Tropical Storm ANA

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SUBTROPICAL STORM ANA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT MON APR 21 2003
 
ANA LOOKED RATHER TROPICAL THIS EVENING...WITH TROPICAL SATELLITE 
INTENSITY ESTIMATES OF 35 KT FROM SAB AND TAFB.  SSM/I AND TRMM 
OVERPASSES NEAR 2330Z EVEN SUGGESTED AN EYE MIGHT BE FORMING.  
HOWEVER...SINCE 00Z THE CONVECTION HAS BECOME LESS ORGANIZED.  
ADDITIONALLY...AN AMSU OVERPASS AT 2200Z DID NOT SHOW A WARM CORE.  
WHILE THIS IS NOT TOTALLY CONCLUSIVE...AS THE AMSU INSTRUMENT MAY 
NOT FULLY RESOLVE A WARM CORE IN A COMPACT SYSTEM LIKE ANA...IT WILL 
REMAIN A SUBTROPICAL STORM FOR NOW.  MAXIMUM WINDS REMAIN 35 KT 
BASED ON THE SATELLITE ESTIMATES AND A 33-KT 1003-MB SHIP SOUTH OF 
THE CENTER.  IT SHOULD BE NOTED THAT QUIKSCAT DATA SUGGESTS THAT ANA 
COULD BE A LITTLE STRONGER THAN 35 KT.

THE INITIAL MOTION IS 100/15...AND THE SHORT-TERM MOTION IS CLOSER 
TO 090/15.  ANA REMAINS EMBEDDED DEEP-LAYER WESTERLY FLOW SOUTH OF
A CYCLONE NEAR 38N60W.  THIS SHOULD MOVE THE SYSTEM EASTWARD FOR
12 HR OR SO WITH A MORE EAST-NORTHEASTWARD MOTION THEREAFTER.  ALL 
GUIDANCE AGREES WITH THIS SCENARIO...AS DOES THE OFFICIAL FORECAST 
WHICH IS BASICALLY A SLIGHTLY FASTER UPDATE OF THE PREVIOUS PACKAGE. 
AFTER 48 HR A FRONTAL SYSTEM COMING FROM THE NORTH MAY TURN ANA BACK 
TO AN EASTWARD MOTION...WHICH IS NOTED IN THE FORECAST TRACK.

VERTICAL SHEAR PRODUCTS FROM CIMSS AT THE UNIVERSITY OF WISCONSIN 
INDICATE 30 KT OF SHEAR OVER ANA.  THIS HAS NOT YET SERIOUSLY
IMPACTED THE CYCLONE...BUT INCREASING SHEAR FORECAST BY ALL 
LARGE-SCALE MODELS SHOULD CAUSE WEAKENING AFTER 12-24 HR.  THE 
INTENSITY FORECAST CALLS FOR A SLOW WEAKENING UNTIL THE CYCLONE IS 
DISSIPATING IN 72 HR...BUT ANA COULD DISSIPATE EARLIER.  THERE IS A 
CHANCE THAT INSTEAD OF DISSIPATING THE SYSTEM COULD CONTINUE 
EASTWARD AS A EXTRATROPICAL WAVE ALONG THE ABOVE-MENTIONED FRONTAL 
SYSTEM.

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     22/0300Z 29.4N  60.5W    35 KTS
12HR VT     22/1200Z 29.4N  58.0W    35 KTS
24HR VT     23/0000Z 29.9N  54.2W    30 KTS
36HR VT     23/1200Z 30.7N  50.4W    30 KTS
48HR VT     24/0000Z 31.4N  46.5W    25 KTS
72HR VT     25/0000Z 32.0N  40.0W    25 KTS...DISSIPATING
 
 
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