ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM HURRICANE MIRIAM DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012 800 PM PDT SUN SEP 23 2012 MIRIAM HAS STRENGTHENED RAPIDLY DURING THE LAST 6 HOURS OR SO. AN EYE...WHICH HAD BEEN EVIDENT IN MICROWAVE DATA EARLIER TODAY... BECAME APPARENT IN GEOSTATIONARY SATELLITE IMAGES A FEW HOURS AGO. THE OVERALL CLOUD PATTERN IS WELL ORGANIZED WITH COLD CLOUD TOPS SURROUNDING THE RAGGED EYE AND BANDING FEATURES LOCATED IN ALL QUADRANTS. SATELLITE INTENSITY ESTIMATES HAVE INCREASED TO 4.0/65 KT FROM TAFB...4.5/77 KT FROM SAB...AND 4.7/82 KT FROM UW-CIMSS. THE INITIAL WIND SPEED IS SET AT 80 KT...NEAR THE HIGH END OF THE ESTIMATES GIVEN THE IMPROVED SATELLITE PRESENTATION SINCE THE TIME OF THE DVORAK CLASSIFICATIONS. ADDITIONAL STRENGTHENING SEEMS LIKELY DURING THE NEXT DAY OR SO AS MIRIAM IS EXPECTED TO REMAIN OVER SEA SURFACE TEMPERATURES OF 27-28C AND IN A FAVORABLE UPPER-LEVEL WIND PATTERN. IN 36 TO 48 HOURS...HOWEVER...MIRIAM IS FORECAST TO BE MOVING OVER COOL WATERS AND IN MODERATE SOUTHWESTERLY WIND SHEAR. THESE UNFAVORABLE CONDITIONS SHOULD END THE STRENGTHENING TREND...AND CAUSE THE CYCLONE TO WEAKEN. THE NHC INTENSITY FORECAST IS HIGHER THAN THE PREVIOUS ONE FOR THE FIRST 36 HOURS AND THEN FALLS IN LINE WITH THE OLD ONE AFTER THAT. MIRIAM IS MOVING NORTHWESTWARD AT ABOUT 10 KT. THIS GENERAL HEADING WITH A SLIGHT REDUCTION IN FORWARD SPEED IS EXPECTED OVER THE NEXT 24 TO 36 HOURS AS THE RIDGE TO THE NORTHEAST OF MIRIAM WEAKENS. AFTER THAT...A TURN TO THE NORTH AT AN EVEN SLOWER FORWARD SPEED IS FORECAST AS THE HURRICANE MOVES INTO A WEAKNESS CAUSED BY A TROUGH OVER THE WESTERN UNITED STATES. THE NHC TRACK FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS ONE...AND REMAINS NEAR THE RIGHT SIDE OF THE GUIDANCE ENVELOPE BETWEEN THE CONSENSUS AIDS TO THE WEST AND THE GFS AND ECMWF MODELS TO THE EAST. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 16.8N 111.3W 80 KT 90 MPH 12H 24/1200Z 17.6N 112.5W 95 KT 110 MPH 24H 25/0000Z 18.5N 113.9W 95 KT 110 MPH 36H 25/1200Z 19.2N 114.8W 90 KT 105 MPH 48H 26/0000Z 19.8N 115.2W 80 KT 90 MPH 72H 27/0000Z 21.2N 115.9W 60 KT 70 MPH 96H 28/0000Z 22.5N 116.0W 45 KT 50 MPH 120H 29/0000Z 24.0N 115.5W 30 KT 35 MPH $$ FORECASTER CANGIALOSI NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:38 UTC