ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM HURRICANE HILARY DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092011 200 PM PDT SAT SEP 24 2011 HILARY STILL IS EXHIBITING THE CLASSIC SIGNATURE OF A VERY INTENSE...BUT TINY...HURRICANE. AS SEEN IN THE INFRARED IMAGERY...VERY COLD SYMMETRIC CLOUD TOPS ARE SURROUNDING A 10 NM WIDE WARM EYE. THE TAFB/SAB SUBJECTIVE DVORAK AND THE CIMSS ADVANCED DVORAK TECHNIQUE CLASSIFICATIONS HAVE DROPPED SLIGHTLY...BUT ARE STILL SUPPORTING AN INTENSITY OF 115 KT. A 1457Z CIRA AMSU PASS PROVIDED GUIDANCE FOR THE WIND RADII ANALYSIS. HILARY CONTINUES TO SHOW SHORT-TERM TROCHOIDAL MOTION OVER THE LAST SEVERAL HOURS...BUT A LONGER TERM DIRECTION AND SPEED OF 270/9 IS ESTIMATED. A MOTION TOWARD THE WEST OR WEST-NORTHWEST AT ABOUT THE SAME SPEED IS EXPECTED DURING THE NEXT THREE DAYS AS HILARY IS STEERED ALONG THE SOUTH SIDE OF A DEEP-LAYER RIDGE. BY DAYS 4 AND 5...A WEAKNESS DEVELOPS IN THE RIDGE DUE TO A MID- TO UPPER-LEVEL LOW MOVING IN FROM THE NORTHWEST. HILARY SHOULD RESPOND BY TURNING SLOWLY NORTHWARD NEAR 115W ON THOSE DAYS. ALL OF THE RELIABLE TRACK MODELS REMAIN IN EXCELLENT AGREEMENT WITH THIS SCENARIO. IN FACT...SOME OF THE GUIDANCE SUGGESTS THAT HILARY WILL UNDERGO A FUJIWARA-TYPE OF INTERACTION WITH THE UPPER-LOW WITH A MUTUAL COUNTER-CLOCKWISE ROTATION OF THE TWO SYSTEMS. THE TRACK FORECAST IS VERY SIMILAR TO THE PREVIOUS ADVISORY AND THE MULTI-MODEL CONSENSUS. THE HURRICANE IS CURRENTLY IN A QUITE CONDUCIVE ENVIRONMENT OF LOW VERTICAL SHEAR...WARM WATERS...AND ABUNDANT MOISTURE. THE CYCLONE IS EXPECTED TO REMAIN A MAJOR HURRICANE FOR THE NEXT TWO DAYS. AFTER WHICH...A DRIER AND MORE STABLE ATMOSPHERE MAY BEGIN SOME SIGNIFICANT WEAKENING OF HILARY. BY THE END OF THE FORECAST PERIOD...STRONG VERTICAL SHEAR AND COOL SSTS SHOULD CAUSE AN EVEN QUICKER DECAY. THE INTENSITY PREDICTION IS BASED UPON THE SHIPS/LGEM/GFDL MODEL CONSENSUS AND IS VERY SIMILAR TO THE PREVIOUS ADVISORY. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 16.9N 106.8W 115 KT 135 MPH 12H 25/0600Z 17.0N 107.9W 115 KT 135 MPH 24H 25/1800Z 17.1N 109.5W 110 KT 125 MPH 36H 26/0600Z 17.2N 111.3W 110 KT 125 MPH 48H 26/1800Z 17.3N 113.0W 105 KT 120 MPH 72H 27/1800Z 18.0N 115.5W 95 KT 110 MPH 96H 28/1800Z 19.5N 116.0W 80 KT 90 MPH 120H 29/1800Z 22.0N 116.0W 60 KT 70 MPH $$ FORECASTER LANDSEA/STEWART NNNN
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