000 WTNT44 KNHC 181440 TCDAT4 TROPICAL STORM NADINE DISCUSSION NUMBER 29 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 1100 AM AST TUE SEP 18 2012 THE STORM HAS BEEN MAINTAINING SOME...NOT MUCH...DEEP CONVECTION NEAR AND JUST NORTH OF THE CENTER. THE CURRENT INTENSITY IS 50 KT BASED ON A DVORAK CLASSIFICATION FROM TAFB. ALTHOUGH THE DYNAMICAL GUIDANCE INDICATES QUITE A BIT OF SHEAR OVER NADINE DURING THE NEXT FEW DAYS...THESE HIGHER-LATITUDE SYSTEMS ARE KNOWN TO BE MORE RESILIENT TO SHEAR. THIS IS CONSISTENT WITH THE LATEST LGEM GUIDANCE WHICH MORE OR LESS MAINTAINS THE CURRENT INTENSITY FOR THE NEXT SEVERAL DAYS. AS INDICATED BELOW...NADINE IS NOT EXPECTED TO MOVE MUCH FARTHER NORTH OVER THE PERIOD. THEREFORE IT IS NOT LIKELY TO ENCOUNTER ENOUGH BAROCLINICITY TO UNDERGO AN EXTRATROPICAL TRANSFORMATION. HOWEVER...SINCE THE SYSTEM IS MOVING OVER MARGINALLY WARM WATERS IT COULD...AT SOME POINT...LOSE ENOUGH DEEP CONVECTION SO THAT IT NO LONGER WOULD QUALIFY AS A TROPICAL CYCLONE. THIS IS REFLECTED IN THE OFFICIAL FORECAST WHICH SHOWS POST-TROPICAL STATUS BY DAY 3. HOWEVER...IT SHOULD BE NOTED THAT THE SPECIFIC TIMING OF SUCH A TRANSITION IS HIGHLY UNCERTAIN. THE TRACK FORECAST REMAINS COMPLICATED AS A HIGHLY ANOMALOUS BLOCKING PATTERN IS FORECAST TO EVOLVE AT MID-TROPOSPHERIC LEVELS OVER THE NORTH ATLANTIC. THE GFS AND ECMWF MODELS...HOWEVER...HAVE COME INTO BETTER AGREEMENT IN THE LATTER PART OF THE FORECAST PERIOD. THE GFS 3-5 DAY PREDICTIONS NOW SHOW NADINE...OR ITS POST-TROPICAL COUNTERPART...BEING DRIVEN SOUTHWARD BY THE FLOW BETWEEN AN INTENSE 500 MB TROUGH TO THE WEST OF EUROPE AND A VERY STRONG ANTICYCLONE CENTERED NORTH OF 40N OVER THE CENTRAL ATLANTIC. BY THE END OF THE PERIOD...THE GFS SHOWS THE CYCLONE MOVING SOUTHWESTWARD ON THE SOUTHEASTERN PERIPHERY OF THE ANTICYCLONE. THE ECMWF SHOWS A SIMILAR BEHAVIOR...BUT TAKES THE SYSTEM FARTHER WEST AT DAYS 4 AND 5. THE OFFICIAL FORECAST SHIFTS THE SYSTEM SOUTHWARD AT DAYS 3-5 BUT DOES NOT YET COMMIT TO THE WESTWARD TURN. THIS IS A LITTLE SOUTH OF THE PREVIOUS FORECAST...BUT NOT AS FAR SOUTH AS THE LATEST MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 34.4N 32.9W 50 KT 60 MPH 12H 19/0000Z 35.4N 32.7W 50 KT 60 MPH 24H 19/1200Z 36.4N 32.5W 50 KT 60 MPH 36H 20/0000Z 36.7N 32.0W 50 KT 60 MPH 48H 20/1200Z 36.5N 31.0W 50 KT 60 MPH 72H 21/1200Z 35.5N 28.5W 50 KT 60 MPH...POST-TROPICAL 96H 22/1200Z 34.0N 28.0W 50 KT 60 MPH...POST-TROPICAL 120H 23/1200Z 33.0N 28.0W 45 KT 50 MPH...POST-TROPICAL $$ FORECASTER PASCH