000 WTNT43 KNHC 080317 TCDAT3 TROPICAL STORM CHANTAL DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013 1100 PM EDT SUN JUL 07 2013 CONVENTIONAL AND MICROWAVE SATELLITE IMAGES SHOW THAT DEEP CONVECTION ASSOCIATED WITH THE STRONG TROPICAL WAVE OVER THE CENTRAL TROPICAL ATLANTIC HAS INCREASED IN ORGANIZATION SINCE THIS AFTERNOON. A RECENT ASCAT PASS INDICATED THAT THE CIRCULATION HAD BECOME BETTER DEFINED SINCE THIS MORNING....WITH SEVERAL UNCONTAMINATED 35-KT WIND VECTORS OVER THE EASTERN PORTION OF THE CIRCULATION. BASED ON THE ASCAT AND AFOREMENTIONED SATELLITE DATA...THE SYSTEM IS UPGRADED TO A 35-KT TROPICAL STORM. THE INITIAL MOTION ESTIMATE IS 275/23. A STRONG SUBTROPICAL HIGH OVER THE CENTRAL ATLANTIC IS EXPECTED TO STEER CHANTAL ON A WESTWARD AND THEN WEST-NORTHWESTWARD TRACK FOR THE NEXT FEW DAYS WITH LITTLE DECREASE IN FORWARD SPEED. A SECOND SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC SHOULD KEEP CHANTAL ON THE SAME HEADING UNTIL A WEAKNESS BEGINS TO DEVELOP OVER EASTERN NORTH AMERICA LATE IN THE PERIOD. AS A RESULT...THE TRACK OF CHANTAL SHOULD BEND MORE NORTHWESTWARD AND THEN POSSIBLY NORTHWARD AND DECELERATE BY DAYS 4 AND 5. THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO THROUGH 48 TO 72 HOURS BUT THEN BEGINS TO DIVERGE AFTER THAT TIME. THE OFFICIAL NHC TRACK FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD. FAVORABLE ENVIRONMENTAL CONDITIONS AND WARM SEA SURFACE TEMPERATURES SHOULD ALLOW CHANTAL TO INTENSIFY SOME DURING THE NEXT FEW DAYS. THE POSSIBILITY OF LAND INTERACTION WITH HISPANIOLA AND CUBA IN ABOUT 72-96 HOURS COMPLICATES THE INTENSITY FORECAST BUT IS LIKELY TO RESULT IN WEAKENING...ESPECIALLY SINCE UPPER-LEVEL WESTERLY FLOW IS FORECAST TO BEGIN TO AFFECT CHANTAL BY THAT TIME. THIS INCREASING WESTERLY FLOW AND LAND INTERACTION COULD EVEN CAUSE CHANTAL TO BECOME A REMNANT LOW OR DISSIPATE LATE IN THE FORECAST PERIOD. THE NHC INTENSITY FORECAST IS A BLEND OF THE SHIPS/LGEM GUIDANCE AS WELL AS THE INTENSITY CONSENSUS AIDS. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 9.8N 47.2W 35 KT 40 MPH 12H 08/1200Z 10.8N 50.8W 40 KT 45 MPH 24H 09/0000Z 12.1N 55.7W 45 KT 50 MPH 36H 09/1200Z 13.9N 60.5W 50 KT 60 MPH 48H 10/0000Z 15.6N 65.1W 55 KT 65 MPH 72H 11/0000Z 18.4N 73.6W 45 KT 50 MPH 96H 12/0000Z 22.0N 77.0W 35 KT 40 MPH 120H 13/0000Z 25.0N 78.0W 30 KT 35 MPH $$ FORECASTER KIMBERLAIN/BROWN