601 
 WTNT42 KNHC 140258
 TCDAT2
 TROPICAL STORM BERTHA DISCUSSION NUMBER  44
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
 1100 PM EDT SUN JUL 13 2008
 
 IT APPEARS THAT BERTHA IS TAPPING LIGHTLY ON THE ACCELERATOR...WITH
 AN INITIAL MOTION ESTIMATE OF 335/3.  MOST OF THE MODELS FORECAST A
 GRADUAL INCREASE IN BERTHA'S FORWARD SPEED WITH A SUBTLE TURN TO
 THE RIGHT DURING THE NEXT COUPLE OF DAYS...AROUND A WEAK MID-LEVEL
 HIGH CURRENTLY JUST EAST OF THE STORM.  BY THAT TIME THE MODELS
 FORECAST BERTHA TO BE NORTH OF THE RIDGE...AND IN BETWEEN A
 MID-LATITUDE TROUGH NEAR THE NORTHEAST U.S. COAST AND A CUTOFF LOW
 OVER THE CENTRAL NORTH ATLANTIC.  BERTHA AND THE CUTOFF LOW ARE
 THEN FORECAST TO INTERACT WITH ONE ANOTHER IN A POTENTIALLY COMPLEX
 MANNER ON DAYS 3 THROUGH 5...ALTHOUGH A GENERALLY EASTWARD MOTION
 WITHIN THE MID-LATITUDE WESTERLIES IS IMPLIED BY THE MODEL
 CONSENSUS.  THE UNUSUAL UNDULATIONS IN THE OFFICIAL TRACK BEYOND 48
 HOURS ARE SUPPORTED BY ALL OF THE DYNAMICAL MODELS...BUT THE DIPS
 AND TURNS IN THE MODEL TRACKS ARE A BIT MORE EXTREME THAN SHOWN IN
 THE OFFICIAL FORECAST.  THERE IS ALSO GREAT DISAGREEMENT IN THE
 GUIDANCE ON THE FORWARD SPEED OF BERTHA DURING THAT TIME
 FRAME...BUT THE FIVE-DAY CONSENSUS POINT IS NOT FAR FROM THAT IN
 THE PREVIOUS ADVISORY...SO ON BALANCE THE NEW TRACK IS NOT THAT
 MUCH OF A CHANGE.
 
 I HAVE NO SOLID REASON TO ALTER THE INITIAL INTENSITY OF 55 KT...AS
 THE SUBJECTIVE DVORAK ESTIMATES HAVE NOT CHANGED MUCH...AND A
 QUIKSCAT OVERPASS AROUND 23Z ONLY CAPTURED THE WESTERN HALF OF THE
 CIRCULATION.  CLOUD TOPS OF THE OUTER BANDS HAVE WARMED DURING THE
 PAST FEW HOURS...BUT IF ANYTHING THE CONVECTION NEAR THE CENTER HAS
 INCREASED EVER SO SLIGHTLY.  A CONSENSUS OF THE VARIOUS INTENSITY
 MODELS DOES NOT SUGGEST MUCH CHANGE IN BERTHA'S STRENGTH DURING THE
 NEXT SEVERAL DAYS AS IT PASSES OVER GRADUALLY COOLER SEA-SURFACE
 TEMPERATURES.  THE NEW OFFICIAL FORECAST HOLDS ON TO THE CURRENT
 INTENSITY THROUGH 36 HOURS AND ONLY SHOWS A SLIGHTLY WEAKER SYSTEM
 BEYOND THAT TIME.  THIS FORECAST IS VERY CLOSE TO THE SHIPS AND
 LGEM...BUT STILL BELOW THE GFDL AND HWRF THAT FORECAST BERTHA TO
 AGAIN BECOME A HURRICANE.  WHILE THAT POSSIBILITY CANNOT BE RULED
 OUT...IT APPEARS TO BE THE LESS LIKELY OPTION...ESPECIALLY GIVEN
 THE CONVOLUTED STATE OF BERTHA'S INNER CORE.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      14/0300Z 30.5N  63.1W    55 KT
  12HR VT     14/1200Z 31.5N  63.5W    55 KT
  24HR VT     15/0000Z 33.0N  63.6W    55 KT
  36HR VT     15/1200Z 34.6N  63.1W    55 KT
  48HR VT     16/0000Z 35.8N  62.0W    50 KT
  72HR VT     17/0000Z 35.5N  59.5W    50 KT
  96HR VT     18/0000Z 34.5N  56.5W    50 KT
 120HR VT     19/0000Z 35.5N  53.0W    50 KT
  
 $$
 FORECASTER KNABB
  
 
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This page was last modified on: , 21 2010 - 2314 UTC
Send comments to: Ryan Lyman