El Niño chances rising for hurricane season

By: Dr. Jeff Masters , 3:38 PM GMT on May 29, 2009

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Sea surface temperatures in the Equatorial Eastern Pacific have been rising steadily for several months, and there is now a very real possibility that an El Niño event could occur during the peak of the Atlantic hurricane season, August - October. This is important, since the number and intensity of Atlantic tropical storms and hurricanes is usually reduced during an El Niño year, thanks to the increased wind shear such events bring to the tropical Atlantic. Last month, Columbia University's International Research Institute (IRI) was giving a 30% chance of an El Niño event for the coming hurricane season; this month, they have bumped their odds up to 45%. The Australian Bureau of Meteorology notes that "recent trends are consistent with the very early stages of a developing El Niño". NOAA's Climate Prediction Center forecasts the current neutral conditions in the Equatorial Eastern Pacific will continue into the summer, but shows that their CFS El Niño model is predicting a moderate El Niño event for the coming hurricane season.


Figure 1. Sea Surface Temperature (SST) departure from average for the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region"). The +0.5°C mark is the threshold for El Niño conditions, and we are very close to that mark now. Image credit: NOAA's Climate Prediction Center.

El Niño forecast models
The latest suite of runs by the various computer models used to forecast El Niño offer two main forecasts for the coming hurricane season: neutral conditions will persist, or an El Niño will develop (Figure 2). There are two types of models used to make these forecasts: statistical models and dynamical models. The statistical models have been around the longest, and they rely on statistics of how past El Niño episodes have developed in order to make a forecast. Dynamical models don't care about what has happened in the past. They make a forecast by taking the current state of the atmosphere, putting the data on a grid covering the entire globe, then solving the equations that govern the physics of the atmosphere and ocean on each point of this grid every few minutes, marching forward in time for many months. These dynamical models, in many cases, are simply modified versions of the same models we use to forecast the short-term weather. For example, the NOAA's Coupled Forecast System (CFS) model is based on the GFS model that we use to track hurricanes and make short-term weather forecasts. The main difference is that the CFS model runs for many months instead of just a few days.


Figure 2. El Niño model forecasts made in mid-May. Note that for the peak part of hurricane season, August-September-October (ASO), most of the dynamical models are forecasting an El Niño event (SST anomaly greater than 0.5°C in the Eastern Equatorial Pacific). Image credit: Columbia University's IRI.

Which model to believe?
As is the case with all seasonal forecasts, El Niño forecasts are not very good, and don't do much better than flipping a coin. However, thanks to intensive research efforts and the doubling of computer power that has been occurring every 1.5 years, the El Niño forecasts by the dynamical models have improved considerably over the past few years. These models now do about as well as the traditional statistical models, and should continue to improve as computer power continues to increase and our understanding of El Niño increases. Over the past two months, the dynamical models have increasingly been forecasting the development of an El Niño this Fall. To illustrate, in March only three of the thirteen dynamical models were predicting an El Niño event for hurricane season. By mid-May, this had increased to nine out of thirteen models. However, none of the eight statistical El Niño models are forecasting an El Niño event for the Fall, and their forecasts should be respected, as well. The IRI web site has a nice tool one can use to study the performance of the individual models. To my eye, the Japanese Meteorological Agency (JMA) dynamical model has made the best El Niño forecasts over the past two years (though I haven't done a rigorous error analysis to verify this). The JMA model is predicting a weak El Niño event for the coming hurricane season, and I am going to go along with that forecast.

What will an El Niño event do to hurricane numbers?
Since the active hurricane period we are in began in 1995, there have been four El Niño events (Figure 3). During these years, the number of named storms, hurricanes, and intense hurricanes 11 named storms, 5 hurricanes, and 3 intense hurricanes. This is close to the average levels we've seen over the past 60 years--10-11 named storms, 6 hurricanes, and 2 intense hurricanes. If, on the other hand, we look at the five years that had neutral conditions, the numbers are considerably higher--18 named storms, 10 hurricanes, and 5 intense hurricanes. So, let's hope for an El Niño this year. Note, though, that one of our worst hurricane years--2004, which featured hurricanes Ivan, Charlie, Frances and Jeanne, which all affected Florida with hurricane conditions--was an El Niño year. It seems that in years like 2004, there is a lag between the time a El Niño event develops and the response of the atmosphere over the Atlantic. There is no way of forecasting at this point whether this could be the case this year. One argument against a repeat of 2004 is the presence of much lower heat content and SSTs in the tropical Atlantic this year compared to 2004.


