766 
 WTPZ41 KNHC 300853
 TCDEP1
 HURRICANE JOHN DISCUSSION NUMBER   8
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
 200 AM PDT WED AUG 30 2006
  
 RADAR FROM ACAPULCO MEXICO SHOWS A WELL-DEFINED EYE AND IT APPEARS
 THAT JOHN HAS GONE THROUGH AN EYE-WALL REPLACEMENT CYCLE.  THIS MAY
 EXPLAIN WHY THE SATELLITE APPEARANCE HAS NOT IMPROVED MUCH SINCE
 YESTERDAY AFTERNOON...HOWEVER WITHIN THE PAST HOUR OR SO A WARM
 SPOT HAS RE-APPEARED IN INFRARED SATELLITE IMAGERY.  DVORAK
 SATELLITE ESTIMATES ARE 102 KT AND 90 KT FROM TAFB AND SAB
 RESPECTIVELY AND THE INITIAL INTENSITY WILL REMAIN 100 KT FOR THIS
 ADVISORY.  AN AIR FORCE HURRICANE HUNTER AIRCRAFT IS CURRENTLY
 EN-ROUTE TO JOHN AND IT SHOULD SOON PROVIDE A MUCH MORE ACCURATE
 MEASURE OF THE HURRICANE'S CURRENT STRENGTH.
  
 JOHN HAS BEEN MOVING BETWEEN WEST-NORTHWEST AND NORTHWEST AND THE
 ESTIMATED MOTION IS 300/10.  THE GLOBAL MODELS KEEP JOHN ON THIS
 GENERAL HEADING FOR THE NEXT 36 HOURS AROUND THE SOUTHWESTERN
 PERIPHERY OF A MID- TO UPPER-LEVEL RIDGE OVER NORTHERN MEXICO.  THE
 GFS REMAINS ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE DUE TO ITS
 WEAKER DEPICTION OF THE CYCLONE.  THE GFDL AND UKMET ARE ON THE
 RIGHT SIDE OF THE GUIDANCE AND BOTH TRACK JOHN ACROSS SOUTHWESTERN
 MEXICO IN 24-36 HOURS.  OUT OF RESPECT FOR THE GFDL AND UKMET THE
 TRACK FORECAST IS AGAIN SHIFTED RIGHT OR CLOSER TO THE COAST OF
 MEXICO.  EVEN THOUGH THE OFFICIAL FORECAST KEEPS THE CENTER JUST
 OFFSHORE...ANY SMALL DEVIATION TO THE RIGHT WILL BRING THE CORE OF
 THIS DANGEROUS HURRICANE OVER SOUTHWEST MEXICO. BEYOND THREE DAYS
 THERE REMAINS SIGNIFICANT DIVERGENCE IN THE MODELS AND HIGHER
 THAN NORMAL UNCERTAINTY IN THE TRACK FORECAST.  AS WITH THE
 PREVIOUS ADVISORY...IT IS ASSUMED THERE WILL BE ENOUGH RIDGING
 TO THE NORTH OF JOHN TO BEND THE TRACK MORE WESTWARD AT DAYS 4
 AND 5.
  
 WITH LOW SHEAR AND WARM SSTS THE INTENSITY GUIDANCE CONTINUES TO
 INDICATE STRENGTHENING.  BECAUSE INTENSIFICATION HAS CEASED OVER
 THE PAST 12 HOURS...PERSISTENCE HAS BECOME LESS OF A POSITIVE 
 FACTOR IN THE SHIPS MODEL AND THEREFORE IT NOW KEEPS THE HURRICANE
 JUST BELOW CATEGORY FOUR STRENGTH. HOWEVER...IT IS ASSUMED THAT
 JOHN HAS JUST COMPLETED AN EYEWALL REPLACEMENT CYCLE AND
 STRENGTHENING SHOULD RESUME.  THE OFFICIAL INTENSITY FORECAST WILL
 CONTINUE TO PREDICT A CATEGORY FOUR WITHIN THE NEXT 24 HOURS...
 VIRTUALLY UNCHANGED FROM THE PREVIOUS ADVISORY.
   
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      30/0900Z 15.6N 101.3W   100 KT
  12HR VT     30/1800Z 16.5N 102.4W   110 KT
  24HR VT     31/0600Z 18.0N 104.2W   120 KT
  36HR VT     31/1800Z 19.5N 106.0W   120 KT
  48HR VT     01/0600Z 20.9N 107.7W   115 KT
  72HR VT     02/0600Z 22.2N 110.7W   105 KT
  96HR VT     03/0600Z 22.8N 114.0W    90 KT
 120HR VT     04/0600Z 23.0N 118.0W    75 KT
  
 $$
 FORECASTER BROWN/STEWART