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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It is Sunday morning.
I am going to sleep.
See you all later.
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later 456
Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting Weather456:


That data would have been analyzed after the season ended. What if the numerical models did not show this in May 2004? The whole purpose of the hypothesis is to assess, from forecasts made by the numerical models, the relationship between MSLP anomalies and storm tracks.


If the forecast is wrong then you can't compare the relationship.

You stated this:

"I have a hypothesis to test this year. that MSLP anomalies may also affect storm tracks. For example, a tropical cyclone would easier flow through a region of anomalous low pressures than anomalous high pressures."

What would be the point in investigating the relationship based on something other than the actual MSLP for the year. We may make a track forecast based partly on the MSLP forecasts by a model, but if the MSLP forecast is wrong then how can we assess the relationship based on something that didn't happen. To investigate the relationship we must look at the actual data, like I posted.
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Until 2mr. Good night all
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting kmanislander:
The Atl wave has run into a brick wall. It has made little or no progress to the West all day.

Trinidad and Tobago may see very little by way of convection out of it.Hit and miss showers at best.


T&T will get convective showers. Dont look at the wave position now.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
ECMWF on pressure anomalies for the July-August-September timeframe:

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462. JRRP
Quoting altesticstorm10:
Let's compare hurricane seasons to baseball players!

2004-Lou Gehrig
2005-Babe Ruth
2010-Barry Bonds

Can you guess what I'm implying? Lol

jajajaja
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Quoting kmanislander:
The Atl wave has run into a brick wall. It has made little or no progress to the West all day.

Trinidad and Tobago may see very little by way of convection out of it.Hit and miss showers at best.

Hi Kman.
It is worthwhile reading back a couple of pages. Some very good discussion...
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The Atl wave has run into a brick wall. It has made little or no progress to the West all day.

Trinidad and Tobago may see very little by way of convection out of it.Hit and miss showers at best.
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Quoting Bordonaro:

Read that article earlier tonight.

It would really be a terrible catastrophe IF Katla, or any other volcano decides to erupt while "Big E" is shooting ash to over 24,000+ feet, plus lava bombs, magma.

That would create a real big nightmare for the European airspace and may shoot ash and SO2 high enough into the stratosphere to temporarily cool the climate. Plus create heath problems. In 1783-4, when Laki went off, thousands of people in the UK dies from SO2 poisoning, plus some of the coldest winters since the "Little Ice Age".

You guys are beginning to worry me now.
My Wife is in England until June 28 or something.
Will I ever see her again??
And the sunspots will probably screw skype.
What to do??
LOL
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Quoting dxdy:


...in the news

Scientists forecast decades of ash clouds
Many more of Iceland’s volcanoes seem to be stirring...

...They have reconstructed a timeline of 205 eruptions in Iceland, spanning the past 1,100 years, and found that they occur in regular cycles — with the relatively quiet phase that dominated the past five decades now coming to an end.

At least three other big Icelandic volcanoes are building towards an eruption, according to Thor Thordarson, a volcanologist at Edinburgh University.

“The frequency of Icelandic eruptions seems to rise and fall in a cycle lasting around 140 years,” he said. “In the latter part of the 20th century we were in a low period, but now there is evidence that we could be approaching a peak.”

http://www.timesonline.co.uk/tol/news/uk/article7127706.ece


I wonder how long Katla will remain silent?


Read that article earlier tonight.

It would really be a terrible catastrophe IF Katla, or any other volcano decides to erupt while "Big E" is shooting ash to over 24,000+ feet, plus lava bombs, magma.

That would create a real big nightmare for the European airspace and may shoot ash and SO2 high enough into the stratosphere to temporarily cool the climate. Plus create heath problems. In 1783-4, when Laki went off, thousands of people in the UK dies from SO2 poisoning, plus some of the coldest winters since the "Little Ice Age".
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Quoting cchsweatherman:


Very close to my thinking for the upcoming season. In looking at the long range models, I don't see many storms curving out to sea harmlessly since the MSLP forecast indicates an expansive ridge across the Central Atlantic to near the Bahamas region.
I can see a scenario for the dual track, depending on how strong that ridge is and how easily impacted by passing troughs the CATL is in the SON period....

I gotta stop posting after I am supposed to get off the blog....
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Quoting Levi32:


This is one example that may end up similar to this year. The infamous 2004, as we all know, was a very bad year for the SE US. Here were the MSLP anomalies during July-October:



Now look at the tracks:



You can see the axis of lowest pressures was north of the Caribbean islands, through the northern Bahamas and a bullseye over Florida. The tracks followed the center line and southward, with the main congregation tracking through the Bahamas, Caribbean, and into Florida, which was the focus-point for the most action that season.

A 2nd region of lowest pressure anomalies occurred out in the central Atlantic, and there was a separate congregation of tracks out there as well, which closely followed the low MSLP anomalies.


