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Tropical Depression ANA


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TROPICAL DEPRESSION ANA DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022009
1100 AM AST MON AUG 17 2009
 
THE CENTER OR WAVE AXIS OF ANA PASSED OVER BUOY 42060 AROUND
0830Z...AND IF A CENTER EXISTED AT THAT TIME IT WAS SOUTH OF THE
BUOY.  THERE WAS ONE SHIP REPORT WITH A LIGHT WEST WIND AT 12Z. 
SINCE THAT TIME...NEW CONVECTION WITH A MID-LEVEL SPIN HAS
DEVELOPED NEAR THE SOUTHEAST COAST OF PUERTO RICO. GIVEN THESE
HINTS...WE WILL CONTINUE ADVISORIES AT LEAST UNTIL A RECONNAISSANCE
AIRCRAFT INVESTIGATES ANA THIS AFTERNOON.

WITH A CENTER POSITION ESTIMATE BASED ON A BLEND OF CONTINUITY AND
THE MID-LEVEL ROTATION SEEN IN THE RADAR DATA...THE INITIAL MOTION
IS 285/24. ANA IS EXPECTED TO CONTINUE ON A GENERAL WEST-
NORTHWESTWARD TRACK TO THE SOUTH OF THE SUBTROPICAL RIDGE FOR THE
NEXT COUPLE OF DAYS...ALTHOUGH SOME ERRATIC MOTION IS POSSIBLE IN
THE SHORT TERM GIVEN THE POOR DEFINITION OF THE CIRCULATION...
INTERACTION WITH LAND...AND POTENTIAL REFORMATION OF THE CENTER.
THE OFFICIAL FORECAST FOLLOWS A BLEND OF THE GFS AND ECMWF
SOLUTIONS FOR THE 850 MB VORTICITY CENTER. TOWARD THE END OF THE
FORECAST PERIOD...ANA OR ITS REMNANTS COULD BE EMBEDDED WITHIN WEAK
STEERING OVER OR NEAR THE GULF OF MEXICO...AND THE OFFICIAL
FORECAST CALLS FOR A GRADUAL SLOWING OF THE FORWARD SPEED.

THE INTENSITY FORECAST IS COMPLICATED BY THE UNCERTAIN EXISTENCE OF
AN ACTUAL TROPICAL CYCLONE...THE LAND MASSES IN THE PATH OF THE
SYSTEM...AND HIGHLY DIVERGENT OBJECTIVE GUIDANCE. THE ENVIRONMENT
OF ANA IS STILL CHARACTERIZED BY SOUTHWESTERLY SHEAR. THE DYNAMICAL
MODELS...BOTH GLOBAL AND REGIONAL...ALMOST UNANIMOUSLY DISSIPATE
THE CYCLONE...WHILE THE STATISTICAL MODELS SHOW RESTRENGHENING. IF
ANA SURVIVES ITS PATH OVER THE GREATER ANTILLES AND EMERGES TO THE
NORTH OF THE DOMINICAN REPUBLIC...THE GLOBAL MODELS SUGGEST THAT A
MORE FAVORABLE UPPER WIND PATTERN WILL BE PRESENT THERE.
CONSEQUENTLY...THE OFFICIAL FORECAST MAINTAINS ANA AS A TROPICAL
CYCLONE THROUGH THE FORECAST PERIOD. THIS IS...ADMITTEDLY...
SOMETHING OF A HEDGE BETWEEN TWO MORE LIKELY ALTERNATIVES...THAT OF
A TROPICAL STORM NORTH OF THE ISLANDS OR IMMINENT DISSIPATION. 


FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/1500Z 17.3N  66.2W    30 KT
 12HR VT     18/0000Z 18.6N  69.4W    30 KT...INLAND
 24HR VT     18/1200Z 20.5N  73.7W    30 KT
 36HR VT     19/0000Z 22.3N  77.0W    30 KT
 48HR VT     19/1200Z 23.7N  79.4W    30 KT
 72HR VT     20/1200Z 26.5N  82.5W    30 KT
 96HR VT     21/1200Z 28.0N  83.0W    30 KT
120HR VT     22/1200Z 30.0N  83.0W    25 KT...INLAND
 
$$
FORECASTER FRANKLIN/CANGIALOSI
 
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