000
WTNT41 KNHC 201439
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  50
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST MON SEP 20 2010
 
STRONG SOUTHERLY SHEAR HAS DISPLACED ALL OF THE DEEP CONVECTION TO
THE NORTH OF THE EXPOSED LOW-LEVEL CENTER.  THERE HAVE BEEN NO
RECENT OBSERVATIONS NEAR THE CENTER OF IGOR...BUT SATELLITE
INTENSITY ESTIMATES SUPPORT AN INTENSITY AT OR JUST BELOW 65 KT.
THE INTENSITY WILL BE HELD AT 65 KT...AND IT IS POSSIBLE THAT IGOR
COULD REGAIN A LITTLE BIT OF STRENGTH AS IT BEGINS TO GO THROUGH
EXTRATROPICAL TRANSITION.  THAT PROCESS IS EXPECTED TO BE COMPLETE
BY 36 HOURS WHEN IGOR SHOULD BE COMPLETELY EMBEDDED WITHIN A
FRONTAL ZONE.  THE OFFICIAL FORECAST SHOWS SOME RE-STRENGTHENING
DURING THE FIRST 24 HOURS AND GRADUAL WEAKENING FROM 36-96 HOURS. 
THE CYCLONE IS EXPECTED TO DISSIPATE BY 120 HOURS.  THIS FORECAST
IS MORE OR LESS A BLEND OF DYNAMICAL GUIDANCE AND GUIDANCE PROVIDED
BY THE OCEAN PREDICTION CENTER.

IGOR CONTINUES TO ACCELERATE TO THE NORTH-NORTHEAST WITH A MOTION OF
025/21.  THERE IS LITTLE SPREAD IN THE TRACK GUIDANCE DURING THE
NEXT 36 HOURS...AND THE OFFICIAL TRACK FORECAST ONLY HAD TO BE
SHIFTED A SMALL DISTANCE TO THE WEST OF THE PREVIOUS FORECAST. 
AFTER 36 HOURS...THERE IS MORE SPREAD IN THE GUIDANCE...BUT THE
BULK OF THE MODELS SHOW POST-TROPICAL IGOR TURNING NORTHWESTWARD
TOWARD GREENLAND.  THE NHC FORECAST BY 96 HOURS IS TO THE WEST OF
THE MODEL CONSENSUS TO PUT MORE WEIGHT ON THE GLOBAL MODELS AND
LESS ON THE GFDL.

THE OCEAN PREDICTION CENTER ALSO PROVIDED THE CURRENT 12-FOOT SEAS
RADII AND THE WIND RADII DURING THE EXTRATROPICAL PHASE...ALL OF
WHICH HAVE BEEN EXPANDED IN THIS ADVISORY PACKAGE.  IGOR WILL
CONTINUE TO BE A LARGE CYCLONE AS IT MOVES PAST NEWFOUNDLAND TOWARD
GREENLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1500Z 36.1N  63.3W    65 KT
 12HR VT     21/0000Z 38.9N  60.6W    70 KT
 24HR VT     21/1200Z 42.9N  55.0W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/0000Z 46.8N  48.9W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/1200Z 50.4N  44.0W    60 KT...POST-TROP/EXTRATROP
 72HR VT     23/1200Z 56.5N  40.5W    55 KT...POST-TROP/EXTRATROP
 96HR VT     24/1200Z 62.5N  47.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     25/1200Z...DISSIPATED
 
$$
FORECASTER BERG