Record warmth in Atlantic Main Development Region for hurricanes

By: Dr. Jeff Masters , 4:52 PM GMT on March 08, 2010

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Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes were at their highest February level on record last month, according to an analysis of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. The region between 10°N and 20°N, between the coast of Africa and Central America, is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)


Figure 1. The departure of sea surface temperature (SST) from average for March 7, 2010, as derived from the AMSR and AVHRR satellite data. Image credit: NOAA.

SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.02°C above average during February. This easily beats the previous record of 0.83°C set in 1998. SSTs in the Main Development Region are already warmer than they were during June of last year, which is pretty remarkable, considering February is usually the coldest month of the year for SSTs in the North Atlantic. The 1.02°C anomaly is the 6th highest monthly SST anomaly for the MDR on record. The only other months with higher anomalies all occurred during 2005 (April, May, June, July, and September 2005 had anomalies of 1.06°C - 1.23°C).

What is responsible for the high SSTs?
Don't blame El Niño for the high Atlantic SSTs. El Niño is a warming of the Pacific waters near the Equator, and has no direct impact on Atlantic SSTs. Instead, blame the Arctic Oscillation (AO) or its close cousin, the North Atlantic Oscillation (NAO). The AO and NAO are climate patterns in the North Atlantic Ocean related to fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores-Bermuda High. They are some of the oldest known climate oscillations; seafaring Scandinavians described the pattern several centuries ago. Through east-west oscillation motions of the Icelandic Low and the Azores-Bermuda High, the AO/NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. The winter of 2009 - 2010 has seen the most negative AO and NAO patterns since record keeping began in 1950, which caused a very cold winter in Florida and surrounding states. A negative AO/NAO implies a very weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region were 1 - 2 m/s (2.2 - 4.5 mph) below average (Figure 2). Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean has heated up significantly, relative to normal, over the winter. This heating is superimposed on the very warm global SSTs we've been seeing over the past decade, leading to the current record warmth. Global and Northern Hemisphere SSTs were the 2nd warmest on record in both December and January.


Figure 2. Sea level pressure averaged for the period December 2009 - February 2010 (left) and the sea level pressure averaged for the period December - February from the long-term mean (1968 - 1998). This winter, the Azores-Bermuda High was about 3 - 4 mb weaker than in a typical winter, due to strongly negative AO/NAO conditions. Image credit: NOAA/ESRL.


Figure 3. Departure of surface wind speed from average for December 2009 - February 2010. Winds were about 1 - 2 m/s (2.2 - 4.5 mph) lower than average over the Atlantic hurricane Main Development Region (MDR). Image credit: NOAA/ESRL.

What does this imply for the coming hurricane season?
According to Dr. Phil Klotzbach of the University of Colorado, February temperatures in the MDR are not strongly correlated with active hurricane seasons. The mathematical correlation between hurricane season Accumulated Cyclone Energy (ACE) and February SSTs is only 0.26, which is considered weak. Past hurricane seasons that had high February SST anomalies include 1998 (0.83°C anomaly), 2007 (0.71°C anomaly), and 1958 (0.68°C anomaly). These three years averaged 13 named storms, 8 hurricanes, and 3 intense hurricanes, which is considerably higher than the average of 10, 6, and 2. The big question is, how long will the strong negative AO/NAO conditions keep the Azores-Bermuda High weak? Well, the AO has risen to near-neutral values over the past week, and the latest 2-week forecast from the GFS model show that the AO and NAO will not be as strongly negative during March. This should allow the Azores-Bermuda High to strengthen some this month and increase the trade winds over the MDR. However, I still expect we'll set a record for warmest-ever March SSTs in the Main Development Region. Longer term, the crystal ball is very fuzzy, as our ability to predict the weather months in advance is poor. The long-range NOAA CFS model is predicting SSTs in the Atlantic MDR will be about 0.70°C above average during the peak months of hurricane season, making it one of the top five warmest years on record--but not as warm as the unbelievable Hurricane Season of 2005, which averaged 0.95°C above normal during August - October. The other big question is, when will El Niño fade? El Niño is currently holding steady at moderate intensity, and I expect that will continue through at least mid-April. It is possible El Niño will linger long enough into the year that it will create increased wind shear that will suppress this year's hurricane season.

