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