07.27.13

Dorian Fades Into Tropical Wave

Posted in Commentary, Storm Preparation, Storm Track, Tracking the Tropi at 6:12 pm by gmachos

Fourth Named Storm of 2013 Atlantic Season Suffers Same Fate As Chantal

Four storms down in the 2013 Atlantic Hurricane Season, and we still wait for the first hurricane of the year.  Like Tropical Storm Chantal before it a few weeks earlier, Tropical Storm Dorian faded to oblivion after a promising start.  The combination of a fast circulation and dry air coupled with strong wind shear proved to be too much for the season’s latest storm to handle.

Marginal sea surface temperatures along with dry air made things difficult for Dorian within 24 hours of formation during the middle of this week.  After emerging, Dorian looked strong with a small, but strong circulation with good outflow coming out of all of its quadrants.  Soon after that though, the storm began to move into an area where sea surface temperatures were just below the 80 degree Fahrenheit threshold that is essential for development.

On top of that, dry, sinking air from a subtropical ridge situated in the Central Atlantic began to attack the storm much like it had done with Chantal earlier this month.  In order for tropical systems to survive and thrive, they need the warmth and moisture of the tropical ocean air to thrive.  If that is hindered by such things as cooler sea surface temps or dry air, then the storm lacks the fuel supply it needs to grow.

Complicating things even more was the fact that the storm’s circulation was moving as fast as 23 miles per hour as of this morning.  When there is such a fast circulation, it often outruns the thunderstorms trying to wrap around and coalesce around it.  Then, winds at different levels start blowing at different speeds and in different directions, which is wind shear.  Tropical storms and hurricanes do not like wind shear.  They need light winds aloft in order to develop. 

The storm had formed in the Eastern Atlantic, one of the earliest storms to form that far east.  Chantal was another storm from this season to share that honor.  However, conditions in the Atlantic are usually not favorable for development in July, and despite these storms defying the odds by forming, they were unable to overcome huge obstacles such as marginal sea surface temperatures in the Atlantic, dry air, and their own fast circulations.

However, the development of these two storms in the Atlantic this early in the season, coupled with the two storms in June have given the 2013 Atlantic season a fast start, and serves as a bad omen for things to come.  Several waves have pushed off West Africa into the Atlantic behind Dorian.  So, the conveyor belt of tropical disturbances is already in place.  Eventually, the Tropical Atlantic will heat up and provide optimal conditions for development, and a much more formidable storm will develop, overcome these obstacles, and become a threat to the Caribbean, Central America, and perhaps the United States.

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