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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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