[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 190839
TCDAT2

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


This weather bulletin was brought to you by:
www.nashvilleweather.net