000 WTNT44 KNHC 182051 TCDAT4 TROPICAL STORM NADINE DISCUSSION NUMBER 30 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 500 PM AST TUE SEP 18 2012 NADINE CONTINUES TO MAINTAIN SOME DEEP CONVECTION NEAR THE CENTER AND OVER THE NORTHERN SEMICIRCLE. ALTHOUGH DVORAK DATA T-NUMBERS HAVE DECREASED SOMEWHAT...AN EARLIER ASCAT PASS OVER THE SYSTEM SUPPORTED AN INTENSITY OF 50 KT. SINCE THE CONVECTION HAS NOT CHANGED MUCH SINCE THAT OVERPASS...THE ADVISORY INTENSITY WILL REMAIN AT 50 KT. BASED ON THE FORECAST TRACK...NADINE SHOULD NOT MOVE OVER MUCH COOLER WATERS...AND THESE HIGHER-LATITUDE CYCLONES TEND TO BE MORE RESILIENT TO VERTICAL SHEAR. THE OFFICIAL INTENSITY FORECAST IS THE SAME AS THE PREVIOUS ONE AND IS VERY SIMILAR TO THE STATISTICAL-DYNAMICAL LGEM GUIDANCE. THE SYSTEM COULD BECOME POST-TROPICAL IF IT LOSES MOST OF ITS DEEP CONVECTION DURING THE FORECAST PERIOD...AND THE OFFICIAL FORECAST SHOWS THIS TRANSITION OCCURRING BY DAY 4. HOWEVER THERE IS GREAT UNCERTAINTY AS TO THE SPECIFIC TIMING OF THIS EVENT AND NADINE COULD LOSE TROPICAL CHARACTERISTICS MUCH SOONER...OR MUCH LATER. THE STORM APPEARS TO HAVE TURNED TOWARD THE NORTH-NORTHEAST AND THE MOTION IS NEAR 030/7. FORECASTING THE TRACK OF THIS CYCLONE CONTINUES TO BE A GREAT CHALLENGE. A HIGHLY ANOMALOUS BLOCKING PATTERN IS PREDICTED BY THE GLOBAL MODELS TO DEVELOP AROUND NADINE IN THE LATTER PART OF THE FORECAST PERIOD...LEADING TO A STRONG MID-LEVEL ANTICYCLONE OVER THE NORTH-CENTRAL ATLANTIC AND AN INTENSE TROUGH/CYCLONE TO THE EAST OF THIS HIGH. THE TRACK GUIDANCE MODELS HAVE BEEN FLIP-FLOPPING ON WHETHER NADINE...OR ITS POST-TROPICAL COUNTERPART...WILL BE STEERED AROUND THE SOUTHEASTERN PERIPHERY OF THE HIGH OR BE DRAWN EASTWARD BY THE TROUGH IN 3-5 DAYS. THE LATEST MODEL RUNS ARE FAVORING THE LATTER SCENARIO...ALTHOUGH THE NEW ECMWF FORECAST SHOWS THE INTENSE TROUGH/CYCLONE ABSORBING NADINE WITHIN 3-4 DAYS. THE OFFICIAL TRACK FORECAST HAS BEEN SHIFTED TO THE EAST OF THE PREVIOUS ONE BUT...IN AN ATTEMPT TO MAINTAIN CONTINUITY...IS NOT NEARLY AS FAR EAST AS THE NEW MODEL CONSENSUS. THE TROPICAL STORM FORCE WIND RADII WERE ADJUSTED OUTWARD BASED ON THE AFOREMENTIONED ASCAT PASS. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 35.2N 32.6W 50 KT 60 MPH 12H 19/0600Z 36.2N 32.3W 50 KT 60 MPH 24H 19/1800Z 36.9N 32.1W 50 KT 60 MPH 36H 20/0600Z 36.8N 31.2W 50 KT 60 MPH 48H 20/1800Z 36.1N 30.0W 50 KT 60 MPH 72H 21/1800Z 34.8N 28.0W 50 KT 60 MPH 96H 22/1800Z 34.0N 27.0W 50 KT 60 MPH...POST-TROPICAL 120H 23/1800Z 33.5N 25.5W 45 KT 50 MPH...POST-TROPICAL $$ FORECASTER PASCH