[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 182056
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


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