That data would have been analyzed after the season ended. What if the numerical models did not show this in May 2004? The whole purpose of the hypothesis is to assess, from forecasts made by the numerical models, the relationship between MSLP anomalies and storm tracks.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting KEEPEROFTHEGATE:
may get some pop up showers nothing too much i will post image in a few just uploading
Yeah, i see some cloud building to my east and south when I look up. Clear overhead.
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Quoting Levi32:


This is one example that may end up similar to this year. The infamous 2004, as we all know, was a very bad year for the SE US. Here were the MSLP anomalies during July-October:



Now look at the tracks:



You can see the axis of lowest pressures was north of the Caribbean islands, through the Bahamas and a bullseye over Florida. The tracks followed the center line and southward, with the main congregation tracking through the Bahamas, Caribbean, and into Florida, which was the focus-point for the most action that season.

A 2nd region of lowest pressure anomalies occurred out in the central Atlantic, and there was a separate congregation of tracks out there as well, which closely followed the low MSLP anomalies.


Very close to my thinking for the upcoming season. In looking at the long range models, I don't see many storms curving out to sea harmlessly since the MSLP forecast indicates an expansive ridge across the Central Atlantic to near the Bahamas region.
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your best bet to see rain is stuff runnin up along the coast to yer se
Member Since: July 15, 2006 Posts: 175 Comments: 54858
thanks for stretching the blog, whoever you are
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Quoting Levi32:


This is one example that may end up similar to this year. The infamous 2004, as we all know, was a very bad year for the SE US. Here were the MSLP anomalies during July-October:



Now look at the tracks:



You can see the axis of lowest pressures was north of the Caribbean islands, through the Bahamas and a bullseye over Florida. The tracks followed the center line and southward, with the main congregation tracking through the Bahamas, Caribbean, and into Florida, which was the focus-point for the most action that season.

Good post, again.
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Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting pottery:
MAN!! It's midnight. It's 81F. Humidity is 84%. Wind is calm. Pressure is 1014 steady.
Hot, muggy, night.
may get some pop up showers nothing too much i will post image in a few just uploading
Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting BahaHurican:
PS, re 429: Not trying to be confrontational - looking for a "thoughtful" answer.... lol


This is one example that may end up similar to this year. The infamous 2004, as we all know, was a very bad year for the SE US. Here were the MSLP anomalies during July-October:



Now look at the tracks:



You can see the axis of lowest pressures was north of the Caribbean islands, through the northern Bahamas and a bullseye over Florida. The tracks followed the center line and southward, with the main congregation tracking through the Bahamas, Caribbean, and into Florida, which was the focus-point for the most action that season.

A 2nd region of lowest pressure anomalies occurred out in the central Atlantic, and there was a separate congregation of tracks out there as well, which closely followed the low MSLP anomalies.
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Quoting altesticstorm10:
Let's compare hurricane seasons to baseball players!

2004-Lou Gehrig
2005-Babe Ruth
2010-Barry Bonds

.

Uh oh, not a season on steroids!
Member Since: Posts: Comments:
446. dxdy
Quoting Bordonaro:
"E" has gone mad, look at this recent pic from 10:46PM CDT. The Mulakot web-cam is about 6 miles from the summit:


...in the news

Scientists forecast decades of ash clouds
Many more of Iceland’s volcanoes seem to be stirring...

...They have reconstructed a timeline of 205 eruptions in Iceland, spanning the past 1,100 years, and found that they occur in regular cycles — with the relatively quiet phase that dominated the past five decades now coming to an end.

At least three other big Icelandic volcanoes are building towards an eruption, according to Thor Thordarson, a volcanologist at Edinburgh University.

“The frequency of Icelandic eruptions seems to rise and fall in a cycle lasting around 140 years,” he said. “In the latter part of the 20th century we were in a low period, but now there is evidence that we could be approaching a peak.”

http://www.timesonline.co.uk/tol/news/uk/article7127706.ece


I wonder how long Katla will remain silent?

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445. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15684
I'm off to bed, ya'll. Didn't realize it was already after midnight here...

Good night.
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MAN!! It's midnight. It's 81F. Humidity is 84%. Wind is calm. Pressure is 1014 steady.
Hot, muggy, night.
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Quoting Levi32:


I would not know. I'm not good at looking up all the papers, but it has been my experience that this is true and it does make sense. I have heard it discussed by other Meteorologists as well. A basic meteorological truth doesn't always have to be well-documented, but I look forward to 456's findings on this.
Something I've discovered by reading back [WAY back] issues of AMA journals etc is that what is accepted met truths of 2010 were once startling new findings... e.g. parabolic movement of storms. So if this is an "accepted truth", I'd bet there's some paper, report, article, journal entry, etc. documenting its "discovery".
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Quoting Levi32:


I would not know. I'm not good at looking up all the papers, but it has been my experience that this is true and it does make sense. I have heard it discussed by other Meteorologists as well. A basic meteorological truth doesn't always have to be well-documented, but I look forward to 456's findings on this.


