ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM HILARY DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT SAT AUG 20 2005 HILARY APPEARS TO HAVE STRENGTHENED OVERNIGHT AT A FAIRLY RAPID PACE. THE LOW LEVEL CENTER IS NOW WELL EMBEDDED BENEATH AN EXPANDING AREA OF CONVECTIVE CLOUD TOPS COLDER THAN -80C... AND THE MODERATE TO WEAK NORTHEASTERLY WIND SHEAR SEEMS TO BE GIVING WAY TO OUTFLOW FROM THE CONVECTION. DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB... AND RECENT ODT ESTIMATES... HAVE INCREASED TO 55 KT... WHICH IS THE BASIS FOR THE ADVISORY INTENSITY... AND HILARY MIGHT HAVE BEEN STRONGER THAN ESTIMATED EARLIER THIS MORNING. LITTLE SEEMS TO STAND IN THE WAY OF CONTINUED INTENSIFICATION... WITH THE NORTHEASTERLY SHEAR EXPECTED TO REMAIN FAIRLY WEAK... AND THE OCEAN IS MORE THAN WARM ENOUGH. COMBINING THESE FORECAST CONDITIONS WITH THE RECENT INTENSITY TREND... THE NEW OFFICIAL FORECAST IS ADJUSTED UPWARD FROM THE PREVIOUS ADVISORY. THE SHIPS... GFDL... AND THE OFFICIAL FORECAST CALL FOR 90 KT BY 48 HOURS. WEAKENING IS EXPECTED BEYOND 72 HOURS WHEN HILARY SHOULD REACH COOLER WATERS. LACKING ANY RECENT MICROWAVE DATA TO REFINE THE POSITION OF THE LOW LEVEL CENTER... THE INITIAL POSITION AND MOTION ARE BASED ON CONTINUITY AND ON FOLLOWING THE CENTROID OF THE DEEP CONVECTION. THE INITIAL MOTION ESTIMATE REMAINS 275/16. HILARY IS BEING STEERED WESTWARD ALONG THE SOUTHERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER THE SOUTHEASTERN UNITED STATES THAT EXTENDS WESTWARD OVER NORTHERN MEXICO AND THE EXTREME EASTERN PACIFIC. DYNAMICAL MODELS FORECAST THIS RIDGE TO REMAIN INTACT AND EXPAND WESTWARD DURING THE NEXT COUPLE OF DAYS. THEREAFTER... A WEAKNESS IN THE RIDGE IS FORECAST TO DEVELOP JUST WEST OF MEXICO AS A MIDLATITUDE TROUGH DEEPENS OVER THE WEST COAST OF THE UNITED STATES. THIS FEATURE SHOULD INDUCE A GRADUAL BEND IN THE TRACK OF HILARY TO THE RIGHT... EVENTUALLY TOWARD THE NORTHWEST WITH A STEADY DECREASE IN FORWARD SPEED. THE NEW OFFICIAL FORECAST IS VERY CLOSE TO THE DYNAMICAL MODEL CONSENSUS... WHICH HAS SHIFTED A LITTLE WESTWARD COMPARED TO THE PREVIOUS ADVISORY... MAINLY DUE TO THE WESTERNMOST SOLUTIONS PROVIDED BY THE GFS AND GFDL. RAINBANDS PRODUCING GUSTY WINDS AND LOCALLY HEAVY RAINFALL COULD AFFECT PORTIONS OF THE SOUTHWESTERN COAST OF MEXICO FROM PUERTO ESCONDIDO WESTWARD TO ZIHUATANEJO DURING THE NEXT DAY OR SO. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 20/1500Z 13.9N 102.1W 55 KT 12HR VT 21/0000Z 14.3N 104.1W 65 KT 24HR VT 21/1200Z 15.1N 106.7W 75 KT 36HR VT 22/0000Z 15.9N 109.1W 85 KT 48HR VT 22/1200Z 16.9N 111.3W 90 KT 72HR VT 23/1200Z 18.5N 114.5W 90 KT 96HR VT 24/1200Z 20.0N 117.0W 80 KT 120HR VT 25/1200Z 22.0N 118.5W 60 KT $$ NNNN
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Page last modified: Saturday, 20-Aug-2005 15:10:10 UTC