By three hours later the system formed a well-defined curved banding features , and Chantal reached maximum systained winds of 50 mph ( 80 km\/h ) at 40.2 Â N. The storm speed up northeastward into an area of cold waters and cooler air , and early on August 1 the National Hurricane Center gave out its last advisory on Chantal as it began extratropical transition . The storm continued northeastward , under the influence of a mid-level trough , and Chantal quickly developed well-defined curved banding features ; six hours after becoming a tropical storm , Chantal reached peak winds of 50 km\/h ( 85 km\/h ) . The storm tracked through an area of progressively cold waters and cooler air , resulting in the weakening of its convection .