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Atlantic Tropical Weather Update 8/14/09

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Tropical Depression Two fell apart so much yesterday that it was downgraded to a remnant low.  That means it didn’t have enough sustained convection to be considered a tropical system any longer.  Interestingly, the remnant low has developed convection around a central low again.  It hasn’t be re-upgraded, but the NHC is giving it a 30-50% chance of being upgraded in the next 48 hours.  It’s quite the interesting storm.  It is expected to keep moving west across the Atlantic over the next two days before turning northwest around the subtropical ridge to its north thereafter.  It should move over 28C waters in the next couple of days.  If it does, it has a higher chance of sustaining convection – nothing has moved over these warm waters all season.  Today’s official track forecast keeps the system to the northeast of the Caribbean Islands.

Further to the east is Invest-90, the broad area of low pressure with numerous convective storms slowly rotating around the center.  It’s organization (i.e. beginning of banded features & outflow aloft) has picked up since yesterday, as expected.  This disturbance should become the first named storm of the 2009 Atlantic season.  Here are its vitals as of this morning:

Center near 12.1N, 26.5W; moving W @ 14mph; maximum sustained winds of 30mph.

That westward motion should continue for the next 24 hours before making a slight turn toward the northwest through the 5-day period.  If this pans out, that would put the system near the northern Windward Islands by the middle of next week.  One of the models that performed well with T.D. 2’s motion, the GFS, is in the middle of the pack – it puts the center of this system just to the south of the most northerly Windward Islands.  GFS ensemble members generate a large fan-like set of solutions around the northern Caribbean and the southeast U.S. in its extended forecast.  Anywhere from Belize to North Carolina are in that solution set.  This isn’t too surprising given the large amount of time between now and the end of the forecast runs.  The official GFS track forecast is at the northern edge of that solution set through the first five days.

Every model is forecasting an increase in intensity over the next five days.  I expected the storm to reach Tropical Depression status already.  Such a designation is likely in the next 48 hours as the NHC gives the disturbance a >50% chance of doing so.  They note that organization has slowed down over the past several hours, but expect things to come together soon.

Lastly, a tropical wave is affecting areas near Cuba and Florida.  It isn’t expected to develop into a Tropical Depression.

[Update 5:30P MDT]:

The remnant low from Tropical Depression Two has regained enough convection, according to a NOAA high altitude jet, and almost enough organization to be reclassified as a Tropical Depression either later tonight or early Saturday.  It is currently centered 1000 miles east of the Lesser Antilles (Windward Islands) in the middle of the Atlantic Ocean.  The NHC has assigned it a >50% chance of tropical formation potential.

The broad area of disturbed weather that came off the African coast a couple of days ago also still has a >50% chance of tropical formation in the next 48 hours.  It has robust convection near the “center”.  Its organization has improved somewhat since earlier today, but will need to organize even further before attaining Tropical Depression status.  Right now, it is more elongated on an east/west axis than being circular.

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One thought on “Atlantic Tropical Weather Update 8/14/09

  1. Pingback: Atlantic Tropical Weather Update 8/16/09 #1 « Weatherdem’s Weblog

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