Tropical Storm JOHN

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TTAA00 KNHC DDHHMM
 
TROPICAL STORM JOHN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102012
200 AM PDT MON SEP 03 2012
 
A BURST OF STRONG CONVECTION HAS DEVELOPED OVER AND SOUTHWEST OF THE
LOW-LEVEL CENTER SINCE THE PREVIOUS ADVISORY. A 02/1730 UTC ASCAT
OVERPASS INDICATED TROPICAL-STORM-FORCE WINDS EXISTED WITH THE
SYSTEM IN THE NORTHEAST QUADRANT...BUT CONVECTION HAD WANED SHORTLY
THEREAFTER. HOWEVER...BASED ON THE INCREASE IN DEEP CONVECTION NEAR
THE CENTER OVER THE PAST 6 HOURS...ALONG WITH AN ADT ESTIMATE OF
T2.5/35 KT...THE SYSTEM HAS BEEN UPGRADED TO TROPICAL STORM JOHN.
MODERATE NORTH TO NORTHEASTERLY VERTICAL WIND SHEAR IS EXPECTED TO
AFFECT THE CYCLONE THROUGHOUT THE FORECAST PERIOD. JOHN IS ALSO
EXPECTED TO REACH SUB-24C SSTS IN ABOUT 36 HOURS. AS A RESULT...
LITTLE OR NO STRENGTHENING SHOULD OCCUR FOR THE NEXT 48 HOURS...
WITH STEADY WEAKENING EXPECTED AFTER THAT. THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY...AND FOLLOWS THE
SHIPS AND LGEM INTENSITY GUIDANCE.

RECENT MICROWAVE FIXES SUGGEST THAT THE INITIAL MOTION IS 305/10.
SINCE JOHN IS ON TRACK...THERE IS NO SIGNIFICANT CHANGE TO THE
PREVIOUS FORECAST TRACK OR REASONING. JOHN IS EXPECTED TO MOVE
GENERALLY NORTHWESTWARD AT A SLOWER FORWARD SPEED AROUND THE
SOUTHWESTERN PERIPHERY OF A MID-TROPOSPHERIC RIDGE CENTERED OVER
THE SOUTH-CENTRAL UNITED STATES DURING THE NEXT FEW DAYS. THE NHC
TRACK FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY TRACK...AND LIES
CLOSE TO THE MULTI-MODEL CONSENSUS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0900Z 19.4N 111.7W   35 KT  40 MPH
 12H  03/1800Z 20.4N 113.4W   35 KT  40 MPH
 24H  04/0600Z 21.7N 115.2W   35 KT  40 MPH
 36H  04/1800Z 22.8N 117.0W   30 KT  35 MPH
 48H  05/0600Z 23.7N 118.5W   30 KT  35 MPH
 72H  06/0600Z 25.0N 121.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  07/0600Z 26.0N 123.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  08/0600Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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