Hurricane HILARY

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HURRICANE HILARY DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092011
200 AM PDT WED SEP 28 2011
 
HILARY CONTINUES TO STEADILY WEAKEN. THOUGH RECENT MICROWAVE IMAGERY
INDICATES THAT THE EYEWALL IS STILL IN TACT...THE ORGANIZATION OF
THE CLOUD PATTERN HAS DECREASED FURTHER DURING THE LAST FEW HOURS.
THE CENTRAL DENSE OVERCAST HAS BECOME MORE RAGGED IN APPEARANCE AND
THE COVERAGE OF DEEP CONVECTION IS GRADUALLY DECREASING. A BLEND OF
THE LATEST DVORAK T AND CI NUMBERS SUPPORT LOWERING THE INTENSITY
TO 80 KT. ALTHOUGH THE VERTICAL SHEAR IS STILL NEGLIGIBLY
LOW...HILARY IS MOVING ALONG A SHARP GRADIENT OF DECREASING SEA
SURFACE TEMPERATURES AND SHOULD CROSS THE 26C-ISOTHERM WITHIN ABOUT
18 HOURS. THIS SHOULD PROMOTE A CONTINUED...STEADY WEAKENING. THE
RATE OF DECAY SHOULD ACCELERATE AFTER 24 HOURS AS SOUTHWESTERLY
SHEAR IS FORECAST TO SUDDENLY INCREASE AND THE CYCLONE INGESTS AN
INCREASINGLY COOLER AND MORE STABLE LOW-LEVEL AIR MASS. THE NHC
INTENSITY FORECAST IS A LITTLE LOWER THAN THE PREVIOUS ONE AND IS
IN GOOD AGREEMENT WITH THE SHIPS/LGEM MODELS THROUGH 24 HOURS AND
THE FSSE GUIDANCE BEYOND THAT TIME.

THE EYE OF HILARY APPEARS TO HAVE JOGGED A BIT TO THE LEFT IN RECENT
HOURS...WITH A LONGER-TERM AVERAGE OF RECENT CENTER FIXES YIELDING
AN INITIAL MOTION ESTIMATE OF 305/06. THE MODEL GUIDANCE IS IN GOOD
AGREEMENT WITH THE SYNOPTIC STEERING PATTERN. HILARY SHOULD TURN
TOWARD THE NORTH-NORTHWEST AND THEN THE NORTH VERY SOON AS IT MOVES
FARTHER INTO A WEAKNESS IN THE SUBTROPICAL RIDGE OVER MEXICO...
CREATED BY A MID-LEVEL TROUGH EXTENDING SOUTHWESTWARD FROM BAJA
CALIFORNIA. THE APPROACH OF AN UPPER-LEVEL LOW CURRENTLY NEAR
27N128W SHOULD THEN CAUSE THE TRACK TO BEND CYCLONICALLY DURING THE
NEXT 24-72 HOURS. AFTER BECOMING A REMNANT LOW...GLOBAL MODELS SHOW
POST-TROPICAL HILARY TURNING WESTWARD OR EVEN SOUTHWESTWARD IN THE
LOW-LEVEL FLOW. THE NEW NHC TRACK FORECAST IS NUDGED SLIGHTLY TO
THE LEFT AND IS A BIT FASTER THAN THE PREVIOUS ONE...BUT REMAINS
CLOSE TO THE MULTI-MODEL AND HFIP CONSENSUS AIDS.

A SIGNIFICANT ADJUSTMENT HAS BEEN MADE TO THE WIND RADII BASED UPON
DATA FROM A 0528 UTC ASCAT OVERPASS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/0900Z 17.7N 118.1W   80 KT  90 MPH
 12H  28/1800Z 18.4N 118.4W   70 KT  80 MPH
 24H  29/0600Z 19.6N 118.7W   60 KT  70 MPH
 36H  29/1800Z 20.8N 118.8W   45 KT  50 MPH
 48H  30/0600Z 22.0N 119.1W   30 KT  35 MPH
 72H  01/0600Z 24.0N 120.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/0600Z 25.0N 120.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/0600Z 25.0N 121.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER KIMBERLAIN
 
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