Atlantic Hurricane Season, tropical storm, May 2012 | The Old Farmer's Almanac

Tropical Storms in May?

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It’s official – the Atlantic Hurricane Season starts on June 1.So why did a number of weather blogs and services speculate on whether the Atlantic would get its first tropical storm during the second week of May?

Why are other services expecting a possible storm or hurricane during the last two weeks of the month? Why is the hurricane season in such a hurry?

The little storm that threatened to become tropical on May 13! (The Azore Islands are in the top right corner.) SOURCE: NOAA

The answer is that the Atlantic is really hot. The Gulf Stream is flowing very fast, carrying tropical warmth throughout the North Atlantic. As a result, the North Atlantic is almost as warm as it normally is in JULY!

The recipe for a hurricane is:

  1. A little storm
  2. Hot water (It provides energy for the storm to grow.)
  3. Favorable winds (Unfavorable winds usually sheer the tops off of growing storms.)

Storms need hot water and favorable winds to grow into hurricanes. SOURCE: USGS

On May 12 and 13, a strange little storm with a strange little name, Invest 92L, hit some hot Atlantic water and started to grow. It was in the middle of the Atlantic, as far north as the northern tip of Africa. Despite its odd name and location, (it was so far north), it started to grow, spin and act tropical. After a few hours of getting weather forecasters excited, it cooled down and fizzled.

Sigh! No one wants a damaging storm. However, it is fun to watch nature’s giant storms swirl through the ocean and the southern US could really use some tropical moisture.

Don’t give up on May, however. Several weather observers have noted that the winds will be more favorable towards the end of the month. Meanwhile, the waters are very warm.

Tropical Storm Aletta didn’t wait for the Pacific Hurricane season to begin. SOURCE: NASA

It could happen. After all, the East Pacific hurricane season is supposed to start on May 15 and Tropical Storm Aletta started one day early. Starting as a small storm off Acapulco, she swirled out to sea and blossomed into a tropical storm four hours before the official deadline.

It has been a strange weather year. Why should anyone expect a “normal” hurricane season?


As many informed weather buffs know, a large portion of the Atlantic was cool in April. The cool region was between Africa and Brazil and had little to no effect on US weather. Waters off the US were warmer than normal.

In May, the Atlantic warmed. The latest satellite map of ocean temperatures shows the tropical Atlantic is warming and the waters off the Gulf and East Coast are still warmer than average. The temperatures are 0.5˚ to 3.5˚C (0.9˚ to 6.3˚ in good ol’ Fahrenheit) warmer than normal. The two cooler areas in the North Atlantic are flowing east towards Europe.

If you are interested in ocean temperatures and want to get the latest information, I recommend http://www.emc.ncep.noaa.gov/research/cmb/sst_analysis/  . They update every Monday.


ONE MORE FOOTNOTE Tropical Storm Alberto started on May 19, four days after I posted this blog. A low drifted off the South Carolina coast, hit the hot water and grew into a tropical storm. Fortunately, experts say it will drift out to sea.


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