Record Atlantic SSTs continue in the hurricane Main Development Region
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
Reader Comments
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the average winds in a tropical wave are less than 25 knots.
the average speed of a tropical wave is 10-20 knots.
i would not look for a tropical wave to upwell ssts enough to cool them by even 1C.
You would also need a series of tropical storms and hurricanes to cool the Atlantic to near normal and offset the rising sun as we near the peak of the NH summer.
No, I dont really think so either. I was being obscure.
But what a strange and peculiar set-up we have right now.
I think I will go and read those ancient Mayan texts again....
Amazing.
Current:
72 hours:
Link to the Iceland ash cloud forecast, ask your sister to call the airport, like, as soon as possible, they might cancel her flight:
Link
Recent article about air space closures in UK:
Link
1 Tropical Storm ARLENE 08-13 JUN 60 30 -
2 Tropical Storm BRET 28-30 JUN 35 1002 -
3 Hurricane CINDY 03-07 JUL 65 992 1
4 Hurricane DENNIS 05-13 JUL 130 930 4
5 Hurricane EMILY 11-21 JUL 135 929 4
6 Tropical Storm FRANKLIN 21-29 JUL 60 997 -
7 Tropical Storm GERT 23-25 JUL 40 1005 -
8 Tropical Storm HARVEY 02-08 AUG 55 994 -
9 Hurricane IRENE 04-18 AUG 85 975 2
10 Tropical Depression TEN 13-14 AUG 30 1008 -
11 Tropical Storm JOSE 22-23 AUG 45 1001 -
12 Hurricane KATRINA 23-31 AUG 150 902 5
13 Tropical Storm LEE 28 AUG-02 SEP 35 1007 -
14 Hurricane MARIA 01-10 SEP 100 960 3
15 Hurricane NATE 05-10 SEP 80 979 1
16 Hurricane OPHELIA 06-18 SEP 80 976 1
17 Hurricane PHILIPPE 17-24 SEP 70 985 1
18 Hurricane RITA 18-26 SEP 150 897 5
19 Tropical Depression NINETE 30 SEP-02 OCT 30 1006 -
20 Hurricane STAN 01-05 OCT 70 979 1
21 Tropical Storm TAMMY 05-06 OCT 45 30 -
22 Tropical Depression TWENTY 08-09 OCT 30 1009 -
23 Hurricane VINCE 09-11 OCT 65 987 1
24 Hurricane WILMA 15-25 OCT 150 882 5
25 Tropical Storm ALPHA 22-24 OCT 45 998 -
26 Hurricane BETA 27-31 OCT 100 960 3
27 Tropical Depression TWENTY 14-16 NOV 30 1004 -
28 Tropical Storm GAMMA 18-21 NOV 40 1004 -
29 Tropical Storm DELTA 23-28 NOV 60 980 -
30 Hurricane EPSILON 29 NOV-08 DEC 75 979 1
31 Tropical Storm ZETA 30 DEC-06 JAN 55 994 -
A more reasonable lower estimate is 15 named storms.
2010 could rank in the top 10, possibly the top 5.
This sounds more in line w/ what I am expecting. I wouldn't be surprised to get to 21, or possibly even 23 (though I don't expect that). But in that active period of the 20s to 40s, there was only one 21+ season; other busy seasons were around 17....
Interesting. On what basis are you saying that 2010 will be lower than 2005?
What existed in 05 that caused the high numbers, that dont exist now?
Thursday, May 20, 11:00 am EDT
Gotta run, but where are Storm, Drak, 456, Sky, Orca and on and on?
Be well all, L8R >>
Hey, it is your contest, I am just the conduit :)
Time is short! >>>> Out :)
See post 315
Very good point.
But the reality is, there were more than 30 storms in the Atl. in 2005.
What is the problem with 40?
Very well stated there man.
Current
72 hours
It's going to be close. Like Bord said, they need to call the airline.
Officials have warned the ash from volcanic eruptions in Iceland could disrupt air travel in both Britain and Germany in the next few days.
The British Department of Transport on Saturday stated a possible closure of parts of British airspace on the weekend, saying those problems could persist through Tuesday.
The department said different parts of British airspace could close at different times in the next few days, which would include England's southeast -- home to Europe's busiest airport at Heathrow as well as Gatwick, Stansted and other major airports.
stormchaser, I believe it's already there, just not visibly, errr, on the surface.
this is a short article but I'd love some intelligent points of view here.
Link
The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history
and hopefully 2010 don't have in its mind to become the greatest season ever cause if it does then it will be an all time record just like the infamous 2005 season
As Baha rightfully said, I cannot conceptualized such numbers. That is super hyper active. Our limit of understand is the hurricane season of 1933. 2005 to us is an anomaly. We are not saying that we cannot have 25+ storms, but how do you make a forecast for such numbers? thats the big question.
A big AMEN to that.
Scientists Find Giant Plumes of Oil Forming Under the Gulf
"Scientists are finding enormous oil plumes in the deep waters of the Gulf of Mexico, including one as large as 10 miles long, 3 miles wide and 300 feet thick. The discovery is fresh evidence that the leak from the broken undersea well could be substantially worse than estimates that the government and BP have given."
Thanks.. Understood.
I am still going with my 19 for the season (total storms)
It is the same with 2010.
still hoping for a comment? could this be correct?
Let's try this:
super sub active 5%
below average 10%
average 20%
above average 50%
super hyper active 15%
I love Allan Huffman's site. Thats the only site I use now for accessing computer models since his site offers pretty much all the models available and so many different products from each model. Now with the ECMWF images, its gonna be even better. I like to call it one stop model surfing.
And that, is the reality of the thing.
Very Well said, Baha.
Man Im glad that ECM is freeing up some of their products to the public. The ECMWF (and its ensembles) have been pretty good this year and it looks like we'll need them a lot for this upcoming Hurricane season.
Thanks for the links Adrian!
Hit the nail on the head. And when we say experiment, we cannot use 2005 since that is one year. We would have to use years where SSTs were at this level and how do we do that when 2010 has the highest? All other selected years will fall short.
Probabilities may help solve the problem but it seems there is a 80% of an above average season.
these are the numbers i believe could be possible
TOTAL STORMS 21 TO 23
TOTAL HURRICANES 11 TO 14
TOTAL MAJORS 5 TO 7
TOTAL CAT 5's 1 TO 3
That is REALLY scary. But I was wondering about that today when I was looking at Gulf currents.
The currents are so mixed up in there, and there are currents and counter-currents and the dam place where the oil is leaking is nearly a MILE deep.
There are bound to be oil-layers moving around under there.
Maybe not as much as that quote said, but who knows?
Hey no problem... 850mb T and anomalies have also been added to the regular site which is also great. graphics will now be out to 240 regularly.
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