in moisture in the western Caribbean next week.



Ike are you ready to stick your 51 year old neck and say you think there will be a weak T.D. or T.S. out there? :)
Member Since: Posts: Comments:
Hi Hurricane4Lex. Hi Orca.

Your welcome Cazatormentas. Sounds like an interesting paper. I didn't know those kinds of storms affected that area. I was last on your side of the North Atlantic in 1980. Although in the more chillier climate of Germany. All I remember about that was it got COLD! Lol. I think I been in Texas too long. :)
Member Since: Posts: Comments:
Here is global warming at it's finest!

Long days and short nights are not normally associated with snow. Nevertheless, a part of Scandinavia may experience both thanks to a strong storm at mid to late week.

The storm will spin up on Wednesday and Thursday over the northern Baltic Sea near southern Finland and eastern Sweden. The storm will draw arctic air southward over Sweden and Norway. It should be cold enough to turn some of the storm's numbingly cold rain into snow over higher ground of central and western Sweden into eastern Norway. Accumulation, even heavy local snowfall, will be possible between late on Wednesday and early on Friday.

Elsewhere, the primary effect of the northern storm will be to spread cool air over northern Europe from Great Britain through Germany and Poland into northwestern Russia.

Member Since: Posts: Comments:
Question of the day??

Why do people keep saying they hope this year is the same as that year..or not the same as another year? I will bet there is not a season that does not bring up bad memories for someone else.

I think we should stick with just higher/lower/same as per the average?

Just a though based on 1 single cup of coffee. I may change it after a second or third cup.

Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting homelesswanderer:


I couldn't find that date specifically just a lot of things over my head that said...warmer SST anomalies in 1980-81. I could find things for North Pacific and the North Sea. Maybe someone else with a little more know-how can help you. Good luck.


Thank you very much ;)

I am writing about the development of this kind of disturbances in the Eastern Atlantic, close to the Iberian Peninsula.
Member Since: Posts: Comments:
Wow Storm. That certainly makes a statement!
Been looking at maps of northern waters. They didn't look like that. Thank Goodness. Lol. Carribean and Gulf heating up.But the Pacific is on fire.
Member Since: Posts: Comments:
Low pressure Florida Straits, Yucatan Channel...


Member Since: July 14, 2008 Posts: 1 Comments: 9630
Quoting homelesswanderer:


I couldn't find that date specifically just a lot of things over my head that said...warmer SST anomalies in 1980-81. I could find things for North Pacific and the North Sea. Maybe someone else with a little more know-how can help you. Good luck.


Took a quick look... proverbial needle in a haystack :(
Member Since: October 1, 2007 Posts: 81 Comments: 26511
I'm really hoping for a 2006 season or better and not a 2004 (that will suck since I'm not at 1st my house) CG2916

PS: Hi StormW Hi HomelessWanderer
Member Since: Posts: Comments:
Oh, I'm sorry, was Googling my lil fingers off, LOL.

Good Morning All.
Good Morning Storm. I'm moving slow this a.m. too. :)
Member Since: Posts: Comments:
Quoting Cazatormentas:
Morning from Spain !

Do you know if it is possible to obtain a map with the North Atlantic SST for 1st october 1980?

Thanks.


I couldn't find that date specifically just a lot of things over my head that said...warmer SST anomalies in 1980-81. I could find things for North Pacific and the North Sea. Maybe someone else with a little more know-how can help you. Good luck.
Member Since: Posts: Comments:
Quoting StormW:


Don't know yet...new day...new analyses...slept in this a.m., just pulling up all my sites for analysis...but looking at POP's for my area (Palm Harbor)...gotta 50-60% chance of precip later this eve. Definitely would be related to the GOMEX area.


Thanks. I look forward to your thoughts!
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Blog Update
Reflector site for those at work, which now also includes Weather456, daily updates


AOI #1

AOI #2
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting StormW:
Good morning all!

Hey.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting StormW:
Good morning all!


Good morning StormW, what is your take on the GOM blob? It looks like we will get storms on the W. coast of FL today. I'm not sure if it is related to the blob or not, but I can see storms on radar already.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
New blog post for me. See it!
Member Since: December 21, 2007 Posts: 13 Comments: 3046
I see the GFS is forecasting some moisture in the Caribbean again. Its been doing that off and on since 5-25.
Member Since: Posts: Comments:
Quoting ackee:
invest92L has 50mph winds how comes its not a subtropical or tropical system ?


NHC thinks its non-tropical and it doesn't have enough t-storm activity.
Member Since: Posts: Comments:

Viewing: 562 - 512

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.