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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Stay safe all, Goodnight
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Member Since: July 15, 2006 Posts: 169 Comments: 53296
Climate:

Houston reached 80 degrees yesterday the first time we have seen 80 since November 15, 2009…now that is impressive this far south and gives a testament to just how cold this winter has been. The area has just suffered through one of the coldest winter periods on record and the month of February averaged significantly below normal. Houston recorded its 5th coldest February on record (6.9 degrees below average), Hobby its 3rd (8.4 degrees below average) and College Station its 5th (7.8 degrees below average). Victoria tied for its 2nd coldest February on record! Houston only had 2 days of temperatures above average during the entire month. From the period of Dec 1-Feb 28th (meteorological winter) Houston suffered its 6th coldest winter ever and the coldest since 1977-1978, Galveston its 5th coldest winter ever, and College Station its 6th coldest winter ever. Additionally, at Corpus Christi, the number of days that were at or above 70 in February 2010 was only 4…last year there were 26 with the average being 12.
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746. WAHA
I have to go to school, we're taking the FCATs so yeah,...bye
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Oklahoma Tornado Video

Link
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741. WAHA
Quoting wunderkidcayman:
hi guys talk to me about our 90 SL/Q/L

Click here.
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Good Morning...
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hi guys talk to me about our 90 SL/Q/L
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Well, there goes my yard work for today!!!

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In January 2010 map of anomalies Met Office Hadley Center SST did not contain data off the coast of Somalia in Africa (2nd map - 9 of empty white cells). However, in February 2010 Met Office Hadley Center, apparently reached an agreement with the pirates (?), And those allowed to perform measurements (1st map) (?)
Link
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Met Office Hadley Center SST anomalies February 2010
Link

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Hi everyone. Not digging the analog years being thrown around lately. They were not good to Texas.

From best I can tell three of the analog years saw no TX storms. 1948 -50 & 66.
The rest sigh. :(
9 of the years had an upper TX coast hit. 14 had one or more TX hits.

That's all interesting... and scary, but more importantly, the best advice I read on here is everyone be prepared. Mother Nature likes her surprises.
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732. HadesGodWyvern (Mod)
Fiji Meteorological Services
Tropical Disturbance Summary
TROPICAL DEPRESSION 13F //
TROPICAL DISTURBANCE 14F

21:00 PM FST March 10 2010
==============================

At 6:00 AM UTC, Tropical Depression 13 (1003 hPa) located at 13.5S 169.5E is reported as moving slowly. Position POOR based on infrared imagery with animation and the latest microwave imagery. Sea surface temperature is around 30C. Vertical wind shear is low.

The potential for this disturbance to form into a significant tropical cyclone within the next 24-48 hrs is MODERATE.

System #2
---------

At 6:00 AM UTC, Tropical Disturbance 14 (1005 hPa) located at 11.5S 170.0W is reported as slowly moving. Position POOR based on infrared imagery with animation and the latest microwave imagery. Sea surface temperature is around 30C. Vertical wind shear is low. The EC global weather model expect 14F to slowly move southwest and gradual intensify.

The potential for this disturbance to form into a significant tropical cyclone within the next 24-48 hours is MODERATE.
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731. HadesGodWyvern (Mod)
Seychelles Meteorological Services
Tropical Disturbance Advisory Number FIVE
DEPRESSION TROPICALE 13-20092010
10:00 AM Réunion March 10 2010
====================================

At 6:00 AM UTC, Tropical Depression 13R (1002 hPa) located at 20.6S 49.6E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as moving west southwest at 5 knots.

Dvorak Intensity: T2.5

Near Gale-Force Winds
=====================
within the center in southern semi-circle

Forecast and Intensity
=====================
12 HRS: 20.7S 48.8E - 35 knots (Tempête Tropicale Moderée)
24 HRS: 20.5S 48.2E - (Depression sur terre)
48 HRS: 19.5S 45.2E - (se Dissipant)

Additional Information
=======================
MSLP has been adjusted 5 hPa higher than normal to take into account the high environemntal pressure (set at 1013 hPa). Convection still remains quite flactuating however with the usual flare up of convection taking place by the end of the night of central dense overcast has redeveloped. Microwave imagery (TRMM) shows a definite improvement of the low level circulation compared to yesterdayl. With a landfall expected to occur on the Malagasy coast next night (between Mananjary and Mahanoro) the favorable window is limited to the coming 12 hours for an intensification that may lead to system reaching the moderate tropical storm stage. The depression is evolving in phase with an upper high cell implying minimal vertical wind shear and rather good upper divergence. The system should track on a more westward direction under the steering influence of low and mid level highs.
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Quoting MTWX:
Well tome for me to go to bed. Y'all have a good night!! Heading to Biloxi this weekend to go fishing, so probably won't be back on till Monday. So I should say have a nice weekend!! Levi, you hold in there and take care of your neighbors!!


