Tropical Storm FRANKLIN

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TROPICAL STORM FRANKLIN DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU JUL 21 2005
 
THE LAST REPORTS FROM THE RECONNAISSANCE AIRCRAFT SHORTLY BEFORE 00Z
INDICATED THAT THE CENTRAL PRESSURE REMAINED 1009 MB... AND MAXIMUM
1000 FT FLIGHT LEVEL WINDS AS STRONG AS 57 KT WERE MEASURED WITHIN
A CONVECTIVE BURST RIGHT NEAR THE CIRCULATION CENTER.  THIS WOULD
NORMALLY CORRESPOND TO SURFACE WINDS OF ABOUT 45 KT... BUT SINCE
THE PRESSURE WAS RELATIVELY HIGH AND THE CONVECTIVE PATTERN REMAINS
QUITE DISORGANIZED... WITH DVORAK T NUMBERS AT 2.0 AND 2.5... THE
INITIAL INTENSITY IS HELD AT 40 KT.  RECON WILL ONCE AGAIN
INVESTIGATE FRANKLIN ON FRIDAY MORNING.

THE INITIAL MOTION IS 310/11.  FRANKLIN IS MOVING TOWARD THE
NORTHWEST WITHIN A RELATIVE WEAKNESS IN THE SUBTROPICAL RIDGE.  IT
IS EXPECTED TO SLOW DOWN DURING THE NEXT COUPLE OF DAYS... AND BE
WITHIN AN AREA OF WEAK STEERING CURRENTS TO THE SOUTH OF A
MIDLATITUDE TROUGH AND TO THE SOUTHEAST OF A BUILDING MID-LEVEL
RIDGE OVER THE SOUTHEASTERN UNITED STATES.  MOST OF THE DYNAMICAL
MODELS FORECAST THE MIDLATITUDE TROUGH TO PROVIDE ENOUGH IMPETUS
TOWARD THE EAST TO RECURVE FRANKLIN TOWARD THE OPEN ATLANTIC. 
HOWEVER... AN ALTERNATIVE SCENARIO IS THAT THE TROUGH WILL BYPASS
FRANKLIN AND ALLOW THE SOUTHEASTERN U.S. RIDGE TO HALT ITS EXODUS
OUT TO SEA AND PERHAPS EVEN EVENTUALLY STEER IT BACK TO THE WEST. 
THE OFFICIAL FORECAST IS A COMPROMISE BETWEEN THESE SCENARIOS AND
IS A LITTLE FASTER TO THE NORTHEAST THAN THE PREVIOUS FORECAST.

FRANKLIN IS LOCATED BETWEEN AN UPPER-LEVEL RIDGE AND AN UPPER-LEVEL
SHEAR AXIS WHICH IS IMPARTING SOME WESTERLY SHEAR.  HOWEVER... THE
SHEAR AXIS IS EXPECTED TO WEAKEN... WHICH COULD ALLOW FRANKLIN TO
GRADUALLY INTENSIFY DURING THE NEXT COUPLE OF DAYS.  ALONG THE
OFFICIAL FORECAST TRACK... THE TROPICAL STORM WOULD REMAIN OVER
27-28C SSTS EVEN LATE IN THE FORECAST PERIOD AND PERHAPS BE
IMPACTED BY MODERATE NORTHERLY SHEAR.  INTENSIFICATION TO A
HURRICANE IS HIGHLY UNCERTAIN.  IF FRANKLIN MOVES MORE QUICKLY OUT
TO SEA... THIS WOULD BE UNLIKELY... BUT IF IT BECOMES TRAPPED SOUTH
OF THE SUBTROPICAL RIDGE LATE IN THE FORECAST PERIOD... THE
ENVIRONMENT COULD BECOME FAVORABLE FOR MORE INTENSIFICATION THAN IS
CURRENTLY FORECAST.

FRANKLIN IS THE EARLIEST SIXTH TROPICAL STORM ON RECORD IN THE
ATLANTIC BASIN.
 
FORECASTER KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0300Z 26.1N  76.3W    40 KT
 12HR VT     22/1200Z 27.2N  77.3W    45 KT
 24HR VT     23/0000Z 28.5N  77.4W    50 KT
 36HR VT     23/1200Z 29.5N  77.1W    55 KT
 48HR VT     24/0000Z 30.0N  76.5W    55 KT
 72HR VT     25/0000Z 30.5N  75.5W    60 KT
 96HR VT     26/0000Z 31.0N  74.5W    60 KT
120HR VT     27/0000Z 31.0N  73.5W    60 KT
 
 
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