Tropical Storm HILDA

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TROPICAL STORM HILDA DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT SUN AUG 10 2003
 
THE LOW-LEVEL CIRCULATION OF HILDA HAS BECOME EXPOSED ON THE NORTH
SIDE OF THE DEEP CONVECTION. THEREFORE...THE INITIAL POSITION HAS
BEEN ADJUSTED FARTHER NORTH THAN ON THE PREVIOUS ADVISORY. WHILE
THE LOW-LEVEL CENTER HAS BECOME PARTLY EXPOSED...THERE IS ENOUGH
STRONG CONVECTION TO THE SOUTH SUCH THAT SHEAR-PATTERN SATELLITE
ESTIMATES ARE STILL AT 35 KT...BUT JUST BARELY. THEREFORE...HILDA
IS MAINTAINED AS A MINIMAL TROPICAL STORM FOR THIS ADVISORY.

THE INITIAL MOTION ESTIMATE IS 300/13. HOWEVER...A GRADUAL TURN BACK
TOWARD THE WEST IS EXPECTED TO OCCUR IN ABOUT 12 HOURS DUE TO THE
STRONG SUBTROPICAL RIDGE TO THE NORTH PRODUCING MODERATE LOW-LEVEL
EASTERLY STEERING FLOW. THE GFS AND UKMET MODELS TAKE HILDA
SOUTHWESTWARD AFTER 48 HOURS...MAINLY DUE TO SIGNIFICANT WEAKENING
OF THE CYCLONE AND SOME LOW-LEVEL RIDGING FORECAST ALONG 135W IN
THE WAKE OF GUILLERMO. SINCE GUILLERMO IS EXPECTED TO REMAIN STEADY
OR WEAKEN SLIGHTLY...IT IS DOUBTFUL THAT MUCH OF A SYMPATHETIC
RIDGE WILL EXIST BETWEEN THE TWO CYCLONES. THE OFFICIAL FORECAST IS
NORTH OF BUT SIMILAR TO THE PREVIOUS FORECAST TRACK AND CALLS FOR A
WEST-NORTHWESTWARD MOTION FOR THE NEXT 12-24 HOURS...AND THEN A
CONTINUED WESTWARD MOTION AFTER THAT. THIS IS SIMILAR TO THE
CONSENSUS OF THE GFDL AND GFS ENSEMBLE MODELS.

UNLIKE GUILLERMO...THE SHIPS INTENSITY MODEL FORECASTS HILDA TO
SIGNIFICANTLY WEAKEN AFTER 72 HOURS AS THE VERTICAL SHEAR IS
EXPECTED TO INCREASE TO MORE THAN 30 KT AND SSTS DROP FROM 27C DOWN
TO 25C. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
FORECAST AND BASICALLY HOLDS THE INTENSITY STEADY FOR 72 HOURS...
WITH GRADUAL WEAKENING OCCURRING AFTERWARDS. THERE COULD BE SOME
FLUCTUATIONS IN THE INTENSITY DEPENDING ON HOW MUCH AND HOW LONG
ANY CONVECTION DEVELOPS NEAR THE LOW-LEVEL CENTER. HOWEVER...
ENVIRONMENTAL CONDITIONS GENERALLY DO NOT FAVOR MORE THAN A 10 KT
INCREASE...AND ARE ACTUALLY MORE CONDUCIVE FOR WEAKENING TO OCCUR.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0300Z 17.0N 119.6W    35 KT
 12HR VT     11/1200Z 17.3N 121.3W    35 KT
 24HR VT     12/0000Z 17.5N 123.6W    40 KT
 36HR VT     12/1200Z 17.6N 125.8W    40 KT
 48HR VT     13/0000Z 17.7N 128.1W    40 KT
 72HR VT     14/0000Z 17.8N 132.5W    35 KT
 96HR VT     15/0000Z 18.0N 137.0W    30 KT
120HR VT     16/0000Z 18.0N 142.0W    25 KT
 
 
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