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Tropical Storm ANA


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TROPICAL STORM ANA DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022009
1100 AM AST SUN AUG 16 2009
 
ANA CONTINUES TO RACE WESTWARD...WITH LIMITED DEEP CONVECTION OVER
THE LOW-LEVEL CENTER. A 0950 UTC QUIKSCAT PASS SHOWED SOME
BELIEVABLE 30 KT WINDS...AND ASSUMING WINDS ARE HIGHER IN THE
CONVECTION NEAR THE CENTER THE INTENSITY IS HELD GENEROUSLY AT 
35 KT FOR THIS PACKAGE. AIRCRAFT RECONNAISSANCE WILL BE
INVESTIGATING THE CYCLONE EARLY THIS AFTERNOON AND SHOULD HELP
DETERMINE IF ANA IS STILL A TROPICAL STORM.

THE ENVIRONMENT NEAR AND AHEAD OF ANA IS RATHER DRY AND DOMINATED BY
SUBSIDENCE...AS INDICATED BY WATER VAPOR IMAGERY AND RADIOSONDE
DATA FROM THE LESSER ANTILLES. THE GFDL...SHIPS...AND LGEM CONTINUE
TO SUGGEST THAT ANA WILL INTENSIFY SOMEWHAT OVER THE NEXT COUPLE OF
DAYS. HOWEVER...GIVEN THE NEGATIVE FACTORS DISCUSSED ABOVE...ONLY
SLIGHT INTENSIFICATION IS SHOWN THROUGH 48 HOURS. BEYOND THAT
TIME...THE INTENSITY OF ANA WILL BE DICTATED PRIMARILY BY ITS
INTERACTION WITH HISPANIOLA AND CUBA...AND THE INTENSITY FORECAST
ACCOUNTS FOR THIS WITH WEAKENING. 

THE TRACK FORECAST IS QUITE SIMILAR TO THE PREVIOUS PACKAGE...
SHOWING A QUICK WESTWARD TO WEST-NORTHWESTWARD MOTION THROUGH THE
FIRST 3 OR 4 DAYS OF THE FORECAST PERIOD. BEYOND THAT TIME THERE
IS A SPLIT IN THE TRACK GUIDANCE...WITH THE ECMWF AND HWRF SHOWING
A TURN TOWARD THE NORTHWEST...WHILE THE UKMET AND NOGAPS SHOW A
CONTINUED WEST-NORTHWEST HEADING. THE OFFICIAL FORECAST IS NUDGED
TOWARD THE MULTI-MODEL CONSENSUS AT DAY 5 AND SHOWS A DECREASE IN
FORWARD SPEED. 

GIVEN THE UNCERTAINTY IN THE INITIAL INTENSITY OF ANA...TROPICAL
STORM WATCHES CONTINUE FOR MOST OF THE NORTHERN LEEWARD ISLANDS...
THE VIRGIN ISLANDS...AND PUERTO RICO. IF AIRCRAFT RECONNAISSANCE
FINDS ANA IS A TROPICAL STORM...WARNINGS WILL LIKELY BE REQUIRED
LATER TODAY. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 14.8N  55.8W    35 KT
 12HR VT     17/0000Z 15.2N  58.7W    35 KT
 24HR VT     17/1200Z 16.1N  62.7W    40 KT
 36HR VT     18/0000Z 17.1N  66.7W    40 KT
 48HR VT     18/1200Z 18.3N  70.7W    45 KT
 72HR VT     19/1200Z 21.0N  77.5W    30 KT...INLAND
 96HR VT     20/1200Z 23.5N  83.0W    30 KT
120HR VT     21/1200Z 25.5N  85.5W    30 KT
 
$$
FORECASTER BRENNAN/ROBERTS
 
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