|
Show Selection: |
| #375517 (Received by flhurricane at: 10:59 AM 12.Sep.2010) TCDAT2 TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 1100 AM AST SUN SEP 12 2010 THE AREA OF LOW PRESSURE ASSOCIATED WITH A STRONG TROPICAL WAVE THAT MOVED OFF THE WEST COAST OF AFRICA YESTERDAY NOW HAS ENOUGH CONVECTIVE ORGANIZATION TO BE DECLARED A TROPICAL DEPRESSION. THE INITIAL INTENSITY IS SET AT 30 KT BASED ON A BLEND OF DVORAK T-NUMBERS OF 2.5 AND 1.5 FROM TAFB AND SAB...RESPECTIVELY. THE DEPRESSION HAS A LARGE CURVED BAND IN THE WESTERN SEMICIRCLE ...AND OUTFLOW IS GOOD IN THAT PORTION OF THE CIRCULATION. ANALYSES FROM UW-CIMSS AND THE SHIPS MODEL SHOW ABOUT 10 KT OF EASTERLY SHEAR OVER THE CYCLONE...HOWEVER THE SHEAR IS EXPECTED TO DIMINISH IN THE NEXT 12 TO 24 HOURS. THE DEPRESSION WILL BE MOVING OVER WARM WATERS FOR THE NEXT COUPLE OF DAYS...AND STEADY INTENSIFICATION IS FORECAST. BEYOND THAT TIME...THE CYCLONE WILL BE MOVING OVER MARGINAL SEA SURFACE TEMPERATURES...AND THE SHIPS MODEL SHOWS THE SHEAR INCREASING. THE STATISTICAL MODELS SHOW SOME WEAKENING AT DAYS 4 AND 5...BUT THE DYNAMICAL MODELS SHOW THEIR PEAK INTENSITY OF THE CYCLONE LATE IN THE PERIOD. AS A COMPROMISE ...THE OFFICIAL FORECAST SHOWS LITTLE CHANGE IN INTENSITY BEYOND 48 HOURS. THE NHC FORECAST IS IN BEST AGREEMENT WITH THE LGEM THROUGH DAY 3 AND CLOSE TO ICON AT DAYS 4 AND 5. THE INITIAL MOTION ESTIMATE IS 275/12...AS THE DEPRESSION IS CURRENTLY LOCATED ON THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE THAT EXTENDS FROM NORTH AFRICA TO THE EASTERN ATLANTIC. THE CYCLONE WILL TURN WEST-NORTHWESTWARD AND NORTHWESTWARD AND SLOW DOWN A LITTLE BY 48 HOURS AS IT APPROACHES A BREAK IN THE RIDGE TO THE SOUTHWEST OF A MID- AND UPPER-LEVEL LOW EAST OF THE AZORES. ON DAYS 4 AND 5 THE MID- TO UPPER-LEVEL LOW MOVES EASTWARD. THIS ALLOWS A MID-LEVEL RIDGE TO BUILD IN EAST AND NORTH OF THE CYCLONE...WHICH SHOULD RESULT IN AN ACCELERATION TOWARD THE NORTHWEST OR WEST- NORTHWEST BY THE END OF THE PERIOD. THE OFFICIAL FORECAST IS CLOSE TO A BLEND OF ALL THE DYNAMICAL MODELS...WITH THE EXCEPTION OF THE NOGAPS...WHICH APPEARS TO BE A SOUTHERLY OUTLIER. FORECAST POSITIONS AND MAX WINDS INITIAL 12/1500Z 12.7N 21.4W 30 KT 12HR VT 13/0000Z 12.8N 23.3W 35 KT 24HR VT 13/1200Z 13.5N 25.5W 45 KT 36HR VT 14/0000Z 14.5N 27.7W 55 KT 48HR VT 14/1200Z 15.7N 29.4W 65 KT 72HR VT 15/1200Z 19.0N 32.5W 65 KT 96HR VT 16/1200Z 23.0N 37.0W 65 KT 120HR VT 17/1200Z 26.5N 43.0W 65 KT $$ FORECASTER BRENNAN |
