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| #151002 (Received by flhurricane at: 4:34 PM 15.Sep.2007) TCDAT3 TROPICAL DEPRESSION INGRID DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082007 500 PM EDT SAT SEP 15 2007 SATELLITE IMAGES SHOW A TIGHT CENTER EMBEDDED WITHIN A WELL-DEFINED AND LARGER LOW-LEVEL CIRCULATION...BUT DEEP CONVECTION IS LIMITED TO THE EASTERN SEMICIRCLE. SOME CONVECTIVE CELLS HAVE BEEN TRYING TO DEVELOP ELSEWHERE...BUT BECOME IMMEDIATELY SHEARED AWAY BY THE STRONG UPPER-LEVEL WINDS. SATELLITE IMAGES SHOW A BAND OF EVEN STRONGER UPPER-LEVEL WINDS HEADING FOR INGRID. THIS COULD FURTHER LESSEN THE DEEP CONVECTION...RESULTING IN ADDITIONAL WEAKENING AS INDICATED IN THE OFFICIAL FORECAST. AS IN THE PREVIOUS FORECAST... INGRID IS KEPT AS A 25-KT DEPRESSION THROUGH DAY 5...SINCE THE DEPRESSION MIGHT SURVIVE THE HOSTILE ENVIRONMENT FOR THE NEXT 48 HOURS. THEREAFTER...THE SHEAR COULD WEAKEN...AND CONSEQUENTLY ALL VERSIONS OF THE SHIPS MODELS SUGGEST A SLIGHT REJUVENATION OF INGRID BEYOND 3 DAYS IN THE SUBTROPICAL ATLANTIC. THIS SOLUTION APPEARS UNLIKELY SINCE BOTH THE SOPHISTICATED GFDL AND HWRF MODELS DISSIPATE THE CYCLONE. BECAUSE THE CYCLONE IS SHEARED AND MORE SHALLOW...DURING THE PAST FEW HOURS IT HAS BEEN STEERED WESTWARD...OR 280 DEGREES AT 10 KNOTS...BY THE LOWER-LEVEL WINDS ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE. THE CYCLONE SHOULD BEGIN TO TURN MORE TO THE NORTHWEST AROUND THE RIDGE DURING THE NEXT 24 HOURS...WITH A DECREASE IN FORWARD SPEED AS THE STEERING CURRENTS WEAKEN. DUE TO THE INITIAL WESTWARD MOTION...THE OFFICIAL FORECAST HAS BEEN SHIFTED A LITTLE BIT FARTHER TO THE WEST FOR THE FIRST 2 TO 3 DAYS...BUT STILL KEEPS THE CYCLONE WELL NORTHEAST OF THE LEEWARD ISLANDS. THE SPREAD IN THE TRACK MODELS HAS INCREASED BEYOND 3 DAYS. SOME SHOW A CONTINUATION OF A WEST-NORTHWEST TRACK...WHILE OTHERS SHOW A TURN TO THE NORTH AND NORTH-NORTHEAST. THE OFFICIAL FORECAST FOLLOWS THE CONSENSUS WHICH IS IN THE MIDDLE OF THE GUIDANCE ENVELOPE. FORECAST POSITIONS AND MAX WINDS INITIAL 15/2100Z 16.5N 55.0W 30 KT 12HR VT 16/0600Z 16.7N 56.2W 25 KT 24HR VT 16/1800Z 17.8N 58.0W 25 KT 36HR VT 17/0600Z 19.0N 59.5W 25 KT 48HR VT 17/1800Z 20.0N 60.5W 25 KT 72HR VT 18/1800Z 22.0N 62.0W 25 KT 96HR VT 19/1800Z 23.5N 63.0W 25 KT 120HR VT 20/1800Z 25.0N 64.0W 25 KT $$ FORECASTER AVILA |
