A weather system off the west coast of Africa on Saturday was given a 70% chance of forming into a tropical depression in two days, and a 90% chance within a week.
The National Hurricane Center said the disturbance was several hundred miles southwest of the Cape Verde Islands and likely to move northwesterly. If it reaches tropical storm status, it will be named Tammy.
Separately, Tropical Depression Sean was delivering thunderstorms to parts of the Atlantic on Saturday and was forecast to dissipate by Monday.