000
WTNT41 KNHC 100833
TCDAT1
TROPICAL DEPRESSION IGOR DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST FRI SEP 10 2010
 
IGOR IS STILL STRONGLY SHEARED WITH THE CENTER LOCATED TO THE EAST
OF A STRONG AND CIRCULAR CONVECTIVE MASS AS OBSERVED IN BOTH
MICROWAVE DATA AND CONVENTIONAL IR IMAGERY. AS WE SPEAK...FIRST
METEOSAT VISIBLE IMAGE CONFIRMED THAT THE CENTER IS EXPOSED BUT
BETTER DEFINED. INITIAL INTENSITY IS KEPT AT 30 KNOTS BUT IT WILL
NOT TAKE MUCH FOR IGOR TO REGAIN TROPICAL STORM STATUS AND IN
FACT...THIS IS EXPECTED TO OCCUR LATER TODAY. THE CYCLONE IS
ESCAPING FROM THE MONSOON-TYPE LOW-LEVEL SOUTHWESTERLY FLOW AND IS
BECOMING EMBEDDED IN THE TRADE WINDS. THIS WOULD RESULT IN LESS
SHEAR AND WILL LEAD TO INTENSIFICATION...AS INDICATED IN THE
OFFICIAL FORECAST. GLOBAL MODELS FORECAST IGOR TO BE A LARGE
HURRICANE OVER THE CENTRAL TROPICAL ATLANTIC BY THE END OF THE
FORECAST PERIOD AND BEYOND.
 
THE INITIAL MOTION IS UNCERTAIN SINCE IT WAS DIFFICULT TO FOLLOW
VARIOUS LOW-LEVEL CENTERS THAT WERE ROTATING AROUND A LARGER GYRE
DURING THE PAST 12 HOURS OR SO. THE BEST ESTIMATE IS 280 DEGREES AT
11 TO 12 KNOTS. THE SUBTROPICAL RIDGE IS FORECAST TO BUILD WESTWARD
AND THIS PATTERN SHOULD STEER IGOR WESTWARD WITH AN INCREASE IN
FORWARD SPEED DURING THE NEXT 3 TO 4 DAYS. BY THE END OF THE
FORECAST PERIOD...IGOR SHOULD BE ON THE SOUTHWESTERN EDGE OF THE
RIDGE AND SHOULD BEGIN TO GAIN MORE LATITUDE. TRACK GUIDANCE
OVERALL IS FAIRLY CONSISTENT IN TAKING IGOR WESTWARD. HOWEVER...A
COUPLE OF MODELS FORECAST A STRONGER SUBTROPICAL RIDGE TO THE NORTH
OF THE CYCLONE...RESULTING IN A MORE PRONOUNCED WESTWARD TRACK. THE
OFFICIAL FORECAST IS HEAVILY BIASED TOWARD THE GFS AND THE ECMWF
MODELS WHICH FORECAST A MODERATE BUT A MORE REALISTIC SUBTROPICAL
RIDGE TO THE NORTH.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 16.0N  29.3W    30 KT
 12HR VT     10/1800Z 16.0N  31.1W    35 KT
 24HR VT     11/0600Z 16.3N  34.2W    40 KT
 36HR VT     11/1800Z 16.5N  37.5W    45 KT
 48HR VT     12/0600Z 16.8N  40.2W    55 KT
 72HR VT     13/0600Z 17.0N  45.0W    65 KT
 96HR VT     14/0600Z 18.0N  49.5W    80 KT
120HR VT     15/0600Z 19.5N  53.5W    90 KT
 
$$
FORECASTER AVILA