Brazilian disturbance
An area of disturbed weather off the coast of Brazil, near 24S 36W, has changed little over the past two days. This disturbance still has a slight potential to develop into subtropical or tropical depression by Wednesday, according to the latest runs of the ECMWF, GFS, and NOGAPS models. Satellite imagery shows little organization to the cloud pattern, and only limited heavy thunderstorm activity. Wind shear over the region is about 20 knots, which is rather high, and should keep any development slow. Sea surface temperatures are about 27°C, about 1°C above average, which is warm enough to support a tropical storm. The system is small, limiting its potential to become a tropical cyclone. I don't think it will become a subtropical depression.

I'll have a new post on Wednesday.
Jeff Masters

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Oz is the official poet laureate of the blog :)
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A poem dedicated to those who were banned before me.

The Future

It is fun to ponder and prognisticate
Look at charts and, uh, think.
The proof's aways off, not at hand,
What roils the water and strikes land.
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So long Snake. Enjoy the Boomers. I cant remember when I last heard one.
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Well, this went through and we got 1/2" out of it in about a half hour. Nice lightning too (wife made me close the blinds). I went outside and it was interesting. The low clouds were going back whence they came, west and quickly, the next level up was headed north, and I can only assume above that was still headed east.

Member Since: August 22, 2008 Posts: 12 Comments: 6010
Take care Pottery, the rainy season is on its way, shutting down now before the boomers get here, will talk to you again.
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Post 642. Talk about Horrid!!
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Interesting stuff there Storm.
And surprising to me, the amount of Atlantic storms there, in spite of the cool (anomolous) SST's in the Atl.
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Oklahoma tornado. Looks like a cross between the Wizard of Oz and Twister.

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Yes indeed Keeper. But if I recall correctly, the last time you pointed your rain-stick at me, we had floods.
We are fine here. Really. No need to worry at all.
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90Q

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Levi and Snake.
Yeah, send some damp stuff down here if you dont mind.
Had a crisis today, when the wife said she needed to get some water from a 400 gal tank we keep for drinking and cooking.
Before I took the water out, I looked inside to see how much we had.
An unpleasant smell was what I found. How did that 30" long snake get in there??
Nothin' smells as bad as a dead reptile.
So now, I have about 300 gals to water plants with. Big loss there. But my own fault for not putting the cover back onto the tank PROPERLY last time I was looking in. BAH!!
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Quoting pottery:
Greetings.
Some good discussion here tonight.
Another 94F day here today. There are recomendations from several quarters, that the Government should declare a "State of Water Crisis".
It's pretty bad.......
need sum rain pottery do ya
Member Since: July 15, 2006 Posts: 169 Comments: 53296
636. xcool
Levi32 anytime.i post image /
Member Since: September 26, 2009 Posts: 2 Comments: 15620
I'll let you know how much this dumped on my house in a few minutes. Nice fireworks with it too.

Member Since: August 22, 2008 Posts: 12 Comments: 6010
Quoting VAbeachhurricanes:



the gulf is cold, and the cold waters are starting to penetrate the Caribbean.


...due to the record cold winter we have been having in the southeast USA. That should change during April and May, and the GOM will warm up to around normal by June 1st. You'd be surprised how little it takes to warm the gulf up.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting pottery:
LOL Levi. It's called desalination (as you know).
We already have one big desal plant. But the problem this year is lack of rain last year. Left the resevoirs low, and it has been particularly hot and dry. We dont expect rain until May at best.
Quoting pottery:
.........and levi, that blizzard looks pretty horrid to me. I think I will stay with the heat!!


Lol...so apparently the desal plant can't keep up with the lack of rain, got it.

