The system organized further , and based on satellite pictures and QuikSCAT data , the National Hurricane Center upgraded the depression to Tropical Storm Chantal at 1215 UTC on July 31 while located about 330 miles ( 530 km ) south of Halifax , Nova Scotia . Convection increased further over the center , and at around 0600 UTC on July 31 the depression intensified into Tropical Storm Chantal while located about 530 miles ( 855 km ) south of Halifax , Nova Scotia .