ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE JOHN DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP112006 200 AM PDT WED AUG 30 2006 RADAR FROM ACAPULCO MEXICO SHOWS A WELL-DEFINED EYE AND IT APPEARS THAT JOHN HAS GONE THROUGH AN EYE-WALL REPLACEMENT CYCLE. THIS MAY EXPLAIN WHY THE SATELLITE APPEARANCE HAS NOT IMPROVED MUCH SINCE YESTERDAY AFTERNOON...HOWEVER WITHIN THE PAST HOUR OR SO A WARM SPOT HAS RE-APPEARED IN INFRARED SATELLITE IMAGERY. DVORAK SATELLITE ESTIMATES ARE 102 KT AND 90 KT FROM TAFB AND SAB RESPECTIVELY AND THE INITIAL INTENSITY WILL REMAIN 100 KT FOR THIS ADVISORY. AN AIR FORCE HURRICANE HUNTER AIRCRAFT IS CURRENTLY EN-ROUTE TO JOHN AND IT SHOULD SOON PROVIDE A MUCH MORE ACCURATE MEASURE OF THE HURRICANE'S CURRENT STRENGTH. JOHN HAS BEEN MOVING BETWEEN WEST-NORTHWEST AND NORTHWEST AND THE ESTIMATED MOTION IS 300/10. THE GLOBAL MODELS KEEP JOHN ON THIS GENERAL HEADING FOR THE NEXT 36 HOURS AROUND THE SOUTHWESTERN PERIPHERY OF A MID- TO UPPER-LEVEL RIDGE OVER NORTHERN MEXICO. THE GFS REMAINS ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE DUE TO ITS WEAKER DEPICTION OF THE CYCLONE. THE GFDL AND UKMET ARE ON THE RIGHT SIDE OF THE GUIDANCE AND BOTH TRACK JOHN ACROSS SOUTHWESTERN MEXICO IN 24-36 HOURS. OUT OF RESPECT FOR THE GFDL AND UKMET THE TRACK FORECAST IS AGAIN SHIFTED RIGHT OR CLOSER TO THE COAST OF MEXICO. EVEN THOUGH THE OFFICIAL FORECAST KEEPS THE CENTER JUST OFFSHORE...ANY SMALL DEVIATION TO THE RIGHT WILL BRING THE CORE OF THIS DANGEROUS HURRICANE OVER SOUTHWEST MEXICO. BEYOND THREE DAYS THERE REMAINS SIGNIFICANT DIVERGENCE IN THE MODELS AND HIGHER THAN NORMAL UNCERTAINTY IN THE TRACK FORECAST. AS WITH THE PREVIOUS ADVISORY...IT IS ASSUMED THERE WILL BE ENOUGH RIDGING TO THE NORTH OF JOHN TO BEND THE TRACK MORE WESTWARD AT DAYS 4 AND 5. WITH LOW SHEAR AND WARM SSTS THE INTENSITY GUIDANCE CONTINUES TO INDICATE STRENGTHENING. BECAUSE INTENSIFICATION HAS CEASED OVER THE PAST 12 HOURS...PERSISTENCE HAS BECOME LESS OF A POSITIVE FACTOR IN THE SHIPS MODEL AND THEREFORE IT NOW KEEPS THE HURRICANE JUST BELOW CATEGORY FOUR STRENGTH. HOWEVER...IT IS ASSUMED THAT JOHN HAS JUST COMPLETED AN EYEWALL REPLACEMENT CYCLE AND STRENGTHENING SHOULD RESUME. THE OFFICIAL INTENSITY FORECAST WILL CONTINUE TO PREDICT A CATEGORY FOUR WITHIN THE NEXT 24 HOURS... VIRTUALLY UNCHANGED FROM THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0900Z 15.6N 101.3W 100 KT 12HR VT 30/1800Z 16.5N 102.4W 110 KT 24HR VT 31/0600Z 18.0N 104.2W 120 KT 36HR VT 31/1800Z 19.5N 106.0W 120 KT 48HR VT 01/0600Z 20.9N 107.7W 115 KT 72HR VT 02/0600Z 22.2N 110.7W 105 KT 96HR VT 03/0600Z 22.8N 114.0W 90 KT 120HR VT 04/0600Z 23.0N 118.0W 75 KT $$ FORECASTER BROWN/STEWART NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:43 UTC