000
WTPZ42 KNHC 200231
TCDEP2
HURRICANE IVO DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122007
800 PM PDT WED SEP 19 2007
 
SATELLITE PRESENTATION HAS CONTINUED TO IMPROVE WITH AN AREA OF DEEP
CONVECTION NEAR THE CENTER AND A WELL ESTABLISHED UPPER-LEVEL
OUTFLOW. DVORAK T-NUMBERS FROM BOTH TAFB AND SAB HAVE INCREASED TO
4.0 AND A RECENT MICROWAVE PASSAGE SHOWS A WELL DEFINED RING OF
CONVECTION RESEMBLING AN EYEWALL. ON THIS BASIS...IVO HAS BEEN
UPGRADED TO A 65 KNOT HURRICANE.  THERE IS A CHANCE FOR IVO TO
STRENGTHEN SOME DURING THE NEXT 24 TO 36 HOURS. THEREAFTER...A
GRADUAL WEAKENING IS FORECAST SINCE THE SHEAR IS EXPECTED TO
INCREASE...AS INDICATED BY THE SHIPS MODELS. IN FACT...SOME OF THE
GLOBAL MODELS WEAKEN OR LOSE THE CYCLONE BEYOND DAY 3. ONLY THE
GFDL KEEPS IVO AS A HURRICANE ALL THE WAY THROUGH THE COAST OF
MAINLAND MEXICO. WE WILL CONTINUE TO CLOSELY MONITOR FUTURE GFDL
RUNS.     

IVO APPEARS TO BE MOVING TOWARD THE NORTHWEST OR 315 DEGREES AT 8
KNOTS AROUND THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE.
THIS RIDGE WILL BE ERODED BY THE DEVELOPMENT OF A LARGE
MID-LATITUDE TROUGH...RESULTING IN VERY WEAK STEERING CURRENTS. IVO
IS EXPECTED TO TURN NORTHWARD VERY SLOWLY AND THEN TURN MORE TO THE
NORTH-NORTHEAST WITHIN THE LIGHT FLOW TO THE SOUTHEAST OF THE
MID-LATITUDE TROUGH. THE TRACK FORECAST BASICALLY FOLLOW THE
SOLUTION OF THE GLOBAL MODELS WITH THE EXCEPTION OF THE GFS
FORECAST WHICH APPEARS TO BE TOO FAR TO THE WEST.

INTERESTS IN SOUTHERN BAJA CALIFORNIA SHOULD CLOSELY MONITOR THE
PROGRESS OF IVO DURING THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 16.1N 112.4W    65 KT
 12HR VT     20/1200Z 16.9N 113.2W    70 KT
 24HR VT     21/0000Z 18.0N 113.5W    75 KT
 36HR VT     21/1200Z 19.0N 113.5W    75 KT
 48HR VT     22/0000Z 20.0N 113.0W    70 KT
 72HR VT     23/0000Z 21.5N 112.0W    60 KT
 96HR VT     24/0000Z 22.5N 111.0W    50 KT
120HR VT     25/0000Z 24.0N 110.0W    50 KT
 
$$
FORECASTER AVILA