Hurricane JOHN

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HURRICANE JOHN DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
800 AM PDT FRI SEP 01 2006
 
A DROPSONDE FROM AN AIR FORCE RESERVE HURRICANE HUNTER JUST REPORTED
A CENTRAL PRESSURE OF 956 MB WITH 19 KT OF SURFACE WINDS...WHICH
INDICATES A CENTRAL PRESSURE OF ABOUT 954 MB. HOWEVER THE PEAK
FLIGHT LEVEL WINDS SO FAR ARE 98 KT. THE PLANE HASN'T SAMPLED THE
ENTIRE STORM... AND WITH SUCH A LOW CENTRAL PRESSURE... THE INITIAL
INTENSITY WILL BE HELD AT 100 KT.  SATELLITE IMAGES INDICATE THAT
THE RING OF THUNDERSTORMS AROUND THE CENTER OF JOHN HAS WARMED SOME
THIS MORNING... THOUGH THE EYE IS BECOMING WARMER AND
BETTER-DEFINED. THESE CHANGES MAY BE DUE TO ONGOING AN EYEWALL
REPLACEMENT CYCLE... AS SEEN ON CABO SAN LUCAS RADAR... WHICH MAKES
INTENSITY ESTIMATES RATHER UNCERTAIN.  
 
JOHN HAS SLOWED CONSIDERABLY... AND IS NOW ESTIMATED TO BE MOVING
310/6. THIS SLOW-DOWN SHOULD BE TEMPORARY WITH HIGH PRESSURE LOCKED
IN PLACE OVER NORTHEAST MEXICO... WHICH SHOULD PUSH JOHN ALONG
SOON. ALL GUIDANCE SHOWS SOME ACCELERATION AND IS TIGHTLY CLUSTERED
NEAR THE SOUTHERN TIP OF BAJA CALIFORNIA IN ABOUT 12 HOURS. THIS
NORTHWESTWARD MOTION SHOULD CONTINUE THROUGH ABOUT 36 HOURS.
THEREAFTER MODELS ARE DIVERGENT... WITH THE GFS/GFDL FARTHER TO THE
RIGHT SHOWING A THREAT TO NORTHERN BAJA CALIFORNIA... WHILE THE
OTHER MODELS INDICATE A TURN TO THE WEST-NORTHWEST AWAY FROM LAND.
THE OFFICIAL FORECAST IS SHIFTED A LITTLE TO NORTH IN THE SHORT-
TERM TO ACCOUNT FOR THE INITIAL MOTION... AND LATER IN THE PERIOD
IS ADJUSTED SLIGHTLY TO THE NORTH OF THE PREVIOUS TRACK CLOSER TO
THE CONSENSUS OF THE GLOBAL MODELS.
 
THERE COULD STILL BE A LITTLE STRENGTHENING BEFORE JOHN NEARS THE
COAST TONIGHT. SHIPS INTENSITY GUIDANCE SHOWS LITTLE SHEAR AND THE
WATERS ARE QUITE WARM IN THAT AREA. THEREAFTER...INTERACTION WITH
LAND AND COOLER WATERS WEST OF THE BAJA PENINSULA SHOULD FORCE A
GRADUAL WEAKENING. JOHN WILL LIKELY WEAKEN AT A FAST RATE BEYOND 48
HOURS AS IT ENCOUNTERS SSTS OF 23-24 DEGREES CELSIUS.... LIKELY
CAUSING DISSIPATION NEAR THE END OF THE PERIOD.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/1500Z 22.0N 108.8W   100 KT
 12HR VT     02/0000Z 22.9N 110.0W   105 KT...INLAND NEAR COAST
 24HR VT     02/1200Z 24.0N 111.5W   100 KT
 36HR VT     03/0000Z 24.8N 112.8W    95 KT
 48HR VT     03/1200Z 25.5N 114.2W    80 KT
 72HR VT     04/1200Z 26.3N 116.6W    60 KT
 96HR VT     05/1200Z 26.5N 119.5W    35 KT
120HR VT     06/1200Z 26.5N 123.0W    25 KT...DISSIPATING
 
$$
FORECASTER BLAKE/AVILA
 
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