Tropical Storm Erin is approaching Puerto Rico and the Virgin Islands, bringing heavy rains that could cause flooding and landslides

The National Hurricane Center is tracking two tropical waves in the eastern and central Atlantic Ocean, far from the U.S. coast.

A hurricane's category only measures wind speed, not how far those winds extend from the center. The size of a storm's wind field is crucial for predicting storm surge and overall reach.

Tropical Storm Erin -- which is forecast to strengthen into the first hurricane of the Atlantic season by Saturday morning -- won't have a direct impact on the U.S., but it will bring dangerous rip currents to the East Coast.