Officials in the northern Caribbean warned Thursday of heavy rains and dangerous swells as Tropical Storm Erin approached the region. The storm is expected to remain over open waters and move north-northeast of islands including Antigua and Barbuda,

With Tropical Storm Erin expected to gain strength into a hurricane this weekend, Royal Caribbean has made the first cruise change due to the storm.

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.