107 
 WTNT41 KNHC 090837
 TCDAT1
 TROPICAL STORM IGOR DISCUSSION NUMBER   4
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
 500 AM AST THU SEP 09 2010
  
 THE CLOUD PATTERN HAS DETERIORATED DURING THE PAST 6 HOURS AND
 CONTINUES TO BE HIGHLY SHEARED.  NEITHER SATELLITE INTENSITY
 ESTIMATES NOR ASCAT MEASUREMENTS SUPPORT TROPICAL STORM INTENSITY.
 THE INITIAL INTENSITY HAS BEEN ADJUSTED DOWN TO 35 KNOTS AND THIS
 ESTIMATE IS GENEROUS. IGOR COULD WEAKEN A LITTLE MORE TODAY BUT
 GIVEN THAT THE CYCLONE STILL HAS A LARGE CIRCULATION AND IS MOVING
 TOWARD A MORE FAVORABLE ENVIRONMENT OF LOWER SHEAR AND WARMER
 OCEAN...A GRADUAL STRENGTHENING COULD BEGIN IN 24 HOUR OR SO.  IGOR
 IS STILL FORECAST TO BECOME A HURRICANE IN ABOUT 3 DAYS.
  
 FIRST VISIBLE SATELLITE IMAGES INDICATE THAT THE CENTER IS STILL
 LOCATED SOUTH OF THE CAPE VERDE ISLANDS SUGGESTING THAT IGOR HAS
 BEEN MEANDERING DURING THE PAST FEW HOURS. HOWEVER...THE LARGE
 CIRCULATION SHOULD BEGIN TO MOVE SLOWLY TOWARD THE WEST-NORTHWEST
 LATER TODAY. THE STEERING PATTERN OVER THE ATLANTIC HAS BEEN QUITE
 PERSISTENT AND CONSISTS OF A SUBTROPICAL RIDGE OVER THE EASTERN
 PART OF THE BASIN AND A BROAD TROUGH OSCILLATING BETWEEN THE
 EASTERN UNITED STATES AND THE WESTERN PORTION OF THE BASIN. THIS
 STEERING PATTERN WHICH IS FORECAST BY THE GLOBAL MODELS TO
 CONTINUE...WOULD FAVOR A GENERAL WESTWARD MOTION WITH AN INCREASE
 IN FORWARD SPEED DURING THE NEXT DAY OR TWO AND THEN A TURN MORE TO
 THE WEST-NORTHWEST BY THE END OF THE FORECAST PERIOD. TRACK
 GUIDANCE DEPICTS THIS SCENARIO WHICH IS REFLECTED IN THE OFFICIAL
 FORECAST.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      09/0900Z 13.8N  24.3W    35 KT
  12HR VT     09/1800Z 14.0N  25.3W    30 KT
  24HR VT     10/0600Z 15.0N  28.0W    40 KT
  36HR VT     10/1800Z 16.0N  31.0W    45 KT
  48HR VT     11/0600Z 16.5N  34.0W    55 KT
  72HR VT     12/0600Z 17.0N  40.0W    65 KT
  96HR VT     13/0600Z 18.0N  44.5W    75 KT
 120HR VT     14/0600Z 19.5N  49.0W    85 KT
  
 $$
 FORECASTER AVILA