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| #375615 (Received by flhurricane at: 4:49 PM 12.Sep.2010) TCDAT2 TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 500 PM AST SUN SEP 12 2010 RECENT SATELLITE IMAGERY SHOWS AN INCREASE IN DEEP CONVECTION JUST TO THE WEST OF THE ESTIMATED CENTER POSITION...HOWEVER THE INTENSITY IS BEING HELD AT 30 KT FOR THIS ADVISORY BASED ON A BLEND OF DVORAK ESTIMATES FROM TAFB AND SAB. THE DEPRESSION IS STILL EXPERIENCING SOME EASTERLY SHEAR...HOWEVER THE SHIPS MODEL FORECASTS THE SHEAR TO WEAKEN IN THE NEXT 12 HOURS AND STAY BELOW 15 KT UNTIL 72 HOURS. THE INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY... SHOWING STEADY STRENGTHENING THROUGH 48 HOURS IN BEST AGREEMENT WITH THE SHIPS MODEL. AFTER THAT TIME...SEA SURFACE TEMPERATURES COOL ALONG THE TRACK AND THE SHEAR INCREASES AS THE CYCLONE INTERACTS WITH AN UPPER-LEVEL TROUGH/LOW AS INDICATED BY SEVERAL OF THE GLOBAL MODELS. GIVEN THE MIXED TRENDS IN THE GUIDANCE AT THIS TIME PERIOD...THE OFFICIAL FORECAST WILL HOLD THE INTENSITY AT 65 KT THROUGH DAY 5. THE CURRENT POSITION IS A LITTLE NORTH OF THE PREVIOUS TRACK...AND THE INITIAL MOTION ESTIMATE IS 280 DEGREES AT 12 KT. THE OVERALL THE SYNOPTIC REASONING REMAINS UNCHANGED. A WEST-NORTHWESTWARD TURN IS EXPECTED SOON AS THE DEPRESSION MOVES AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC. THIS MOTION IS EXPECTED CONTINUE THROUGH 36 TO 48 HOURS WHEN THE DEPRESSION WILL TURN NORTHWESTWARD INTO A BREAK IN THE RIDGE. AT DAYS 4 AND 5 A TURN BACK TOWARD THE WEST-NORTHWEST IS EXPECTED WITH AN INCREASE IN FORWARD SPEED AS CYCLONE MOVES AROUND THE EASTERN SIDE OF A UPPER-LEVEL LOW THAT CUTS OFF NEAR 40W. THE OFFICIAL NHC FORECAST IS NORTH OF THE PREVIOUS ONE THROUGH 36 HOURS DUE TO THE INITIAL POSITION AND MOTION...AND BEYOND THAT TIME IS BASICALLY AN EXTENSION OF THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 12/2100Z 13.3N 22.8W 30 KT 12HR VT 13/0600Z 13.7N 24.6W 35 KT 24HR VT 13/1800Z 14.6N 27.1W 45 KT 36HR VT 14/0600Z 15.6N 29.0W 55 KT 48HR VT 14/1800Z 16.9N 30.6W 65 KT 72HR VT 15/1800Z 20.4N 34.2W 65 KT 96HR VT 16/1800Z 24.0N 39.5W 65 KT 120HR VT 17/1800Z 27.1N 45.5W 65 KT $$ FORECASTER BRENNAN |
