000
WTPZ41 KNHC 071443
TCDEP1
 
HURRICANE IRWIN DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112011
800 AM PDT FRI OCT 07 2011

IRWIN HAS A FAIRLY CIRCULAR CENTRAL DENSE OVERCAST WITH SEVERAL
SURROUNDING CONVECTIVE BANDS...BUT AN EYE IS NOT VISIBLE ON
SATELLITE IMAGES AT THIS TIME.  BASED ON THE DVORAK EMBEDDED CENTER
PATTERN FOR ESTIMATING INTENSITY...THE CURRENT WIND SPEED IS SET TO
75 KT.  ASSUMING THAT THE SYSTEM MOVES ENOUGH SO THAT THE INFLUENCE
OF OCEANIC UPWELLING IS MINIMAL...ADDITIONAL STRENGTHENING IS
ANTICIPATED DURING THE NEXT DAY OR SO.  BEYOND ABOUT 48 HOURS...
INCREASING EASTERLY SHEAR SHOULD CAUSE GRADUAL WEAKENING.  THE
OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE STATISTICAL-DYNAMICAL
GUIDANCE.

THE HURRICANE APPEARS TO HAVE SLOWED DOWN AND THE INITIAL MOTION IS
ESTIMATED TO BE 300/7.  THERE HAS NOT BEEN MUCH CHANGE TO THE TRACK
FORECAST PHILOSOPHY.  IRWIN IS EXPECTED TO TURN TOWARD THE EAST
OVER THE NEXT COUPLE OF DAYS AS IT COMES UNDER THE INFLUENCE OF
BROAD MID- TO LOW-LEVEL WESTERLY FLOW.  THE OFFICIAL TRACK FORECAST
IS MORE OR LESS ALONG THE SAME TRAJECTORY AS THE PREVIOUS ONE...BUT
SLIGHTLY SLOWER.  THIS IS CLOSE TO THE LATEST MULTI-MODEL
CONSENSUS.  AS HAS BEEN THE CASE IN PREVIOUS RUNS...THE GFS IS
FASTER THAN THE OFFICIAL FORECAST AND MOST OF THE OTHER DYNAMICAL
MODELS.

THE WIND RADII HAVE BEEN ADJUSTED USING DATA FROM AN EARLIER ASCAT
PASS WHICH SHOWS THE CYCLONE TO BE SMALLER THAN PREVIOUSLY
ESTIMATED OVER THE NORTHERN SEMICIRCLE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 13.9N 120.4W   75 KT  85 MPH
 12H  08/0000Z 14.2N 120.7W   80 KT  90 MPH
 24H  08/1200Z 14.6N 120.6W   90 KT 105 MPH
 36H  09/0000Z 14.7N 120.2W   90 KT 105 MPH
 48H  09/1200Z 14.7N 119.5W   90 KT 105 MPH
 72H  10/1200Z 14.9N 117.0W   80 KT  90 MPH
 96H  11/1200Z 15.5N 113.0W   75 KT  85 MPH
120H  12/1200Z 16.5N 109.0W   70 KT  80 MPH
 
$$
FORECASTER PASCH