Record Atlantic SSTs continue in the hurricane Main Development Region

By: Dr. Jeff Masters , 8:03 PM GMT on May 15, 2010

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Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest April on record, 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 area between 10°N and 20°N, between the coast of Africa and Central America (20°W - 80°W), 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.) SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.46°C above average during April. This is the third straight record warm month, and the warmest anomaly measured for any month--by a remarkable 0.2°C. The previous record warmest anomalies for the Atlantic MDR were set in June 2005 and March 2010, at 1.26°C.


Figure 1. The departure of sea surface temperature (SST) from average for May 13, 2010. Image credit: NOAA/NESDIS.

What is responsible for the high SSTs?
As I explained in detail in a post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are largely to blame for the record SSTs. 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. If the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), this creates a weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, we had the most negative AO/NAO since records began in 1950, and this caused trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region to slow to 1 - 2 m/s (2.2 - 4.5 mph) below average. 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 heated up significantly, relative to normal, over the winter. Negative AO/NAO conditions have been dominant much of this spring as well, resulting in further anomalous heating of the MDR waters. This heating is superimposed on the very warm global SSTs we've been seeing over the past few decades due to global warming. Global and Northern Hemisphere SSTs were the 2nd warmest on record this past December, January, and February, the warmest on record in March, and will likely be classified as the warmest or second warmest on record for April, since NASA just classified April as the warmest April on record for the globe. We are also in the warm phase of a decades-long natural oscillation in Atlantic ocean temperatures called the Atlantic Multi-decadal Oscillation (AMO). This warm phase began in 1995, and has been partially responsible for the high levels of hurricane activity we've seen since 1995.

What does this imply for the coming hurricane season?
The high April SST anomaly does not bode well for the coming hurricane season. The three past seasons with record warm April SST anomalies all had abnormally high numbers of intense hurricanes. Past hurricane seasons that had high March SST anomalies include 1969 (0.90°C anomaly), 2005 (1.19°C anomaly), and 1958 (0.97°C anomaly). These three years had 5, 7, and 5 intense hurricanes, respectively. Just two intense hurricanes occur in an average year. The total averaged activity for the three seasons was 15 named storms, 11 hurricanes, and 6 intense hurricanes (an average hurricane season has 10, 6, and 2.) Both 1958 and 2005 saw neutral El Niño conditions, while 1969 had a weak El Niño.

The SSTs are already as warm as we normally see in July between Africa and the Caribbean, and we have a very July-like tropical wave approaching the Lesser Antilles Islands this weekend. However, wind shear is still seasonably high, and the tropical waves coming off of Africa are still too far south to have much of a chance of developing. The GFS model is indicating that shear will start to drop over the Caribbean the last week of May, so we may have to be on the watch for tropical storms forming in the Caribbean then.

For those of you interested in a more detailed look at the early season tropical weather outlook, consult the excellent wunderblogs of StormW and Weather456. I'll be back with a new post on Monday.

Jeff Masters

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969. Skyepony (Mod)
Nice ASCAT of 93A


93A is bottom center in the Arabian Sea, 92B is to the right of there.

Checking the rainrate 92B is putting out more..
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Member Since: July 15, 2006 Posts: 173 Comments: 54325
Quoting Patrap:
GOM SST May 15 2010



2009





IT WILL NOT MATTER AT THIS POINT IF THE GULF IS NOT AT 27C IT ONLY TAKE A LITTLE TO WARM IT UP.




I BELIEVE THAT THIS YEAR WILL BE VERY CLOSE TO PASS 2005 RECORD OR EVEN GO OVER BY 1 MAYBE 2 STORMS
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Quoting CycloneOz:
tornadodude is in the lion's den.
where is he oz
Member Since: July 15, 2006 Posts: 173 Comments: 54325
965. JRRP
Quoting Stormchaser2007:
Might be something to keep an eye on during the week.


nice low at 180 hr
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tornadodude is in the lion's den.
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Quoting StormW:


Well...kinda! Hey mobilegirl...how are you this eve?
Great storm, seems almost all signals are in place for an active season.
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Might be something to keep an eye on during the week.

Member Since: June 9, 2007 Posts: 4 Comments: 15921
Quoting CybrTeddy:


2005 right?


Yup, my bad.

Just fixed it.
Member Since: June 9, 2007 Posts: 4 Comments: 15921
Quoting Stormchaser2007:


Those are inaccurate I guess.
2010 compared to 2010.




2005 right?
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18z GFS develops a broad low in the Caribbean in 96 hours.

GFS 18z at 150 hours

Member Since: June 9, 2007 Posts: 4 Comments: 15921
Quoting Stormchaser2007:


Those are inaccurate I guess.
2010 compared to 2010.


I think so too.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
May 16, 2005



May 16, 2010



*2005 looking warmer, imo.


