Tropical Storm HARVEY

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TROPICAL STORM HARVEY DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082011
500 PM EDT FRI AUG 19 2011
 
EARLIER REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
INDICATED THAT TROPICAL DEPRESSION EIGHT WAS ON THE VERGE OF
BECOMING A TROPICAL STORM.  SINCE THAT TIME...THE CONVECTIVE
BANDING HAS BECOME MORE PRONOUNCED AND SATELLITE ESTIMATES FROM SAB
AND TAFB HAVE INCREASED TO 45 KT.  BASED ON THESE DATA...THE
DEPRESSION WAS UPGRADED TO TROPICAL STORM HARVEY AT 1800 UTC AND IS
NOW ESTIMATED TO HAVE WINDS OF 40 KT.  THE NEXT AIRCRAFT IS
SCHEDULED TO REACH THE STORM NEAR 00Z.
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/10. THERE IS NO
CHANGE IN THE SYNOPTIC REASONING FOR THE TRACK FORECAST. A
LOW/MID-LEVEL RIDGE OVER THE GULF OF MEXICO AND THE NORTHERN GULF
COAST IS EXPECTED TO GRADUALLY STRENGTHEN DURING THE NEXT 48-72
HOURS...AND THIS SHOULD STEER THE CYCLONE GENERALLY WESTWARD TO
WEST- NORTHWESTWARD THROUGH ITS LIFETIME. ONE CHANGE SINCE THE LAST
ADVISORY IS THAT THE GUIDANCE ENVELOPE AND THE FORECAST TRACK HAVE
SHIFTED A LITTLE TO THE NORTH...BRINGING THE CENTER BRIEFLY OVER
THE BAY OF CAMPECHE BETWEEN 48-72 HOURS. THE NEW FORECAST TRACK IS
IN THE CENTER OF THE GUIDANCE ENVELOPE NEAR THE VARIOUS CONSENSUS
MODELS.
 
CURRENT CONVECTIVE TRENDS AND GOOD CIRRUS OUTFLOW IN THE
NORTHWESTERN SEMICIRCLE SUGGEST HARVEY SHOULD CONTINUE TO
STRENGTHEN UNTIL LANDFALL IN BELIZE.  THE NEW INTENSITY FORECAST
CALLS FOR A PEAK INTENSITY OF 55 KT NEAR LANDFALL IN BEST AGREEMENT
WITH THE SHIPS AND LGEM MODELS.  THEREAFTER...HARVEY SHOULD SLOWLY
WEAKEN AND EVENTUALLY DISSIPATE OVER SOUTHEASTERN MEXICO.  THERE
ARE TWO NOTES ABOUT THE INTENSITY FORECAST.  FIRST...THE RAPID
INTENSIFICATION INDEX OF THE SHIPS MODEL SHOWS A 40 PERCENT CHANCE
OF 25 KT OF INTENSIFICATION DURING THE NEXT 24 HOURS...AND THE
INTENSITY PROBABILITIES TABLE SHOWS A 13 PERCENT CHANCE OF HARVEY
BEING A HURRICANE IN 24 HOURS.  SECOND...THE INTENSITIES LATER IN
THE FORECAST PERIOD COULD REQUIRE ADJUSTMENT IF THE CENTER MOVES
FARTHER OUT INTO THE BAY OF CAMPECHE THAN CURRENTLY FORECAST.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/2100Z 16.5N  84.7W   40 KT  45 MPH
 12H  20/0600Z 16.7N  86.1W   45 KT  50 MPH
 24H  20/1800Z 17.1N  87.9W   55 KT  65 MPH
 36H  21/0600Z 17.6N  89.9W   40 KT  45 MPH...INLAND
 48H  21/1800Z 18.0N  91.9W   30 KT  35 MPH...INLAND
 72H  22/1800Z 18.5N  96.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  23/1800Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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