Yup it's nasty here we've gotten 42 inches of new snow during the last 3 days. Our suburban is buried up to the top of the wheel-wells since the last time we got it out of our driveway.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
More of this, I wish I could send this your way:
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Hi there Snake.
How is the weather up your end?
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Quoting Levi32:
An interesting thing is when looking at analogs for this year, theoretically there should be a few from back in the last similar climate cycle during the mid-late 1940s, but a lot of data becomes unavailable for years prior to 1950, specifically the ONI, so it's hard to see what years from before that point may have been similar to this year.

So, the next best thing is to look at analogs from our current climate cycle, since we are currently in a period of transition. Therefore, our best analogs are really the recent ones since 1995, which makes 1995, 1998, 2003, 2005, and 2007 our best analogs, if we rely on our position in the oceanic-climate cycle. Out of all of these, 1998 is my favorite, as I can't find a more perfect analog in terms of global SST profile (maps only go back to 1996).

Yes there are a few differences, especially the sheer strength of the 1998 El Nino which was decaying by this time, and was centered farther east over the eastern Pacific because it marked the end of the warm PDO cycle, but no year was this similar when you look at global or Atlantic SSTs.

March 1998:



March 2010:






the gulf is cold, and the cold waters are starting to penetrate the Caribbean.
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Yo, Pottery, good to see you ole chap!
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.........and levi, that blizzard looks pretty horrid to me. I think I will stay with the heat!!
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LOL Levi. It's called desalination (as you know).
We already have one big desal plant. But the problem this year is lack of rain last year. Left the resevoirs low, and it has been particularly hot and dry. We dont expect rain until May at best.
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Quoting xcool:





That's an awesome site xcool thanks :)
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Blizzard is still in progress here in Alaska, for the 25th straight hour in visibilities less than 1/4 mile.






Current Conditions

Homer, Alaska (Airport)
Updated: 4 min 58 sec ago

7 °F
Heavy Snow
Windchill: -14 °F

Humidity: 79%
Dew Point: 1 °F
Wind: 22 mph from the SW

Wind Gust: 31 mph
Pressure: 29.10 in (Steady)
Visibility: 0.2 miles
Elevation: 82 ft
Member Since: November 24, 2005 Posts: 635 Comments: 26547
624. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting pottery:
Greetings.
Some good discussion here tonight.
Another 94F day here today. There are recomendations from several quarters, that the Government should declare a "State of Water Crisis".
It's pretty bad.......


Haven't they invented technology to extract and filter fresh water from the ocean yet? That sounds pretty horrid living on an isolated island.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Greetings.
Some good discussion here tonight.
Another 94F day here today. There are recomendations from several quarters, that the Government should declare a "State of Water Crisis".
It's pretty bad.......
Member Since: Posts: Comments:
621. xcool
opps
Member Since: September 26, 2009 Posts: 2 Comments: 15620
620. MTWX
Quoting msgambler:
I'm from Gulfport but now I live 10 miles North of Dauphin Island

I lived in Biloxi for a year, but now I have resided in Columbus, MS for the last 5 years
Member Since: July 20, 2009 Posts: 23 Comments: 1392
619. MTWX
Quoting msgambler:
I have been overprepared since the day I got my own place 25 years ago. learned well for my parents. Always have a hurricane supply kit on hand. After the season we donate the can goods and restock at the first of the year. Did the main. on generator this weekend. I'm ready on that standpoint. Just keep them away. I even have 7 cases of MRE's in the closet...lol

Some of thase MRE's are half way decent. I've been through quite a few of those. The pound cake is the best!!! LOL
Member Since: July 20, 2009 Posts: 23 Comments: 1392
An interesting thing is when looking at analogs for this year, theoretically there should be a few from back in the last similar climate cycle during the mid-late 1940s, but a lot of data becomes unavailable for years prior to 1950, specifically the ONI, so it's hard to see what years from before that point may have been similar to this year.

So, the next best thing is to look at analogs from our current climate cycle, since we are currently in a period of transition. Therefore, our best analogs are really the recent ones since 1995, which makes 1995, 1998, 2003, 2005, and 2007 our best analogs, if we rely on our position in the oceanic-climate cycle. Out of all of these, 1998 is my favorite, as I can't find a more perfect analog in terms of global SST profile (maps only go back to 1996).