Figure 3. Looking at the numbers of Atlantic names storms, hurricanes, and intense hurricanes since 1995.

Tropical Depression One
The season's first tropical depression formed yesterday off the coast of North Carolina, but has missed its opportunity to become the Tropical Storm Ana. Tropical Depression One is headed east-northeastward out to sea, and is now entering a region with cooler water temperatures and increased wind shear of 15 - 20 knots. The heavy thunderstorm activity associated with TD One has shrunk this morning, and high wind shear has pushed these thunderstorms to the east side of the center, exposing the surface circulation to view. Tropical Depression One will not hold together much longer, and should be history by Saturday night.

Is the formation of TD One a harbinger of an active hurricane season?
Probably not. Early season storms occurring near the U.S. coast have not been shown to be correlated with an active main portion of hurricane season during August - October. However, the situation is different if we start getting June and July storms in the deep tropics between Africa and the Lesser Antilles Islands. This was the case last year, when the formation of Hurricane Bertha in the deep tropics in July presaged an active 2008 hurricane season. According to the Hurricane FAQ, "as shown in (Goldenberg 2000), if one looks only at the June-July Atlantic tropical storms and hurricanes occurring south of 22°N and east of 77°W (the eastern portion of the Main Development Region [MDR] for Atlantic hurricanes), there is a strong association with activity for the remainder of the year. According to the data from 1944-1999, total overall Atlantic activity for years that had a tropical storm or hurricane form in this region during June and July have been at least average and often times above average. So it could be said that a June/July storm in this region is pretty much a "sufficient" condition for a year to produce at least average activity."

I'll have a detailed outlook of the coming hurricane season on Monday, the first day of the Atlantic hurricane season.

Jeff Masters

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Stillwaitn--
I agree with ya.. I don't want the destruction or death but Love watching formation... And that is exactly why everyone is on here...
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worst storm i went through wind wise was Rita.. water wise was IKE... cool wise Humberto... dud was Eduard.
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Homelesswanderer...lolz at RINA... That would be horrible if we got RINA here in SeTx...
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Worst hurricane ever? Andrew. I lived in South Kendall, there was a camper in a tree. A CAMPER!
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Link

Interesting Article from the Miami Herald "be a survivor not a victim"
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Quoting FloridaTigers:
Hurricane Fred will landfall where Hurricane Wilma did.


Bite Your Tounge!!! we have been affected by Frances, Jean, Wilma. Wilma was the scariest - seeing my glass doors bow! And I think the silliest thing I ever did was to go outside to check something during a nasty Katrina feeder band as it passed through on its way to destruction and having to hide my face against the wall till it passed. Definitely not one of my brightest moments. Cheers for an uneventful season and safety to all.
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that is true (still waiting ) i agree
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Quoting CaneWarning:


Those names do not scare me.


The name I'm dreading is the "R" name in 2011.

Its RINA. Don't know why but something about that name don't sound good. Geesh a combination of the terrible twins. Who picks these names? lol
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most people here don't honestly want a slow hurricane season,do we??,lets be realistic most of us are probably borderline obsessed w/weather,no???...now I'm not saying that I want death and destruction,but watching these storms is hella fun to me and I love it,it really is the people's responsiblities whom can be effect by these storms to take pro-active action in either leaving or stocking up and "sticking it out"..either way mother nature w/do her thing this year and I hope everyone stays well and safe,But I'd love a busy season,honestly....
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RRM34667 :0)

Nite Sweetie....


Taco :0)
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Hurricane Fred will landfall where Hurricane Wilma did.
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later alkl next up the docs outlook and the 3 hr season opener of hurr.bob show tonight at 8 pm

off to bed for me work in the morning
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Quoting taco2me61:


You are so funny..... Thank you and have a good nite....

Taco :0)


Nite taco!!
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Quoting RMM34667:


I think Hurricane Fred will be a problem. Fred's been a problem for me ever since he married my sister!!


You are so funny..... Thank you and have a good nite....

Taco :0)
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next shuttle mission going up on june 13th,if all goes as planned
111....patrap????,think you could help me a little here????,lol
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Good Nite all
see you tomorrow....

Taco :0)
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Quoting CaneWarning:


Those names do not scare me.