Those are inaccurate I guess.
2010 compared to 2005.


Member Since: June 9, 2007 Posts: 4 Comments: 15921
nw atl basin wv image 601 20 mins ago
Member Since: July 15, 2006 Posts: 173 Comments: 54325
Quoting mobilegirl81:
Ive heard everyone talking about how all signals are go for conducive atmospheric conditions this season. Just a question of the way everything aligns and the timing. The only thing we can do is speculate.


The formation of tropical cyclones is the topic of extensive ongoing research and is still not fully understood. While six factors appear to be generally necessary, tropical cyclones may occasionally form without meeting all of the following conditions. In most situations, water temperatures of at least 26.5 °C (79.7 °F) are needed down to a depth of at least 50 metres (160 ft); waters of this temperature cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms. Another factor is rapid cooling with height, which allows the release of the heat of condensation that powers a tropical cyclone.High humidity is needed, especially in the lower-to-mid troposphere; when there is a great deal of moisture in the atmosphere, conditions are more favorable for disturbances to develop. Low amounts of wind shear are needed, as high shear is disruptive to the storm's circulation. Tropical cyclones generally need to form more than 555 kilometres (345 mi) or 5 degrees of latitude away from the equator, allowing the Coriolis effect to deflect winds blowing towards the low pressure center and creating a circulation. Lastly, a formative tropical cyclone needs a pre-existing system of disturbed weather, although without a circulation no cyclonic development will take place.

Member Since: July 15, 2006 Posts: 173 Comments: 54325
tornadodude reports its totally dropping something!

XtremeHurricanes.com Live Webcam!!!

Hear tornadodude LIVE ON THE CELL PHONE!

It's pretty intense!

Click the Live Tornado Chase Button...

I'll be in the chat!
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Ive heard everyone talking about how all signals are go for conducive atmospheric conditions this season. Just a question of the way everything aligns and the timing. The only thing we can do is speculate.
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May 16, 2005



May 16, 2010



*2005 looking warmer, imo.
Member Since: September 2, 2009 Posts: 130 Comments: 21194




2010 Hurricane Preparation..re-loaded
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Rain on the increase for so. Fla. tonight and especially tomorrow and Tuesday.

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Quoting Patrap:


Wishcasting on the wunderground,...explained



Tunnels?
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Quoting Chucktown:


What up Cyber? Just preparing for another hurricane season here along the SE coast.


You and everyone else.. best get it early. Anyone that needs help with supplies should refer to Pat, he usually knows what to get.

There's also a list, er, or should be, on how to deal with WU blogging on Dr. Jeff Masters blog.. Advil especially is key.

Good thing I got the iPad, so I can blog now on my pool deck and enjoy life..
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945. JRRP
Quoting Patrap:
..We were promised flying cars in the 60's..

Im still waiting

jajajajaja
well
we will see if Global Warming....
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Quoting Drakoen:
The ridge the ECMWF is showing over the northeast will keep things interesting as far as track for any prospective storm...
192 Hours - May 24th

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Patrap:
..We were promised flying cars in the 60's..

Im still waiting


you didn't watch Dukes of Hazard? .. the General Lee flew all the time...
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ROFL That is one of my all time favorite diatribes, thanks for posting!
Quoting Patrap:


Wishcasting on the wunderground,...explained

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The ridge the ECMWF is showing over the northeast will keep things interesting as far as track for any prospective storm...
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Quoting Patrap:



One can follow the Global 26C Isotherm here


A little spot of yellow where the oil slick is. Oil being dark as it is, might absorb a lot of solar radiation.
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hey cybrteddy could I get the link to that modelthe Euro one thank you
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The model consensus for shear is not looking good. However, it could be the models poor to handle change in vertical shear as the MJO passes. The MJO promotes upward and outward motion which reduces the magnitude of upper level winds.

Because of this, development is not a certain thing, only a possibility.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
What the ECMWF shows is a broad but closed area of low pressure. Not really considering that development.

When we get something solid on the ECMWF is when I will really take notice.
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..We were promised flying cars in the 60's..

Im still waiting
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Quoting CybrTeddy:


Euro is also on board last I checked. Models bring it towards Cuba then eject it out to sea, easily could foresee that. GFS has been on board with a system developing in May for a while.. I learned my lesson from Bertha: If any model predicts a tropical cyclone to form for weeks, no matter how strange it might be, and then later on models start jumping on we're most likely going to get something. Not saying that applies here..
GFS has it close to Haiti. They do not need any storms.
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Quoting CybrTeddy:
.. I must have, maybe I should keep him there for the sake of continuity.

EDIT: no wait, I see Chucktown..

How is it going Chucktown?


