Reply #18: NOAA Update: 5PM: NOW CAT 3

[Chico Man]

000
WTNT43 KNHC 152051
TCDAT3
HURRICANE ISABEL DISCUSSION NUMBER 39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT MON SEP 15 2003

AIRCRAFT RECONNAISSANCE OBSERVATIONS CONFIRM THAT ISABEL HAS
WEAKENED TO CATEGORY THREE STATUS. PEAK FLIGHT LEVEL WINDS OF 120
KT SUPPORT SURFACE WINDS OF ABOUT 110 KT...WHICH IS THE ADVISORY
INTENSITY...ALTHOUGH DROPSONDES IN THE EYEWALL SUGGEST THE WINDS
MIGHT BE EVEN A LITTLE BIT LESS. THERE IS NOT MUCH EVIDENCE OF
SHEAR AND THE OUTFLOW PATTERN STILL LOOKS STRONG. HOWEVER...THE
EYEWALL CONVECTION REMAINS ASYMMETRIC AND THE WEST SIDE OF THE
CIRCULATION LOOKS A LITTLE DRY. ALTHOUGH ISABEL HAS BEEN
WEAKENING...AND MAY WEAKEN FURTHER...THERE IS SOME MODEL GUIDANCE
THAT SUGGESTS THAT A MORE FAVORABLE UPPER WIND PATTERN...WITH
ENHANCED ANTICYCLONIC OUTFLOW...MAY DEVELOP IN THE LAST 24 HOURS
BEFORE LANDFALL. HOWEVER...DYNAMICAL MODELS HAVE LIMITED SKILL IN
PREDICTING SUCH PATTERNS...IN PARTICULAR THEY OFTEN OVER-DEVELOP
UPPER-LEVEL ANTICYCLONES OVER TROPICAL CYCLONES. THE OFFICIAL
FORECAST SIMPLY CALLS FOR LITTLE CHANGE IN STRENGTH...AND
ANTICIPATES A MAJOR HURRICANE...CATEGORY THREE OR HIGHER...AT
LANDFALL.

THE INITIAL MOTION IS NOW 305/7...OR NORTHWEST. MODEL GUIDANCE
REMAINS VERY TIGHTLY CLUSTERED...EVEN MORE SO THAN THIS MORNING AS
THE 12Z GFS IS A LITTLE FASTER THAN ITS EARLIER RUN. THERE HAS BEEN
NO SIGNIFICANT CHANGE TO THE FORECAST TRACK. HOWEVER...SOME OF THE
GUIDANCE IS SUGGESTING THAT THE MOTION OVER THE NEXT DAY OR TWO MAY
BE A LITTLE MORE NORTHWARD BEFORE ISABEL TURNS BACK TO THE
NORTHWEST...AFTER THE UPPER TROUGH CURRENTLY OVER THE GREAT LAKES
MOVES OUT AND HIGH PRESSURE BUILDS AGAIN NORTH OF THE HURRICANE.
BY 48 HOURS OR SO...AN APPROACHING MID- TO UPPER-LEVEL TROUGH FROM
THE WEST WILL HELP ACCELERATE ISABEL NORTH-NORTHWESTWARD AROUND THE
WEST SIDE OF THE DEEP-LAYER RIDGE ANCHORED NEAR 35N AND 60 W.

FORECASTER FRANKLIN/PASCH

FORECAST POSITIONS AND MAX WINDS

INITIAL 15/2100Z 25.6N 70.0W 110 KT
12HR VT 16/0600Z 26.3N 70.8W 110 KT
24HR VT 16/1800Z 27.5N 71.6W 105 KT
36HR VT 17/0600Z 29.0N 72.3W 105 KT
48HR VT 17/1800Z 30.8N 73.2W 105 KT
72HR VT 18/1800Z 35.5N 76.0W 100 KT...INLAND
96HR VT 19/1800Z 42.0N 79.0W 50 KT...INLAND
120HR VT 20/1800Z 52.0N 80.0W 30 KT...EXTRATROPICAL