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TROPICAL STORM ARTHUR DISCUSSION NUMBER   6
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT MON JUL 15 2002

SATELLITE IMAGES INDICATE A GREATER SEPARATION DISTANCE BETWEEN THE 
LOW-CLOUD CENTER AND THE DEEP CONVECTION.  ACCORDINGLY...DVORAK 
T-NUMBERS FROM BOTH TAFB AND SAB HAVE COME DOWN A BIT.  HOWEVER 
THERE WAS A 45 KT WIND REPORT FROM A SHIP...WITH CALL SIGN LAFQ5...  
SOUTH-SOUTHEAST OF THE CENTER.  THEREFORE THE INTENSITY IS 
MAINTAINED AT 50 KT FOR THIS ADVISORY.  THE SHIP REPORT ALSO 
SUGGESTS AN EXPANSION OF THE WIND FIELD...SO ARTHUR MAY ALREADY BE 
TAKING ON SOME EXTRATROPICAL CHARACTERISTICS.  THE SYSTEM IS 
APPROACHING SUBSTANTIALLY COOLER WATERS SO THE STRENGTHENING 
INDICATED IN THE OFFICIAL FORECASTS ASSUMES A BAROCLINIC SOURCE OF 
ENERGY.  BASED ON THE LATEST NCEP GLOBAL MODEL RUN...ARTHUR SHOULD 
MERGE WITH ANOTHER EXTRATROPICAL CYCLONE BEFORE REACHING 
NEWFOUNDLAND.

ARTHUR'S FORWARD SPEED HAS INCREASED TO ABOUT 25 KT.  THE STORM IS 
EMBEDDED IN THE FLOW TO THE SOUTHEAST OF AN AMPLIFYING MID- TO 
UPPER-LEVEL CYCLONE...WHICH IS DROPPING SOUTH-SOUTHEASTWARD. 
NUMERICAL GUIDANCE INDICATES A GRADUAL TURN TO THE LEFT WITH 
CONSIDERABLE DECELERATION AS ARTHUR ROTATES AROUND THE LARGER 
CYCLONE.  THIS REFLECTED IN THE OFFICIAL TRACK FORECAST AS WELL.

WIND AND SEAS RADII HAVE BEEN FURTHER INCREASED BASED ON SHIP 
OBSERVATIONS.

THE CANADIAN HURRICANE CENTRE HAS ISSUED GALE AND STORM WARNINGS FOR 
THEIR APPROPRIATE COASTAL WATERS.

FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     16/0300Z 38.7N  63.9W    50 KTS
12HR VT     16/1200Z 40.5N  60.0W    50 KTS
24HR VT     17/0000Z 43.0N  58.0W    55 KTS...BECOMING EXTRATROPICAL
36HR VT     17/1200Z 45.0N  57.5W    60 KTS...EXTRATROPICAL
48HR VT     18/0000Z 46.0N  57.0W    55 KTS...EXTRATROPICAL
72HR VT     19/0000Z...MERGING WITH EXTRATROPICAL LOW
 
 
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