Tropical Storm ISELLE

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TROPICAL STORM ISELLE DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP102008
200 AM PDT FRI AUG 15 2008
 
CONVECTION CONTINUES TO GRADUALLY DECREASE IN BOTH COVERAGE AND
DEPTH.  AN ASCAT OVERPASS AT ABOUT 05Z RETRIEVED WINDS OF ABOUT 35
KT IN THE EASTERN SEMICIRCLE OF THE CIRCULATION...AND WHILE THOSE
VALUES COULD HAVE BEEN SLIGHT UNDERESTIMATES THAT ARE COMMON WITH
THAT INSTRUMENT...THE WEAKENING CONVECTION SUGGESTS THE WINDS HAVE
PROBABLY COME DOWN SINCE THEN.  THE ADVISORY INTENSITY IS LOWERED
SLIGHTLY TO 35 KT...WHICH IS CONSISTENT WITH THE LATEST SUBJECTIVE
DVORAK CI NUMBERS FROM TAFB AND SAB.  EASTERLY SHEAR IS TAKING ITS
TOLL ON ISELLE AND IS FORECAST BY THE DYNAMICAL MODELS TO GET A
LITTLE STRONGER AND PERSIST THROUGHOUT THE FIVE-DAY FORECAST
PERIOD.  AS A RESULT...DESPITE RELATIVELY WARM SEA-SURFACE
TEMPERATURES ALONG THE FORECAST TRACK FOR THE NEXT 2-3 DAYS...ALL OF
THE OBJECTIVE INTENSITY GUIDANCE FORECASTS STEADY WEAKENING...AND
SO DOES THE OFFICIAL FORECAST.  THE CYCLONE COULD DEGENERATE INTO A
REMNANT LOW AT JUST ABOUT ANY TIME WITHIN THE NEXT COUPLE OF DAYS.

MIDDLE- AND UPPER-LEVEL RIDGING CENTERED OVER NORTHWESTERN MEXICO IS
STEERING ISELLE TOWARD THE WEST OR ABOUT 270/7.  AS THE CYCLONE
WEAKENS...IT OR WHATEVER IS LEFT OF IT WILL CONTINUE GENERALLY
WESTWARD BUT PROBABLY SLOW DOWN...SINCE IT WILL REMAIN WELL EAST OF
THE MAIN BELT OF LOW-LEVEL EASTERLY TRADES.  THE NEW OFFICIAL TRACK
FORECAST IS A LITTLE SOUTH OF THE PREVIOUS ONE AND IS GENERALLY A
BLEND OF THE NOGAPS AND UKMET.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0900Z 17.7N 111.7W    35 KT
 12HR VT     15/1800Z 17.9N 112.6W    30 KT
 24HR VT     16/0600Z 18.3N 113.8W    30 KT
 36HR VT     16/1800Z 18.5N 114.8W    25 KT...REMNANT LOW
 48HR VT     17/0600Z 18.5N 115.7W    25 KT...REMNANT LOW
 72HR VT     18/0600Z 18.5N 117.5W    20 KT...REMNANT LOW
 96HR VT     19/0600Z 18.5N 119.0W    20 KT...REMNANT LOW
120HR VT     20/0600Z 18.5N 120.5W    20 KT...REMNANT LOW
 
$$
FORECASTER KNABB
 
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