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Tropical Storm ISELLE
ZCZC MIATCDEP5 ALL
TTAA00 KNHC DDHHMM
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
NNNN
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