487 
 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