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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Quoting GTcooliebai:

I can't even see Florida
And I live there, lol, not good.
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Quoting stormpetrol:

I'll be in your country( Belize) Leaving Grand cayman on May 27 and returning on June 3, sure hope no tropical weather disrupts our family travels plans, looking forward to visiting for the first time.
I think you well be disrupted greatly by the upcoming upward motion MJO. Plus models are showing development in that region for those dates.
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1964, My birth year Nov 3, to be exact.
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Quoting MiamiHurricanes09:
Sum of storm tracks of 7 analog seasons (1958, 1964, 1966, 1969, 1995, 1998, 2005)


I can't even see Florida
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Hello everyone
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113. xcool
18z come soon
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Quoting belizeit:
I believe shear will not really let that next tropical wave to develop as it comes of Africa

I'll be in your country( Belize) Leaving Grand cayman on May 27 and returning on June 3, sure hope no tropical weather disrupts our family travels plans, looking forward to visiting for the first time.
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Sum of storm tracks of 7 analog seasons (1958, 1964, 1966, 1969, 1995, 1998, 2005)

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Link Just look i am going to get some rain at last
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Quoting P451:
Good afternoon. 12HR WV Ending 2045Z


Thank you again this year for these loops!
They do help me see what is taking place.

CRS
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I believe shear will not really let that next tropical wave to develop as it comes of Africa
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2010 sure to have some twists and turns aussie..so I expect the norm can be tossed out in the MDR if these Temps increase, even slightly.


A Wave or impulse in the Caribbean last week of May can spawn trouble for many depending on track as well.
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting all4hurricanes:

wow look at that we have a significant blob in the Atl
That's the 12z, I'll post the 18z when it comes out.
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The Icelandic Volcano wont have a effect on the MDR in the Atlantic..and is way too North for any foreseeable effect as well.

Member Since: July 3, 2005 Posts: 421 Comments: 127636
GFS and GEFS forecasting that the next upward MJO pulse will skip the western pacific altogether.

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Quoting Patrap:
CV waves season typically begins late July,..thru the October early time frame.

We dont look to Africa and the Eastern Atlantic in Mid May nor June hardly.

The West Caribbean and the GOM proper usually give way to the early third of the seasonal action.


True Pat I know, but it sames like everything these days are defying the norm was just wondering that's all.
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wow look at that we have a significant blob in the Atl
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CV waves season typically begins late July,..thru the October early time frame.

We dont look to Africa and the Eastern Atlantic in Mid May nor June hardly.

The West Caribbean and the GOM proper usually give way to the early third of the seasonal action.



Member Since: July 3, 2005 Posts: 421 Comments: 127636
Will this possibly be a Cape Verde Season( another anomaly in the books) in late May or early June?
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Impressive area of low pressure (1006 MB) about to emerge off of Africa, and it's much more north than all the other ones we have seen so far.

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Good evening everybody,

looks like we will be busy this year as we were in 05. With Weather456 and StormW both saying this could be "Bad" for the Season, well I have to agree with them... I hate the fact that we could be looking at another Katrina or even a Andrew Type Storm this year really bothers me..... Then lets add all the Oil in the Gulf on top of that.... It does look bad....

Thanks for the Update Guys...

Taco :o(
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Current NAO.
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100421-G-XXXXA-002 - Air Station New Orleans hoists survivor from assist vessel

Date: 04/21/2010
Views: 558
Full size: 960x540





NEW ORLEANS A Coast Guard MH-65C rescue helicopter and crew from Coast Guard Air Station New Orleans hoists a survivor from the mobile offshore drilling unit (MODU) Deepwater Horizon April 21, 2010. Multiple Coast Guard helicopters, planes and cutters are responding to rescue 126 people after the Coast Guard eighth district command center received a report that the Deepwater Horizon had experienced an explosion at approximately 10 p.m. April 20, 2010. U.S. Coast Guard video by Coast Guard Air Station New Orleans.
Member Since: July 3, 2005 Posts: 421 Comments: 127636
USCG VIDEO

100421-G-XXXXL- Deepwater Horizon fire

NEW ORLEANS - Fire boat response crews battle the blazing remnants of the off shore oil rig Deepwater Horizon April 21, 2010. A Coast Guard MH-65C Dolphin rescue helicopter and crew document the fire aboard the mobile offshore drilling unit Deepwater Horizon, while searching for survivors April 21, 2010. Multiple Coast Guard helicopters, planes and cutters responded to rescue the Deepwater Horizon's 126 person crew.
Member Since: July 3, 2005 Posts: 421 Comments: 127636
All regions of the North Atlantic are above average in shear right now.. With the exception of the East Coast. Caribbean looks like it's gonna take a dip soon as well.










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I was watching that bunch of clouds yesterday and even this morning but now they are starting to look a little more serious.. or am I just seeing things.. will read back...
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Deepwater Horizon Response Press Conference, Part 1

Joint Public Affairs Support Element More Videos from Joint Public Affairs Support Element RSS
Video by Lt. Scott Sagisi


Date Taken: 05.15.2010
Posted: 05.15.2010 16:02
Video Location: LA, US
Brief the media on the continued efforts to combat the oil spill from the Deepwater Horizon well. Part 1 of 2. Oilspill10
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting wadedanielsmith:


You ever try pushing a 21inch diameter plunger vs ~22500psi? Not happening! That's 7.8 million pounds. Now if you factor out the 6 inch diameter pipe, then you reduce the net force down to 7.15 million pounds.

The point is, they don't have a machine strong enough to foce the "plug" into the pipe against that kind of pressure.

