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 514 
 WTNT43 KNHC 302047
 TCDAT3
 TROPICAL STORM FIONA DISCUSSION NUMBER   1
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
 500 PM EDT MON AUG 30 2010
  
 EARLIER TODAY...ABOUT 30 DROPSONDES WERE RELEASED DURING A G-V
 RESEARCH MISSION BEING CONDUCTED BY THE NATIONAL CENTER FOR
 ATMOSPHERIC RESEARCH NEAR THE AREA OF LOW PRESSURE LOCATED ABOUT
 800 MILES EAST OF THE LESSER ANTILLES.  ONE OF THE DROPSONDES
 MEASURED A SURFACE WIND OF 35 KT APPROXIMATELY 120 N MI TO THE
 NORTHEAST OF THE ESTIMATED CENTER.  THIS MEASUREMENT AGREES WITH AN
 ASCAT PASS FROM 1208 UTC...WHICH SHOWED A SWATH OF 30-35 KT WINDS
 IN THAT SAME AREA.  CONVECTION HAS BEEN A LITTLE THIN FOR MOST OF
 THE DAY...BUT BANDING FEATURES HAVE RECENTLY BECOME MORE PROMINENT
 MAINLY OVER THE WESTERN SEMICIRCLE.  GIVEN THE INCREASE IN
 CONVECTION AND SINCE TROPICAL STORM FORCE WINDS ARE ALREADY
 OCCURRING...THE SYSTEM IS BEING DIRECTLY UPGRADED TO TROPICAL STORM
 FIONA.
 
 SINCE FIONA STILL LACKS SOME ORGANIZATION AND THE WIND FIELD IS
 SOMEWHAT LARGE...THE CYCLONE WILL LIKELY HAVE A DIFFICULT TIME
 INTENSIFYING OVER THE NEXT DAY OR SO.  I DO NOT BELIEVE THIS
 STRUCTURE IS HANDLED WELL BY THE STATISTICAL INTENSITY
 GUIDANCE...WHICH INTENSIFY FIONA TO A HURRICANE IN 36 TO 48
 HOURS...SO I AM INCLINED TO LEAN CLOSER TO THE DYNAMICAL GFDL AND
 HWRF AT THIS POINT.  IN FACT...THE GFS DISSIPATES THE CYCLONE WITHIN
 2 TO 3 DAYS.  THE OFFICIAL FORECAST THEREFORE SHOWS MINIMAL
 STRENGTHENING OVER THE NEXT 1 TO 2 DAYS AND THEN LEVELS OUT THE
 INTENSITY FOR DAYS 3 THROUGH 5...WHEN IT APPEARS THAT INCREASING
 VERTICAL SHEAR COULD BECOME A LIMITING FACTOR. 
 
 THE SURFACE CENTER HAS BEEN A LITTLE DIFFICULT TO LOCATE...AND THE
 INITIAL MOTION IS AN UNCERTAIN 270/21.  TRACK MODEL GUIDANCE IS IN
 GOOD AGREEMENT FOR THE NEXT 48 HOURS AND SHOWS FIONA TURNING TOWARD
 THE NORTHWEST...GENERALLY FOLLOWING EARL AROUND THE WESTERN
 PERIPHERY OF THE SUBTROPICAL RIDGE.  AFTER THAT...THE
 GFDL...HWRF...AND GFS KEEP FIONA AS A WEAK SYSTEM AND SHOW IT
 CONTINUING TO THE NORTH IN THE LOW-LEVEL FLOW BEHIND EARL.  THE
 ECMWF...ON THE OTHER HAND...SHOWS A STRONGER FIONA AND SUGGESTS
 THAT THE SUBTROPICAL RIDGE COULD BUILD BACK TO THE WEST BEFORE THE
 CYCLONE CAN RECURVE.  THE OFFICIAL FORECAST IS VERY CLOSE TO THE
 MODEL CONSENSUS TVCN FOR THE FIRST 48 HOURS BUT THEN LIES A LITTLE
 NORTH OF THE CONSENSUS IN FAVOR OF THE TRACKS OF THE WEAKER GFDL
 AND HWRF.
  
