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Atlantic hurricane season preview: what are SSTs doing?

By: Dr. Jeff Masters , 4:18 PM GMT on March 07, 2007

Atlantic hurricane season is still a long way off, but we can start looking at Sea Surface Temperatures (SSTs) in the Atlantic to get some idea of the severity of the coming season. A plot of the current SST anomalies (that is, the departure of the temperature from average) shows that the Caribbean and Atlantic waters stretching to the coast of Africa remain much warmer than normal, as they have been since 2004 (Figure 1). How does this warmth compare to the record-breaking SSTs observed during the disastrous Hurricane Season of 2005? Figure 2 show the difference in SST between 2007 and 2005 for February, and we can see that SST were about 0.5 C warmer in February 2005 vs. February 2007 in the region we care about--the hurricane Main Development Region (MDR) between 10 N and 20 N extending from Africa to the Central American coast.


Figure 1. The departure of Sea Surface Temperature from average for March 7, 2007. Image credit: NOAA/NESDIS.


Figure 2. The difference in Sea Surface Temperature (SST) between February 2007 and February 2005. Cool colors (blues and purples) are shown where the SSTs were warmer during 2005. Warm colors (yellows and oranges) are shown where it was warmer in 2007. Note the presence of an El Nino event in 2007 but not 2005 caused warmer SSTs in the Equatorial Eastern Pacific. SSTs in the Hurricane Main Development Region (red box) were about 0.5 C warmer in February 2005 vs. February 2007. Image credit: NOAA Earth System Research Lab.

The SST forecast
What can we expect SSTs to do in the coming months? NOAA's SST forecast (Figure 3) for the peak months of hurricane season (August, September, and October) projects a continuation of the above-normal SSTs at about 0.5 C above normal. This is a lot of extra energy to fuel intense hurricanes, but not nearly as extreme as the 1-2 C above normal SSTs observed in 2005. Long range forecasts of SST are not very reliable, but this forecast appears to be a reasonable one. It would take a major reduction in the trade winds over the coming months to allow SSTs to climb to levels seen in 2005 (slower trade winds reduce the amount of evaporative cooling, resulting in increased SSTs). While it is impossible to predict what the trade winds might do over the next few months, a sustained weakening of the trade winds for many months is an event that is unlikely. The best guess right now is that SSTs will be above normal this hurricane season, but nothing like observed in 2005. Based on this expectation, plus the demise of El Nino, and the fact we are in an active hurricane period that began in 1995, I am expecting a hurricane season perhaps 50% above average in number of storms and intense storms--but not a repeat of 2005.


Figure 3. The departure of Sea Surface Temperature (SST) from a 1990-2003 average as forecast by NOAA's Climate Forecast System (CFS) model. Note that this model is forecasting a moderate La Nina event in the Eastern Pacific during the 2007 hurricane season, and SSTs about 0.5 C above normal in the Main Development Region (MDR) for Atlantic hurricanes. The MDR is the region between 10 N and 20 N extending from Africa to the Central American coast, and includes all of the Caribbean Sea.

The steering pattern forecast
The next key question is--what will the steering pattern be for 2007? Will there be a trough of low pressure over the Eastern U.S. that recurves storms out to sea, as happened in 2006? Or, will a ridge of high pressure set up, steering hurricanes into the Caribbean, Florida, and U.S. Gulf coast, as happened in 2004 and 2005? I won't have a speculation on that until late May.

My next blog will be Friday, when I plan to review a just-released book about the most intense tornado of all time--the May 3, 1999 Oklahoma City twister. It's a great read.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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311. Ictaluruspunctatus
5:25 PM GMT on March 09, 2007
Taz -

DST has NO EFFECT. What don't you understand about this? Just because you arbitrarily change the time on the clock doesn't mean you get an additional hour of daylight. Sure, by the clock the sun sets an hour later, but it also rises an hour later. There is no increase in the actual day length.
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310. TS3
1:51 PM GMT on March 09, 2007
Either he is making up a 'whole load of trash'

Or it is his computer.
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309. jake436
1:50 PM GMT on March 09, 2007
I clicked on TS3's pics, and no pop ups appeared on my screen.
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308. TS3
9:39 AM GMT on March 09, 2007
Stormeygace, i would like to applaud you for manners, i'm sorry to say that if pop-ups come up on your screen when you click my pics then that's not my problem.

If that were to happen to me then i would have installed a pop-up blocker (which i have already got) to stop the pop-ups getting through.
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307. HadesGodWyvern (Mod)
7:43 AM GMT on March 09, 2007
The area is already under a Cyclone Warning from George. :X
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306. HadesGodWyvern (Mod)
7:42 AM GMT on March 09, 2007
Tropical Cyclone Jacob [CAT 2]
14.5S 108.1E -- 60 knots 968 hPa

wind gusts up to 85 knots

Tropical Cyclone Advice #14
============================

Tropical Cyclone Jacob was estimated to be 520 km south-southeast of Christmas Is and 1160 km northwest of Karratha and moving southeast at 6 knots.

Tropical Cyclone Jacob has intensified slightly and is continuing to moving to the southeast. This movement is likely to continue during the next 24 to 48 hours during which the cyclone may accelerate slightly and intensify further. The cyclone may approach the Pilbara coast late on Sunday.

