ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE JOHN DISCUSSION NUMBER 17 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP112006 800 AM PDT FRI SEP 01 2006 A DROPSONDE FROM AN AIR FORCE RESERVE HURRICANE HUNTER JUST REPORTED A CENTRAL PRESSURE OF 956 MB WITH 19 KT OF SURFACE WINDS...WHICH INDICATES A CENTRAL PRESSURE OF ABOUT 954 MB. HOWEVER THE PEAK FLIGHT LEVEL WINDS SO FAR ARE 98 KT. THE PLANE HASN'T SAMPLED THE ENTIRE STORM... AND WITH SUCH A LOW CENTRAL PRESSURE... THE INITIAL INTENSITY WILL BE HELD AT 100 KT. SATELLITE IMAGES INDICATE THAT THE RING OF THUNDERSTORMS AROUND THE CENTER OF JOHN HAS WARMED SOME THIS MORNING... THOUGH THE EYE IS BECOMING WARMER AND BETTER-DEFINED. THESE CHANGES MAY BE DUE TO ONGOING AN EYEWALL REPLACEMENT CYCLE... AS SEEN ON CABO SAN LUCAS RADAR... WHICH MAKES INTENSITY ESTIMATES RATHER UNCERTAIN. JOHN HAS SLOWED CONSIDERABLY... AND IS NOW ESTIMATED TO BE MOVING 310/6. THIS SLOW-DOWN SHOULD BE TEMPORARY WITH HIGH PRESSURE LOCKED IN PLACE OVER NORTHEAST MEXICO... WHICH SHOULD PUSH JOHN ALONG SOON. ALL GUIDANCE SHOWS SOME ACCELERATION AND IS TIGHTLY CLUSTERED NEAR THE SOUTHERN TIP OF BAJA CALIFORNIA IN ABOUT 12 HOURS. THIS NORTHWESTWARD MOTION SHOULD CONTINUE THROUGH ABOUT 36 HOURS. THEREAFTER MODELS ARE DIVERGENT... WITH THE GFS/GFDL FARTHER TO THE RIGHT SHOWING A THREAT TO NORTHERN BAJA CALIFORNIA... WHILE THE OTHER MODELS INDICATE A TURN TO THE WEST-NORTHWEST AWAY FROM LAND. THE OFFICIAL FORECAST IS SHIFTED A LITTLE TO NORTH IN THE SHORT- TERM TO ACCOUNT FOR THE INITIAL MOTION... AND LATER IN THE PERIOD IS ADJUSTED SLIGHTLY TO THE NORTH OF THE PREVIOUS TRACK CLOSER TO THE CONSENSUS OF THE GLOBAL MODELS. THERE COULD STILL BE A LITTLE STRENGTHENING BEFORE JOHN NEARS THE COAST TONIGHT. SHIPS INTENSITY GUIDANCE SHOWS LITTLE SHEAR AND THE WATERS ARE QUITE WARM IN THAT AREA. THEREAFTER...INTERACTION WITH LAND AND COOLER WATERS WEST OF THE BAJA PENINSULA SHOULD FORCE A GRADUAL WEAKENING. JOHN WILL LIKELY WEAKEN AT A FAST RATE BEYOND 48 HOURS AS IT ENCOUNTERS SSTS OF 23-24 DEGREES CELSIUS.... LIKELY CAUSING DISSIPATION NEAR THE END OF THE PERIOD. FORECAST POSITIONS AND MAX WINDS INITIAL 01/1500Z 22.0N 108.8W 100 KT 12HR VT 02/0000Z 22.9N 110.0W 105 KT...INLAND NEAR COAST 24HR VT 02/1200Z 24.0N 111.5W 100 KT 36HR VT 03/0000Z 24.8N 112.8W 95 KT 48HR VT 03/1200Z 25.5N 114.2W 80 KT 72HR VT 04/1200Z 26.3N 116.6W 60 KT 96HR VT 05/1200Z 26.5N 119.5W 35 KT 120HR VT 06/1200Z 26.5N 123.0W 25 KT...DISSIPATING $$ FORECASTER BLAKE/AVILA NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:43 UTC