Forecasters are tracking a new disturbance in the Atlantic Ocean as Hurricane Erin, a Category 5 storm, undergoes an eyewall replacement cycle, according to a Saturday night update from the National Hurricane Center.

A westward-moving tropical wave could produce an area of low pressure in the tropical Atlantic late in the week of Aug. 18, the hurricane center said on Aug. 16. The center shows a 20% chance of storm formation over the next week.

Hurricane Erin is rapidly intensifying as it tracks above the northeastern Caribbean Saturday, churning up rough surf and sending rain and gusty winds to islands south of its path.