Tropical Storm BRET

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TROPICAL STORM BRET DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL022011
1100 PM EDT SUN JUL 17 2011
 
THE AIR FORCE HURRICANE HUNTER AIRCRAFT MADE TWO ADDITIONAL PASSES
THROUGH THE CENTER OF THE TROPICAL CYCLONE AFTER THE RELEASE OF THE
2100 UTC NHC ADVISORY.  DURING THOSE PASSES...PEAK FLIGHT-LEVEL
WINDS OF 43-45 KT WERE RECORDED ALONG WITH A FEW BELIEVABLE SFMR
SURFACE WINDS JUST ABOVE TROPICAL STORM FORCE.  BASED ON THESE
OBSERVATIONS AND THE DEVELOPMENT OF NEW CONVECTION JUST NORTHEAST
OF THE CENTER AROUND 0000 UTC...THE DEPRESSION WAS UPGRADED TO A
TROPICAL STORM AT THAT TIME.  MICROWAVE AND SATELLITE IMAGERY SHOW
THAT MOST OF THE ASSOCIATED DEEP CONVECTION IS LOCATED OVER THE
EASTERN SEMICIRCLE OF THE CIRCULATION DUE TO MODERATE WESTERLY
SHEAR.  THE SHEAR IS FORECAST TO DECREASE SLIGHTLY DURING THE NEXT
12-24 HOURS...WHICH SHOULD ALLOW AN OPPORTUNITY FOR SOME
STRENGTHENING.  THE NHC INTENSITY FORECAST IS IN GOOD AGREEMENT
WITH THE SHIPS/LGEM GUIDANCE AND SHOWS PEAK INTENSITY OCCURRING
BETWEEN 24-36 HOURS.  WEAKENING IS INDICATED BEYOND 36 HOURS WHEN
THE GLOBAL MODELS PREDICT AN INCREASE IN UPPER-LEVEL NORTHEASTERLY
WINDS OVER THE CYCLONE.

BRET HAS BEEN DRIFTING EASTWARD DURING THE PAST FEW HOURS...BUT A
LONGER-TERM MOTION YIELDS 145/2.  THE TROPICAL STORM IS NOT
FORECAST TO MOVE VERY MUCH DURING THE NEXT 12-18 HOURS AS IT
REMAINS IN AN AREA OF WEAK STEERING CURRENTS.  IN 24-36 HOURS...THE
RIDGE TO THE SOUTHEAST OF BRET IS FORECAST TO STRENGTHEN WHICH
SHOULD PRODUCE A NORTHEASTWARD MOTION.  AS BRET GAINS LATITUDE IN
2-3 DAYS...IT SHOULD ACCELERATE EAST-NORTHEASTWARD WITHIN AN AREA
OF DEEP-LAYER WESTERLY FLOW.  THE LATEST HWRF AND GFDL MODEL
FORECASTS SHOW A MORE NORTH-NORTHEASTWARD MOTION WITH A TRACK MUCH
CLOSER TO THE UNITED STATES THAN THE USUALLY RELIABLE ECMWF AND GFS
MODELS.  THIS SCENARIO APPEARS UNLIKELY DUE TO THE STRENGTH OF THE
MID- TO UPPER-LEVEL RIDGE FORECAST OVER THE CENTRAL UNITED STATES. 
FOR NOW...THE OFFICIAL FORECAST PLACES MORE WEIGHT ON THE GLOBAL
MODELS AND IS VERY SIMILAR TO THE PREVIOUS NHC TRACK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/0300Z 27.5N  78.0W   35 KT  40 MPH
 12H  18/1200Z 27.7N  77.9W   40 KT  45 MPH
 24H  19/0000Z 28.5N  77.4W   50 KT  60 MPH
 36H  19/1200Z 29.7N  76.7W   50 KT  60 MPH
 48H  20/0000Z 30.7N  75.5W   45 KT  50 MPH
 72H  21/0000Z 32.5N  71.5W   40 KT  45 MPH
 96H  22/0000Z 34.5N  65.5W   35 KT  40 MPH
120H  23/0000Z 36.5N  58.5W   30 KT  35 MPH
 
$$
FORECASTER BROWN/BERG
 
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