Sometimes studies on the most obvious things reveal things about the least obvious.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Right now, based on the evolving pattern across the Atlantic basin and long-range computer model data, it would appear that we'll have two main storm tracks developing throughout the upcoming hurricane season. (1) Long track storms moving westward through the Caribbean and (2) Storms moving into and curving near Florida on both sides. I really don't believe the Western Gulf will be targeted this season unless a storm develops in the Central Gulf which doesn't seem that likely considering the long range forecasts for rather unfavorable wind shear over the region.
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Indian ocean heating up. One on the western edge, one on the eastern, and one headed towards australia.

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PS, re 429: Not trying to be confrontational - looking for a "thoughtful" answer.... lol
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Quoting BahaHurican:
So what, if any, documentation of that correlation is out there, Levi? U'd think if it was "accepted thinking" there'd be some kind of write-up on it....

I do know that just because something seems logical doesn't always mean it is the "correct" expanation.... or the only explanation. I suppose that's why we do studies.... lol


I would not know. I'm not good at looking up all the papers, but it has been my experience that this is true and it does make sense. I have heard it discussed by other Meteorologists as well. A basic meteorological truth doesn't always have to be well-documented, but I look forward to 456's findings on this.
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Quoting GainesvilleGator:
We will find out how much of an anomoly 2005 was after this season. It seems like the environmental conditions of 2010 mirror that of 2005 except SSTs are warmer now.

Maybe 28 named storms is par for the course under similar environmental factors. We will find out this year. If we ONLY have 20 named storms this year then you can say 2005 was an anomaly. Otherwise we may have to evaluate our forcasting based on higher SST temps in the future.

Yep! Nice post.
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Korean Ensemble MSLP anomaly forecasts for MJJ, issued in April:

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Quoting altesticstorm10:
So are we going to have a ENSO-neutral with a slight cool bias, weak La Nina, weak moderate La Nina, strong moderate La Nina, strong La Nina, or very strong La Nina?
Based on what I've seen so far, prolly the 1st and 2nd before the season is over, with the 3rd as a lesser possibility towards the end of the season.
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Related to my post #428...see post #19 that Weather456 posted. The graphic didn't copy.
Member Since: July 21, 2008 Posts: 0 Comments: 365
We will find out how much of an anomoly 2005 was after this season. It seems like the environmental conditions of 2010 mirror that of 2005 except SSTs are warmer now.

Maybe 28 named storms is par for the course under similar environmental factors. We will find out this year. If we ONLY have 20 named storms this year then you can say 2005 was an anomaly. Otherwise we may have to evaluate our forcasting based on higher SST temps in the future.
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Quoting Levi32:


I didn't know that was supposed to be something new. That seems like a basic forecasting technique to me. When I see that swath of low pressures on the European model, I think to myself that tracks will likely follow the middle to southern portion of the swath the most. The middle for the reason you mentioned, that the path of lowest pressure is the easiest and supports the most upward motion, and the southern part because that's where trade winds are reduced in the deep tropics supporting more formations and tracks in that area.
So what, if any, documentation of that correlation is out there, Levi? U'd think if it was "accepted thinking" there'd be some kind of write-up on it....

I do know that just because something seems logical doesn't always mean it is the "correct" expanation.... or the only explanation. I suppose that's why we do studies.... lol
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Quoting Weather456:
Thanks for the acknowledgement Dr. Masters.

In other news...this is the type of high we might be seeing often this hurricane season


THIS is the post earlier today that really flipped me out. Makes it look like everything from S.Carolina around to the south Tx coast including the Caribbean basin is in the line of fire. Think I'm gong to have to speed up preparations here in Houston and get em done by June the latest. The run on supplies when one marches into the Gulf is CRAZY!
Member Since: July 21, 2008 Posts: 0 Comments: 365
(wow, these guys are waxing poetic tonight)
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Quoting BahaHurican:
This is a very interesting hypothesis. I hope u are going to document as u go along - never know where that might lead research-wise. I for one would like to see what u find out. Certainly seems to bear out what we were saying earlier about N Antilles / Bahamas / FL tracks....



It begins with an assessment of numerical models forecast for MSLP. The analysis of actual MSLP anomaly at season ends, storm tracks and comparison with previous years.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting SouthALWX:

I was thinking roughly the same thing. what else would cause a precip pattern like that? not saying it is right (and being in the bullseye this far out is always comforting, you know!) but it certainly is eye catching
This is what I was alluding to earlier about the two typical track patterns for an ENSO-neutral season being represented on the forecast map. Note the increased moisture along the typical Antilles, FL, East Coast parabola, and a matching more easterly recurve pattern east of Bermuda....
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Sleep well, Aqua.
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Quoting BahaHurican:
I keep hoping that if this is going to be an anomalous year, it will be anomalous in that Haiti will not be hit by even one tropical system..... Just pray they stay east and west.....


Exactly.
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Quoting BahaHurican:
This is a very interesting hypothesis. I hope u are going to document as u go along - never know where that might lead research-wise. I for one would like to see what u find out. Certainly seems to bear out what we were saying earlier about N Antilles / Bahamas / FL tracks....


Yeah. What he said...
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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.