ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM HILARY DISCUSSION NUMBER 33 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092011 200 AM PDT THU SEP 29 2011 COLDER WATER AND INCREASING SHEAR ARE TAKING A TOLL ON HILARY. THE COVERAGE OF DEEP CONVECTION HAS BEEN SHRINKING AND CLOUD TOP TEMPERATURES ARE WARMING. IN ADDITION...MICROWAVE IMAGES INDICATE THAT THE LOW-LEVEL CENTER OF HILARY HAS BECOME DETACHED FROM THE HIGHER-LEVEL CIRCULATION. IN ACCORDANCE WITH A BLEND OF T- AND CI- NUMBERS FROM TAFB AND SAB AND THE LATEST UW-CIMSS ADT VALUES...THE INITIAL INTENSITY IS REDUCED TO 50 KT. THE RATE OF DECAY IS LIKELY TO ACCELERATE FURTHER NOW THAT A DECOUPLING OF THE CIRCULATION HAS OCCURRED...NOT TO MENTION THE EVEN HIGHER SHEAR FORECAST AND COLDER WATERS ALONG THE TRACK. THE CIRCULATION IS EXPECTED TO QUICKLY SPIN DOWN...AND REMNANT LOW STATUS IS LIKELY IN ABOUT 24 HOURS. THE NEW OFFICIAL FORECAST IS NEARLY IDENTICAL TO THE PREVIOUS ONE AND IN LINE WITH THE STATISTICAL/ DYNAMICAL GUIDANCE. THE CENTER OF HILARY IS NEARLY IMPOSSIBLE TO LOCATE USING GEOSTATIONARY SATELLITE IMAGERY. LUCKILY...A COUPLE OF EARLIER MICROWAVE OVERPASSES SUGGESTED THAT THE TROPICAL CYCLONE IS MAINTAINING A NORTHWESTWARD HEADING...325 DEGREES...AT 6 KNOTS. SO LONG AS THE CIRCULATION OF HILARY MAINTAINS SOME VERTICAL INTEGRITY...THE TRACK SHOULD DUMBBELL CYCLONICALLY AROUND A MID- TO UPPER-LEVEL LOW APPROACHING THE STORM FROM THE WEST. AFTER THE DECOUPLING OF THE CIRCULATION IS COMPLETE...THE SHALLOW CIRCULATION AND ULTIMATELY ITS REMNANT SHOULD TURN WESTWARD AND THEN SOUTHWESTWARD IN THE LOW-LEVEL FLOW ASSOCIATED WITH THE EASTERN PACIFIC SUBTROPICAL HIGH. AS HAS BEEN THE CASE IN PREVIOUS FORECASTS...THE LATEST TRACK PREDICTION HAS BEEN SHIFTED A LITTLE TO THE LEFT FOLLOWING THE MULTI-MODEL CONSENSUS...BUT IS NOT MATERIALLY DIFFERENT FROM THE PREVIOUS ONE. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 20.0N 119.9W 50 KT 60 MPH 12H 29/1800Z 20.8N 120.4W 40 KT 45 MPH 24H 30/0600Z 22.0N 121.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 30/1800Z 23.0N 121.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 01/0600Z 23.5N 122.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 02/0600Z 23.5N 124.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 03/0600Z 22.5N 125.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 04/0600Z...DISSIPATED $$ FORECASTER KIMBERLAIN NNNN
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