000
WTPZ44 KNHC 261436
TCDEP4

HURRICANE HILARY DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092011
800 AM PDT MON SEP 26 2011

THE SATELLITE PRESENTATION OF HILARY HAS MADE A BIT OF A COMEBACK
OVER THE PAST FEW HOURS...WITH CLOUD TOP TEMPERATURES COOLING
AROUND A CONTRACTING EYE. BASED ON A BLEND OF THE LATEST SUBJECTIVE
AND OBJECTIVE DVORAK ESTIMATES...THE INITIAL INTENSITY IS RAISED TO
110 KT. RECENT MICROWAVE IMAGERY SUGGESTS THAT HILARY MAY HAVE
UNDERGONE AN EYEWALL REPLACEMENT CYCLE OVERNIGHT...AND ADDITIONAL
EYEWALL CYCLES ARE STILL POSSIBLE OVER THE NEXT DAY OR SO. OUTSIDE
OF THESE INNER-CORE PROCESSES...ALL OF THE GUIDANCE SUGGESTS THAT
SLOW WEAKENING IS IN ORDER OVER THE NEXT DAY OR TWO. THAT TREND IS
REFLECTED IN THE OFFICIAL FORECAST...WHICH IS CLOSE TO THE
INTENSITY CONSENSUS THROUGH 48 HOURS. BY 72 HOURS...HILARY WILL
BEGIN MOVING ACROSS MUCH COOLER WATERS AND INTO AN ENVIRONMENT OF
INCREASING SHEAR...WHICH SHOULD RESULT IN RAPID WEAKENING. AT DAYS
3 THROUGH 5 THE NHC FORECAST IS A LITTLE LOWER THAN THE LGEM MODEL
GIVEN THE VERY UNFAVORABLE ENVIRONMENT.

THE INITIAL MOTION ESTIMATE IS 265/09...AS HILARY CONTINUES TO BE
STEERED WESTWARD BY THE WEAKENING MID-LEVEL RIDGE ITS NORTH. THIS
RIDGE WILL CONTINUE WEAKENING OVER THE NEXT COUPLE OF DAYS...WHICH
SHOULD RESULT IN A DECREASE IN FORWARD SPEED AND A GRADUAL TURN
TOWARD THE WEST-NORTHWEST BY 36 HOURS. AFTER THAT TIME A SHARP
NORTHWARD TURN IS INDICATED BY ALL OF THE GUIDANCE AS HILARY BEGINS
TO INTERACT WITH A MID-LEVEL LOW CURRENTLY LOCATED NEAR 27N 132W.
THIS LOW IS FORECAST TO INTENSIFY AND MOVE EASTWARD TO A POSITION
JUST WEST OF HILARY IN 3 OR 4 DAYS. THE BIGGEST CHANGE IN THE
GUIDANCE THIS CYCLE IS AN EASTWARD SHIFT OF THE GFS AT DAYS 4 AND
5...AS THAT MODEL SHOWS A WEAKER MID-LEVEL RIDGE OVER THE
SOUTHWESTERN UNITED STATES DURING THAT TIME. THIS MORE EASTWARD
TRACK PUTS THE GFS WELL TO THE RIGHT OF THE REST OF THE DYNAMICAL
GUIDANCE...INCLUDING THE GFS ENSEMBLE MEAN AND MOST OF THE ECMWF
ENSEMBLE MEMBERS. GIVEN THIS LARGE SHIFT...I PREFER TO WAIT FOR THE
FULL SUITE OF 12Z GLOBAL MODEL GUIDANCE BEFORE MAKING ANY
SIGNIFICANT ADJUSTMENTS TO THE TRACK FORECAST. THE NEW NHC TRACK IS
ESSENTIALLY AN UPDATE OF THE PREVIOUS ONE AND LIES A BIT TO THE
EAST OF THE TVCE CONSENSUS THROUGH THE PERIOD...AND IS BETWEEN THE
ECMWF MODEL AND THE GFS ENSEMBLE MEAN AT DAYS 3 THROUGH 5.

THE INITIAL WIND RADII WERE ADJUSTED BASED ON A 0430 UTC ASCAT PASS
AND RECENT AMSU WIND RADII ANALYSES.


FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 16.7N 113.1W  110 KT 125 MPH
 12H  27/0000Z 16.8N 114.3W  105 KT 120 MPH
 24H  27/1200Z 16.9N 115.6W  100 KT 115 MPH
 36H  28/0000Z 17.3N 116.4W   95 KT 110 MPH
 48H  28/1200Z 18.1N 116.7W   90 KT 105 MPH
 72H  29/1200Z 20.4N 116.7W   70 KT  80 MPH
 96H  30/1200Z 23.5N 116.5W   45 KT  50 MPH
120H  01/1200Z 26.5N 117.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER BRENNAN