Yes there are a few differences, especially the sheer strength of the 1998 El Nino which was decaying by this time, and was centered farther east over the eastern Pacific because it marked the end of the warm PDO cycle, but no year was this similar when you look at global or Atlantic SSTs.

March 1998:



March 2010:



Member Since: November 24, 2005 Posts: 635 Comments: 26547
617. xcool
<< slidell la
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting MTWX:

Where are you at in MS?? Biloxi??
I'm from Gulfport but now I live 10 miles North of Dauphin Island
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615. MTWX
Quoting Levi32:


The only reason for that is because weather satellites didn't come into existence until the 1960s. Hurricanes out in the middle of the ocean had to be encountered by ships or nobody would know they even existed. This is why there is an undercount bias of all hurricane seaons prior to the 1960s.

AAHHH got it!! Knew something didn't look right!! :)
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Quoting MTWX:

Just hope for the best... prepare for the worst... It is never a bad thing to be over prepared!!
I have been overprepared since the day I got my own place 25 years ago. learned well for my parents. Always have a hurricane supply kit on hand. After the season we donate the can goods and restock at the first of the year. Did the main. on generator this weekend. I'm ready on that standpoint. Just keep them away. I even have 7 cases of MRE's in the closet...lol
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Quoting MTWX:


I notice that there are not very many CV storms though


The only reason for that is because weather satellites didn't come into existence until the 1960s. Hurricanes out in the middle of the ocean had to be encountered by ships or nobody would know they even existed. This is why there is an undercount bias of all hurricane seaons prior to the 1960s.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
1947 and '50 looked rough for our neck of the woods. Don't want to see a repeat this year or any year. But I know...it will happen again.
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610. MTWX
Quoting Levi32:


Yes, because the AMO went into its warm cycle in 1995. In terms of the PDO/AMO ocean-climate cycle, we are in roughly the same position as the mid-late 1940s, when the PDO was going cold and the AMO had been warm for a little while. This period was pretty bad for Florida:















I notice that there are not very many CV storms though
Member Since: July 20, 2009 Posts: 23 Comments: 1392
609. MTWX
Quoting msgambler:
Just keep AL, MS coastlines out of the radar sites. Not ready for anymore storms

Where are you at in MS?? Biloxi??
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Quoting StormW:


One thing you have to bear in mind though...If memory serves me right...all the maps prior to the 1995 map were when we were in the inactive cycle...so ya really want to look from 1995, on.


Yes, because the AMO went into its warm cycle in 1995. In terms of the PDO/AMO ocean-climate cycle, we are in roughly the same position as the mid-late 1940s, when the PDO was going cold and the AMO had been warm for a little while. This period was pretty bad for Florida:













Member Since: November 24, 2005 Posts: 635 Comments: 26547
607. MTWX
Quoting GeoffreyWPB:
Well...I am prepared for every season, no matter what the early indications may present. Everyone should be ready for the worse.
Quoting msgambler:
Just keep AL, MS coastlines out of the radar sites. Not ready for anymore storms

Just hope for the best... prepare for the worst... It is never a bad thing to be over prepared!!
Member Since: July 20, 2009 Posts: 23 Comments: 1392
Just keep AL, MS coastlines out of the radar sites. Not ready for anymore storms
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Well...I am prepared for every season, no matter what the early indications may present. Everyone should be ready for the worse.
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Quoting StormW:
Here are Levi's Analog Years, with my 1995, 1998, 2003 thrown in:

Quoting GeoffreyWPB:
I like those maps Storm! Not a lot of Fla. hits.


Here are all the tracks from those analogs combined (though I didn't include 2003 when I made this map). Heaviest concentrations of storm tracks are circled in blue. Florida does appear to get a break during a lot of these years, but the surrounding coastal states don't get so lucky.

Member Since: November 24, 2005 Posts: 635 Comments: 26547
In all actuality, it is still way too early to predict with any precision what this season will bring us. Late April and May will give us a much better idea of what may come to pass.
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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.