Tropical Cyclone Watches and Warnings
=====================================
A CYCLONE WATCH for CATEGORY 2 CYCLONE JACOB has been declared for coastal areas from Coral Bay to Sandfire, extending inland to include Tom Price and Marble Bar.
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305. Tazmanian
5:12 AM GMT on March 09, 2007
i will not commet you stormygace goodbye troll
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303. weatherboykris
4:16 AM GMT on March 09, 2007
I thought the saying was if it reaches 20N before 60W you don't have to worry about it?
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302. Skyepony (Mod)
4:13 AM GMT on March 09, 2007
The saying goes if it's a hurricane before it reaches 40, it's going out to sea. If it becomes a hurricane after 40 lookout. The map of 2004 that Kris posted is an excellent example of this.
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300. weatherboykris
3:58 AM GMT on March 09, 2007
Very nice, man.I applaud your manners.
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299. stormygace
3:40 AM GMT on March 09, 2007
ts3 - why di popups appear if i click on your pic? That is poor form dudette. I recommend not clicking on ts3's pics unless you like a stream of total trash to ensue.
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297. 882MB
12:55 AM GMT on March 09, 2007
Dahm i cant get the NEW 12Z NOGAPS!
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296. TS3
12:42 AM GMT on March 09, 2007
Click on pic for larger view.

Free Image Hosting at www.ImageShack.us
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295. TS3
12:34 AM GMT on March 09, 2007
Proposed Extratropical System

Click for larger picture


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294. plywoodstatenative
12:33 AM GMT on March 09, 2007
mention was made about the bermuda high this year, what is the predicted location of the high this year?
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293. pottery
12:30 AM GMT on March 09, 2007
Hello.

hot and dry here again. Lots of haze and smoke. Visibility 5 miles. No sahara dust for a change, but with the smoke around it was pretty grim.
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292. Tazmanian
12:12 AM GMT on March 09, 2007
bumpy
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291. TS3
10:36 PM GMT on March 08, 2007
ok kris
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290. weatherboykris
10:35 PM GMT on March 08, 2007
bbl
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289. weatherboykris
10:33 PM GMT on March 08, 2007
Sullivan,maybe I should've phrased it differently.What I meant was just an observation.I knew I'd posted 2004.
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288. TS3
10:32 PM GMT on March 08, 2007
After reading that, who knows where the storms are going to form this year
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287. sullivanweather
10:30 PM GMT on March 08, 2007
STL, however, most of those storms in 2005 had developed west of 50W whereas most of the 2006 storms developed east of 50W
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286. TS3
10:30 PM GMT on March 08, 2007
I agree with kris
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285. weatherboykris
10:27 PM GMT on March 08, 2007
I've said before that trade winds lower the chances of storms.
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284. sullivanweather
10:26 PM GMT on March 08, 2007
you do realize that you posted a map of the 2004 hurricane season??

I'm talking about 2006, dude.

Strong high pressure and dry air over the eastern Atlantic surpressed most of the tropical systems until they past 50W longitude.
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283. weatherboykris
10:26 PM GMT on March 08, 2007
I didn't say they didn't STL.I said that the map I posted was a 500mb geopotential height anomaly map.
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281. weatherboykris
10:23 PM GMT on March 08, 2007
This year didn't have a problem east of 50W:


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280. TS3
10:22 PM GMT on March 08, 2007
yes i am TS2 kris
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278. weatherboykris
10:21 PM GMT on March 08, 2007
Actually,some of the strongest storms moved at a pretty fast speed.Examples are Andrew and Charley,just to name some off the top of my head.
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277. weatherboykris
10:20 PM GMT on March 08, 2007
Hi;you are TS2,right?
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276. TS3
10:19 PM GMT on March 08, 2007
and hi STL
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275. TS3
10:19 PM GMT on March 08, 2007
Woooops i forgot to say hi kris
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274. TS3
10:17 PM GMT on March 08, 2007
(storms don't like moving too fast)



They can move at quite a bit and maintain some power like Hurricane Gordon demonstrated last year
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273. sullivanweather
10:15 PM GMT on March 08, 2007
They don't take well to all that subsidence either.

All one has to do is look back to the tropical systems of '06 that developed in the east Atlactic. They had a really tough time getting going until they past 50W longitude
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272. weatherboykris
10:15 PM GMT on March 08, 2007
The 500mb geopotential height map.
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271. weatherboykris
10:14 PM GMT on March 08, 2007
STl,that's the 500mb map I posted.Not the surface.
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269. TS3
10:09 PM GMT on March 08, 2007
no doubt it will be bad news
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268. weatherboykris
10:04 PM GMT on March 08, 2007
That could be bad news.
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267. weatherboykris
10:03 PM GMT on March 08, 2007
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266. TS3
10:00 PM GMT on March 08, 2007
Click for larger view

Free Image Hosting at www.ImageShack.us
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265. ProgressivePulse
9:46 PM GMT on March 08, 2007
171mph gusts! :-O That's cookin! Strong Storm!
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264. Vanagew
9:22 PM GMT on March 08, 2007
Image Hosted by ImageShack.us

Severe Tropical Cyclone George has made landfall at 916hpa as a Category Four. Wind gusts of 275 kmph have been recorded at Kilburra. George's well defined eye has collapsed inward as George moves inland where it is weakening. Expected to redevelop in about two days time where it should make its second landfall near Perth.
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263. TS3
8:58 PM GMT on March 08, 2007
Hi again
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262. livinginnavarre
8:49 PM GMT on March 08, 2007
Thanks for the info
I love reading this blog, its been some of my best reading for the past few seasons.
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261. sullivanweather
7:39 PM GMT on March 08, 2007
Unfortunately for the hurricane lovers the system forecast to develop off the southeastern coastline this weekend is nothing more than a gale center. It has no tropical characteristics on forecast models.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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