ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NADINE DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012 1100 PM AST TUE SEP 11 2012 SINCE THE PREVIOUS ADVISORY...DEEP CONVECTION HAS INCREASED OVER THE CENTER OF THE CYCLONE AND A CURVED BAND OF CONVECTION HAS DEVELOPED IN THE NORTHWEST QUADRANT. SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS T2.5/35 KT FROM TAFB...SAB...AND UW-CIMSS ADT. THEREFORE...THE DEPRESSION HAS BEEN UPGRADED TO TROPICAL STORM NADINE...THE FOURTEENTH NAMED STORM OF THE 2012 ATLANTIC SEASON. THE INITIAL MOTION ESTIMATE IS 300/13 KT. NADINE MADE A SLIGHT JOG TO THE WEST DURING THE PAST 6 HOURS...BUT THIS IS EXPECTED TO BE A TRANSIENT MOTION DUE TO REFORMATION OF THE CENTER WITHIN THE LARGER CYCLONIC ENVELOPE. NOW THAT CONVECTION HAS FORMED OVER THE CENTER...THE VORTEX COLUMN SHOULD BECOME VERTICALLY DEEPER AND MORE STABLE...RESULTING IN LESS WOBBLE IN THE TRACK MOTION. OTHERWISE... THERE IS NO CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. THE NHC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH 72 HOURS ON NADINE MOVING NORTHWESTWARD TOWARD A BREAK IN THE SUBTROPICAL RIDGE ALONG ROUGHLY 55W LONGITUDE. AFTER THAT...THE MODELS DIVERGE SIGNIFICANTLY ON HOW SOON AND HOW MUCH NADINE WILL INTERACT WITH AN UPPER-LEVEL TROUGH/LOW FORECAST TO DEVELOP TO THE WEST OF THE CYCLONE ON DAYS 3-5. GIVEN THE UNCERTAINTY IN THE EXACT LOCATION AND STRENGTH OF DEVELOPMENT OF THE AFOREMENTIONED LOW...THE OFFICIAL FORECAST TRACK INDICATES ONLY A DECREASE IN FORWARD SPEED AND A GRADUAL TURN TOWARD THE EAST-NORTHEAST ON DAY 4...AND TOWARD THE EAST ON DAY 5. THE OFFICIAL ADVISORY TRACK IS CLOSE TO THE PREVIOUS TRACK AFTER 24 HOURS...AND IS SLIGHTLY TO THE RIGHT OF AND SLOWER THAN THE CONSENSUS MODELS TVCN AND TV15. THE LAST FEW VISIBLE IMAGES INDICATED NADINE HAD DEVELOPED A TIGHT INNER-CORE CIRCULATION. NOW THAT DEEP CONVECTION AND A POSSIBLE CDO FEATURE HAVE FORMED OVER THE WELL-DEFINED LOW-LEVEL CENTER...THE POSSIBILITY OF RAPID INTENSIFICATION SOMETIME DURING THE NEXT 24-36 HOURS EXISTS OWING TO THE LOW VERTICAL SHEAR AND OTHER FAVORABLE ENVIRONMENTAL CONDITIONS THAT ARE EXPECTED. LATE IN THE FORECAST PERIOD...WESTERLY SHEAR AHEAD OF AN APPROACHING MID-LATITUDE TROUGH IS EXPECTED TO INCREASE TO 20-25 KT...WHICH SHOULD BEGIN TO INDUCE A SLOW WEAKENING TREND. THE OFFICIAL INTENSITY FORECAST IS SLIGHTLY HIGHER THAN THE PREVIOUS ADVISORY...BUT IS NOT AS ROBUST AS THE HWRF MODEL...WHICH MAKES NADINE A MAJOR HURRICANE BY 96 HOURS. FORECAST POSITIONS AND MAX WINDS INIT 12/0300Z 17.8N 45.2W 35 KT 40 MPH 12H 12/1200Z 18.9N 46.9W 40 KT 45 MPH 24H 13/0000Z 20.5N 49.2W 50 KT 60 MPH 36H 13/1200Z 22.2N 51.2W 60 KT 70 MPH 48H 14/0000Z 24.4N 53.0W 70 KT 80 MPH 72H 15/0000Z 28.0N 53.8W 75 KT 85 MPH 96H 16/0000Z 30.0N 51.9W 70 KT 80 MPH 120H 17/0000Z 31.5N 48.0W 65 KT 75 MPH $$ FORECASTER STEWART NNNN
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