I think Hurricane Fred will be a problem. Fred's been a problem for me ever since he married my sister!!
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got 2 cases of mre's w/heaters stocked here in sarasota,fl...just need to by some gas,fruit,water and TP when a TC threatens my area I've got over 24,000 calories combined between the 2 cases,should provide meals for me and whoever else I can help for 72hrs after.....I do need to buy some batteries however.....
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Quoting RMM34667:
lifting my almost empty glass to a quiet and uneventful 2009 Hurricane Season. Lots of blobs and wannabe hurricane. Too Many interesting recurves (out to sea of course). Cheers!


("") ("") ("") my cups are running over ...

Lets have a very quite season....

Taco :0)
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873. JRRP
see you tomorrow
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Goodnight everyone. I'll be back tomorrow for Dr. Master's season outlook.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
870. JRRP
Quoting dis1322:
here a topic what the worst hurricane that you guys went throught ?????????

Georges 1998
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well for me was hurricane dolly which was a category 2 we had a category 5 that was beaulah in 1969 but i wasnt alive
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Quoting SLU:
Welcome everyone to the 2009 Atlantic Hurricane Season. Let's all hope for a quiet year with lots of invests and many "fish storms" so that we can all sit infront of our computers and admire them with no fear on this blog.

2009
Ana
Bill
Claudette
Danny
Erika
Fred
Grace
Henri
Ida
Joaquin
Kate
Larry
Mindy
Nicholas
Odette
Peter
Rose
Sam
Teresa
Victor
Wanda


Those names do not scare me.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
lifting my almost empty glass to a quiet and uneventful 2009 Hurricane Season. Lots of blobs and wannabe hurricane. Too Many interesting recurves (out to sea of course). Cheers!
Member Since: Posts: Comments:
866. SLU
Welcome everyone to the 2009 Atlantic Hurricane Season. Let's all hope for a quiet year with lots of invests and many "fish storms" so that we can all sit infront of our computers and admire them with no fear on this blog.

2009
Ana
Bill
Claudette
Danny
Erika
Fred
Grace
Henri
Ida
Joaquin
Kate
Larry
Mindy
Nicholas
Odette
Peter
Rose
Sam
Teresa
Victor
Wanda
Member Since: Posts: Comments:
It's 12:00
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Frances here. Here's to a safe season for everyone.
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863. JRRP
and the month with more waves since 2005 till now is june 2005 with 15 TW
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Ivan and Katrina here....
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welcome 2009 atlantic hurricane season!!!
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Happy official start to Hurricane season. May we all be safe and prepared.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting dis1322:
here a topic what the worst hurricane that you guys went throught ?????????


Ivan for me in 2004
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Quoting KEEPEROFTHEGATE:
Link


Thats cool as all get out....
i like that

Thanks
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Quoting dis1322:
here a topic what the worst hurricane that you guys went throught ?????????


Andrew.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
2 more mins...ready to ''pop'' the champagne?
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here a topic what the worst hurricane that you guys went throught ?????????
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Since it's quiet, I'll get on my soapbox. PLEASE, as you prepare for yourself and your family for this upcoming season, prepare for your pets as well. And if you have to evacuate, please take your pets with you.
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Link
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Quoting WeatherStudent:
Any final train of thoughts which made our off-season a memorable one, folks?
the return of jfv
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Quoting CaneWarning:


I hope we have blobs to watch and even a hurricane or two...all staying out to sea touching no land.


Agree 100%

They all can stay out there and not hit anything....

Taco :0)
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Quoting JRRP:
Some of them have vanished of the map.... but yes we have had 6 wave


I guess I haven't followed them all that much unless they were classified as an invest.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
849. JRRP
Some of them have vanished of the map.... but yes we have had 6 wave
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Quoting WeatherStudent:
Any final train of thoughts which made our off-season a memorable one, folks?


I hope we have blobs to watch and even a hurricane or two...all staying out to sea touching no land.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting taco2me61:


Yes watching Twister on TNT and bring in Hurricane season.... All I can say is "OMG"

Taco :0)


OMG.. goosebumps. again
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Quoting CaneWarning:


We've had 6 waves already?

Yep. The SAL and shear have been fairly active so far this year, and the ITCZ has been VERY far south so far, so while waves tend to hang around 5-15 degrees north, they have been closer to straddling the equator.
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Quoting WeatherStudent:


Welcome, Chicklet!


Yes watching Twister on TNT and bring in Hurricane season.... All I can say is "OMG"

Taco :0)
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Quoting JRRP:

yeah


But only two were invests.
Member Since: April 26, 2009 Posts: 3 Comments: 3667

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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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