The hurricane center explicitly calls for Erin to rapidly intensify before the weekend — a term used when a storm’s sustained winds get at least 35 mph stronger in 24 hours. In this case, forecasters expect Erin to leap from a Tropical Storm on Friday to a major Category 3 hurricane by Sunday.

Tropical Storm Erin is forecast to rapidly strengthen into a hurricane this weekend as it nears the northeastern Caribbean and Bahamas, raising concerns for strong winds, heavy rain, and dangerous surf along the islands.