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| #130868 (Received by flhurricane at: 4:34 AM 10.May.2007) TCDAT1 SUBTROPICAL STORM ANDREA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012007 500 AM EDT THU MAY 10 2007 ANDREA CONTINUES TO APPEAR RATHER UNIMPRESSIVE...WITH LATEST SATELLITE IMAGERY AND RADAR INDICATING SOME WEAK PULSATING CONVECTION TO THE EAST OF THE CENTER WHILE THE WESTERN HALF REMAINS NEARLY CONVECTION FREE. SATELLITE INTENSITY ESTIMATES HAVE DECREASED TO 25 TO 30 KNOTS...AND THE INITIAL INTENSITY HAS BEEN ADJUSTED DOWNWARD CONSERVATIVELY TO 35 KT. AN AIR FORCE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM LATER THIS MORNING TO PROVIDE A BETTER ESTIMATE OF THE INTENSITY. WATER VAPOR IMAGERY DEPICTS VERY DRY AIR SURROUNDING THE CYCLONE IN ALL QUADRANTS EXPECT FOR THE NORTH. LATEST SHEAR ANALYSIS FROM CIMSS SHOWS 20 KNOTS OF NORTHWEST SHEAR IMPINGING UPON THE CYCLONE. THIS COMBINATION OF SHEAR AND DRY AIR IS INHIBITING CONVECTION AND DISPLACING THE CONVECTION THAT DOES EXIST TO THE EAST OF THE CENTER. BOTH THE SHIPS AND GFDL GUIDANCE SUGGEST POSSIBLE STRENGTHENING. HOWEVER GIVEN THE CURRENT NORTHWESTERLY SHEAR AND THE ABUNDANCE OF DRY AIR...THE OFFICIAL FORECAST CALLS FOR GRADUAL WEAKENING AND DISSIPATION IN 96 HOURS...IF NOT SOONER. THERE IS A CAVEAT TO THE INTENSITY FORECAST...IN THAT A MID- TO UPPER-LEVEL LOW CURRENTLY OVER TEXAS MAY INTERACT WITH ANDREA IN 72 HOURS. THE CYCLONE HAS DRIFTED SLIGHTLY TO THE SOUTHWEST...AS A RESULT OF BEING EMBEDDED IN A LARGE DEEP-LAYER TROUGH. THE TRACK FORECAST IS A BIT COMPLEX. MOST OF THE MODEL GUIDANCE TAKES THE CYCLONE GENERALLY SOUTHWARD OVER THE NEXT TWO TO THREE DAYS...AS THE UPPER-LEVEL TROUGH THAT THE SYSTEM IS CURRENTLY EMBEDDED IN OPENS UP AND MOVES EASTWARD...AND THE LOW-LEVEL STEERING REMAINS WEAK. IF ANDREA STILL EXISTS AFTER 72 HOURS...THE UKMET...GFS...AND ECMWF FORECASTS A FRONT EXITING THE EASTERN U.S. PUSHING THE DISSIPATING CYCLONE EASTWARD. GIVEN THE UNCERTAINTIES IN THE FORECAST TRACK AND INTENSITY...THE TROPICAL STORM WATCH REMAINS UNCHANGED AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INITIAL 10/0900Z 30.4N 80.0W 35 KT 12HR VT 10/1800Z 30.2N 80.1W 30 KT 24HR VT 11/0600Z 29.9N 80.2W 30 KT 36HR VT 11/1800Z 29.7N 80.2W 25 KT 48HR VT 12/0600Z 29.5N 80.1W 25 KT 72HR VT 13/0600Z 29.3N 79.9W 25 KT...DISSIPATING 96HR VT 14/0600Z...DISSIPATED $$ FORECASTER MAINELLI |
