ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM MIRIAM DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012 800 AM PDT WED SEP 26 2012 THE CLOUD PATTERN OF MIRIAM HAS BECOME POORLY ORGANIZED. THE CENTRAL DENSE OVERCAST HAS DEGENERATED INTO A LONG BAND WRAPPING AROUND THE WESTERN SIDE OF THE CIRCULATION. SATELLITE DATA ALSO INDICATE AN INCREASING SEPARATION BETWEEN THE LOW- TO MID-LEVEL CENTERS DUE TO 20-25 KT OF SOUTHWESTERLY SHEAR ASSOCIATED WITH A SHORTWAVE TROUGH ROTATING AROUND THE NORTHWESTERN SIDE OF THE STORM. SATELLITE INTENSITY ESTIMATES RANGE FROM 55-65 KT...AND GIVEN THE DETERIORATING SATELLITE APPEARANCE...THE INITIAL INTENSITY IS LOWERED TO 55 KT. FURTHER GRADUAL WEAKENING IS LIKELY AS MIRIAM ENCOUNTERS CONTINUED MODERATE OR STRONG SOUTHWESTERLY SHEAR... GRADUALLY DECREASING SSTS...AND A DRIER AND MORE STABLE AIR MASS. THE NHC INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS ONE AND IS CLOSE TO THE SHIPS AND LGEM OUTPUT. THE LONG-TERM INITIAL MOTION ESTIMATE IS 330/05...BUT RECENT MICROWAVE DATA SUGGEST THAT THE SHORT-TERM MOTION COULD BE FARTHER TO THE RIGHT. AS THE PREVIOUSLY MENTIONED SHORTWAVE TROUGH DIGS TO THE WEST OF MIRIAM DURING THE NEXT DAY OR SO...THE CYCLONE SHOULD MAINTAIN A SLOW NORTH-NORTHWESTWARD MOTION. A BEND OF THE TRACK TOWARD THE NORTHWEST IS FORECAST WHEN THE SHORTWAVE REACHES A POSITION TO THE SOUTH OF STORM IN 24-36 HOURS. IF MIRIAM DECOUPLES SOONER THAN EXPECTED...THE LOW-LEVEL CENTER COULD MOVE MORE TO THE LEFT THAN FORECAST. THE NHC TRACK FORECAST IS NEAR OR SLIGHTLY TO THE LEFT OF THE PREVIOUS ONE AND IS CLOSE TO THE FSU SUPERENSENSEMBLE AND THE MULTI-MODEL CONSENSUS THROUGH 24 HOURS AND THEN CLOSE TO THE GFS AFTER THAT. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 20.0N 115.7W 55 KT 65 MPH 12H 27/0000Z 20.9N 115.9W 45 KT 50 MPH 24H 27/1200Z 22.0N 116.3W 40 KT 45 MPH 36H 28/0000Z 22.6N 116.7W 35 KT 40 MPH 48H 28/1200Z 23.0N 117.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 29/1200Z 23.2N 117.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 30/1200Z 23.4N 117.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 01/1200Z...DISSIPATED $$ FORECASTER KIMBERLAIN NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:38 UTC