000 WTNT44 KNHC 180837 TCDAT4 TROPICAL STORM NADINE DISCUSSION NUMBER 28 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 500 AM AST TUE SEP 18 2012 MOST OF THE DEEP CONVECTION NEAR THE CENTER OF NADINE HAS DIMINISHED...AND THE STRONGEST ACTIVITY IS LOCATED WITHIN A BAND TO THE WEST AND NORTHWEST OF THE CENTER. THIS COULD SUGGEST THAT NADINE IS BEGINNING TO LOSE SOME TROPICAL CHARACTERISTICS. THE INTENSITY REMAINS 50 KT BASED ON DVORAK ESTIMATES OF T3.0 FROM SAB AND T3.5 FROM TAFB. JUST ABOUT EVERY ASPECT OF THE FORECAST IS COMPLICATED. THERE IS RELATIVELY HIGH CONFIDENCE IN THE TRACK FORECAST FOR THE FIRST 2 DAYS...WITH ALL OF THE MODELS SHOWING A SLOW NORTHEASTWARD TO NORTHWARD MOTION AS NADINE MOVES ALONG THE WESTERN SIDE OF A MID-LEVEL ANTICYCLONE. THE DISAGREEMENT AMONG THE MODELS INCREASES SUBSTANTIALLY BEYOND 3 DAYS. THE MAJORITY OF THE GUIDANCE SHOWS NADINE INTERACTING WITH A DEVELOPING CUT-OFF LOW TO ITS NORTH AND EITHER MOVING EASTWARD AS ITS OWN ENTITY...OR IN THE CASE OF THE 00Z GFS...MOVING EASTWARD AND BECOMING ABSORBED BY THE CUT-OFF LOW. ON THE OTHER HAND...THE ECMWF SHOWS THE CUT-OFF LOW BYPASSING NADINE AND BEING REPLACED BY AN ANTICYCLONE...WHICH PUSHES NADINE BACK TO THE SOUTH AND WEST. DUE TO THE IMMENSE UNCERTAINTY...THE OFFICIAL FORECAST INDICATES VERY LITTLE MOTION AT THE END OF THE FORECAST PERIOD. AT THIS POINT...THE STEERING PATTERN IS TOO COMPLEX TO KNOW EXACTLY WHICH SCENARIO WILL VERIFY. ALTHOUGH NADINE WILL BE MOVING OVER PROGRESSIVELY COOLER SSTS DURING THE NEXT FEW DAYS...BAROCLINIC PROCESSES ARE LIKELY TO OFFSET ANY WEAKENING THAT THE COLDER WATERS WOULD INDUCE. THE GUIDANCE AS A WHOLE AGREES THAT NADINE SHOULD CHANGE VERY LITTLE IN INTENSITY DURING THE FORECAST PERIOD...WHICH IS REFLECTED IN THE OFFICIAL FORECAST. ONLY SOME OF THE GLOBAL MODELS HAVE NADINE BECOMING FULLY INVOLVED WITH A FRONT...MAKING IT EXTRATROPICAL IN 3 TO 4 DAYS. THE OTHER MODELS...INCLUDING THE ECMWF...SHOW NADINE STAYING AWAY FROM THE STRONGEST TEMPERATURE GRADIENT AND MOVING BACK TO THE SOUTH AS A NON-FRONTAL CYCLONE. EVEN IF THE ECMWF SOLUTION VERIFIES...NADINE IS STILL LIKELY TO BECOME POST-TROPICAL DUE TO A LACK OF DEEP CONVECTION OVER COLD WATERS. THE OFFICIAL FORECAST SHOWS NADINE BECOMING POST-TROPICAL IN 3 DAYS...WITHOUT SPECIFYING WHETHER OR NOT THE CYCLONE WILL BE FRONTAL. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 34.3N 33.6W 50 KT 60 MPH 12H 18/1800Z 35.1N 32.9W 50 KT 60 MPH 24H 19/0600Z 36.2N 32.7W 50 KT 60 MPH 36H 19/1800Z 36.9N 32.6W 50 KT 60 MPH 48H 20/0600Z 36.8N 31.9W 50 KT 60 MPH 72H 21/0600Z 35.5N 28.5W 50 KT 60 MPH...POST-TROPICAL 96H 22/0600Z 35.0N 26.0W 50 KT 60 MPH...POST-TROPICAL 120H 23/0600Z 35.0N 26.0W 50 KT 60 MPH...POST-TROPICAL $$ FORECASTER BERG