Tropical Depression SIX

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TROPICAL DEPRESSION SIX DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062011
1100 PM EDT FRI AUG 12 2011

THROUGH 0000 UTC...THE DEPRESSION WAS MAINTAINING A CENTRAL DENSE
OVERCAST...WITH SSM/IS AND TRMM DATA NEAR 2330 UTC SHOWING SOME
CONVECTIVE CURVATURE NEAR THE CENTER.  SINCE THEN...THE CONVECTION
HAS DIMINISHED...ALTHOUGH IT IS UNCLEAR WHETHER THIS IS A DIURNAL
MINIMUM OR THE START OF A WEAKENING TREND.  SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB ARE 30 KT...AND THAT REMAINS THE
INITIAL INTENSITY.

THE INITIAL MOTION IS 065/19.  THE DEPRESSION IS MOVING ALONG THE
SOUTHEASTERN EDGE OF THE WESTERLIES AND TO THE NORTHWEST OF THE
SUBTROPICAL RIDGE.  ALL GUIDANCE AGREES THAT THE SYSTEM SHOULD MOVE
GENERALLY EAST-NORTHEASTWARD FOR 24 HR OR SO...FOLLOWED BY A MOTION
TOWARD THE EAST THAT SHOULD CONTINUE UNTIL DISSIPATION.  THE NEW
FORECAST TRACK IS A LITTLE SOUTH OF THE PREVIOUS TRACK BASED ON THE
INITIAL POSITION AND MOTION...AND IT LIES NEAR THE CENTER OF THE
TRACK GUIDANCE ENVELOPE.

THE DEPRESSION IS JUST SOUTHEAST OF A FRONTAL SYSTEM AND IS MOVING
TOWARD COOLER WATERS.  IN ADDITION...VERTICAL WIND SHEAR IS FORECAST
TO INCREASE AFTER 6-12 HOURS.  THEREFORE...THERE IS ONLY A SHORT
WINDOW FOR INTENSIFICATION.  THE INTENSITY FORECAST CALLS FOR
MODEST STRENGTHENING DURING THE NEXT 12 HOURS...FOLLOWED BY
EXTRATROPICAL TRANSITION AS THE DEPRESSION MERGES WITH THE FRONTAL
SYSTEM.  THE CYCLONE IS FORECAST TO DISSIPATE COMPLETELY WITHIN THE
FRONTAL ZONE BY 72 HR...AND THIS COULD EVEN OCCUR EARLIER.  THE
INTENSITY FORECAST IS A LITTLE LESS INTENSE THAN THE FORECAST OF
THE SHIPS AND LGEM MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0300Z 36.6N  61.3W   30 KT  35 MPH
 12H  13/1200Z 37.8N  58.4W   35 KT  40 MPH
 24H  14/0000Z 39.3N  54.2W   35 KT  40 MPH
 36H  14/1200Z 40.3N  50.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  15/0000Z 40.3N  45.6W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  16/0000Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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