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#442613 (Received by flhurricane at: 4:58 PM 18.Jul.2011) TCDAT2 TROPICAL STORM BRET DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022011 500 PM EDT MON JUL 18 2011 VISIBLE SATELLITE IMAGERY THIS AFTERNOON SHOWED A RAGGED EYE-LIKE FEATURE...SUGGESTING THAT SOME INTENSIFICATION HAD TAKEN PLACE. THIS WAS CONFIRMED BY OBSERVATIONS FROM THE AIR FORCE HURRICANE HUNTER AIRCRAFT. USING A BLEND OF PEAK FLIGHT-LEVEL...SFMR...AND DROPSONDE WIND SPEED MEASUREMENTS THE CURRENT INTENSITY IS SET AT 55 KT. THE SHIPS MODEL OUTPUT SHOWS A SUBSTANTIAL INCREASE IN VERTICAL SHEAR WITHIN 12 TO 24 HOURS...SO BRET HAS A NARROW WINDOW OF OPPORTUNITY TO STRENGTHEN SOME MORE BEFORE REACHING A LESS CONDUCIVE ENVIRONMENT...AND IT COULD BE NEAR HURRICANE STRENGTH BY EARLY TOMORROW OR SOONER. THE OFFICIAL FORECAST FOLLOWS THE INTENSITY MODEL CONSENSUS...IVCN. AIRCRAFT AND SATELLITE FIXES GIVE A MOTION ESTIMATE OF AROUND 030/6. THE TRACK FORECAST PHILOSOPHY HAS NOT CHANGED MUCH. BRET SHOULD BE STEERED NORTH-NORTHEASTWARD TO NORTHEASTWARD AROUND THE NORTHWESTERN PERIPHERY OF A MID-LEVEL SUBTROPICAL HIGH OVER THE NEXT COUPLE OF DAYS. LATER IN THE FORECAST PERIOD...THE CYCLONE SHOULD ACCELERATE SOMEWHAT TOWARD THE EAST-NORTHEAST AS IT BECOMES MORE EMBEDDED WITHIN HIGHER-LATITUDE WESTERLY FLOW. THE NHC FORECAST FOR THIS ADVISORY IS SOMEWHAT FASTER THAN...AND SLIGHTLY TO THE LEFT OF...THE PREVIOUS ONE. THIS IS RATHER CLOSE TO THE LATEST ECMWF TRACK. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 28.3N 77.0W 55 KT 65 MPH 12H 19/0600Z 29.2N 76.5W 60 KT 70 MPH 24H 19/1800Z 30.4N 75.6W 60 KT 70 MPH 36H 20/0600Z 31.5N 74.4W 55 KT 65 MPH 48H 20/1800Z 33.0N 72.5W 50 KT 60 MPH 72H 21/1800Z 35.5N 67.5W 40 KT 45 MPH 96H 22/1800Z 39.0N 60.0W 35 KT 40 MPH 120H 23/1800Z 43.0N 52.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ FORECASTER PASCH |