Hurricane JOHN

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HURRICANE JOHN DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
800 PM PDT TUE AUG 29 2006
 
JOHN'S EARLIER RAPID INTENSIFICATION APPEARS TO HAVE ABATED FOR NOW.
THE EYE HAS BECOME INCREASINGLY OBSCURED DURING THE LAST FEW
HOURS...WITH ONLY A RELATIVE WARM SPOT VISIBLE IN RECENT INFRARED 
IMAGERY.  SUBJECTIVE SATELLITE INTENSITY ESTIMATES ARE 90 KT FROM
BOTH TAFB AND SAB.  GIVEN THE RESTRICTIONS OF THE DVORAK TECHNIQUE
AND RAW DATA T-NUMBERS THAT REMAIN NEAR 115 KT...THE INITIAL
INTENSITY IS HELD AT 100 KT.  INNER CORE STRUCTURAL CHANGES MAY BE
RESPONSIBLE FOR THE DEGRADATION OF THE SATELLITE APPEARANCE AND 
THERE ARE NO OBVIOUS ENVIRONMENTAL FACTORS TO PREVENT FURTHER
STRENGTHENING.  THE GFDL MODEL FORECASTS JOHN TO MOVE INLAND OVER
MEXICO RESULTING IN RAPID WEAKENING AFTER 24 HOURS...HOWEVER SINCE
THE OFFICIAL TRACK FORECAST KEEPS THE CYCLONE OVER WATER JOHN IS
FORECAST TO BECOME A CATEGORY 4 HURRICANE IN 24 HOURS. 
 
JOHN HAS BEEN MOVING MORE TOWARD THE NORTHWEST NEAR 300/10 DURING
THE LAST 6 TO 12 HOURS...AND THIS MOTION IS A LITTLE TO THE RIGHT
OF THE PREVIOUS TRACK.  MOST OF THE GLOBAL MODELS SHOW JOHN
CONTINUING ON A GENERAL WEST-NORTHWEST TO NORTHWEST MOTION DURING
THE NEXT 48 HOURS AS THE CYCLONE ROUNDS THE SOUTHWESTERN PERIPHERY
OF A MIDDLE TO UPPER-LEVEL RIDGE OVER NORTHERN MEXICO.  THE GFS 
CONTINUES TO HAVE A WEAKER REPRESENTATION OF THE CYCLONE...
RESULTING IN A MORE WESTWARD TRACK.  CONVERSELY...THE GFDL CONTINUES
TO LIE ALONG THE FAR RIGHT SIDE OF THE MODEL SUITE...TAKING JOHN
INLAND OVER MEXICO IN THE NEXT 24 HOURS. GIVEN THE MORE NORTHWARD
INITIAL MOTION...THE EASTWARD TREND IN THE GLOBAL MODEL GUIDANCE...
AND THE PERSISTENCE OF THE GFDL...THE OFFICIAL FORECAST IS SHIFTED 
CLOSER TO THE MEXICAN COAST FOR THE FIRST 72 HOURS.  THIS REQUIRES
THE ISSUANCE OF HURRICANE WATCHES AND WARNINGS AT THIS TIME. 

BEYOND 72 HOURS...SIGNIFICANT DIVERGENCE EXISTS IN THE MODEL
GUIDANCE.  THE GFS...NOGAPS...AND UKMET SHOW A MIDDLE- TO
UPPER-LEVEL RIDGE BUILDING WESTWARD FROM NORTHERN MEXICO...
RESULTING IN A SHARP TURN TOWARD THE WEST.  THE ECMWF AND THE GFDL
SHOW LITTLE OR NO RIDGING NORTH OF THE CYCLONE...ALLOWING A
CONTINUATION OF THE NORTHWESTWARD TRACK.  THE OFFICIAL FORECAST IS
NUDGED NORTHWARD AT DAYS 4 AND 5 IN CONSIDERATION OF THE GFDL AND
ECMWF BUT STILL SHOWS A TURN TOWARD THE WEST.  IT SHOULD NOTED THAT
THERE IS GREATER THAN USUAL UNCERTAINTY IN THE TRACK FORECAST AT
THE LATER PERIODS...DUE TO THE MODEL SPREAD AND POSSIBLE
INTERACTION WITH A TROPICAL DISTURBANCE LOCATED FARTHER WEST. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      30/0300Z 15.2N 100.4W   100 KT
 12HR VT     30/1200Z 16.0N 101.7W   115 KT
 24HR VT     31/0000Z 17.2N 103.7W   120 KT
 36HR VT     31/1200Z 18.8N 105.7W   120 KT
 48HR VT     01/0000Z 20.2N 107.6W   115 KT
 72HR VT     02/0000Z 21.8N 111.0W   110 KT
 96HR VT     03/0000Z 22.5N 114.5W   100 KT
120HR VT     04/0000Z 22.5N 118.0W    90 KT
 
$$
FORECASTER RHOME/FRANKLIN
 
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