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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next one spinning up strong
Member Since: July 15, 2006 Posts: 163 Comments: 52257
Quoting GeoffreyWPB:
Just funnin Storm...We do have a lot of very smart and talented bloggers this year and I look forward to reading each and every one of their posts...


Why, thank you Geoff (lol, I wish).
Just a quick hello, my one and only baby boy (age 32) is finally flying "home" from Hawaii for a visit tomorrow.

One of our local mets is "concerned" about flooding around here this weekend...we're supposed to get rain all weekend, Fri. thru' Sun. You know how much I hate flooding... saw way more than enough of that down your way in '05.
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good evening all,

man does it feel good outside! now these nights feel way too much like summer, but fear not, spring break is next week (:
Member Since: June 28, 2006 Posts: 24 Comments: 8185
698. MTWX
latest from the SPC for tomorrow...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ERN PLAINS/OZARKS TO
THE CNTRL GULF COAST......

...SYNOPSIS...
NEXT IN A SERIES OF SRN-BRANCH SHORTWAVE TROUGHS IS EXPECTED TO
CONTINUE ESE FROM SRN NV TODAY...INTO NM TONIGHT...THEN EVENTUALLY
EJECTING NE INTO WRN MO/AR BY EARLY THURSDAY. ATTENDANT SFC LOW
WILL STRENGTHEN OVER NWRN OK WEDNESDAY AFTN...TRACKING TO NW MO BY
12Z THURSDAY. TRAILING THE LOW...A DRYLINE/CDFNT WILL SWEEP EWD
INTO WRN PARTS OF MO...AR AND E TX.

...NERN TX...ERN-NRN OK...SRN KS TO THE MID-SOUTH/OZARKS...
SVR THREATS WILL INCREASE WEDNESDAY AFTN/NIGHT ACROSS THE ERN
PORTIONS OF THE SRN PLAINS TO THE MID-SOUTH WITH RISKS FOR
TORNADOES...DMGG WINDS AND LARGE HAIL.

FAIRLY RAPID RETURN OF MOISTURE IS EXPECTED IN ADVANCE OF THE
APPROACHING SYSTEM AS PREVIOUS DISTURBANCE/FRONT STALLS ALONG THE
NWRN GULF COAST. EXPECT THAT BY LATE WEDNESDAY AFTN...SFC DEW
POINTS NEAR 50F WILL BE COMMON NEAR THE TRIPLE POINT ACROSS SRN
KS/NRN OK TO 60+F FROM AR SWD. COOL MID-LVL THERMAL PROFILES OVER
THE MOISTENING WARM SECTOR WILL CONTRIBUTE TO MLCAPES OF 500-1000
J/KG NEAR THE SFC LOW TO 1500+ FROM PARTS OF ERN OK/AR SWD TO THE
GULF COAST.

AS THE NOSE OF AN 85+ KT MID-LVL JET PUNCHES ENE ALONG THE BASE OF
THE UPR LOW...INCREASING ASCENT AND LOW-LVL CONVERGENCE INVOF THE
TRIPLE POINT WILL YIELD STG/SVR TSTM INITIATION OVER SCNTRL KS OR
NCNTRL OK BY MID-AFTN. ACTIVITY WILL THEN DEVELOP ESE ALONG THE
DRYLINE/OCCLUDED FRONT FROM SERN KS...ERN OK AND PERHAPS NERN TX
DURING THE LATE AFTN. FORECAST HODOGRAPHS EXHIBIT SUBSTANTIAL
LOW-LVL CURVATURE WITH SUFFICIENT DEEP-LAYER FLOW TO SUPPORT
SUSTAINED SUPERCELLS. THOUGH BOUNDARY LAYER MOISTURE WILL BE
SOMEWHAT MINIMAL...RELATIVELY LOW-LCLS...AMBIENT LOW-LVL VORTICITY
AND BENT-BACK ORIENTATION OF THE BOUNDARY IN NE QUAD OF THE SFC LOW
WILL BE FAVORABLE FOR TORNADOES ALONG WITH SVR HAIL AND DMGG WIND
GUSTS. WHILE ACTIVITY TRANSITIONS INTO LINES DURING THE EVENING
OVER ERN KS AND MO WITH SPORADIC HAIL/DMGG WINDS...SRN SECTIONS OF
THE ACTIVITY MAY REMAIN DISCRETE INTO THE MID-EVENING BEFORE GOING
QUASI-LINEAR. THUS...TORNADO POTENTIAL MAY LAST A FEW HOURS AFTER
DARK OVER PARTS OF AR/EXTREME SRN MO BEFORE HAIL/DMGG WINDS BECOME
MORE LIKELY OVER THE MID-SOUTH/MS RVR VLY OVERNIGHT.