   
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      30/2100Z 14.4N  48.7W    35 KT
  12HR VT     31/0600Z 14.9N  51.9W    35 KT
  24HR VT     31/1800Z 15.8N  55.9W    40 KT
  36HR VT     01/0600Z 17.2N  59.2W    45 KT
  48HR VT     01/1800Z 19.3N  62.0W    45 KT
  72HR VT     02/1800Z 24.0N  66.0W    40 KT
  96HR VT     03/1800Z 27.5N  68.0W    40 KT
 120HR VT     04/1800Z 29.0N  69.0W    40 KT
  
 $$
 FORECASTER BERG
  
 
 
 120 
 WTNT42 KNHC 302047
 TCDAT2
 HURRICANE EARL DISCUSSION NUMBER  22
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
 500 PM AST MON AUG 30 2010
  
 THE RECONNAISSANCE AIRCRAFT MEASURED 116 KT FLIGHT-LEVEL WINDS AND
 108 KT SFMR SURFACE WINDS SHORTLY AFTER 1500 UTC.  THIS WAS THE
 BASIS FOR THE EARLIER INCREASE IN INTENSITY.  SINCE THAT TIME...THE
 PRESSURE HAS CONTINUED TO DROP AND WAS DOWN TO 955 MB ON THE LAST
 DROPSONDE RELEASED IN THE EYE AROUND 1700 UTC.  SINCE THE AIRCRAFT
 DEPARTED EARL...THE EYE HAS CONTINUED TO CLEAR AND IS SURROUNDED BY
 CLOUD TOPS TO -70 DEGREES CELSIUS OR COLDER.  OBJECTIVE SATELLITE
 INTENSITY ESTIMATES HAVE INCREASED TO JUST ABOVE 6.0 ON THE DVORAK
 SCALE AND SUPPORT AN INITIAL INTENSITY OF 115 KT...CATEGORY FOUR ON
 THE SAFFIR-SIMPSON HURRICANE WIND SCALE.
  
 EARL IS EXPECTED TO REMAIN IN A LOW SHEAR ENVIRONMENT AND OVER WARM
 WATER DURING THE NEXT FEW DAYS AND SOME ADDITIONAL STRENGTHENING IS
 LIKELY IN THE SHORT TERM.  THEREAFTER...EYEWALL CYCLES WILL LIKELY
 INDUCE SOME FLUCTUATIONS IN INTENSITY...WHICH ARE DIFFICULT TO
 PREDICT.  THE NHC FORECAST IS AGAIN NEAR THE HIGH END OF THE
 INTENSITY GUIDANCE. AT DAYS 4 AND 5...THE HURRICANE IS FORECAST TO
 MOVE OVER COOLER WATER AND INTO AN AREA OF INCREASING SHEAR WHICH
 SHOULD RESULT IN WEAKENING.
  
 THE INITIAL MOTION IS 290/13.  THE FORECAST REASONING REMAINS
 UNCHANGED AS EARL IS EXPECTED TO TURN NORTHWESTWARD IN ABOUT 24
 HOURS AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. THE
 TRACK GUIDANCE HAS SHIFTED NOTICEABLY WESTWARD DURING THE FIRST
 48 HOURS...WITH THE GFS AND ECMWF ON THE EASTERN EDGE OF THE
 ENVELOPE.  THE OFFICIAL FORECAST HAS BEEN ADJUSTED WESTWARD...
 PRIMARILY THROUGH 72 HOURS...AND LIES BETWEEN THE GFS/ECMWF AND THE
 MULTI-MODEL CONSENSUS.
   
 THIS IS A GOOD TIME TO REMIND EVERYONE THAT NHC AVERAGE TRACK
 FORECAST ERRORS ARE 200 TO 300 MILES AT DAYS 4 AND 5.  GIVEN THIS
 UNCERTAINTY...IT IS TOO SOON TO DETERMINE WHAT PORTION OF THE U.S.
 EAST COAST MIGHT SEE DIRECT IMPACTS FROM EARL.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      30/2100Z 19.3N  64.7W   115 KT
  12HR VT     31/0600Z 20.2N  66.3W   125 KT
  24HR VT     31/1800Z 21.7N  68.1W   130 KT
  36HR VT     01/0600Z 23.4N  70.1W   130 KT
  48HR VT     01/1800Z 25.8N  72.1W   125 KT
  72HR VT     02/1800Z 31.6N  74.7W   115 KT
  96HR VT     03/1800Z 38.0N  71.0W    95 KT
 120HR VT     04/1800Z 45.5N  63.0W    70 KT...INLAND
  
 $$
 FORECASTER BROWN
  
 
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