Tropical Storm HERNAN

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TROPICAL STORM HERNAN DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092008
200 AM PDT TUE AUG 12 2008
 
NEARLY ALL OF THE DEEP CONVECTION HAS DISSIPATED...AND HERNAN NOW
CONSISTS OF A SWIRL OF LOW CLOUDS WITH SOME MID-LEVEL DEBRIS
CLOUDINESS.  IN ADDITION...MICROWAVE IMAGES SUGGEST THE LOW-LEVEL
CIRCULATION HAS BECOME DETACHED FROM THE MID-LEVEL CIRCULATION.
BOTTOM LINE...HERNAN HAS FINALLY SUCCUMBED TO COOL WATERS AND IS
RAPIDLY WEAKENING.  AN EARLIER QUIKSCAT PASS AT 0328 UTC SUGGESTED
THAT THE INTENSITY WAS NEAR 50 KT AT THAT TIME.  GIVEN THE LACK OF
DEEP CONVECTION...THE INITIAL INTENSITY IS SET JUST BELOW THAT
ESTIMATE AT 45 KT.  CONTINUED WEAKENING IS FORECAST DURING THE NEXT
SEVERAL DAYS AS THE CIRCULATION GRADUALLY SPINS DOWN...AND HERNAN
IS EXPECTED TO WEAKEN TO A TROPICAL DEPRESSION DURING THE NEXT DAY
OR SO.  IN FACT...IF HERNAN CANNOT GENERATE NEW CONVECTION
SOON...IT COULD WEAKEN FASTER THAN WHAT IS SHOWN IN THE OFFICIAL
FORECAST.  
 
A SERIES OF MICROWAVE PASSES SUGGEST THAT HERNAN IS MOVING JUST
SOUTH OF DUE WEST OR 265/08.  A TURN TOWARD THE WEST-SOUTHWEST IS
EXPECTED LATER TODAY AS THE INCREASINGLY SHALLOW CYCLONE IS STEERED
BY THE LOW-LEVEL FLOW.  TRACK GUIDANCE REMAINS IN GOOD AGREEMENT...
AND THE NEW OFFICIAL TRACK FORECAST IS ESSENTIALLY AN UPDATE OF THE
PREVIOUS ONE. 

THE WIND RADII HAVE BEEN ADJUSTED BASED ON A RECENT QUIKSCAT
PASS...AND THE RADIUS OF 12 FT SEAS HAVE BEEN DECREASED BASED ON
ESTIMATES PROVIDED BY THE TROPICAL ANALYSIS AND FORECAST BRANCH. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0900Z 18.5N 132.7W    45 KT
 12HR VT     12/1800Z 18.3N 134.0W    40 KT
 24HR VT     13/0600Z 17.8N 135.4W    35 KT
 36HR VT     13/1800Z 17.3N 137.0W    30 KT
 48HR VT     14/0600Z 16.7N 138.6W    25 KT...REMNANT LOW
 72HR VT     15/0600Z 15.5N 142.5W    25 KT...REMNANT LOW
 96HR VT     16/0600Z 15.0N 146.5W    25 KT...REMNANT LOW
120HR VT     17/0600Z 15.0N 151.0W    20 KT...REMNANT LOW
 
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FORECASTER RHOME
 
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