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TROPICAL STORM IVO DISCUSSION NUMBER 7
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT WED SEP 12 2001
THE INITIAL MOTION ESTIMATE IS 300/14. THE AVIATION MODEL MAINTAINS
A RIDGE OVER MEXICO AND A GENERAL NORTH-NORTHWEST TO NORTHWEST
MOTION WITH A DECREASE IN FORWARD SPEED IS EXPECTED TO CONTINUE FOR
THE NEXT 72 HOURS. THE GFDL MODEL WHICH HAS PREVIOUSLY MOVED THE
STORM ACROSS BAJA CALIFORNIA NOW HAS A TRACK THAT REMAINS OFFSHORE
LIKE THE OTHER GUIDANCE...EXCEPT THE GFDL MODEL RUN IN THE
NOGAPS ENVIRONMENT...IT STILL MOVES THE CENTER NORTHWARD OVER LAND.
THE OFFICIAL FORECAST IS A CONSENSUS OF THE MODELS AND IS QUITE
SIMILAR TO THE PREVIOUS FORECAST.
THE INITIAL WIND SPEED IS INCREASED TO 40 KNOTS BASED ON SOME
QUIKSCAT WINDS. THERE HAS BEEN TREMENDOUS CONVECTION NORTH OF THE
CENTER BUT THE TOPS THERE ARE NOW WARMING. DECREASING SHEAR ALLOWS
FOR SOME STRENGTHENING BEFORE COLD WATER IS ENCOUNTERED AFTER 48
HOURS. THE OFFICIAL FORECAST FOLLOWS THE SHIPS MODEL. OTHER
GUIDANCE WEAKENS THE STORM.
FORECASTER LAWRENCE
FORECAST POSITIONS AND MAX WINDS
INITIAL 12/0900Z 18.8N 108.5W 40 KTS
12HR VT 12/1800Z 19.9N 110.0W 45 KTS
24HR VT 13/0600Z 21.7N 112.2W 50 KTS
36HR VT 13/1800Z 23.1N 114.2W 55 KTS
48HR VT 14/0600Z 24.3N 116.1W 55 KTS
72HR VT 15/0600Z 26.0N 119.0W 55 KTS
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