354 
 WTNT42 KNHC 072035
 TCDAT2
 HURRICANE BERTHA DISCUSSION NUMBER  19
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
 500 PM EDT MON JUL 07 2008
  
 BERTHA'S SATELLITE PRESENTATION HAS CONTINUED TO IMPROVE THIS
 AFTERNOON WITH A VERY DISTINCT EYE NOW SURROUNDED BY A RING OF COLD
 CLOUD TOPS. SUBJECTIVE DVORAK T NUMBERS WERE UNANIMOUSLY 5.0 BUT
 OBJECTIVE NUMBERS HAVE INCREASED TO 6.0 FOR THE PAST 3 HOURS. THIS
 SUPPORTS AN INITIAL INTENSITY OF 100 KT MAKING BERTHA A MAJOR
 CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE.
 BERTHA'S INTENSIFICATION TO MAJOR HURRICANE TODAY HIGHLIGHTS THE
 DIFFICULTIES OF FORECASTING RAPID INTENSITY CHANGES. IN THE
 SHORT-TERM...SHEAR IS EXPECTED TO BE LOW AND THE INTENSITY WILL BE
 PRIMARILY CONTROLLED BY EYEWALL CYCLES. AS A RESULT...SOME
 FLUCTUATIONS IN INTENSITY ARE LIKELY. IN A DAY OR TWO...THE GFS
 MODEL STILL INDICATES INCREASING SHEAR. THE SHIPS AND LGEM
 STATISTICAL MODELS...WHICH BASE THEIR SHEAR ESTIMATES FROM THE
 GFS...SHOW WEAKENING BEYOND 24 HOURS AND SO DOES THE OFFICIAL
 FORECAST.
  
 BERTHA HAS BEEN MOVING MORE TOWARDS THE NORTHWEST DURING THE LAST
 COUPLE OF HOURS WITH A REDUCTION IN FORWARD SPEED...BOTH INDICATIONS
 THAT THE HURRICANE HAS REACHED THE MUCH-ANTICIPATED WEAKNESS IN THE
 RIDGE.  SINCE BERTHA COULD BE WOBBLING...THE INITIAL MOTION
 ESTIMATE BASED ON A 12 HOUR AVERAGE IS 300/10.  TRACK GUIDANCE
 REMAINS IN GOOD AGREEMENT ON A GRADUAL NORTHWARD TURN DURING THE
 NEXT 2-3 DAYS.  THEREAFTER...GLOBAL MODELS SUGGEST THAT THE
 STEERING CURRENTS COULD BECOME WEAK LEADING TO INCREASED UNCERTAINTY
 IN THE TRACK FORECAST.  EVEN THOUGH THE OFFICIAL FORECAST IS
 SHIFTED A LITTLE TO THE EAST...IT IS STILL WAY TOO SOON TO
 DETERMINE WHETHER OR NOT BERTHA WILL AFFECT BERMUDA.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      07/2100Z 20.1N  52.1W   100 KT
  12HR VT     08/0600Z 20.8N  53.5W   100 KT
  24HR VT     08/1800Z 21.7N  55.4W    95 KT
  36HR VT     09/0600Z 22.9N  57.3W    90 KT
  48HR VT     09/1800Z 24.0N  59.0W    85 KT
  72HR VT     10/1800Z 26.5N  61.5W    80 KT
  96HR VT     11/1800Z 29.0N  62.5W    75 KT
 120HR VT     12/1800Z 31.5N  62.5W    75 KT
  
 $$
 FORECASTER RHOME
  
 
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