ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM HURRICANE HILARY DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092011 800 AM PDT FRI SEP 23 2011 HILARY IS MAINTAINING ITSELF AS AN IMPRESSIVE MAJOR HURRICANE WITH VERY COLD AND SYMMETRIC CLOUD TOPS SURROUNDING A SMALL WARM EYE. BOTH THE TAFB AND SAB SUBJECTIVE AND ADVANCED DVORAK TECHNIQUES SUGGEST WINDS OF AT LEAST 125 KT...WHICH IS THE INTENSITY ANALYZED THIS MORNING. THE SIZE OF THE CYCLONE CONTINUES TO BE QUITE SMALL AS INDICATED BY A LACK OF TROPICAL-STORM-FORCE WINDS ON THE EAST SIDE OF A NEARBY ASCAT PASS AND A CIRA AMSU WIND RADII ESTIMATE. ALSO...NO TROPICAL-STORM-FORCE WINDS HAVE BEEN REPORTED ALONG THE COAST OF MEXICO THIS MORNING. THE HURRICANE IS MOVING TOWARD THE WEST AT ABOUT 9 KT...PRIMARILY BEING STEERED BY THE INFLUENCE OF A ZONALLY-ORIENTED DEEP-LAYERED RIDGE NORTH OF HILARY. THE CYCLONE SHOULD CONTINUE WITH THIS GENERAL MOTION FOR THE NEXT THREE DAYS OR SO. AT THE EXTENDED RANGE...HOWEVER...THERE EXISTS A LARGE SPREAD IN THE TRACK GUIDANCE. THE REGIONAL HURRICANE MODELS RECURVE HILARY TOWARD MEXICO DUE TO A VIGOROUS SHORTWAVE TROUGH IMPINGING UPON THE AFOREMENTIONED RIDGE...WHILE THE 00Z UKMET AND ECMWF MODELS INDICATE A CONTINUED WEST-NORTHWESTWARD MOTION. OF NOTE IS THAT THE GFS AND NOGAPS MODELS ARE NOW SPLITTING THE DIFFERENCE WITH A NORTHWARD MOTION INDICATED AT DAYS 4 AND 5 AFTER PREVIOUSLY SHOWING A MORE WESTWARD TRAJECTORY. THE OFFICIAL FORECAST SHOWS NO CHANGE FROM THE PREVIOUS ADVISORY AT THIS POINT...THOUGH MORE OF A TURN TOWARD THE NORTH OR EVEN NORTHEAST AT THE EXTENDED RANGE COULD BE MADE LATER IF THE 12Z MODEL SUITE AGREES WITH THE TREND IN THE GUIDANCE. THE INTENSITY...FOR ONCE...MAY BE EASIER TO PREDICT THAN THE TRACK FORECAST. HILARY SHOULD REMAIN OVER VERY WARM WATERS...IN MOIST AIR...AND WITHIN LOW VERTICAL WIND SHEAR FOR THE NEXT TWO TO THREE DAYS. SO IT IS QUITE LIKELY THAT HILARY WILL CONTINUE AS A MAJOR HURRICANE DURING THAT TIME. INTENSITY VARIATIONS THAT OCCUR MAY BE DOMINATED BY INTERNAL DYNAMICS...SUCH AS EYEWALL REPLACEMENT CYCLES...WHICH WE HAVE VERY LIMITED ABILITY TO ANTICIPATE. BY DAYS 4 AND 5...THE CYCLONE SHOULD ENCOUNTER GRADUALLY DECREASING SSTS... LESS UNSTABLE AIR...AND INCREASING VERTICAL SHEAR SHOULD LIKELY RESULT IN A WEAKENING TREND. THE INTENSITY FORECAST IS BASED UPON THE LGEM AND SHIPS STATISTICAL MODELS AND IS QUITE CLOSE TO THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 16.1N 102.5W 125 KT 145 MPH 12H 24/0000Z 16.2N 103.8W 130 KT 150 MPH 24H 24/1200Z 16.5N 105.5W 125 KT 145 MPH 36H 25/0000Z 17.0N 107.3W 120 KT 140 MPH 48H 25/1200Z 17.4N 108.9W 115 KT 135 MPH 72H 26/1200Z 18.0N 111.5W 105 KT 120 MPH 96H 27/1200Z 19.0N 114.0W 95 KT 110 MPH 120H 28/1200Z 21.0N 115.0W 80 KT 90 MPH $$ FORECASTER LANDSEA/STEWART NNNN
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