ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM BRET DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022011 500 AM EDT TUE JUL 19 2011 DEEP CONVECTION HAS ALL BUT DISAPPEARED NEAR THE CENTER OF BRET IN THE PAST FEW HOURS...LIKELY DUE TO THE ENTRAINMENT OF DRY AIR INTO THE CYCLONE CORE AS SEEN IN SATELLITE IMAGERY AND DEWPOINT DATA FROM THE AIR FORCE RESERVE UNIT HURRICANE HUNTER AIRCRAFT. THE INITIAL INTENSITY IS LOWERED TO 45 KT BASED ON A 850-MB FLIGHT- LEVEL WIND MAXIMUM OF 55 KT AND A PEAK SFMR WIND OF 43 KT. THE DRIER ENVIRONMENT AND A FORECAST OF INCREASING VERTICAL WIND SHEAR ARE NOT FAVORABLE FOR RESTRENGTHENING...AND THE INTENSITY GUIDANCE SHOWS BRET SLOWLY WEAKENING FROM THIS POINT FORWARD. THE NEW NHC FORECAST FOLLOWS THIS REASONING AND SHOWS LITTLE CHANGE THROUGH 12 HOURS FOLLOWED BY GRADUAL WEAKENING UNTIL DISSIPATION IN ABOUT 96 HOURS...IN BEST AGREEMENT WITH THE LGEM. HOWEVER...IF DEEP CONVECTION DOES NOT RETURN...BRET COULD WEAKEN AND DISSIPATE MORE QUICKLY THAN INDICATED HERE. AIRCRAFT FIXES SUGGEST THAT THE LONG-TERM INITIAL MOTION IS TOWARD THE NORTH-NORTHEAST OR 025 DEGREES AT AROUND 6 KT...A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST TRACK. OVERALL...THE TRACK FORECAST REASONING REMAINS UNCHANGED AS BRET WILL GRADUALLY ACCELERATE TOWARD THE NORTHEAST OVER THE NEXT COUPLE OF DAYS AS A MID-LEVEL RIDGE BUILDS TO THE SOUTHEAST OF THE CYCLONE. THROUGH 48 HOURS...THE GUIDANCE IS TIGHTLY CLUSTERED AND THE NEW OFFICIAL FORECAST HAS BEEN ADJUSTED A LITTLE TO THE LEFT OF THE PREVIOUS ONE TO ACCOUNT FOR THE INITIAL POSITION AND MOTION. AT 72 HOURS A MORE SUBSTANTIAL ADJUSTMENT WAS MADE...TO THE LEFT OF AND SLOWER THAN THE PREVIOUS NHC FORECAST...TRENDING TOWARD THE NEW MULTI-MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 29.3N 76.4W 45 KT 50 MPH 12H 19/1800Z 30.0N 75.8W 45 KT 50 MPH 24H 20/0600Z 30.9N 74.8W 40 KT 45 MPH 36H 20/1800Z 32.1N 73.4W 35 KT 40 MPH 48H 21/0600Z 33.6N 71.9W 35 KT 40 MPH 72H 22/0600Z 36.5N 68.0W 30 KT 35 MPH 96H 23/0600Z...DISSIPATED $$ FORECASTER BRENNAN NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:43:43 UTC