Tropical Storm JOHN

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TTAA00 KNHC DDHHMM
 
TROPICAL STORM JOHN DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102012
200 PM PDT MON SEP 03 2012
 
SATELLITE IMAGERY SHOWS THAT THE ORGANIZATION OF JOHN IS 
GRADUALLY DECLINING WITH THE CENTER EXPOSED WELL TO THE NORTH 
OF THE REMAINING CONVECTIVE BAND.  RECENT ASCAT DATA WERE NOT 
HELPFUL FOR DETERMINING THE CURRENT INTENSITY AS THE OVERPASS ONLY
SAMPLED THE WESTERN PORTION OF THE CIRCULATION.  A SHIP OBSERVATION
OF 28 KT OVER THE FAR NORTHEASTERN PORTION OF THE LARGE CIRCULATION
SUGGESTS THAT 30 TO 35 KT WINDS ARE LIKELY STILL OCCURRING NEARER
TO THE CENTER.  BASED ON THE SHIP OBSERVATION AND A DVORAK
CI-NUMBER OF T2.5 FROM SAB...THE INITIAL WIND SPEED IS HELD AT 
35 KT.  THE NORTHEASTERLY SHEAR AFFECTING JOHN IS EXPECTED TO
CONTINUE AS THE CYCLONE MOVES OVER PROGRESSIVELY COOLER WATERS
DURING THE FORECAST PERIOD.  THESE FACTORS SHOULD CAUSE GRADUAL
WEAKENING AND JOHN IS FORECAST TO BECOME A TROPICAL DEPRESSION
WITHIN 12 HOURS...AND A REMNANT LOW WITHIN A COUPLE OF DAYS.
 
JOHN HAS BEEN MOVING NORTHWESTWARD OR 305 DEGREES AT 12 KT. THE
CYCLONE SHOULD CONTINUE HEADING NORTHWESTWARD AROUND THE
SOUTHWESTERN PORTION OF A MID-LEVEL RIDGE OVER THE SOUTH-CENTRAL
UNITED STATES. THE MODELS ARE IN GOOD AGREEMENT ON THIS SCENARIO
AND THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY...AND
NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
 
SOME MOISTURE FROM JOHN WILL LIKELY SPREAD OVER THE SOUTHERN
PORTIONS OF THE BAJA PENINSULA DURING THE NEXT DAY OR TWO.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/2100Z 21.1N 114.0W   35 KT  40 MPH
 12H  04/0600Z 22.1N 115.6W   30 KT  35 MPH
 24H  04/1800Z 23.4N 117.4W   30 KT  35 MPH
 36H  05/0600Z 24.6N 119.0W   25 KT  30 MPH
 48H  05/1800Z 25.6N 120.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  06/1800Z 27.0N 122.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  07/1800Z 27.5N 122.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  08/1800Z...DISSIPATED
 
$$
FORECASTER BROWN
 
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