202 
 WTNT42 KNHC 080832
 TCDAT2
 HURRICANE BERTHA DISCUSSION NUMBER  21
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
 500 AM EDT TUE JUL 08 2008
 
 THE EYE OF THE HURRICANE HAS BECOME A LITTLE LESS DISTINCT OVER THE
 PAST SEVERAL HOURS.  NONETHELESS...BERTHA HAS BEEN MAINTAINING A
 FAIRLY SYMMETRICAL RING OF COLD CLOUD TOPS AROUND THE CENTER. 
 SUBJECTIVE AND OBJECTIVE DVORAK T-NUMBERS HAVE COME DOWN SLIGHTLY
 BUT CURRENT INTENSITY ESTIMATES...BOTH OBJECTIVE AND SUBJECTIVE...
 REMAIN CLOSE TO 105 KT.  HENCE THE ADVISORY INTENSITY IS UNCHANGED. 
 SOME FLUCTUATIONS IN STRENGTH ASSOCIATED WITH EYEWALL REPLACEMENTS
 COULD OCCUR WITHIN THE NEXT 12 HOURS OR SO.  IN THE LONGER-TERM...
 THE ENVIRONMENT IS EXPECTED TO GRADUALLY BECOME LESS CONDUCIVE FOR
 STRENGTHENING AS BERTHA MOVES TOWARDS HIGHER LATITUDES.  THIS IS
 REFLECTED IN THE SHIPS MODEL...WHICH WEAKENS BERTHA TO MINIMAL
 HURRICANE STRENGTH BY 72 HOURS.  THE OFFICIAL INTENSITY FORECAST
 CLOSELY FOLLOWS THE INTENSITY MODEL CONSENSUS ICON.
 
 EYE FIXES GIVE A MOTION ESTIMATE OF 310/9 WHICH IS SLIGHTLY TO THE
 RIGHT OF PREVIOUS ESTIMATES.  GLOBAL MODELS ARE NOW IN FAIRLY GOOD
 AGREEMENT THAT BERTHA WILL HEAD FOR A WEAKNESS IN THE
 MID-TROPOSPHERIC SUBTROPICAL RIDGE AND TURN NORTHWARD LATER IN THE
 FORECAST PERIOD.  IT SHOULD BE NOTED THAT THE GFDL AND HWRF MODELS
 HAVE BEEN CALLING FOR THIS SCENARIO MORE CONSISTENTLY THAN THE
 OTHER GUIDANCE OVER THE PAST COUPLE OF DAYS.  THE OFFICIAL TRACK
 FORECAST IS ADJUSTED EAST OF THE PREVIOUS ONE BUT IS STILL TO THE
 WEST OF MOST OF THE DYNAMICAL MODEL TRACKS AS WELL AS THE MODEL
 CONSENSUS.  BY DAY 5...STEERING CURRENTS COULD BECOME QUITE WEAK
 AND BERTHA MAY MOVE SLOWLY AND ERRATICALLY AS IT WAITS TO BE
 EVENTUALLY PICKED UP BY A TROUGH IN THE WESTERLIES.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      08/0900Z 21.4N  53.3W   105 KT
  12HR VT     08/1800Z 22.2N  54.4W   100 KT
  24HR VT     09/0600Z 23.4N  55.9W    95 KT
  36HR VT     09/1800Z 24.7N  57.4W    90 KT
  48HR VT     10/0600Z 26.0N  58.6W    85 KT
  72HR VT     11/0600Z 28.0N  59.5W    80 KT
  96HR VT     12/0600Z 30.0N  59.5W    75 KT
 120HR VT     13/0600Z 32.0N  59.0W    70 KT
  
 $$
 FORECASTER PASCH
  
 

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