Tropical Storm JOHN

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TROPICAL STORM JOHN DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
800 AM PDT SUN SEP 03 2006

JOHN CONTINUES TO PRODUCE CONVECTION NEAR THE CENTER. HOWEVER
WESTERLY SHEAR IS TAKING A TOLL ON THE SYSTEM WITH ALMOST ALL OF
THE THUNDERSTORM ACTIVITY IN THE EASTERN SEMICIRCLE. A MEXICAN NAVY
STATION AT SANTA ROSALIA RECENTLY REPORTED A PRESSURE OF 996.1 MB
AND 34 KT SUSTAINED WINDS... SO THE INITIAL INTENSITY WILL BE
DECREASED ONLY SLIGHTLY TO 40 KT. CONTINUED WEAKENING IS LIKELY DUE
TO THE HIGH TERRAIN OF BAJA CALIFORNIA IN COMBINATION WITH THE
MODERATE WESTERLY SHEAR. DISSIPATION IS LIKELY IN ABOUT 36 HOURS...
IF NOT SOONER.
 
JOHN IS MOVING ABOUT THE SAME AS BEFORE... 325/8. THE TRACK FORECAST
ISN'T EASY THIS MORNING WITH THE SAME PROBLEMS FOR THE LAST COUPLE
OF DAYS PERSISTING. THE BIG QUESTION REMAINS EXACTLY WHEN THE
LOW-LEVEL CENTER OF JOHN WILL DECOUPLE FROM THE MIDDLE-LEVEL
CENTER. THE NOGAPS AND UKMET SUGGEST THE CIRCULATION WILL REMAIN
INTACT ENOUGH TO TAKE THE SYSTEM INTO THE SOUTHWESTERN UNITED
STATES AS A WEAKENING DEPRESSION. HOWEVER THE ECMWF/GFDL/GFS SHOW A
MORE RAPIDLY DECAYING SYSTEM AND A WESTWARD TURN IN A DAY OR SO
FOLLOWING THE LOW-LEVEL REMNANT. OVER THE PAST FEW DAYS... THE
MODEL CONSENSUS HAS BEEN A GOOD TOOL TO SMOOTH THROUGH THESE
DIFFERENCES AND HAS VERIFIED WELL. THEREFORE.. THE OFFICIAL IS
NUDGED NORTHWARD IN BETWEEN THE PREVIOUS FORECAST AND MODEL
CONSENSUS. 

REGARDLESS OF THE TRACK... LOCALLY HEAVY RAINS ARE POSSIBLE OVER THE
SOUTHWESTERN UNITED STATES AS A RESULT OF MIDDLE TO UPPER-LEVEL
MOISTURE FROM JOHN.   
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/1500Z 27.1N 112.5W    40 KT...INLAND
 12HR VT     04/0000Z 28.0N 113.3W    35 KT...INLAND
 24HR VT     04/1200Z 28.9N 114.1W    30 KT...INLAND
 36HR VT     05/0000Z 29.8N 115.1W    25 KT...DISSIPATING
 48HR VT     05/1200Z 30.2N 116.0W    20 KT...REMNANT LOW
 72HR VT     06/1200Z 30.5N 118.0W    20 KT...REMNANT LOW
 96HR VT     07/1200Z...DISSIPATED
 
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FORECASTER BLAKE/FRANKLIN
 
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