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TROPICAL STORM JOSEPHINE DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT WED SEP 18 2002
 
SURFACE OBSERVATIONS FROM SHIP PDKK AT 03Z AND 06Z INDICATE THAT 
TROPICAL DEPRESSION ELEVEN STRENGTHENED SLIGHTLY INTO TROPICAL STORM 
JOSEPHINE. SHIP PDKK REPORTED ESTIMATED WINDS OF 37 KT AT 03Z... 
WHICH IS SUPPORTED BY EARLIER QUIKSCAT AND SSM/I WINDS OF 35 KT... 
AND A DVORAK SATELLITE INTENSITY ESTIMATE OF T2.5...OR 35 KT...FROM 
THE TAFB. DUSTING OFF THE OLD METEOROLOGY BOOKS AND MAKING SOME 
GRADIENT WIND COMPUTATIONS USING THE 6-7 MB PER 60 NMI PRESSURE 
GRADIENT BETWEEN THE 03Z AND 06Z PDKK SHIP OBS ALSO SUPPORTS 
TROPICAL STORM STRENGTH. 
 
THE INITIAL MOTION ESTIMATE IS 020/12. TROPICAL STORM JOSEPHINE 
LIKELY PEAKED SEVERAL HOURS AGO AND IS NOW ON THE DOWNSLIDE. THE 
LACK OF DEEP CONVECTION NEAR THE CENTER DURING THE PAST 2 HOURS HAS 
ALLOWED THE LOW-LEVEL CENTER TO MAKE A JOG TOWARD THE NORTH UNDER 
THE INFLUENCE OF MODERATE SOUTHERLY LOW-LEVEL FLOW ON THE WEST SIDE 
OF A SUBTROPICAL HIGH LOCATED WELL TO THE NORTHEAST. HOWEVER...AN 
APPROACHING FRONTAL TROUGH SHOULD GRADUALLY TURN THE LOW-LEVEL 
STEERING FLOW AROUND TO THE SOUTHWEST AND CAUSE JOSEPHINE TO 
ACCELERATE OFF TO THE NORTHEAST. ALL OF THE NHC MODEL GUIDANCE IS IN 
EXCELLENT AGREEMENT ON THIS SCENARIO...BUT THERE ARE DIFFERENCES IN 
TIMING. THE OFFICIAL FORECAST IS CLOSE TO THE AVN AND UKMET MODELS 
WHICH HAVE SHIFTED MORE TO THE LEFT OF THEIR PREVIOUS FORECAST 
TRACKS. REGARDLESS OF THE EXACT MOTION TO THE NORTHEAST...JOSEPHINE 
IS EXPECTED TO SLOWLY WEAKEN AND MERGE WITH A STRONG FRONTAL SYSTEM 
APPROACHING FROM THE WEST AND BECOME ABSORBED IN 36 TO 48 HOURS...IF 
NOT SOONER.
 
JOSEPHINE HAS PASSED ITS PEAK AND SHOULD SLOWLY WEAKEN...DESPITE THE 
SHIPS INTENSITY MODEL BRINGING THE CYCLONE UP TO 57 KT IN 36 HOURS. 
WHILE THERE MAY BE INTERMITTENT BRIEF BURSTS OF CONVECTION NEAR THE 
CENTER...MID-LEVEL DRY AIR INTRUSION FROM THE SOUTHWEST COMBINING 
WITH INCREASING SOUTHWEST AND WESTERLY UPPER-LEVEL SHEAR SHOULD 
PREVENT ANY SUSTAINED CONVECTION FROM DEVELOPING OVER THE LOW-LEVEL 
CENTER.  HOWEVER...THE PRESSURE GRADIENT REMAINS VERY TIGHT ON THE 
EAST SIDE AS JOSEPHINE MOVES UP THE WEST SIDE OF A STRONG SURFACE 
HIGH TO THE NORTHEAST...SO THE WIND FIELD ON THE EAST SIDE WILL 
REMAIN AROUND 25 TO 30 KT FOR THE NEXT 12 TO 24 HOURS DESPITE THE 
LACK OF ANY PERSISTENT DEEP CONVECTION. ALSO...NONE OF THE GLOBAL 
MODELS SUGGEST ANY BAROCLINIC DEEPENING WILL OCCUR ONCE THE 
JOSEPHINE CIRCULATION MERGES WITH AND BECOMES ABSORBED BY THE 
FRONTAL APPROACHING FRONTAL ZONE.
 
FORECASTER STEWART
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     18/0900Z 35.2N  52.2W    35 KTS
12HR VT     18/1800Z 37.1N  50.7W    30 KTS
24HR VT     19/0600Z 39.9N  46.5W    25 KTS...BECOMING EXTRATROPICAL
36HR VT     19/1800Z 43.2N  41.5W    25 KTS...EXTRATROPICAL
48HR VT     20/0600Z...ABSORBED BY LARGER EXTRATROPICAL LOW
 
 
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