684 
 WTPZ44 KNHC 090253
 TCDEP4
 HURRICANE HERNAN DISCUSSION NUMBER  10
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP092008
 800 PM PDT FRI AUG 08 2008
  
 HERNAN NOW HAS A PERSISTENT CLOUD-FILLED EYE EMBEDDED IN A
 WELL-DEFINED CENTRAL DENSE OVERCAST...WITH MICROWAVE IMAGERY
 INDICATING THE EYE IS ABOUT 25 N MI WIDE.  AT 00Z...SATELLITE
 INTENSITY ESTIMATES FROM TAFB AND SAB WERE 77 KT.  SINCE THAT
 TIME...THE EYE HAS BECOME BETTER DEFINED AND THE AREA OF COLD CLOUD
 TOPS AROUND IT HAS EXPANDED.  BASED ON THIS...THE INITIAL INTENSITY
 IS INCREASED TO 80 KT.  THE CIRRUS OUTFLOW IS GOOD TO EXCELLENT IN
 THE WESTERN SEMICIRCLE AND POOR TO NONE ELSEWHERE.
  
 HERNAN HAS TURNED TO THE RIGHT DURING THE PAST FEW HOURS AND THE
 INITIAL MOTION IS NOW 285/10.  WATER VAPOR IMAGERY CONTINUES TO
 SHOW A LARGE MID/UPPER-LEVEL TROUGH OVER THE AREA NORTH OF 20N
 BETWEEN 130-145W...AND WHAT APPEARS TO BE A SMALL MID/UPPER-LEVEL
 ANTICYCLONE NEAR 21N 121W.  THE LATTER FEATURE REMAINS POORLY-
 RESOLVED IN THE LATEST LARGE-SCALE MODEL RUNS...WHICH AGAIN TURN
 HERNAN MORE TO THE RIGHT THAN WHAT HAS ACTUALLY OCCURRED.  BASED ON
 THIS AND CURRENT TRENDS...THE FIRST 48 HR OF THE TRACK FORECAST IS
 NUDGED TO THE NORTH OF THE PREVIOUS FORECAST...BUT STILL LIES ALONG
 THE LEFT EDGE OF THE MODEL ENVELOPE.  AFTER 48 HR...THE TROUGH
 WEAKENS AND A WEAK MID-LEVEL RIDGE DEVELOPS TO THE NORTH AND
 NORTHWEST OF HERNAN.  THE TRACK GUIDANCE MODELS ARE IN GOOD
 AGREEMENT ON THIS...FORECASTING THE CYCLONE TO TURN WESTWARD BY 72
 HR AND WEST-SOUTHWESTWARD BY 120 HR.  THE OFFICIAL FORECAST WILL
 FOLLOW THIS SCENARIO...WITH THE 72-120 HR PART OF THE TRACK MORE OF
 LESS IN THE MIDDLE OF THE GUIDANCE ENVELOPE.
  
 HERNAN IS MOVING OVER COOLER SEA SURFACE TEMPERATURES AND SHOULD
 REACH THE 26C ISOTHERM IN ABOUT 36 HR.  WHILE SOME ADDITIONAL
 STRENGTHENING IS POSSIBLE TONIGHT...HERNAN SHOULD START TO WEAKEN IN
 24-36 HR EVEN THOUGH THE EASTERLY SHEAR THAT HAS HAMPERED THE
 SYSTEM IS FORECAST TO DIMINISH.  THE NEW INTENSITY FORECAST IS AN
 UPDATE OF THE PREVIOUS FORECAST...CALLING FOR HERNAN TO REACH A
 PEAK INTENSITY OF 85 KT IN ABOUT 12 HR...WEAKEN TO A TROPICAL STORM
 IN ABOUT 48 HR...AND WEAKEN TO A TROPICAL DEPRESSION IN ABOUT 120
 HR.  THE INTENSITY FORECAST IS A BIT ABOVE THE MODEL GUIDANCE FOR
 THE FIRST 36 HR...AND IN GOOD AGREEMENT WITH THE GFDL AND FLORIDA
 STATE SUPERENSEMBLE FROM 96-120 HR.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      09/0300Z 15.1N 121.7W    80 KT
  12HR VT     09/1200Z 15.4N 123.0W    85 KT
  24HR VT     10/0000Z 16.0N 124.6W    80 KT
  36HR VT     10/1200Z 16.6N 126.1W    70 KT
  48HR VT     11/0000Z 17.1N 127.7W    60 KT
  72HR VT     12/0000Z 17.5N 130.5W    45 KT
  96HR VT     13/0000Z 17.5N 132.5W    35 KT
 120HR VT     14/0000Z 16.5N 134.5W    25 KT
  
 $$
 FORECASTER BEVEN