000 WTNT44 KNHC 202042 TCDAT4 TROPICAL STORM NADINE DISCUSSION NUMBER 38 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 500 PM AST THU SEP 20 2012 THERE HAS BEEN LITTLE CHANGE TO THE STRUCTURE OF NADINE OVER THE PAST FEW HOURS. AFTER INCREASING A LITTLE EARLIER...CONVECTIVE TOPS NEAR THE CENTER HAVE WARMED AND DIMINISHED OVER THE PAST COUPLE OF HOURS. THE INITIAL INTENSITY IS 45 KT...IN AGREEMENT WITH THE LATEST DVORAK ESTIMATE FROM TAFB. LITTLE CHANGE IN INTENSITY IS EXPECTED DURING THE FORECAST PERIOD...AS NADINE WILL BE IN A MARGINAL THERMODYNAMIC ENVIRONMENT FOR INTENSIFICATION VIA LATENT HEAT RELEASE WHILE LACKING ANY SIGNIFICANT SOURCE OF BAROCLINIC INTENSIFICATION. ADDITIONALLY...NADINE COULD BECOME POST-TROPICAL AT JUST ABOUT ANYTIME DURING THE FORECAST PERIOD IF THE DEEP CONVECTION DISSIPATES. THE NEW NHC INTENSITY FORECAST IS THE SAME AS THE PREVIOUS ADVISORY. NADINE HAS JOGGED EASTWARD THIS AFTERNOON...AND THE LONG TERM INITIAL MOTION ESTIMATE IS 110/09. OTHER THAN AN EASTWARD ADJUSTMENT DUE TO THE INITIAL POSITION AND MOTION...THE TRACK FORECAST THROUGH 48 HOURS REMAINS LARGELY UNCHANGED. DURING THIS TIME NADINE SHOULD BE STEERED SOUTHEASTWARD AHEAD OF A MID/ UPPER-LEVEL TROUGH OVER THE NORTHEASTERN ATLANTIC. BEYOND THAT TIME...THERE CONTINUES TO BE LARGE SPREAD IN THE TRACK GUIDANCE AT DAYS 3 THROUGH 5. THE LATEST GFS NOW SHOWS A QUICKER EASTWARD MOTION...AS NADINE ACCELERATES AHEAD OF ANOTHER DIGGING MID- TO UPPER-LEVEL TROUGH. WHILE THE ECMWF ALSO SHOWS AN EASTWARD MOTION BY DAY 5...THIS MODEL HAS TRENDED ABOUT 500 MILES WESTWARD COMPARED TO ITS PREVIOUS RUN. ON THE OTHER SIDE OF THE GUIDANCE ENVELOPE...THE HWRF SHOWS A SOUTHWESTWARD MOTION LATE IN THE PERIOD WHILE THE UKMET SHOWS A SLOW WESTWARD DRIFT. THE LATEST ECMWF AND GFS ENSEMBLE MEMBERS REMAIN ALMOST EVENLY SPLIT BETWEEN AN EASTWARD AND WESTWARD COMPONENT OF MOTION BY DAY 5. GIVEN THE PERSISTENT UNCERTAINTY...THE NHC FORECAST CONTINUES TO SHOW NO MOTION BEYOND 72 HOURS. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 36.1N 28.2W 45 KT 50 MPH 12H 21/0600Z 35.3N 27.2W 45 KT 50 MPH 24H 21/1800Z 34.0N 26.3W 45 KT 50 MPH 36H 22/0600Z 32.9N 25.3W 45 KT 50 MPH...POST-TROPICAL 48H 22/1800Z 32.5N 24.7W 45 KT 50 MPH...POST-TROPICAL 72H 23/1800Z 32.5N 24.5W 45 KT 50 MPH...POST-TROPICAL 96H 24/1800Z 32.5N 24.5W 45 KT 50 MPH...POST-TROPICAL 120H 25/1800Z 32.5N 24.5W 45 KT 50 MPH...POST-TROPICAL $$ FORECASTER BRENNAN