...LWR MS RVR VLY/GULF COAST...
ANOTHER POTENTIAL MAXIMUM IN SVR RISKS WILL OCCUR OVER PORTIONS OF
THE LWR MS RVR VLY/GULF COAST. CONVECTION IS APT TO BE OCCURRING AT
THE START OF THE PERIOD OVER THE CNTRL GULF COAST REGION AS HIGHER
PW AIR MASS GRADUALLY ADVECTS NWD. HEATING/DEGREE OF
SFC-DESTABILIZATION IS IN QUESTION DUE TO PERSISTENT CLOUDS/PCPN.
BUT...INCREASING ASCENT IN THE EXIT REGION OF A STRONG SUBTROPICAL
JET COULD RESULT IN AN INCREASE IN SVR POTENTIAL DURING THE AFTN/EVE
FROM PARTS OF THE UPR TX COAST EWD. AMPLE VERTICAL SHEAR WILL EXIST
TO SUPPORT SUPERCELLS WITHIN LARGER-SCALE TSTM CLUSTERS. HIGHEST
PROBABILITIES FOR SVR WEATHER APPEAR TO BE DURING THE LATE
AFTN/OVERNIGHT FROM SRN LA TO PERHAPS THE FAR WRN FL PNHDL.
HERE...SRN FRINGES OF THE WARM-ADVECTION DERIVED STORMS WILL LIKELY
BE ROOTED CLOSER TO THE SFC AMIDST RETURN OF HIGHER QUALITY BOUNDARY
LAYER MOISTURE.
Member Since: July 20, 2009 Posts: 23 Comments: 1391


new storm total precip image
Member Since: July 15, 2006 Posts: 163 Comments: 52257


here is some new images i am creating by entering in lat lon and data coming from source great info may start using them on regular basis
Member Since: July 15, 2006 Posts: 163 Comments: 52257
Quoting Skyepony:
90Q
Click to loop



lookin rough
looks not to be there much longer
we could call it the invest that never was

Member Since: July 15, 2006 Posts: 163 Comments: 52257
694. Skyepony (Mod)
90Q
Click to loop

Member Since: August 10, 2005 Posts: 156 Comments: 36083
693. flsky
Quoting Jeff9641:
Here is the Friday's Severe Wx Outbreak!

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/00/fp0_072.shtml

This seem quite a bit different from GFS is predicting.
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Quoting beell:


That's what I thought they were, Keep!
Got labels and everything on them lol.
they do where i don't see'em

lol
Member Since: July 15, 2006 Posts: 163 Comments: 52257
Just funnin Storm...We do have a lot of very smart and talented bloggers this year and I look forward to reading each and every one of their posts. I also hope Weather 456, I think that was his handle, makes a return.
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Quoting StormW:
Time for me to sign off. Been nice answering questions, and Levi, been nice swapping info with ya!


Same here Storm! Have a good night.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting GeoffreyWPB:


Our premier chief met. has to delete the word "dat" from his vocabulary during Hurricane season. :)


Nooo let him keep it lol. It's great.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
684. JRRP

Quoting StormW:


This is the forecast plumes from the ECMWF (European Center for Medium range Weather Forecasting), which is a pretty accurate model, and usually is pretty right on with forecasting the SST departures. These plumes indicate that neutral conditions should take over beginning around MAY/JUN. Neutral being below 0.5C.


looks like we will see la Niña before the HS end
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Quoting StormW:


Gotta say I agree with dat!


Our premier chief met. has to delete the word "dat" from his vocabulary during Hurricane season. :)
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Quoting StormW:


Me too! I've noticed over the past 2 seasons, it's had the Nino's pegged. It does a decent job as far as hurricane stuff in the Atlantic, but it's Forte is PAC storms...it is usually deadly accurate with tracks over there.


