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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