ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE JOHN DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP112006 200 AM PDT THU AUG 31 2006 THE EYE REMAINS OBSCURED IN INFRARED SATELLITE IMAGERY...BUT SUCCESSIVE 0231 AND 0232 UTC MICROWAVE OVERPASSES AND THE CUYUTLAN MEXICO RADAR CONTINUE TO DEPICT A WELL-DEFINED EYE...AND THERE IS PLENTY OF VERY DEEP CONVECTION. THE SOMEWHAT DEGRADED SATELLITE APPEARANCE IS POSSIBLY DUE TO A LITTLE BIT OF WIND SHEAR AND THE INTERACTION OF THE CIRCULATION WITH LAND. THE INITIAL INTENSITY IS MAINTAINED AT 110 KT BASED ON A BLEND OF THE VARIOUS DVORAK ESTIMATES THAT RANGE FROM 100 TO 115 KT. JOHN REMAINS A DANGEROUS CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON SCALE. THE INTENSITY FORECAST REMAINS A CHALLENGE GIVEN THE CLOSE PROXIMITY TO LAND. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND KEEPS JOHN OFFSHORE FROM MAINLAND MEXICO BUT NEAR OR OVER THE SOUTHERN BAJA CALIFORNIA PENINSULA IN ROUGHLY 36 HOURS. THEREFORE...DUE TO THE VERY WARM WATERS...ADDITIONAL STRENGTHENING IS POSSIBLE AND ONLY A SLIGHT AMOUNT OF STRENGTHENING WOULD MAKE JOHN A CATEGORY FOUR HURRICANE...AND THIS POSSIBILITY IS SUPPORTED BY ALL AVAILABLE INTENSITY GUIDANCE. ONCE IT PASSES WEST OF BAJA...COOLER WATERS SHOULD INDUCE A STEADY WEAKENING TREND...BUT SINCE JOHN IS SO STRONG NOW IT WILL TAKE A WHILE FOR THE CYCLONE TO SPIN DOWN LATE IN THE FORECAST PERIOD. THE OFFICIAL FORECAST KEEPS JOHN A TROPICAL STORM AT DAY 5. THE INITIAL MOTION IS ABOUT THE SAME AS BEFORE...300/12...SO JOHN IS RIGHT ON THE PREVIOUS ADVISORY TRACK. GLOBAL MODELS REMAIN IN GOOD AGREEMENT ON JOHN CONTINUING TO PARALLEL THE COAST OF MAINLAND MEXICO ALONG THE SOUTHWESTERN PERIPHERY OF A MIDDLE- TO UPPER-LEVEL RIDGE. THE GFDL HAS SHIFTED A LITTLE BACK TO THE RIGHT OR EAST AGAIN AND TAKES JOHN INLAND ALONG THE EAST COAST OF THE GULF OF CALIFORNIA...BUT THE OTHER MODELS HAVE OVERALL CHANGED LITTLE SINCE THE PREVIOUS CYCLE. THE MODELS STILL DIVERGE AFTER THE WESTWARD TURN NEAR SOUTHERN BAJA DUE TO DIFFERING SOLUTIONS FOR THE UPPER TROUGH OFF THE WEST COAST OF THE UNITED STATES. THE NEW OFFICIAL FORECAST...LIKE THE PREVIOUS ADVISORY...PRESUMES THAT THE MAJORITY OF THE MODELS ARE CORRECT IN BUILDING A MID-LEVEL RIDGE TO THE NORTH OF JOHN THAT WILL TURN THE TROPICAL CYCLONE WESTWARD. THE GFDL CONTINUES TO INSIST OTHERWISE...WHICH KEEPS THE CONSENSUS TRACKS SLOWER THAN THEY WOULD BE IN ITS ABSENCE. PAYING SOME ATTENTION TO THE GFDL SOLUTION...THE OFFICIAL FORECAST IS CLOSE TO THE CONSENSUS ON THE WESTWARD PROGRESSION OF JOHN. FORECAST POSITIONS AND MAX WINDS INITIAL 31/0900Z 18.7N 105.3W 110 KT 12HR VT 31/1800Z 20.0N 106.6W 115 KT 24HR VT 01/0600Z 21.6N 108.0W 115 KT 36HR VT 01/1800Z 22.7N 109.3W 115 KT 48HR VT 02/0600Z 23.4N 110.6W 105 KT 72HR VT 03/0600Z 24.0N 113.5W 90 KT 96HR VT 04/0600Z 24.0N 117.5W 70 KT 120HR VT 05/0600Z 24.0N 122.0W 50 KT $$ FORECASTER KNABB NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:43 UTC