Hurricane JOHN

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HURRICANE JOHN DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
800 PM PDT THU AUG 31 2006
 
ENHANCED AND SHORTWAVE INFRARED IMAGERY DEPICT THAT THE EYE HAS
BECOME OBSCURED THIS EVENING.  LOS CABOS MEXICO RADAR ANIMATION
INDICATES THE EXISTENCE OF A BANDING EYE FEATURE OVER THE WESTERN
PORTION OF THE SYSTEM.  THE INITIAL INTENSITY IS MAINTAINED AT 90
KT BASED ON A BLEND OF DVORAK SATELLITE INTENSITY ESTIMATES RANGING
FROM 90 TO 102 KT.  WATER VAPOR IMAGERY AND A CIMSS WIND SHEAR
ANALYSIS SUGGEST THAT JOHN HAS OUT RUN THE LARGE SCALE ANTICYCLONE
AND NOW HAS MOVED WITHIN 10 TO 20 KT OF SOUTHEASTERLY SHEAR.

NO SIGNIFICANT CHANGES TO THE INTENSITY FORECAST FROM THE PREVIOUS
PACKAGE...WITH SOME STRENGTHENING STILL POSSIBLE DURING THE NEXT 12
HOURS...AND LITTLE CHANGE THROUGH 48 HOURS.  THEREAFTER...JOHN
SHOULD BEGIN TO WEAKEN AS IT PASSES WEST OF THE BAJA PENINSULA AND
MOVES OVER COOLER WATERS.  
 
THE INITIAL MOTION IS ESTIMATED AT 315/11.  JOHN REMAINS WITHIN THE
SOUTHWEST PERIPHERY OF A DEEP-LAYER RIDGE EXTENDING OVER THE BAJA
PENINSULA FROM NORTHERN MEXICO.  THE DYNAMICAL MODELS CONTINUE TO
CLUSTER INTO TWO GROUPS.  THE GFDL...NAVY GFDN...AND GFS INDICATE A
NORTHWEST MOTION THROUGH THE ENTIRE FORECAST PERIOD...WITHIN A
DEVELOPING WEAKNESS ALONG THE CALIFORNIA COAST.  THE ECMWF...GFS
ENSEMBLE...NOGAPS...FSU SUPERENSEMBLE...AND THE UKMET ALL SUGGEST
THAT THE MID-LEVEL TROUGH WILL LIFT NORTHEAST OVER THE WESTERN
UNITED STATES...ALLOWING THE MID-TROPOSPHERIC RIDGE TO BUILD NORTH
OF THE TROPICAL CYCLONE FROM MEXICO. THE OFFICIAL FORECAST IS JUST
TO THE NORTH OF THE PREVIOUS TRACK AND IS HEDGED CLOSELY TO A
CONSENSUS OF THE SECOND DYNAMICAL MODEL CLUSTER...WHICH INDICATES A
WESTWARD MOTION BEYOND DAY 3. 

BECAUSE OF THE SLIGHT FORECAST ADJUSTMENT TO THE NORTH OF THE
PREVIOUS TRACK...A TROPICAL STORM WARNING HAS BEEN ISSUED FOR BOTH
COASTS OF THE CENTRAL BAJA PENINSULA. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0300Z 21.4N 107.8W    90 KT
 12HR VT     01/1200Z 22.4N 108.9W    95 KT
 24HR VT     02/0000Z 23.4N 110.3W    90 KT
 36HR VT     02/1200Z 24.2N 111.7W    90 KT
 48HR VT     03/0000Z 24.8N 113.2W    85 KT
 72HR VT     04/0000Z 25.5N 116.0W    65 KT
 96HR VT     05/0000Z 26.0N 119.0W    50 KT
120HR VT     06/0000Z 26.0N 124.0W    40 KT
 
$$
FORECASTER ROBERTS/BEVEN
 
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