Hurricane HILARY

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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
 
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