000 WTNT43 KNHC 020838 TCDAT3 TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132011 400 AM CDT FRI SEP 02 2011 SATELLITE IMAGERY...SURFACE OBSERVATIONS...AND AN EARLIER ASCAT OVERPASS INDICATE THAT TROPICAL DEPRESSION THIRTEEN HAS A ELONGATED CENTER OF CIRCULATION...WITH THE ELONGATION CURRENTLY FROM EAST-NORTHEAST TO WEST-SOUTHWEST. THE ASSOCIATED CONVECTION IS CURRENTLY POORLY ORGANIZED...ALTHOUGH A STRONG BURST HAS RECENTLY FORMED NEAR THE EAST-NORTHEASTERN END OF THE CENTER. THE INITIAL INTENSITY REMAINS 30 KT BASED ON THE ASCAT OVERPASS AND REPORTS FROM OIL RIGS IN THE NORTHERN GULF. WHILE THERE IS GOOD OUTFLOW OVER THE EASTERN SEMICIRCLE...AN UPPER-LEVEL TROUGH IS PRESENT OVER THE WESTERN SIDE OF THE CIRCULATION. THE DEPRESSION HAS NOT MOVED MUCH DURING THE PAST SEVERAL HOURS... WITH THE INITIAL MOTION A HIGHLY UNCERTAIN 315/2. THE CYCLONE IS CURRENTLY IN AN AREA OF LIGHT STEERING CURRENTS SOUTH OF A MID-LEVEL RIDGE OVER THE MISSISSIPPI VALLEY. THE DYNAMICAL MODELS FORECAST THIS RIDGE TO MOVE EASTWARD AND WEAKEN AS A DEEP-LAYER TROUGH MOVES SOUTHEASTWARD INTO THE OHIO VALLEY. THIS EVOLUTION SHOULD ALLOW THE DEPRESSION TO MOVE SLOWLY NORTHWESTWARD TO NORTHWARD FOR THE NEXT 24-36 HR...FOLLOWED BY A GRADUAL TURN TOWARD THE NORTHEAST. MOST OF THE DYNAMICAL MODELS NOW SHOW THIS SCENARIO...ALTHOUGH THERE REMAINS ENOUGH DISAGREEMENT BETWEEN THEM TO KEEP THIS A LOW CONFIDENCE FORECAST. THE NEW FORECAST TRACK IS ADJUSTED SOUTH AND EAST OF THE PREVIOUS FORECAST BASED MAINLY ON THE INITIAL POSITION...AND LIES CLOSE TO THE VARIOUS CONSENSUS MODELS FOR THE FIRST THREE DAYS OF THE FORECAST. IT SHOULD BE NOTED THAT REFORMATIONS OF THE CENTER COULD CAUSE ERRATIC MOTION AND ADJUSTMENTS TO THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS. THE CURRENT INTERACTION WITH THE UPPER-LEVEL TROUGH IS FORECAST BY THE DYNAMICAL MODELS TO CONTINUE FOR AT LEAST THE NEXT COUPLE OF DAYS...RESULTING IN VERTICAL WIND SHEAR CONDITIONS THAT...AT BEST...WILL BE MARGINALLY FAVORABLE FOR INTENSIFICATION. THIS INTERACTION...COMBINED WITH THE CURRENT ORGANIZATION OF THE SYSTEM...SUGGESTS THAT STRENGTHENING SHOULD BE SLOW. THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY AND LIES BETWEEN THE STRONGER SHIPS AND WEAKER LGEM MODELS. THE LARGE SIZE AND SLOW MOTION OF THE CYCLONE DURING THE NEXT 5 DAYS IS LIKELY TO PRODUCE A PROLONGED PERIOD OF TROPICAL STORM CONDITIONS AND HEAVY RAINFALL OVER PORTIONS OF THE NORTHERN GULF COAST. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 26.5N 91.7W 30 KT 35 MPH 12H 02/1800Z 27.0N 92.1W 35 KT 40 MPH 24H 03/0600Z 27.6N 92.3W 40 KT 45 MPH 36H 03/1800Z 28.2N 92.2W 45 KT 50 MPH 48H 04/0600Z 28.8N 92.0W 50 KT 60 MPH 72H 05/0600Z 29.5N 91.5W 50 KT 60 MPH...INLAND 96H 06/0600Z 30.5N 90.0W 40 KT 45 MPH...INLAND 120H 07/0600Z 31.5N 88.5W 25 KT 30 MPH...POST-TROP/EXTRATROP $$ FORECASTER BEVEN