ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE JOHN DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP112006 200 PM PDT THU AUG 31 2006 REPORTS FROM THE AIR FORCE RECONNAISSANCE AIRCRAFT THIS AFTERNOON INDICATE THAT JOHN IS WEAKER THAN EARLIER INTENSITY ESTIMATES. A DROPSONDE IN THE EYE MEASURED A CENTRAL PRESSURE OF 973 MB WITH A 20 KT SURFACE WIND...SO THE ACTUAL MINIMUM PRESSURE IS ACTUALLY A LITTLE LOWER. CURRENT INTENSITY IS SET AT 90 KT...IN REASONABLE AGREEMENT WITH A SURFACE WIND MEASUREMENT FROM A GPS DROPSONDE IN THE EASTERN EYEWALL. ASIDE FROM THE EYEWALL REPLACEMENT OBSERVED YESTERDAY...IT IS NOT CLEAR WHY JOHN HAS WEAKENED SO MUCH. PERHAPS IT WAS DUE TO THE INTERACTION OF THE CIRCULATION WITH THE MOUNTAINOUS LANDMASS OF SOUTHWESTERN MEXICO. ALTHOUGH JOHN HAS WEAKENED...IT STILL HAS A WELL-ESTABLISHED UPPER-LEVEL OUTFLOW PATTERN AND THERE IS AN OPPORTUNITY FOR SOME RESTRENGTHENING BEFORE THE CENTER REACHES SOUTHERN BAJA CALIFORNIA. ONCE JOHN STARTS MOVING AWAY FROM THE BAJA PENINSULA...IT SHOULD BEGIN TRAVERSING SIGNIFICANTLY COOLER SEA SURFACE TEMPERATURES AND STEADILY WEAKEN. THE INITIAL MOTION IS 315/11...SLIGHTLY TO THE RIGHT OF THE PREVIOUS ESTIMATE. JOHN CONTINUES TO MOVE ALONG THE SOUTHWESTERN PERIPHERY OF A MIDDLE- TO UPPER-LEVEL RIDGE...WITH SOME POSSIBLE INTERACTION WITH THE SMALLER HURRICANE...KRISTY...LOCATED SOME 600 MILES TO ITS WEST. NOW THAT THE GFDL MODEL HAS SHIFTED FURTHER TO THE LEFT... THE TRACK MODEL GUIDANCE IS NOW IN BETTER AGREEMENT ON A TRACK THAT WOULD TAKE JOHN NEAR OR OVER THE SOUTHERN BAJA PENINSULA...AND THEN TAKES JOHN ON A MORE WESTWARD TRACK THEREAFTER. THE HURRICANE WARNING HAS BEEN EXTENDED A LITTLE NORTHWARD ALONG BOTH COASTS OF THE BAJA PENINSULA. THE WIND RADII HAVE BEEN ADJUSTED FROM THE OBSERVATIONS REPORTED BY THE RECONNAISSANCE AIRCRAFT. FORECAST POSITIONS AND MAX WINDS INITIAL 31/2100Z 20.7N 107.0W 90 KT 12HR VT 01/0600Z 21.8N 108.0W 95 KT 24HR VT 01/1800Z 22.8N 109.4W 95 KT 36HR VT 02/0600Z 23.5N 110.7W 90 KT 48HR VT 02/1800Z 24.1N 112.2W 85 KT 72HR VT 03/1800Z 24.7N 115.0W 65 KT 96HR VT 04/1800Z 25.0N 119.0W 55 KT 120HR VT 05/1800Z 25.0N 123.0W 40 KT $$ FORECASTER MAINELLI/PASCH NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:43 UTC