Forecasters are tracking three systems in the Atlantic basin, including one with a medium chance of becoming a tropical depression later this week.

Hurricane Erin is a huge Category 4 storm and is expected to both grow larger and stronger today as it moves toward the west-northwest. The center of the storm is expected to remain offshore as it moves between the U.S. and Bermuda.

The hatched areas on the National Hurricane Center's tropical outlook map indicate "areas where a tropical cyclone — which could be a tropical depression, tropical storm or hurricane — could develop," said National Hurricane Center Deputy Director Jamie Rhome.