Will do MTWX, have a good weekend :)
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting MTWX:
Well tome for me to go to bed. Y'all have a good night!! Heading to Biloxi this weekend to go fishing, so probably won't be back on till Monday. So I should say have a nice weekend!! Levi, you hold in there and take care of your neighbors!!


have a good one! enjoy the fish :P
Member Since: June 28, 2006 Posts: 24 Comments: 8201
728. MTWX
Well tome for me to go to bed. Y'all have a good night!! Heading to Biloxi this weekend to go fishing, so probably won't be back on till Monday. So I should say have a nice weekend!! Levi, you hold in there and take care of your neighbors!!
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was just on I-90 last month up in Chicago :p
Member Since: June 28, 2006 Posts: 24 Comments: 8201
Quoting AwakeInMaryland:
Levi,
I had to chuckle (at myself) -- I had to look up I-90 -- the mess I was thinking about was mostly I-95.

Oh, and I think we've got more idiots who try to go out. :)

Really putting 'puter in sleep mode now.
Stay safe all.



Oh dang I think I meant I-95 up and down the eastern seaboard LOL. Sorry...I-90 runs across the northern USA.

You can really tell I don't live there...
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting KEEPEROFTHEGATE:
in about three weeks maybe current pattern looks to last for awhile yet


Well the ensembles show the upper low shifting eastward over us as this low exits, leaving calmer but frigid weather over us for the rest of the week. The next storm doesn't move in until this weekend, and will be much weaker than these storms. Thereafter I think the pattern will shift back to normal to above-normal temperatures as a southerly flow aloft develops over the state for the last half of March, which is typical of this winter so far, which has averaged well above normal until this past week.

It's funny how the correlation works....SE USA gets a horrid winter and we get a very warm one, then the SE USA gets a 1-week break and winter comes to hammer us for that week instead.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Levi,
I had to chuckle (at myself) -- I had to look up I-90 -- the mess I was thinking about was mostly I-95.

Oh, and I think we've got more idiots who try to go out. :)

Really putting 'puter in sleep mode now.
Stay safe all.

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723. xcool
anyone have win 7
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722. MTWX
Quoting MTWX:

Being from Montana I know exactly what you are talking about population density wise. Believe it or not we don't get that much snow up there really, it just gets rediculously cold!!

The only time that the schools closed due to weather when I live there was on a nice sunny day. air temp: -42F wind chill: -64F
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721. xcool
16-7-4 2010
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720. MTWX
Quoting Levi32:


I know it bugs me lol. Nobody, TWC, Accuweather, National news, even cares what goes on up here, but I guess that's sort of understandable when we have an average of less than 1 person per square mile.

But it's ridiculous....weather sites can't even bother to put rain/ice/snow algorithms on our radar imagery! That particular little issue I have never understood. Thank God for WU's rain/mix/snow local radar product.

Being from Montana I know exactly what you are talking about population density wise. Believe it or not we don't get that much snow up there really, it just gets rediculously cold!!
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Quoting MTWX:
Levi you will have to get us some pictures once the weather finally lets up... Whenever that is!!


I shall try.

Quoting AwakeInMaryland:
710. Thanks, Levi,
Funny how your paragraph 1 is SO completely different than living here ... the Bos-Wash corridor is so densely populated;

But para. 2, exactly the same, no different, than here during our big -- approx. once(?) a decade -- snowstorms!

Take care!

Time for me to hit the hay, good night!


Yeah I can only imagine how crippling it is down there in the I-90 corridor.

Have a good night AIM :)
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting MTWX:
Levi you will have to get us some pictures once the weather finally lets up... Whenever that is!!
in about three weeks maybe current pattern looks to last for awhile yet
Member Since: July 15, 2006 Posts: 169 Comments: 53296
710. Thanks, Levi,
Funny how your paragraph 1 is SO completely different than living here ... the Bos-Wash corridor is so densely populated;

But para. 2, exactly the same, no different, than here during our big -- approx. once(?) a decade -- snowstorms!

Take care!

