ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM HILARY DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT SAT AUG 20 2005 HILARY HAS CONTINUED TO BECOME BETTER ORGANIZED DURING THE PAST 6 HOURS WITH INCREASED BANDING FEATURES AND A SMALL CDO-LIKED FEATURE ...WITH TOPS TO -80C AND COLDER...DEVELOPING NEAR AND TO THE SOUTH OF THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL INTENSITY HAS BEEN INCREASED TO 40 KT BASED SATELLITE INTENSITY ESTIMATES OF 45 KT... 35 KT...AND 25 KT FROM TAFB...SAB...AND AFWA...RESPECTIVELY...AND THE SMALL CDO-LIKE FEATURE THAT HAS FORMED SINCE 0615Z. THE INITIAL MOTION ESTIMATE IS 275/16...BASED ON MICROWAVE POSITION ESTIMATES DURING THE PAST 5 HOURS. THIS MOTION AND INITIAL POSITION ARE A LITTLE SOUTH OR LEFT OF THE PREVIOUS TRACKS AND POSITIONS. OTHER THAN THAT...THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACKS OR REASONINGS. HILARY IS EXPECTED TO TRACK AROUND THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE THAT EXTENDS EAST-WEST ACROSS MEXICO. THE MOTION OVER THE NEXT 24 HOURS OR SO COULD BE MORE WESTWARD...BUT THE CYCLONE IS GRADUALLY EXPECTED TO TURN WEST-NORTHWESTWARD IN THE 24-72H PERIOD...AND THEN TURN NORTHWESTWARD AT SPEEDS LESS THAN 10 KT AFTER THAT AS A STRONG MID-LATITUDE TROUGH DIGS SOUTHEASTWARD OFF THE CALIFORNIA COAST AND ERODES THE RIDGE TO THE NORTH OF HILARY. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS TRACK AND THE NHC MODEL CONSENSUS. THE SHIPS INTENSITY MODEL INDICATES NORTHEASTERLY SHEAR OF 10-15 KT IS EXPECTED TO AFFECT THE CYCLONE THROUGH 72 HOURS. USUALLY SUCH MODERATE SHEAR CONDITIONS ARE NOT CONDUCIVE TO RAPID STRENGTHENING ...BUT A NORMAL INTENSIFICATION RATE OF 20 KT PER 24 HOURS SEEMS REASONABLE GIVEN THE HIGH SSTS AND VERY MOIST MID-LEVELS. THE OFFICIAL FORECAST IS CLOSE TO THE SHIPS MODEL...BUT HIGHER THAN THE GFDL...WHICH ONLY BRINGS HILARY UP TO 70 KT IN 84 HOURS. RAINBANDS PRODUCING GUSTY WINDS AND LOCALLY HEAVY RAINFALL WILL AFFECT PORTIONS OF THE SOUTHWESTERN COAST OF MEXICO FROM PUERTO ESCONDIDO WESTWARD TO ZIHUATANEJO DURING THE NEXT DAY OR TWO. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 20/0900Z 13.7N 100.6W 40 KT 12HR VT 20/1800Z 14.0N 102.8W 50 KT 24HR VT 21/0600Z 14.6N 105.4W 60 KT 36HR VT 21/1800Z 15.5N 107.8W 70 KT 48HR VT 22/0600Z 16.4N 109.9W 80 KT 72HR VT 23/0600Z 18.0N 113.0W 80 KT 96HR VT 24/0600Z 19.5N 115.5W 75 KT 120HR VT 25/0600Z 21.5N 117.5W 60 KT $$ NNNN
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Page last modified: Saturday, 20-Aug-2005 08:55:10 UTC