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Tropical Storm JOHN (Text)

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TROPICAL STORM JOHN DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
800 PM PDT SAT SEP 02 2006
 
SATELLITE IMAGERY AND SURFACE OBSERVATIONS FROM CIUDAD CONSTITUCION
SHOW THAT THE CENTER OF JOHN IS MOVING 320/7 OVER THE BAJA
CALIFORNIA PENINSULA.  THE CENTRAL CONVECTION HAS DECREASED DURING
THE PAST FEW HOURS...AND ON THIS BASIS THE INITIAL INTENSITY IS
LOWERED TO 50 KT.

JOHN IS ON THE WEST SIDE OF A MID/UPPER-LEVEL ANTICYCLONE CENTERED
OVER NORTHERN MEXICO...WITH WATER VAPOR IMAGERY SHOWING THE RIDGE
AMPLIFYING NORTHWARD INTO THE SOUTHWESTERN UNITED STATES AS A
SHORTWAVE RIDGE IN THE WESTERLIES MOVES THROUGH THAT AREA.  THE GFS
AND ECMWF MODELS FORECAST THE SHORTWAVE RIDGE TO RAISE HEIGHTS OVER
THE SOUTHWESTERN U. S. ENOUGH TO TURN JOHN WESTWARD INTO THE
PACIFIC.  ON THE OTHER HAND...THE UKMET AND THE NOGAPS SHOW ENOUGH
WEAKNESS IN THE RIDGE TO ALLOW JOHN TO CONTINUE NORTHWARD INTO THE
NORTHERN GULF OF CALIFORNIA.  THE MODELS AGREE THAT JOHN WILL
CONTINUE NORTHWESTWARD FOR 24 HR OR SO...WITH THE MAJOR DIVERGENCE
THEREAFTER.  THE FORECAST TRACK CALLS FOR A GRADUAL WESTWARD TURN
IN BETWEEN THESE TWO EXTREMES...WITH A SLOWING OF THE FORWARD
MOTION OVER THE PACIFIC AFTER 36 HR.  THE NEW TRACK IS AN UPDATE OF
THE PREVIOUS PACKAGE AND IS A LITTLE TO THE LEFT OF THE MODEL
CONSENSUS.  REGARDLESS OF THE EXACT TRACK...MIDDLE TO UPPER-LEVEL
MOISTURE FROM JOHN IS LIKELY TO ENHANCE RAINFALL IN THE DESERT
SOUTHWEST MONSOON AREAS.

JOHN SHOULD CONTINUE TO WEAKEN AS THE CENTER INTERACTS WITH THE
MOUNTAINOUS TERRAIN OF BAJA CALIFORNIA...AND AS THE WESTERN SIDE OF
THE STORM OVER THE PACIFIC ENCOUNTERS PROGRESSIVELY COOLER WATER. 
SEA SURFACE TEMPERATURES ALONG THE FORECAST TRACK IN THE PACIFIC
ARE NEAR OR BELOW 22C...SO WHAT IS LEFT OF THE CYCLONE SHOULD
WEAKEN QUICKLY.  THE INTENSITY FORECAST CALLS FOR WEAKENING TO A
DEPRESSION BEFORE EMERGING INTO THE PACIFIC...THEN BECOMING A
NON-CONVECTIVE LOW BY 72 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0300Z 25.6N 111.7W    50 KT
 12HR VT     03/1200Z 26.4N 112.5W    45 KT...INLAND
 24HR VT     04/0000Z 27.4N 113.6W    35 KT...INLAND
 36HR VT     04/1200Z 28.3N 114.6W    30 KT
 48HR VT     05/0000Z 29.0N 115.5W    25 KT...DISSIPATING
 72HR VT     06/0000Z 29.5N 117.0W    20 KT...REMNANT LOW
 96HR VT     07/0000Z 29.5N 119.5W    20 KT...REMNANT LOW
120HR VT     08/0000Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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