ZCZC MIATCDEP5 ALL 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 NNNN
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Page last modified: Monday, 31-Dec-2012 12:10:29 UTC