000 WTPZ44 KNHC 260847 TCDEP4 HURRICANE HILARY DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092011 200 AM PDT MON SEP 26 2011 THE SATELLITE PRESENTATION OF HILARY HAS DEGRADED SLIGHTLY DURING THE PAST SEVERAL HOURS. THE CENTRAL DENSE OVERCAST IS SOMEWHAT LESS SYMMETRIC AND THE CLOUD PATTERN HAS BECOME A BIT ELONGATED FROM NORTH TO SOUTH. THE INNER CORE CONVECTION HAS BEEN FLUCTUATING IN INTENSITY...WITH CLOUD TOP TEMPERATURES RECENTLY BEGINNING TO COOL AGAIN. DVORAK T-NUMBERS AT 0600 UTC DECREASED TO T5.5 FROM BOTH AGENCIES. BASED UPON THESE DATA AND THE SLIGHTLY LESS ORGANIZED APPEARANCE OF THE HURRICANE...THE INITIAL INTENSITY IS SET TO 105 KT. ALTHOUGH HILARY HAS LOST SOME LATITUDE DURING THE LAST 6-12 HOURS...A LONGER-TERM MOTION FROM RECENT FIXES IS 270/09. GLOBAL MODELS SHOW A WEAKENING DEEP-LAYER RIDGE OVER WEST-CENTRAL MEXICO STEERING HILARY ON A WESTWARD COURSE WITH A DECREASE IN FORWARD SPEED DURING THE NEXT 36 HOURS. IN ABOUT 48 HOURS...THE MODEL GUIDANCE CALLS FOR A RATHER ABRUPT NORTHWARD TURN AS HILARY BEGINS TO DUMBBELL AROUND A CUT-OFF LOW CURRENTLY SEEN IN WATER VAPOR IMAGERY NEAR 26N 132W. MODEL DIFFERENCES IN HOW QUICKLY THIS FEATURE PROGRESSES EASTWARD AND EXACTLY HOW HILARY INTERACTS WITH IT ACCOUNT FOR TRACK FORECAST VARIATIONS AMONGST THE MODELS LATER IN THE PERIOD. THE OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED SLIGHTLY TOWARD THE SOUTH AND IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH 36 HOURS. BEYOND THAT TIME...THE TRACK FORECAST IS ADJUSTED SLIGHTLY TOWARD THE WEST BUT IS RIGHT OF THE MULTI-MODEL AND HFIP CONSENSUS AIDS. FOR THE NEXT 48 HOURS...HILARY IS EXPECTED TO BE IN AN ENVIRONMENT OF GRADUALLY DECREASING SEA SURFACE TEMPERATURES AND LIGHT EASTERLY SHEAR. THE ONLY NEGATIVE FACTOR COULD BE AN ANOMALOUSLY DRY AIR MASS TO THE NORTHWEST WHICH MAY OR MAY NOT BE INGESTED BY HILARY. ON THE ASSUMPTION THAT THE LATTER WILL NOT PRODUCE A PARTICULARLY ADVERSE EFFECT...ONLY A SLOW DECREASE IN STRENGTH IS FORECAST DURING THIS TIME. A RAPID DECAY IS ANTICIPATED AFTER 72 HOURS AS SHIPS MODEL OUTPUT INDICATES AN INCREASE IN SOUTHWESTERLY SHEAR ASSOCIATED WITH THE AFOREMENTIONED CLOSED LOW AND A DRAMATIC COOLING OF THE WATERS ALONG THE FORECAST TRACK. THE NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS IN BEST AGREEMENT WITH A BLEND OF THE SHIPS AND FSSE MODEL OUTPUTS. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 16.9N 112.2W 105 KT 120 MPH 12H 26/1800Z 16.8N 113.5W 100 KT 115 MPH 24H 27/0600Z 16.9N 114.9W 100 KT 115 MPH 36H 27/1800Z 17.0N 116.0W 95 KT 110 MPH 48H 28/0600Z 17.6N 116.6W 90 KT 105 MPH 72H 29/0600Z 19.6N 116.7W 70 KT 80 MPH 96H 30/0600Z 22.6N 116.4W 45 KT 50 MPH 120H 01/0600Z 25.5N 117.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ FORECASTER KIMBERLAIN