Time for me to hit the hay, good night!
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716. MTWX
Quoting KEEPEROFTHEGATE:

Nothing severe yet... I think I only heard one rumble of thunder earlier today... got some good rain this morning though.
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Quoting MTWX:

You never hear anything about storms like that on the Weather Channel or any of the news networks. People just act like Alaska doesn't exist. Anyone in the lower 48 would think the world has ended if anything like that hit us!!


I know it bugs me lol. Nobody, TWC, Accuweather, National news, even cares what goes on up here, but I guess that's sort of understandable when we have an average of less than 1 person per square mile.

But it's ridiculous....weather sites can't even bother to put rain/ice/snow algorithms on our radar imagery! That particular little issue I have never understood. Thank God for WU's rain/mix/snow local radar product.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
714. MTWX
Levi you will have to get us some pictures once the weather finally lets up... Whenever that is!!
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Member Since: July 15, 2006 Posts: 169 Comments: 53296
712. MTWX
Quoting Levi32:


Lol, well when you live in a state that is 3 times bigger than any other state in the union, and our total state population is less than the average U.S. city, there aren't that many major "official" things to be done. Up in our biggest city, Anchorage, where nearly half of our state population lives (300,000) they do get alerts out and snow crews mobilized.

In my home town though we just all hunker down and get cozy. Nobody has been able to go anywhere for 3 days, all the schools have been closed. We're all just stuck at home not knowing what to do lol. Everyone knows it's life-threatening to go outside, so nobody with sense attempts it.

You never hear anything about storms like that on the Weather Channel or any of the news networks. People just act like Alaska doesn't exist. Anyone in the lower 48 would think the world has ended if anything like that hit us!!
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Oh, and we all check in with each other on Facebook =)
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting AwakeInMaryland:
Levi, how are you all coping?
Does everyone call their neighbors to check in?
Does Fire & Rescue go out at all? or send out alerts and messages?
I'm just trying to get a feel for what it's like for you; it's hard to imagine except for our "snowmageddon" which probably made you all chuckle.


Lol, well when you live in a state that is 3 times bigger than any other state in the union, and our total state population is less than the average U.S. city, there aren't that many major "official" things to be done. Up in our biggest city, Anchorage, where nearly half of our state population lives (300,000) they do get alerts out and snow crews mobilized.

In my home town though we just all hunker down and get cozy. Nobody has been able to go anywhere for 3 days, all the schools have been closed. We're all just stuck at home not knowing what to do lol. Everyone knows it's life-threatening to go outside, so nobody with sense attempts it.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting Levi32:


Lol...we've got 42 inches of new snow :D




with some more yet to come
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Levi, how are you all coping?
Does everyone call their neighbors to check in?
Does Fire & Rescue go out at all? or send out alerts and messages?
I'm just trying to get a feel for what it's like for you; it's hard to imagine except for our "snowmageddon" which probably made you all chuckle.
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Member Since: June 28, 2006 Posts: 24 Comments: 8201
Quoting MTWX:

Holy Cow man!!! I personally haven't seen anything like that since I lived in Upstate NY in '93


Lol...we've got 42 inches of new snow :D
Member Since: November 24, 2005 Posts: 635 Comments: 26547
705. MTWX
Quoting Levi32:
Going into our 29th straight hour of blizzard conditions....


Current Conditions

Homer, Alaska (Airport)
Updated: 9 min 5 sec ago

8 °F
Heavy Snow Freezing Fog
Windchill: -11 °F

Humidity: 87%
Dew Point: 5 °F
Wind: 20 mph from the SSW

Wind Gust: 29 mph
Pressure: 29.12 in (Rising)
Visibility: 0.2 milesElevation: 82 ft

Holy Cow man!!! I personally haven't seen anything like that since I lived in Upstate NY in '93
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Going into our 29th straight hour of blizzard conditions....


Current Conditions

Homer, Alaska (Airport)
Updated: 9 min 5 sec ago

8 °F
Heavy Snow Freezing Fog
Windchill: -11 °F

Humidity: 87%
Dew Point: 5 °F
Wind: 20 mph from the SSW

Wind Gust: 29 mph
Pressure: 29.12 in (Rising)
Visibility: 0.2 miles
Elevation: 82 ft
Member Since: November 24, 2005 Posts: 635 Comments: 26547


here is another angle
Member Since: July 15, 2006 Posts: 169 Comments: 53296
I hate flooding in Indiana, too.
And Missouri.
And New Mexico.

But especially Texas.
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next one spinning up strong
Member Since: July 15, 2006 Posts: 169 Comments: 53296

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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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