Tropical Depression # 8 Forms.... Tropical Update 5pm Wednesday...

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.

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