Its likely going to take the relief well with some sort of exotic concrete that doesn't use water, since the methane will rob the water content and ruin the curing process. It also needs to be ridiculously dense, far more dense than "normal" concrete, which probably means using pure metallic ball bearings (steel or lead) as the aggragate instead of gravel...Anything else won't be dense enough or strong enough to block off the flow.


That's bogus science... they are not pushing against all that pressure, they are pushing against flow.
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Hi StormW,

Is that bunch of Clouds by South America really something to watch?
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Radar Image from CSTARS, May 14, 2010

ESL by LSU
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Im going with 16 8 4 hopefully no more than that will form but all the signs seem to be pointing in that direction,,
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Thanks Weather456
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Tropical Wave Bears Watching by South America ,imo
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Quoting MiamiHurricanes09:
What is 2010 showing so far?


We basically went from a favorable pattern during the winter due to El Nino and -NAO (top image) to an unfavorable pattern (bottom 2 images). By looking at changes since January 1, we can see the pattern changing and then project this based on the forecast. We use this to speculate unfavorable storm tracks this hurricane season.

Jan 1 - May 13


April 1 - May 13



May 1 - May 13




We can use this to get an idea of the grand scheme of things but its impossible to know how the pattern maybe like on September 10 2010. That we cannot predict with any good accuracy. What we strive to do is give an idea of the long-term pattern.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting P451:
Good afternoon. 12HR WV Ending 2045Z

The band to the northwest of the strongest convection makes it look like a TS.
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81. JRRP

activity near 17n 70w
Member Since: August 16, 2007 Posts: 0 Comments: 5481
79. JRRP
Quoting pottery:

I tend to agree with you. But 09 had lots of shear too.

so do you really think that may be we will see 42 name storms? :O
Member Since: August 16, 2007 Posts: 0 Comments: 5481
OK, I'm out until later.
And for anyone new lurking around, please note that my comments about 42 storms, mega-canes, hyper-activity etc, have absolutely no basis in fact.
Laters.....
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Quoting Weather456:


I know I heard him talked about that. The high that parks over Texas is called a continental ridge and forms from the expansion of heat over the summer landscape. It is tied to the North American Monsoon but that is a story in its self. The high that parks over Texas sometimes protect the state from tropical cyclones.

It has found that anomalous high heights over Eastern Canada during the peak of hurricane season creates a blocking pattern for mid-latitude storms to the north which help recurve cyclones and help steer cyclones into the CONUS from the south.


Unfavorable Years - focus on Eastern Canada

2005



2004



2008



Favorable Years

2006



2009



1998





What is 2010 showing so far?
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Quoting Skyepony:
Dr Masters~ Great blog & on a Saturday:) I was wundering..Do you think there is still no chance we will ever see another season like 2005 again in our lifetime?


I know, we were all here that first summer of weather blogs in 2005 and it was so crazy...

we all "cut our blogging teeth" on a really unusual historic hurricane season.
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Quoting CybrTeddy:
I understand why now 2005 and 2010 are so similar.. 2005 had every single ingredient come together for an insane season.. 2010 has followed the same footprints. Same TCHP, SSTs, dying (now dead) El Nino, same amount of tornadoes in the US, negative NAO. To boot, we have something that if 2005 had, would have been way worse, low dust in the Atlantic.
Correct.
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El Nino officially dead.

ENSO Wrap-Up

The El Niño event of 2009/10 has concluded, with all the major indicators now below El Niño thresholds. Latest observations show that sea surface temperatures, trade winds, the Southern Oscillation Index and cloudiness over the Pacific have all returned to levels considered typical of neutral (i.e. neither El Niño nor La Niña) conditions. The timing of the decline in the 2009/10 El Niño event has been fairly typical, with the event peaking over summer then decaying during autumn.

Historically, about 40% of El Niño events are immediately followed by a La Niña. Current conditions below the surface of the Pacific Ocean show large volumes of cooler than normal water, indicating that further cooling of the surface is likely.

The majority of climate model predictions suggest the tropical Pacific will cool further during the coming months, with the possible development of La Niña conditions by late winter or spring. No climate models suggest a return to El Niño conditions. As autumn is a typical transitional period for ENSO, model predictions through and beyond autumn are generally less reliable than at other times of the year.
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Quoting pottery:

Or maybe just one continuous, mega-cane that goes on for 6 months....


Oh NOOOOOO!!!!!


We had such a cold and wet winter/dry season and now an earlier than normal hot and humid... anything could happen.
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Quoting CybrTeddy:
I understand why now 2005 and 2010 are so similar.. 2005 had every single ingredient come together for an insane season.. 2010 has followed the same footprints. Same TCHP, SSTs, dying (now dead) El Nino, same amount of tornadoes in the US, negative NAO. To boot, we have something that if 2005 had, would have been way worse, low dust in the Atlantic.

I tend to agree with you. But 09 had lots of shear too.
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Quoting tramp96:
basically yes but we still have to account for the timing of other features that affect steering.

Levi talked about high pressure parking near Hudson Bay. Is that something that is similar to the high that parks over Texas every year and if so what are the consequences?


I know I heard him talked about that. The high that parks over Texas is called a continental ridge and forms from the expansion of heat over the summer landscape. It is tied to the North American Monsoon but that is a story in its self. The high that parks over Texas sometimes protect the state from tropical cyclones.

It has found that anomalous high heights over Eastern Canada during the peak of hurricane season creates a blocking pattern for mid-latitude storms to the north which help recurve cyclones and help steer cyclones into the CONUS from the south.


Unfavorable Years - focus on Eastern Canada

2005



2004



2008



Favorable Years

2006



2009



1998





Member Since: July 24, 2005 Posts: 407 Comments: 19076

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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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