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| #542372 (Received by flhurricane at: 4:35 PM 12.Sep.2012) TCDAT4 TROPICAL STORM NADINE DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD 500 PM AST WED SEP 12 2012 THE SYSTEM HAS BECOME A LITTLE MORE ASYMMETRIC...WITH A COMMA-TYPE CLOUD APPEARANCE ON SATELLITE IMAGERY. DRY AIR ROTATING AROUND THE NORTHERN SIDE OF THE CYCLONE COULD BE ERODING CONVECTION OVER THE WESTERN SEMICIRCLE. HOWEVER...THE CENTRAL DENSE OVERCAST HAS INCREASED SOMEWHAT IN SIZE AND DVORAK INTENSITY ESTIMATES ARE 55 KT FROM BOTH AGENCIES. ON THIS BASIS...THE ADVISORY INTENSITY HAS BEEN INCREASED TO 55 KT. CIRRUS CLOUD MOTIONS CONTINUE TO INDICATE A WELL-DEFINED UPPER-TROPOSPHERIC OUTFLOW PATTERN...AND DYNAMICAL GUIDANCE INDICATES THE VERTICAL WIND SHEAR SHOULD REMAIN MODERATE FOR THE NEXT 36-48 HOURS. LATER IN THE FORECAST PERIOD AS NADINE MOVES NORTH OF 30N LATITUDE...THE GLOBAL MODELS SHOW A SIGNIFICANT INCREASE IN THE UPPER-LEVEL WESTERLY FLOW NEAR AND OVER NADINE. THEREFORE...STRENGTHENING SHOULD BE LIMITED TO THE EARLY PART OF THE FORECAST PERIOD AND A WEAKENING TREND SHOULD COMMENCE WITHIN A COUPLE OF DAYS. IT SHOULD BE NOTED THAT THE LGEM GUIDANCE SHOWS MORE WEAKENING THAN THE OFFICIAL FORECAST DURING THE LATTER HALF OF THE PERIOD. WHILE THE 1200 UTC ECMWF SOLUTION SHOWS THE POSSIBILITY OF EXTRATROPICAL TRANSITION AT THE END OF THE PERIOD...THE MAJORITY OF THE 1200 UTC GLOBAL GUIDANCE DOES NOT. UNTIL THERE IS GREATER AGREEMENT AMONGST THE GLOBAL GUIDANCE...THIS TRANSITION WILL NOT BE INDICATED IN THE OFFICIAL FORECAST. THE HEADING OF THE STORM HAS SHIFTED SLIGHTLY TO THE RIGHT AND THE MOTION IS NOW ABOUT 310/14. THERE HAS BEEN LITTLE CHANGE TO THE TRACK FORECAST PHILOSOPHY. NADINE IS EXPECTED TO ROUND THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE OVER THE EAST-CENTRAL ATLANTIC WITHIN THE NEXT COUPLE DAYS. THE CYCLONE SHOULD THEN TURN EAST-NORTHEASTWARD TO EASTWARD AFTER MOVING NORTH OF THE RIDGE AXIS. THE GLOBAL MODEL TRACK GUIDANCE...IN PARTICULAR THE ECMWF.. HAS SHIFTED SOUTHWARD IN THE LATTER PART OF THE FORECAST PERIOD. THE 4- AND 5-DAY NHC TRACK HAS BEEN ADJUSTED SOUTH OF THE PREVIOUS ONE...AND IS CLOSEST TO THE FLORIDA STATE UNIVERSITY SUPERENSEMBLE. THIS GUIDANCE HAS BEEN A STRONG PERFORMER FOR TRACK PREDICTION THIS YEAR. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 20.0N 48.9W 55 KT 65 MPH 12H 13/0600Z 21.3N 50.4W 65 KT 75 MPH 24H 13/1800Z 23.3N 52.3W 70 KT 80 MPH 36H 14/0600Z 25.5N 53.8W 75 KT 85 MPH 48H 14/1800Z 28.0N 54.0W 75 KT 85 MPH 72H 15/1800Z 31.0N 51.0W 70 KT 80 MPH 96H 16/1800Z 32.5N 46.0W 70 KT 80 MPH 120H 17/1800Z 33.0N 40.0W 65 KT 75 MPH $$ FORECASTER ROTH/PASCH |
