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Tropical Storm HILDA


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TROPICAL STORM HILDA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112009
200 AM PDT SUN AUG 23 2009
 
ALTHOUGH THE CIRCULATION CENTER OF HILDA REMAINS PARTIALLY EXPOSED
THIS EVENING...SPIRAL BANDING OVER THE WESTERN PORTION OF THE
CYCLONE HAS BECOME BETTER ORGANIZED.  FURTHERMORE...ENHANCED
INFRARED IMAGERY INDICATES VERY COLD CLOUD TOP TEMPERATURES
ASSOCIATED WITH THE BANDING FEATURE AND A FEW RECENT BURSTS OF DEEP
CONVECTION NEAR THE CENTER.  BASED ON THE IMPROVED CLOUD PATTERN
AND A COMPROMISE OF THE DVORAK INTENSITY ESTIMATES...THE INITIAL
INTENSITY IS RAISED TO 40 KT.  THE OCEANIC ENVIRONMENT IS EXPECTED
TO BE REMAIN FAVORABLE DURING THE FORECAST PERIOD...BUT THE UPPER
WIND PATTERN WILL BE ONLY MARGINALLY CONDUCIVE FOR STRENGTHENING
DUE TO PERSISTENT NORTHEASTERLY SHEAR.  CONSEQUENTLY...THE
INTENSITY FORECAST CALLS FOR GRADUAL INTENSIFICATION DURING THE
NEXT 5 DAYS...SIMILAR TO THE ICON INTENSITY CONSENSUS MODEL.
 
INITIAL MOTION IS ESTIMATED AT 275/8...WITHIN THE DEEP-LAYER
EASTERLY FLOW OF A HIGH PRESSURE TO THE NORTH.  A MID- TO UPPER
LEVEL TROUGH LOCATED A FEW HUNDRED MILES EAST-NORTHEAST OF THE
HAWAIIAN ISLANDS SHOULD CAUSE THE CYCLONE TO SLOW A BIT AND
TURN MORE TOWARD THE WEST-NORTHWEST...AS INDICATED BY THE
GFDL/GFS AND ECMWF...AROUND MID-PERIOD.  AFTERWARD...RIDGING IS
FORECAST TO BUILD NORTHWEST OF HILDA IN RESPONSE TO THE
AFOREMENTIONED TROUGH FILLING AND MOVING NORTHEASTWARD OUT OF THE
AREA.  THIS CHANGE IN THE STEERING PATTERN NEAR DAY 3 IS EXPECTED
TO TURN THE CYCLONE BACK TOWARD THE WEST.  THE OFFICIAL FORECAST IS
CLOSE TO THE PREVIOUS TRACK AND COINCIDES WITH THE DYNAMICAL MODEL
CONSENSUS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 13.7N 139.3W    40 KT
 12HR VT     23/1800Z 13.9N 140.6W    40 KT
 24HR VT     24/0600Z 14.3N 142.2W    45 KT
 36HR VT     24/1800Z 14.6N 144.0W    45 KT
 48HR VT     25/0600Z 14.8N 145.7W    50 KT
 72HR VT     26/0600Z 15.0N 149.0W    50 KT
 96HR VT     27/0600Z 15.0N 152.0W    55 KT
120HR VT     28/0600Z 15.0N 155.0W    55 KT
 
$$
FORECASTER ROBERTS/BROWN
 
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