000 WTNT43 KNHC 081501 TCDAT3 TROPICAL STORM CHANTAL DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013 1100 AM AST MON JUL 08 2013 CONVECTIVE ORGANIZATION OF HAS IMPROVED SLIGHTLY IN SATELLITE IMAGERY SINCE THE PREVIOUS ADVISORY WITH FRAGMENTED CURVED BANDS DEVELOPING IN THE NORTHERN SEMICIRCLE...ALTHOUGH THE CORE CONVECTION HAS WEAKENED SOME. THE INITIAL INTENSITY OF 40 KT IS BASED ON A BLEND OF TAFB...SAB...ADT...AND AMSU SATELLITE INTENSITY ESTIMATES. VISIBLE AND WATER VAPOR IMAGERY ALSO INDICATE THAT CHANTAL HAS DEVELOPED SOME WEAK ANTICYCLONIC OUTFLOW. THE INITIAL MOTION ESTIMATE REMAINS A RATHER BRISK 280/23 KT. NO CHANGES WERE MADE TO THE PREVIOUS FORECAST TRACK. CHANTAL IS FORECAST TO MOVE QUICKLY WEST-NORTHWESTWARD TO THE SOUTH OF A STRONG DEEP-LAYER SUBTROPICAL RIDGE FOR THE NEXT 48 HOURS. BY DAY 3 AND BEYOND...A VIGOROUS MID-/UPPER-LEVEL LOW CURRENTLY JUST EAST OF THE BAHAMAS IS EXPECTED TO MOVE WESTWARD AND MERGE WITH A MID-LATITUDE TROUGH...CREATING A BREAK IN THE SUBTROPICAL RIDGE OVER THE SOUTHEASTERN U.S. AND THE BAHAMAS. CHANTAL IS FORECAST TO SLOW DOWN AND TURN NORTHWESTWARD BY 72 HOURS AS IT APPROACHES THIS DEVELOPING WEAKNESS IN THE RIDGE...AND THEN MOVE SLOWLY NORTH-NORTHWESTWARD THROUGH THE WEAKNESS ON DAYS 4 AND 5. THE OFFICIAL FORECAST TRACK IS A LITTLE TO THE LEFT OF THE MODEL CONSENSUS AND LIES ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE...CLOSE TO THE GFS AND FSSE MODELS. OTHER THAN THE FAST FORWARD SPEED OF CHANTAL...ENVIRONMENTAL CONDITIONS ARE FAIRLY FAVORABLE FOR AT LEAST SOME MODEST STRENGTHENING TO OCCUR DURING THE NEXT 48 HOURS OR SO WHILE THE CYCLONE REMAINS UNDERNEATH A 200 MB RIDGE AXIS. INTERACTION WITH THE MOUNTAINOUS TERRAIN OF HISPANIOLA AND EASTERN CUBA IN ABOUT THREE DAYS...COUPLED WITH INCREASING WESTERLY VERTICAL WIND SHEAR...IS EXPECTED TO CAUSED TO CHANTAL TO WEAKEN CONSIDERABLY BY DAY 3...AND CONTINUE INTO DAYS 4 AND 5 AS THE CYCLONE MOVES UNDERNEATH AN UPPER-LEVEL TROUGH. THE OFFICIAL INTENSITY FORECAST FOLLOWS THE ICON INTENSITY CONSENSUS MODEL AND THE FSSE MODEL. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 10.9N 51.7W 40 KT 45 MPH 12H 09/0000Z 12.0N 55.0W 45 KT 50 MPH 24H 09/1200Z 13.6N 59.6W 50 KT 60 MPH 36H 10/0000Z 15.2N 64.1W 55 KT 65 MPH 48H 10/1200Z 16.8N 68.2W 60 KT 70 MPH 72H 11/1200Z 19.8N 74.1W 50 KT 60 MPH 96H 12/1200Z 23.3N 76.8W 35 KT 40 MPH 120H 13/1200Z 26.0N 78.1W 30 KT 35 MPH $$ FORECASTER STEWART