Tropical Storm HILARY

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TROPICAL STORM HILARY DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 AM PDT SAT AUG 20 2005
 
HILARY HAS CONTINUED TO BECOME BETTER ORGANIZED DURING THE PAST 6
HOURS WITH INCREASED BANDING FEATURES AND A SMALL CDO-LIKED FEATURE
...WITH TOPS TO -80C AND COLDER...DEVELOPING NEAR AND TO THE SOUTH
OF THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL INTENSITY HAS BEEN
INCREASED TO 40 KT BASED SATELLITE INTENSITY ESTIMATES OF 45 KT...
35 KT...AND 25 KT FROM TAFB...SAB...AND AFWA...RESPECTIVELY...AND
THE SMALL CDO-LIKE FEATURE THAT HAS FORMED SINCE 0615Z.
 
THE INITIAL MOTION ESTIMATE IS 275/16...BASED ON MICROWAVE POSITION
ESTIMATES DURING THE PAST 5 HOURS. THIS MOTION AND INITIAL POSITION
ARE A LITTLE SOUTH OR LEFT OF THE PREVIOUS TRACKS AND POSITIONS.
OTHER THAN THAT...THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS
FORECAST TRACKS OR REASONINGS. HILARY IS EXPECTED TO TRACK AROUND
THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE THAT
EXTENDS EAST-WEST ACROSS MEXICO. THE MOTION OVER THE NEXT 24 HOURS
OR SO COULD BE MORE WESTWARD...BUT THE CYCLONE IS GRADUALLY
EXPECTED TO TURN WEST-NORTHWESTWARD IN THE 24-72H PERIOD...AND THEN
TURN NORTHWESTWARD AT SPEEDS LESS THAN 10 KT AFTER THAT AS A STRONG
MID-LATITUDE TROUGH DIGS SOUTHEASTWARD OFF THE CALIFORNIA COAST AND
ERODES THE RIDGE TO THE NORTH OF HILARY. THE OFFICIAL FORECAST IS
SIMILAR TO THE PREVIOUS TRACK AND THE NHC MODEL CONSENSUS.
 
THE SHIPS INTENSITY MODEL INDICATES NORTHEASTERLY SHEAR OF 10-15 KT
IS EXPECTED TO AFFECT THE CYCLONE THROUGH 72 HOURS. USUALLY SUCH
MODERATE SHEAR CONDITIONS ARE NOT CONDUCIVE TO RAPID STRENGTHENING
...BUT A NORMAL INTENSIFICATION RATE OF 20 KT PER 24 HOURS SEEMS
REASONABLE GIVEN THE HIGH SSTS AND VERY MOIST MID-LEVELS. THE
OFFICIAL FORECAST IS CLOSE TO THE SHIPS MODEL...BUT HIGHER THAN THE
GFDL...WHICH ONLY BRINGS HILARY UP TO 70 KT IN 84 HOURS.
 
RAINBANDS PRODUCING GUSTY WINDS AND LOCALLY HEAVY RAINFALL WILL
AFFECT PORTIONS OF THE SOUTHWESTERN COAST OF MEXICO FROM PUERTO
ESCONDIDO WESTWARD TO ZIHUATANEJO DURING THE NEXT DAY OR TWO.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 13.7N 100.6W    40 KT
 12HR VT     20/1800Z 14.0N 102.8W    50 KT
 24HR VT     21/0600Z 14.6N 105.4W    60 KT
 36HR VT     21/1800Z 15.5N 107.8W    70 KT
 48HR VT     22/0600Z 16.4N 109.9W    80 KT
 72HR VT     23/0600Z 18.0N 113.0W    80 KT
 96HR VT     24/0600Z 19.5N 115.5W    75 KT
120HR VT     25/0600Z 21.5N 117.5W    60 KT

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