Tropical Storm GENEVIEVE

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TROPICAL STORM GENEVIEVE DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP082008
800 PM PDT TUE JUL 22 2008
 
GENEVIEVE CONTINUES TO SLOWLY STRENGTHEN IN THE FACE OF MODERATE
EASTERLY SHEAR.  THE INITIAL INTENSITY IS RAISED TO 55 KT BASED ON
UNANIMOUS SUBJECTIVE AND OBJECTIVE DVORAK SATELLITE CLASSIFICATIONS. 
MULTIPLE FACTORS COMPLICATE THE INTENSITY FORECAST.  ON ONE
HAND...VERTICAL SHEAR IS EXPECTED TO WEAKEN DURING THE NEXT 12 TO
24 HOURS AND ALL OF THE INTENSITY GUIDANCE SHOWS STRENGTHENING.
HOWEVER...SATELLITE BASED SST ESTIMATES INDICATE THAT THE CYCLONE
IS ABOUT TO MOVE OVER A COLD WAKE GENERATED BY FAUSTO. WHILE THE
POCKET OF COOLER WATER IS NOT THAT LARGE...IT COULD SLOW OR EVEN
STOP DEVELOPMENT IN THE SHORT-TERM. BEYOND 24 HOURS...GENEVIEVE
SHOULD BE BACK OVER SUFFICIENTLY WARM WATERS WHERE IT WILL HAVE
ABOUT A 48 HOUR WINDOW TO STRENGTHEN BEFORE SHEAR INCREASES AGAIN.
IN LIGHT OF THE AFOREMENTIONED COLD WAKE...THE OFFICIAL FORECAST IS
BELOW THE INTENSITY MODEL CONSENSUS EARLY IN THE FORECAST.
 
GENEVIEVE CONTINUES WESTWARD AT ABOUT 10 KT UNDER THE INFLUENCE OF A
MIDDLE TO UPPER LEVEL RIDGE OVER NORTHERN MEXICO.  WHILE DYNAMICAL
MODELS GENERALLY AGREE THAT THIS RIDGE WILL NOSE WESTWARD INTO THE
EASTERN PACIFIC...THEY DISAGREE ON THE STRENGTH OF THE RIDGE.
ADDITIONALLY...THE VARIOUS MODELS DIFFER IN THEIR FORECASTS OF THE
STRENGTH AND DEPTH OF THE CYCLONE.  THOSE MODEL DEPICTING A WEAK
SYSTEM MOVE IT SOUTHWESTWARD WHILE THOSE MODELS WHICH DEPICT A
STRONG SYSTEM TURN THE CYCLONE WEST-NORTHWESTWARD OR NORTHWESTWARD.
ALL THIS RESULTS IN A HUGE DIVERGENCE OF THE TRACK MODELS BEYOND A
DAY OR SO.  IN FACT...THE TRACK MODEL ENVELOPE SPANS APPROXIMATELY
1000 MILES AT DAY 5.  GIVEN THE EXTREME UNCERTAINTY...THE OFFICIAL
FORECAST MAINTAINS A DUE WESTWARD MOTION THROUGH 5 DAYS.  THIS
RESULTS IN A SLIGHT NORTHWARD SHIFT OF THE NEW OFFICIAL TRACK
FORECAST BUT IT STILL LIES SIGNIFICANTLY SOUTH OF THE DYNAMICAL
MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0300Z 14.3N 108.2W    55 KT
 12HR VT     23/1200Z 14.4N 109.7W    55 KT
 24HR VT     24/0000Z 14.4N 111.3W    60 KT
 36HR VT     24/1200Z 14.4N 112.8W    65 KT
 48HR VT     25/0000Z 14.4N 114.2W    65 KT
 72HR VT     26/0000Z 14.4N 117.2W    65 KT
 96HR VT     27/0000Z 14.5N 120.0W    55 KT
120HR VT     28/0000Z 14.5N 123.5W    45 KT
 
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FORECASTER RHOME
 
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