By early on July 31 , ship reports and QuikSCAT observations detected winds of 35 mph ( 55 km\/h ) , and the center was well-involved enough with the convection for the National Hurricane Center to name it as Tropical Depression Three while it was located about 270 miles ( 435 km ) north-northwest of Bermuda , or about 445 miles ( 710 km ) south-southeast of Chatham , Massachusetts . By early on July 31 , ship reports and QuikSCAT observations suggested winds of 35 mph ( 55 km\/h ) , and the center was well-involved enough with the convection for the National Hurricane Center to classify it as Tropical Depression Three while it was located about 270 miles ( 435 km ) north-northwest of Bermuda , or about 445 miles ( 710 km ) south-southeast of Chatham , Massachusetts .