Tropical Storm LISA

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TROPICAL STORM LISA DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT WED SEP 22 2004
 
A BURST OF CONVECTION EARLY THIS AFTERNOON OBSCURED THE CENTER...BUT
THAT CONVECTION IS NOW FADING AND BEING BLOWN OFF BY EASTERLY
SHEARING WINDS ALOFT.  THE INITIAL INTENSITY IS HELD AT 45 KT IN
ACCORD WITH AN EARLIER QUIKSCAT PASS AND A DVORAK CLASSIFICATION OF
3.0 FROM TAFB.  THE INTENSITY FORECAST IS COMPLICATED BY THE
PRESENCE OF A LARGE TROPICAL DISTURBANCE ONLY 300 MILES TO THE EAST
OF LISA.  THE UPPER-FLOW OVER THIS LATTER FEATURE IS MORE FAVORABLE
FOR DEVELOPMENT THAN THE SHEARING FLOW OVER LISA...AND IT IS HARD
TO IMAGINE BOTH OF THESE SYSTEMS BEING TROPICAL CYCLONES IN 48
HOURS.  IT IS QUITE POSSIBLE THAT LISA WILL END UP BEING ABSORBED
BY THE EASTERN DISTURBANCE WITHIN A COUPLE OF DAYS.  SHOULD IT
SURVIVE...UPPER-LEVEL WINDS COULD BECOME MORE FAVORABLE IN 2-3 DAYS
AND THE OFFICIAL FORECAST SHOWS SOME INTENSIFICATION FOLLOWING THE
SHIPS AND GFDL GUIDANCE.  NEAR THE END OF THE FORECAST PERIOD
HOWEVER...A STRONG 200 MB TROUGH IS EXPECTED TO DIG DEEP INTO THE
CENTRAL TROPICAL ATLANTIC...WHICH WOULD INCREASE THE SHEAR OVER
WHICHEVER OF LISA OR THE DISTURBANCE STILL EXISTS.   

THE INITIAL MOTION ESTIMATE IS 240/5.  LISA AND THE DISTURBANCE ARE
BEGINNING TO REVOLVE AROUND A COMMON CENTER OF ROTATION SOUTH OF A
NARROW RIDGE TO THE SOUTH OF KARL.  THE GFS SHOWS THE STRONGEST
INTERACTION BETWEEN THE TWO TROPICAL SYSTEMS...TAKING LISA
SOUTHWARD AND EASTWARD BEFORE DISSIPATING IT.  THE GFDL...
NOGAPS...AND UKMET MERELY CONTINUE A SLOW SOUTHWESTWARD MOTION FOR
ABOUT TWO DAYS...KEEPING LISA AS THE STRONGER SYSTEM.  BY THE TIME
THIS INTERACTION IS OVER...THE STRONG UPPER-LEVEL TROUGH NOTED
ABOVE IS EXPECTED TO IMPART MORE OF A NORTHWARD MOTION BY DAYS 4
AND 5.  THE OFFICIAL FORECAST IS IN BEST AGREEMENT WITH THE GFDL
GUIDANCE.

 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/2100Z 13.7N  41.9W    45 KT
 12HR VT     23/0600Z 13.4N  42.3W    45 KT
 24HR VT     23/1800Z 13.0N  42.8W    45 KT
 36HR VT     24/0600Z 12.7N  43.5W    45 KT
 48HR VT     24/1800Z 12.5N  44.5W    45 KT
 72HR VT     25/1800Z 14.0N  45.5W    55 KT
 96HR VT     26/1800Z 17.0N  46.5W    65 KT
120HR VT     27/1800Z 20.0N  48.0W    65 KT
 
 
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