000 WTNT44 KNHC 161443 TCDAT4 HURRICANE NADINE DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 1100 AM AST SUN SEP 16 2012 FIRST FEW VISIBLE SATELLITE IMAGES INDICATE THE INNER-CORE BANDING FEATURES OF NADINE HAVE IMPROVED...AND RECENT MICROWAVE IMAGERY ALSO SUGGESTS THAT THE EASTWARD TILT TO THE EYE HAS DECREASED. SINCE A BANDING EYE HAS BEEN TRYING TO DEVELOP OVER THE PAST FEW HOURS...THE INITIAL INTENSITY WILL REMAIN AT 70 KT. CONVENTIONAL AND MICROWAVE SATELLITE FIXES INDICATE NADINE HAS ACCELERATED EASTWARD SINCE THE PREVIOUS ADVISORY...AND THE INITIAL MOTION ESTIMATE IS NOW 090/20 KT. NADINE IS EXPECTED TO REMAIN NORTH OF A DEEP-LAYER SUBTROPICAL RIDGE AND BE STEERED QUICKLY EASTWARD WITHIN MID- TO UPPER-LEVEL WESTERLY FLOW FOR NEXT 24 HOURS OR SO. AFTER THAT TIME...THE GLOBAL AND REGIONAL MODELS REMAIN IN GOOD AGREEMENT ON THE DEVELOPMENT OF A DEEP-LAYER LOW TO THE WEST OF NADINE...WHICH IS EXPECTED TO LIFT THE CYCLONE OUT TO THE NORTHEAST AT A SLOWER FORWARD SPEED. BY DAYS 4 AND 5...NADINE IS FORECAST TO BEGIN TO INTERACT WITH A SEPARATE MID- TO UPPER-LEVEL LOW OVER THE NORTHEASTERN ATLANTIC...WHICH COULD RESULT IN ERRATIC MOTION OCCURRING WHEN THE CYCLONE IS LOCATED JUST SOUTHWEST OF THE AZORES. ALTHOUGH SOME OF THE MODELS INDICATE THAT MERGING COULD OCCUR WITH THE AFOREMENTIONED NON-TROPICAL LOW...THE CURRENT FORECAST IS DISCOUNTING THAT SCENARIO AT THIS TIME...AND ONLY BINARY INTERACTION BETWEEN THE TWO LOWS IS EXPECTED. THE OFFICIAL FORECAST TRACK HAS BEEN SHIFTED SLIGHTLY TO THE EAST OF THE PREVIOUS TRACK...WHICH IS PRIMARILY DUE TO THE MORE EASTWARD INITIAL POSITION...AND LIES BETWEEN THE CONSENSUS MODELS TV15 AND TVCA...AND THE FLORIDA STATE SUPERENSEMBLE MODEL. LITTLE CHANGE IN VERTICAL SHEAR IS EXPECTED FOR THE NEXT 72 HOURS... SO THE MAIN WEAKENING FACTOR WILL BE COOLER OCEAN TEMPERATURES AHEAD OF THE CYCLONE. AFTERWARDS...HOWEVER...THE SHEAR IS FORECAST TO INCREASE TO NEAR 30 KT FROM THE SOUTHWEST AS A STRONG NORTHEAST ATLANTIC LOW DROPS SOUTHWARD AND IMPINGES ON THE CYCLONE...AND MORE SIGNIFICANT WEAKENING IS EXPECTED. THE NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS FORECAST...AND FOLLOWS THE TREND SHIPS...LGEM...AND FSSE INTENSITY CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 30.5N 41.7W 70 KT 80 MPH 12H 17/0000Z 30.9N 39.3W 70 KT 80 MPH 24H 17/1200Z 31.7N 36.4W 65 KT 75 MPH 36H 18/0000Z 32.8N 34.2W 65 KT 75 MPH 48H 18/1200Z 34.0N 32.9W 60 KT 70 MPH 72H 19/1200Z 36.3N 31.6W 55 KT 65 MPH 96H 20/1200Z 37.0N 30.5W 50 KT 60 MPH 120H 21/1200Z 37.0N 29.0W 45 KT 50 MPH $$ FORECASTER STEWART