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April 9, 2010

Cool Gulf may be suppressing tornado season

The three-month stretch from January through March this year was the coldest such period on record for Florida, the second-coldest for Louisiana and the third-coldest for Mississippi and Alabama. The fact is, the Gulf of Mexico itself is colder  (yellow shows temperatures on top map; blue on the lower map shows departures below the average, while yellow shows departures above the average in the Atlantic) than normal this spring, and that may be why the spring tornado season - which is fueled in part by heat and humidity off the Gulf - has been so Sea surface temperaturesslow.

NOAA's National Climatic Data Center and the Storm Prediction Center said this week that the preliminary U.S. tornado count for March was just 36. That was a tie for the fourth-quietest March for tornado activity since they started keeping records in 1950. The three-year average for March tornados is 138.

On average, however, the contiguous 48 states were warmer and drier than average, NOAA says. Thirteen states had average March temperatures that ranked among their 10 warmest. Rhode Island had its warmest March ever. Maine had its second-warmest and New Hampshire had its third-warmest.

Dry weather was the rule in Michigan, which saw its driest January-to-March period ever. Wisconsin saw its fourth-driest while Montana and Wyoming had their sixth driest.NOAA

Big coastal storms brought parts of the mid-Atlantic and New England states wet weather and flooding in March. It was the wettest January-to-March on record for Massachusetts, Rhode Island (photo, right) and New Jersey. Delaware and Vermont saw their second- and fifth-wettest Marches on record.

And just so you know, mid-March ice cover on the Great Lakes (yes, they record such things) was at a record low, just 3.5 percent of the lakes' surface. The average ice extent for that period is 31 percent, according to records dating back to 1973.

(AP PHOTO/Joe Giblin)

Posted by Frank Roylance at 1:59 PM | | Comments (2)
Categories: Tornadoes


I'm confused. In your previous post you said the higher hurricane forecast was due to "unusually warm sea surface temperatures in the tropical Atlantic". In this post, you have a picture showing that the Gulf of Mexico is cooler this spring.

Is there some reason to expect that the cooler water in the Gulf (which looks to me like it's part of the Atlantic Ocean) will warm up so that it will be warmer than normal? Is there a part of the Atlantic that is warmer than normal and other parts that are cooler than normal?

As I said, I'm confused.

FR: As I understand it, the warm surface temperatures in the tropical Atlantic are part of a multi-decadal cycle that began in 1995. The cool surface temps in the Gulf - which is much smaller and shallower - are the result of cold weather across the South this winter. It will warm up quickly this summer. You can already see a tongue of warmer water in that satellite map, moving up into the Gulf between the Yucatan and Cuba.

Frank - Nice use of the SST graphics! A better one might be the SST anomaly graphic at

For much of the late winter and early spring (now), the northern Gulf of Mexico has been 2 to 4 degrees Celsius below normal, quite significant.

The SST anomaly map would help with the tropical question as well. Also, the GOM is like a big bathtub and will have no problem warming up. Many parts of the GOM see surface water temps near 90F come late summer, so even if it's a tad cooler than normal, there's still plenty of potential.

Keep up the good work with your blog.

FR: Thanks!

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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