Here we go, Hurricane Season Begins

By: Levi32 , 5:02 PM GMT on June 01, 2009

The 2009 Hurricane Season begins today. Hopefully everyone that lives in hurricane-prone areas are prepared for the potential threats to come.

We're getting off to a quiet start right now, with nothing of interest in the Atlantic, and nothing forecast to form by the models. This is fairly typical of the month of June, where only roughly 1 out of every 3 years sees a named storm during this month. Let's look at the historical tracks of all storms in June:

You can see that all but one of the storms in the past 150 years have formed as "home-brew" close to the coast in either the Caribbean, Gulf of Mexico, or off the Southeast US. These developments are most commonly triggered by trough splits or old fronts getting stranded and acting as trigger points for tropical formation. This is the case because African tropical waves are still mostly too far south at this time of year to form storms, and the SSTs in the tropical Atlantic are still too cool.

Right now the sub-tropical jetstream is sitting pretty far south over the Caribbean, Gulf of Mexico, and all of the tropical Atlantic, causing too much wind shear for anything to form south of 20N.

The GFS is forecasting this shear to start to lift in the Caribbean 2 weeks from now, which would open the door for possible development there. Until then the only area with low enough shear to allow development is off the Southeast US coast, which has been sitting between the sub-tropical jet and the polar jet, allowing lower than average winds in the upper atmosphere. This can be seen in this graph of wind shear compared to the climatological average (black line), which shows how wind shear off the eastern seaboard has been generally lower than normal during the month of May. This gap in the wind shear field is what allowed TD One and Invest 90L to form in May.

How are SSTs doing so far this year?

Well they're definitely much lower than the record year of 2005, and are pretty similar to last year. Generally they are about average, which is lower than the above-average temperatures we have been usually seeing during the past 10-15 years. SSTs may be cooler than normal in the tropical Atlantic MDR(Main Development Region) this year.

2009 Hurricane Season Outlook in a nutshell:

I'm also expecting an about average year number-wise, with 12 named storms, 7 of those hurricanes, and 2 of those major hurricanes. However, it only takes one storm to turn a "normal" season into one that's impossible to forget. I believe threats to the coast will be significant this year, with a quieter Cape Verde season, fewer long-track storms, and more developments close to home. El Nino will be a factor by the middle of the season, and will probably cause conditions to become less favorable in the MDR. With storms forming closer to the coast, everyone should be ready to act quickly in the event of something spinning up close to their area. The official 2009 NHC Hurricane Outlook can be found here.

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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Tropical Tidbits from the Tundra

About Levi32

Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.

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