000
WTPZ44 KNHC 282041
TCDEP4
 
HURRICANE HILARY DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092011
200 PM PDT WED SEP 28 2011
 
A NOAA HURRICANE HUNTER AIRCRAFT ON A RESEARCH MISSION HAS FOUND
THAT THE MAXIMUM WINDS IN HILARY REMAIN AROUND 70 KT...BASED ON A
PEAK SFMR WIND OF 68 KT AND A FLIGHT-LEVEL WIND MAXIMUM OF 82 KT.
THE CENTRAL PRESSURE OF 980 MB IS BASED ON A DROPSONDE MEASUREMENT
OF 982 MB WITH 17 KT OF WIND AT THE SURFACE. HILARY IS CURRENTLY
MOVING ACROSS THE 26C ISOTHERM...AND THE COMBINATION OF MUCH COOLER
WATERS AND INCREASING VERTICAL SHEAR WILL LEAD TO RAPID WEAKENING
AS THE MID-LEVEL CIRCULATION SHEARS OFF AND LEAVES THE LOW-LEVEL
CIRCULATION BEHIND OVER THE NEXT DAY OR TWO. BY 48 HOURS THE
CYCLONE SHOULD BECOME A REMNANT LOW AS IT MOVES OVER SUB-23C
WATERS. GLOBAL MODEL FIELDS SHOW THAT THE REMNANT LOW WILL
DISSIPATE BY 96 HOURS...OR POSSIBLY SOONER. THE NHC FORECAST IS IN
GOOD AGREEMENT WITH THE LGEM THROUGH DISSIPATION.
 
THE AIRCRAFT FIXED THE CENTER A LITTLE TO THE LEFT OF THE PREVIOUS
FORECAST TRACK...AND THE INITIAL MOTION ESTIMATE IS 325/07. HILARY
SHOULD TURN TOWARD THE NORTH-NORTHWEST BY TONIGHT AND CONTINUE ON
THAT HEADING FOR THE NEXT COUPLE OF DAYS AS IT IS PULLED NORTHWARD
BY A MID-LEVEL LOW MOVING SOUTHWARD ALONG 128W. AS THE CYCLONE
SHEARS APART...THE LOW-LEVEL CENTER WILL TURN TOWARD THE WEST AND
THEN SOUTH OF DUE WEST ON DAYS 3 AND 4 AS IT COMES UNDER THE
INFLUENCE OF THE LOW-LEVEL SUBTROPICAL RIDGE. THE TRACK GUIDANCE
HAS SHIFTED AGAIN TOWARD THE WEST FOR THIS CYCLE...AND THE OFFICIAL
FORECAST HAS BEEN ADJUSTED IN THAT DIRECTION. THE NHC TRACK LIES A
LITTLE TO THE RIGHT OF THE MULTI-MODEL CONSENSUS THROUGH 48 HOURS
AND IS A LITTLE TO THE RIGHT OF THE FASTER ECMWF MODEL AFTER THAT
TIME.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/2100Z 19.0N 118.9W   70 KT  80 MPH
 12H  29/0600Z 19.8N 119.4W   60 KT  70 MPH
 24H  29/1800Z 21.0N 120.0W   50 KT  60 MPH
 36H  30/0600Z 22.1N 120.5W   40 KT  45 MPH
 48H  30/1800Z 23.2N 121.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  01/1800Z 24.5N 123.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/1800Z 23.5N 125.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN