Tropical Depression EIGHT

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TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012
500 PM EDT WED AUG 15 2012
 
THE LOW PRESSURE SYSTEM THAT HAS BEEN MOVING ACROSS THE EASTERN AND
CENTRAL ATLANTIC OCEAN FOR THE PAST WEEK HAS FINALLY ACQUIRED
ENOUGH PERSISTENT ORGANIZED CONVECTION TO BE CLASSIFIED AS A
TROPICAL DEPRESSION. ALTHOUGH CLOUD TOPS ARE NOT PARTICULARLY
COLD...THE CONVECTION IS DEEP ENOUGH TO MEET THE CRITERIA FOR
DVORAK SATELLITE CLASSIFICATIONS...WHICH ARE T1.5/25 KT FROM TAFB
AND SAB. HOWEVER...CONVECTIVE BANDING HAS IMPROVED SINCE THE 18Z
CLASSIFICATIONS. ALSO...A RECENT UW-CIMSS SATELLITE INTENSITY
ESTIMATE INDICATES THE INTENSITY IS NEAR 30 KT...AND THAT IS THE
INTENSITY USED FOR THIS ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 355/16 KT BASED ON A BLEND OF VISIBLE
AND MICROWAVE SATELLITE FIXES OVER THE PAST 12 HOURS. THE NHC MODEL
GUIDANCE IS IN EXCELLENT AGREEMENT ON THE CYCLONE MOVING NORTHWARD
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE FOR THE NEXT
12 HOURS OR SO. AFTER THAT...A SHARP TURN TOWARD THE NORTHEAST AND
EVENTUALLY TOWARD THE EAST IS EXPECTED AS THE CYCLONE BECOMES
EMBEDDED IN THE DEEP-LAYER MID-LATITUDE WESTERLIES ACROSS THE NORTH
ATLANTIC. BY DAYS 4 AND 5...THE CYCLONE IS FORECAST TO BECOME
CAPTURED BY A SHORTWAVE TROUGH AND LIFT OUT TO THE NORTHEAST
TOWARD THE AZORES ISLANDS. THE OFFICIAL TRACK FORECAST CLOSELY
FOLLOWS THE CONSENSUS MODELS TVCA AND TV15.
 
THE DEPRESSION HAS A RELATIVELY SMALL CIRCULATION THAT IS SURROUNDED
BY VERY DRY MID-LEVEL AIR. ALTHOUGH THE CYCLONE WILL REMAIN OVER
FAVORABLE SEA-SURFACE TEMPERATURES FOR THE NEXT 2-3 DAYS AND IN A
LOW VERTICAL SHEAR ENVIRONMENT...OCCASIONAL INTRUSIONS OF DRY AIR
ARE EXPECTED TO KEEP THE SYSTEM CONVECTIVELY CHALLENGED THROUGHOUT
THE FORECAST PERIOD. ALTHOUGH NOT EXPLICITLY FORECAST...THE BEST
OPPORTUNITY FOR THE CYCLONE TO ACHIEVE HURRICANE STATUS WOULD BE
BETWEEN 48 AND 72 HOURS PRIOR TO THE ONSET OF STRONG WESTERLY
VERTICAL WIND SHEAR ON DAY 3. THE OFFICIAL INTENSITY FORECAST IS
BELOW THE MAJORITY OF THE GUIDANCE DUE TO THE POTENTIALLY NEGATIVE
EFFECTS OF THE SURROUNDING DRY ENVIRONMENT...BUT ABOVE THE GFDL
WHICH SHOWS LITTLE STRENGTHENING.
 
THIS SYSTEM IS EXPECTED TO REMAIN WELL TO THE EAST OF BERMUDA AND...
THEREFORE...SHOULD NOT HAVE ANY DIRECT IMPACT ON THAT ISLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/2100Z 29.9N  55.1W   30 KT  35 MPH
 12H  16/0600Z 31.6N  55.0W   35 KT  40 MPH
 24H  16/1800Z 33.5N  53.4W   40 KT  45 MPH
 36H  17/0600Z 34.6N  50.4W   45 KT  50 MPH
 48H  17/1800Z 35.0N  46.5W   50 KT  60 MPH
 72H  18/1800Z 35.2N  38.3W   60 KT  70 MPH
 96H  19/1800Z 36.6N  29.7W   60 KT  70 MPH
120H  20/1800Z 38.8N  23.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 
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