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| #461582 (Received by flhurricane at: 10:59 AM 24.Sep.2011) TCDAT1 TROPICAL STORM OPHELIA DISCUSSION NUMBER 15 NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011 1100 AM AST SAT SEP 24 2011 DURING THE PAST 6 HOURS...DEEP CONVECTION HAS REDEVELOPED OVER AND TO THE NORTHEAST OF THE PREVIOUSLY EXPOSED LOW-LEVEL CIRCULATION CENTER. SATELLITE CURRENT INTENSITY ESTIMATES ARE T3.0/45 KT FROM TAFB AND T3.1/47 KT FROM UW-CIMSS ADT. THEREFORE...THE INITIAL INTENSITY WILL REMAIN AT 45 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 310/11 KT. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK REASONING. A FAIRLY LARGE SPREAD REMAINS IN THE MODEL GUIDANCE WITH THE GFS AND GFS ENSEMBLE MODELS SHOWING A MORE WESTWARD MOTION DUE TO A WEAKER CYCLONE EXPECTED...WHEREAS THE GFDL AND HWRF MODELS SHOW A MORE NORTHERLY TRACK DUE TO A MORE ROBUST AND STRONGER SYSTEM. THE ECMWF... UKMET...AND NOGAPS MODELS ARE IN BETWEEN THESE TWO EXTREMES AND ARE FAIRLY SIMILAR TO EACH OTHER IN BOTH TRACK AND INTENSITY. AS A RESULT...THE OFFICIAL FORECAST TRACK IS VERY NEAR THE PREVIOUS ADVISORY TRACK...AND LIES DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE AND TO THE LEFT OF THE CONSENSUS MODEL..TVCN...AFTER 72 HOURS. SIMILAR TO THIS TIME YESTERDAY...VERY COLD-TOPPED CONVECTION HAS REDEVELOPED IN THE FORM OF A CURVED BAND IN THE NORTHEAST QUADRANT. GIVEN THAT OPHELIA IS EXPECTED TO REMAIN A LARGER THAN AVERAGE TROPICAL CYCLONE...AND THE FACT THAT IT HAS ALREADY SURVIVED SOUTHWESTERLY VERTICAL SHEAR OF NEAR 30 KT...I SEE NO REASON WHY THIS CYCLONE SHOULD DISSIPATE DURING THE FORECAST PERIOD LIKE SOME OF THE GUIDANCE IS INDICATING. THE CURRENT SHEAR OF 25 KT IS EXPECTED TO CONTINUE FOR THE NEXT 48 HOURS OR SO...WITH A GRADUAL INCREASE TO 30 KT AFTER THAT. HOWEVER...AS THE PREVIOUS DISCUSSION ALLUDED TO...THE GLOBAL MODELS ARE STILL SUGGESTING THAT AN UPPER-LEVEL TROUGH NORTH OF THE LESSER ANTILLES COULD FRACTURE AND ALLOW RESTRENGTHENING OF THE TROPICAL CYCLONE AFTER 72 HOURS AS THE OPHELIA MOVES INTO THIS REGION OF UPPER-LEVEL DIVERGENCE. THIS SCENARIO IS MAINTAINED IN THE OFFICIAL INTENSITY FORECAST...WHICH SHOWS MODEST STRENGTHENING AT DAYS 4 AND 5 WHILE THE CYCLONE IS STILL OVER SSTS OF NEAR 28C. THE INTENSITY FORECAST LEANS TOWARD THE INTENSITY CONSENSUS MODEL...ICON...THROUGH 72 HOURS...AND IS A LITTLE LOWER THAN THE CONSENSUS AFTER THAT. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 17.8N 56.0W 45 KT 50 MPH 12H 25/0000Z 18.8N 57.4W 40 KT 45 MPH 24H 25/1200Z 19.9N 59.1W 40 KT 45 MPH 36H 26/0000Z 20.9N 60.7W 35 KT 40 MPH 48H 26/1200Z 21.6N 61.8W 35 KT 40 MPH 72H 27/1200Z 23.3N 63.1W 35 KT 40 MPH 96H 28/1200Z 25.3N 63.4W 40 KT 45 MPH 120H 29/1200Z 27.3N 63.4W 50 KT 60 MPH $$ FORECASTER STEWART |