Indeed, it really impressed me last year with the EPAC storms.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting Grothar:


What do you think of this Geoff????


Hawk!!!!
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Quoting StormW:


This is the forecast plumes from the ECMWF (European Center for Medium range Weather Forecasting), which is a pretty accurate model, and usually is pretty right on with forecasting the SST departures. These plumes indicate that neutral conditions should take over beginning around MAY/JUN. Neutral being below 0.5C.



I love the Euro....it seems to pick up on the ENSO trends months before the CFS models pick up on the correct trend. It picked up the death of the El Nino this summer 2 months before the CFS.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting GeoffreyWPB:
I heard on the news that aftershocks in Chile could last for months.


Not surprising. Aftershocks from the mag. 7.9 Sichuan earthquake continued for over a year.

Quoting Jeff9641:
Severe wx with the possibility of tornadoes from Florida to Kentucky is looking more and more likely with each model run for Friday. Could be a very large severe wx outbreak on Friday and maybe worse than Wednesday. So guys get ready!!


That low pressure system seems to be strengthening and the first cold front appears to be moving quickly and spiralling outward and slicing toward Ontario. We're currently expected to get about 35 mm from this storm from tomorrow night to Tuesday. Could we see some snow after that?
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Quoting StormW:
Here's one for ya...check out these anomalies...we had 15 named storms that season.



16 storms in 2003


I love 2000. It was a complete fall off a cliff from the 1997-98 El Nino, and marked the end of the warm PDO cycle. 2000 was the center year of a 3 and a half year long La Nina, which peaked during the winter of 1999-2000. This year in my mind proved once and for all that SSTs are not the sole determiner of an active hurricane season. By 2000 the world oceans had been very cold since the latter half of 1998, and the tropics had very little heat. It's amazing how cold the oceans were as a whole looking at that anomaly map. And yet 15 storms still formed despite cold waters in the tropical Atlantic and little heat in the tropical atmosphere world-wide. This was because of favorable upper-level conditions that existed over the tropical Atlantic during 2000, due to the La Nina, which allowed many storms to form. This debunks the belief that without warm SSTs hurricane seasons have no chance.

ONI from 1997-2002:

Member Since: November 24, 2005 Posts: 628 Comments: 26455
673. JRRP
,
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Grothar...Some good chances of rain starting tomorrow and going possibly thru Saturday. And then some cooler, though seasonable, temps.
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thanks StormW....When is el nino expected to go towards neutral?
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Quoting StormW:


The ones of the globe are Sea Surface Temperature Anomalies. From top to bottom are from Feb 15, 2010 to Mar 7, 2010, showing the demise of El Nino.


Thank you Storm...that is exactly what I am talking about. Just a brief explanation of what is being posted.
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What do you think of this Geoff????
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Jeffs...do you ever post some good news? :)
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Thank you KOG...as we get closer to Hurricane season, a lot of us would like a brief explanation of what certain graphs and such mean.
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664. beell
Quoting KEEPEROFTHEGATE:
my image i posted is three day average sst temps for east pacific gom atlantic basins ending march 9 2010


That's what I thought they were, Keep!
Got labels and everything on them lol.
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StormW...what are the maps you post indicating?
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Quoting GeoffreyWPB:
Love it when bloggers post graphs and pics, and don't explain what they are showing. Maybe they don't even know!
my image i posted is three day average sst temps for east pacific gom atlantic basins ending march 9 2010
Member Since: July 15, 2006 Posts: 163 Comments: 52257
Love it when bloggers post graphs and pics, and don't explain what they are showing. Maybe they don't even know!
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Ah, needs work, but also needs to be said.
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658. JRRP
Quoting StormW:









goodbye Niño
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Member Since: July 15, 2006 Posts: 163 Comments: 52257
Goodevening and goodnight!
Looks like Alabama and Georgia should get some rain. Loop
Here's the national loop should you want to see the whole picture. Natloop
I am exhausted. Have a nice evening everyone.
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I heard on the news that aftershocks in Chile could last for months.
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I wonder where Grothar is tonight?
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still shaking in chile
Member Since: July 15, 2006 Posts: 163 Comments: 52257
Oz is the official poet laureate of the blog :)
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About JeffMasters

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