396 
 WTNT41 KNHC 091459
 TCDAT1
 SUBTROPICAL STORM ANDREA DISCUSSION NUMBER   1
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL012007
 1100 AM EDT WED MAY 09 2007
  
 AN AIR FORCE RECONNAISSANCE PLANE HAS BEEN INVESTIGATING THE LOW
 PRESSURE SYSTEM OFF THE SOUTHEAST U.S. COAST SINCE EARLY THIS
 MORNING.  THE INITIAL LEG OF THE MISSION WAS FLOWN AT 300 MB FROM
 WEST TO EAST OVER THE CIRCULATION CENTER...AND SEVERAL DROPSONDES
 WERE RELEASED.  THE TEMPERATURE PROFILES REVEAL A RATHER FLAT
 THERMAL CROSS-SECTION...NOT INDICATING A DISCERNIBLE WARM OR COLD
 CORE AT ANY VERTICAL LEVEL.  THE WIND PROFILES...HOWEVER...SHOW
 WINDS INCREASING WITH HEIGHT IN THE WESTERN HALF OF THE CIRCULATION
 AND DECREASING WITH HEIGHT IN THE EASTERN HALF.  GOES IMAGERY
 INDICATES THAT...COMPARED TO YESTERDAY...THE THUNDERSTORM ACTIVITY
 HAS CONSOLIDATED CLOSER TO THE CENTER...BUT PRIMARILY IN THE
 EASTERN SEMICIRCLE.  THERE IS ALSO A SLIGHT HINT OF UPPER-LEVEL
 OUTFLOW WHICH WAS COMPLETELY ABSENT YESTERDAY...BUT THE SYSTEM
 REMAINS EMBEDDED WITHIN A LARGE DEEP-LAYER TROUGH.  ALSO...THE
 RADIUS OF MAXIMUM WINDS HAS CONTRACTED FROM MORE THAN 100 N MI
 YESTERDAY TO ABOUT 50-60 N MI THIS MORNING.  BASED ON THE HYBRID
 STRUCTURE OF THE SYSTEM...ADVISORIES ARE BEING INITIATED ON
 SUBTROPICAL STORM ANDREA.  THE 40 KT INITIAL INTENSITY IS BASED ON
 AN EARLY MORNING QUIKSCAT PASS AND RECENT AIRCRAFT DATA FROM 850
 MB.
 
 THE INITIAL MOTION IS SLOW AND GENERALLY WESTWARD...ABOUT 270
 DEGREES AT 4 KT.  SINCE ANDREA IS ESSENTIALLY TRAPPED WITHIN A
 MIDDLE- TO UPPER-LEVEL TROUGH THAT THE DYNAMICAL MODELS FORECAST TO
 NOT MOVE MUCH DURING THE NEXT FEW DAYS...ANDREA WILL PROBABLY
 CONTINUE TO MOVE SLOWLY...BUT IN THE GENERAL DIRECTION OF THE
 NORTHEAST FLORIDA COAST.  THE OFFICIAL FORECAST GENERALLY FOLLOWS
 THE SCENARIO PAINTED BY ALL OF THE MODELS...TAKING THE SYSTEM
 SLOWLY SOUTHWESTWARD AND THEN SOUTHWARD DURING THE NEXT 3 DAYS OR
 SO.  NONE OF THE MODELS BRING ANDREA INLAND...AND NEITHER DOES THE
 OFFICIAL FORECAST.  ANDREA IS CURRENTLY OVER SEA-SURFACE
 TEMPERATURES OF NO MORE THAN ABOUT 25 CELSIUS...AND THEY WILL NOT
 GET ANY WARMER ALONG THE FORECAST TRACK.  THEREFORE A SLOW
 WEAKENING TREND IS ANTICIPATED AND THE OFFICIAL FORECAST SHOWS
 DISSIPATION NEAR THE COAST IN LESS THAN FIVE DAYS.  HOWEVER...SINCE
 ANDREA MIGHT BRING WINDS OF TROPICAL STORM FORCE TO THE COAST...A
 TROPICAL STORM WATCH HAS BEEN ISSUED.
 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      09/1500Z 30.8N  79.3W    40 KT
  12HR VT     10/0000Z 30.6N  79.9W    40 KT
  24HR VT     10/1200Z 30.2N  80.6W    35 KT
  36HR VT     11/0000Z 29.8N  81.0W    35 KT
  48HR VT     11/1200Z 29.6N  81.0W    30 KT
  72HR VT     12/1200Z 29.5N  81.0W    25 KT
  96HR VT     13/1200Z 29.5N  81.0W    25 KT...DISSIPATING
 120HR VT     14/1200Z...DISSIPATED
  
 $$
 FORECASTER KNABB