Tropical Storm HERNAN

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TROPICAL STORM HERNAN DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092008
200 AM PDT FRI AUG 08 2008
 
THE CLOUD PATTERN HAS NOT CHANGED VERY MUCH DURING THE PAST SEVERAL
HOURS AND DUE TO SHEAR...THE LOW-LEVEL CENTER STILL APPEARS TO BE
LOCATED ON THE EDGE OF THE DEEP CONVECTION. LATEST MICROWAVE DATA
REVEAL THAT THE LOW- AND MID -LEVEL CENTERS ARE A LITTLE MORE
ALIGNED THAN A FEW HOURS AGO BUT MOST OF THE DEEP CONVECTION REMAINS
SOUTH OF THE CENTER.  THE OUTFLOW IS ESTABLISHED ONLY IN THE
WESTERN SEMICIRCLE.  DVORAK T-NUMBERS HAVE BEEN STEADY FOR ABOUT 18
HOURS SUGGESTING AN INITIAL INTENSITY OF 55 KNOTS. INTENSITY
GUIDANCE IS NOT SHOWING ANY SIGNIFICANT INTENSIFICATION. IN
FACT...MOST OF THE MODELS SUGGEST THAT HERNAN HAS PEAKED ALREADY.
BASED ON CONTINUITY...THE OFFICIAL FORECAST STILL SHOWS A VERY
MODEST STRENGTHENING DURING THE NEXT 24 HOURS BRINGING HERNAN TO
HURRICANE STATUS. THIS IS BECOMING LESS LIKELY TO OCCUR SINCE THE
SHEAR IS NOT RELAXING AS ANTICIPATED. A GRADUAL WEAKENING SHOULD
BEGIN BEYOND 24-36 HOURS AS HERNAN APPROACHES COOLER WATERS.
 
HERNAN HAS BEEN MOVING TOWARD THE WEST OR 270 DEGREES AT 11 KNOTS.
HOWEVER...A WEAKNESS IN THE SUBTROPICAL RIDGE ALONG 130 DEGREES
WEST WILL PROBABLY INDUCE A MORE WEST-NORTHWEST TRACK IN THE NEXT 2
TO 3 DAYS. THEREAFTER...HERNAN IS FORECAST TO WEAKEN AND BECOME
STEERED WESTWARD OR EVEN SOUTH OF DUE WEST BY THE LOW-LEVEL FLOW.
MOST OF THE TRACK GUIDANCE SHOWS THE INITIAL WEST-NORTHWEST TRACK
AND THE TURN TO THE WEST AND WEST-SOUTHWEST BEYOND 96 HOURS...AND
SO DOES THE OFFICIAL FORECAST.
 
THE INITIAL WIND RADII WAS ADJUSTED USING LATEST AVAILABLE QUIKSCAT.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 15.0N 118.9W    55 KT
 12HR VT     08/1800Z 15.1N 120.4W    60 KT
 24HR VT     09/0600Z 15.4N 122.2W    65 KT
 36HR VT     09/1800Z 16.0N 124.0W    55 KT
 48HR VT     10/0600Z 17.0N 125.5W    50 KT
 72HR VT     11/0600Z 18.0N 128.5W    45 KT
 96HR VT     12/0600Z 18.0N 131.5W    30 KT
120HR VT     13/0600Z 17.5N 134.0W    20 KT...REMNANT LOW
 
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FORECASTER AVILA
 
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