What up Cyber? Just preparing for another hurricane season here along the SE coast.
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933. JRRP
Quoting CybrTeddy:


Euro is also on board last I checked. Models bring it towards Cuba then eject it out to sea, easily could foresee that. GFS has been on board with a system developing in May for a while.. I learned my lesson from Bertha: If any model predicts a tropical cyclone to form for weeks, no matter how strange it might be, and then later on models start jumping on we're most likely going to get something. Not saying that applies here..

yeah
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Conservatively, 17-9-5
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Quoting Drakoen:
I see the GFS is forecasting for development in the southern Caribbean which coincides with its forecast for a decent MJO pulse which the other models continue to downplay.


Euro is also on board last I checked. Models bring it towards Cuba then eject it out to sea, easily could foresee that. GFS has been on board with a system developing in May for a while.. I learned my lesson from Bertha: If any model predicts a tropical cyclone to form for weeks, no matter how strange it might be, and then later on models start jumping on we're most likely going to get something. Not saying that applies here..
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Quoting kimoskee:
We were promised rain today. Not one drop. Sigh.


You can have some from here...my yard is a pool right now. At least the streets finally cleared up and drained out.
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We were promised rain today. Not one drop. Sigh.
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Quoting xcool:
MJO wet pulse


GFS has been hurrying it, it's better to just look at this graph:

Member Since: September 2, 2009 Posts: 130 Comments: 21194
I see the GFS is forecasting for development in the southern Caribbean which coincides with its forecast for a decent MJO pulse which the other models continue to downplay.
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Quoting HaboobsRsweet:


First off I did not use the word wishcasting. Just stated a few things that I see on why I dont think anything is going to happen until mid June. Doesnt mean I am right, I can be wrong. You are totally entitled to your opinion. I just feel too many people are looking at all the small things that are important to tropical development but sometimes overlook the big picture. If you have followed what I have been saying for the last week or so, that is my forecast on when I think the first storm will be.

I see what 456 is talking about the STJ. The STJ could produce high levels of shear, but I may have missed placed it and will take another look at it.


Wasnt a reaction to your post, I know you didnt call anyone a wishcaster
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Quoting Hurricanes101:
wishcasting?

cuz some of us feel that there could be development in the SW Caribbean next week?

Really??

Wow guess we just shouldnt talk about it at all then lol. So when should I be back to talk tropics? June 13th? Ok see you guys then lol


First off I did not use the word wishcasting. Just stated a few things that I see on why I dont think anything is going to happen until mid June. Doesnt mean I am right, I can be wrong. You are totally entitled to your opinion. I just feel too many people are looking at all the small things that are important to tropical development but sometimes overlook the big picture. If you have followed what I have been saying for the last week or so, that is my forecast on when I think the first storm will be.

I see what 456 is talking about the STJ. The STJ could produce high levels of shear, but I may have missed placed it and will take another look at it.
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.. I must have, maybe I should keep him there for the sake of continuity.

EDIT: no wait, I see Chucktown..

How is it going Chucktown?
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923. JRRP
Quoting xcool:
i think 16-5-8

excuse me xcool but 5 hurricanes and 8 mayor hurricanes ??
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Quoting CybrTeddy:


I don't see anyone calling anyone a wishcaster.. nor any wishcasting going on.

5 years of this and still going strong..

.. its a wonder how I haven't suffered heart failure.. after big 'K' 'R' 'W' 'D' 'F' 'G' and big 'I'.. god knows what letter of the alphabet I'll have to add to that list this year.. big 'Z' for all I know.


You must have Chucktown on ignore, post 909 he said the wishcasting was already ridiculous
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Quoting Chucktown:


Better solution is to wait to see IF something develops then discuss where it may go or develop further, the models, especially the GFS is very climatologically driven beyond 7 days.


but discussing the possibilites is not wishcasting whatsoever

To compare the two is ridiculous and undercuts any sort of conversation that can be had here

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Quoting Hurricanes101:
wishcasting?

cuz some of us feel that there could be development in the SW Caribbean next week?

Really??

Wow guess we just shouldnt talk about it at all then lol. So when should I be back to talk tropics? June 13th? Ok see you guys then lol


I don't see anyone calling anyone a wishcaster.. nor any wishcasting going on.

5 years of this and still going strong..

.. its a wonder how I haven't suffered heart failure.. after big 'K' 'R' 'W' 'D' 'F' 'G' and big 'I'.. god knows what letter of the alphabet I'll have to add to that list this year.. big 'Z' for all I know.
Member Since: Posts: Comments:
Quoting Hurricanes101:
wishcasting?

cuz some of us feel that there could be development in the SW Caribbean next week?

Really??

Wow guess we just shouldnt talk about it at all then lol. So when should I be back to talk tropics? June 13th? Ok see you guys then lol


Better solution is to wait to see IF something develops then discuss where it may go or develop further, the models, especially the GFS is very climatologically driven beyond 7 days.
Member Since: Posts: Comments:

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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.