A cold front moved off the east coast of the United States late on July 13. While it was over the western Atlantic Ocean, it stopped moving. The front then died out, but it left behind two areas of low pressure. The southern one was about 200 miles (320 km) to the south of Cape Hatteras, North Carolina. The northern weather system was about 290 miles (470 km) to the south-southeast of Cape Cod, Massachusetts. The northern one became an extratropical cyclone, a type of weather system, on July 16. It moved to the northwest over warm water temperatures. These temperatures were 80–82º F (27–28º C). A large group of thunderstorm formed near the center of the storm. It turned into a tropical depression on July 17, when it was about 240 miles (390 km) to the southeast of Nantucket, Massachusetts.