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HURRICANE ISIDORE DISCUSSION NUMBER 29
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT MON SEP 23 2002
A RECONNAISSANCE AIRCRAFT IS TRACKING THE CENTER OVER LAND. THE
INITIAL MOTION IS 210/04. THE GUIDANCE INSISTS ON A TURN TOWARD
THE NORTHWEST IN THE NEXT 24 HOURS FOLLOWED BY A NORTH-NORTHWEST TO
NORTHWARD MOTION THROUGH 72 HOURS. THIS IS IN RESPONSE TO A
DEEP-LAYER-MEAN LOW EAST OF FLORIDA BEING REPLACED BY A RIDGE TO
DRIVE ISIDORE NORTHWARD. THE FORECAST TRACK IS SIMILAR TO THE
PREVIOUS ADVISORY AND IS IN GOOD AGREEMENT WITH THE GLOBAL FORECAST
SYSTEM MODEL PREVIOUSLY KNOWN AS THE AVIATION MODEL. THE FORECAST
TRACK SHOWS A POTENTIAL THREAT IN ABOUT FOUR DAYS TO THE NORTHWEST
OR NORTHCENTRAL GULF OF MEXICO COAST.
THE LATEST SURFACE PRESSURE ESTIMATED BY AIRCRAFT IS 952 MB WHILE
THE MAX WIND REPORTED AT 700 MB FLIGHT LEVEL IS 76 KNOTS NORTHWEST
OF THE CENTER. THE WIND SPEED IS REDUCED TO 65 KNOTS BASED ON THIS
DATA. FURTHER WEAKENING IS EXPECTED FOR 12 MORE HOURS WHILE THE
CENTER IS OVER LAND. THEN STRENGTHENING IS EXPECTED WHEN THE
CENTER MOVES OVER THE GULF WATERS. VERTICAL SHEAR IS FORECAST TO
REMAIN LOW AND IF THE PRESSURE STAYS IN THE 950 RANGE...THIS COULD
HASTEN THE INTENSIFICATION PROCESS. HOW STRONG WILL ISIDORE GET?
I DO NOT KNOW. THE SHIPS STATISTICAL-DYNAMICAL MODEL CALLS FOR 99
KNOTS IN 72 HOURS. THE OFFICIAL FORECAST IS TO 100 KNOTS IN 48
HOURS. THIS IS LESS THAN THE 125 KNOTS FROM THE PREVIOUS ADVISORY
...BUT THAT VALUE WAS ORIGINALLY BASED ON THE CENTER REMAINING OVER
WATER. AND A FORECAST OF 100 KNOTS DOES NOT PRECLUDE THE
POSSIBILITY OF 125 KNOTS.
FORECASTER LAWRENCE
FORECAST POSITIONS AND MAX WINDS
INITIAL 23/0900Z 20.4N 89.8W 65 KTS
12HR VT 23/1800Z 20.3N 90.6W 60 KTS
24HR VT 24/0600Z 21.2N 91.7W 75 KTS
36HR VT 24/1800Z 22.2N 92.2W 90 KTS
48HR VT 25/0600Z 23.1N 92.6W 100 KTS
72HR VT 26/0600Z 26.0N 93.5W 100 KTS
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