Complex sentence: After the cyclone turned northward, it threatened Bermuda, which prompted a tropical storm watch for the island on July 16, which was canceled on July 18 as the storm passed well northwest of the island.
Split into simpler sentences: After the cyclone turned northward, it threatened Bermuda, which prompted a tropical storm watch for the island on July 16. The watch was canceled on July 18 as the storm passed well northwest of the island.