000
WTPZ44 KNHC 110834
TCDEP4
HURRICANE HERNAN DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092008
200 AM PDT MON AUG 11 2008
 
AT 0600 UTC...DVORAK INTENSITY ESTIMATES FROM BOTH SAB AND TAFB WERE
UNCHANGED AT 77 KT. SINCE THAT TIME...CLOUD TOP TEMPERATURES HAVE
WARMED AND ADT ESTIMATES HAVE FALLEN. THE INITIAL INTENSITY IS THUS
LOWERED TO 70 KT. GRADUAL WEAKENING IS EXPECTED TO CONTINUE AS
HERNAN MOVES OVER EVEN COOLER WATERS TODAY AND TOMORROW.
THEREAFTER...SSTS ALONG THE FORECAST TRACK BEGIN TO RISE...SO THE
RATE OF DECAY COULD SLOW OR EVEN STOP...AND HERNAN COULD STUBBORNLY
HANG ON TO ITS STATUS AS A TROPICAL CYCLONE FOR SEVERAL DAYS. WHILE
THE OFFICIAL FORECAST CALLS FOR THE CYCLONE TO DEGENERATE INTO A
REMNANT LOW IN 5 DAYS...IT IS POSSIBLE THAT HERNAN WILL REMAIN A
TROPICAL CYCLONE...ALBEIT WEAK...AS IT MOVES INTO THE CENTRAL
PACIFIC.
 
HERNAN HAS STARTED TO TURN TOWARD THE WEST WITH AN INITIAL MOTION
ESTIMATE OF 280/9.  WITH A MIDDLE TO UPPER-LEVEL RIDGE NOW BUILDING
TO THE NORTHWEST OF THE CYCLONE...A TURN TOWARD THE WEST-SOUTHWEST
IS EXPECTED DURING THE NEXT 12-24 HOURS.  BEYOND 96 HOURS...THE
OFFICIAL FORECAST ASSUMES THAT HERNAN WILL BECOME AN INCREASINGLY
SHALLOW CYCLONE RESULTING IN A TURN BACK TOWARD THE WEST UNDER THE
INFLUENCE OF THE LOWER LEVEL EASTERLY FLOW.  TRACK MODELS HAVE NOT
CHANGED SIGNIFICANTLY...AND THE NEW OFFICIAL FORECAST TRACK IS
SIMILAR TO...BUT SLIGHTLY FASTER THAN...THE PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 18.7N 129.3W    70 KT
 12HR VT     11/1800Z 18.7N 130.4W    65 KT
 24HR VT     12/0600Z 18.4N 131.9W    55 KT
 36HR VT     12/1800Z 18.0N 133.2W    45 KT
 48HR VT     13/0600Z 17.5N 134.6W    40 KT
 72HR VT     14/0600Z 16.5N 137.5W    35 KT
 96HR VT     15/0600Z 15.5N 141.0W    30 KT
120HR VT     16/0600Z 15.5N 145.5W    25 KT...REMNANT LOW
 
$$
FORECASTER RHOME