Tropical Storm Erin is expected to become a hurricane later today, Aug. 15, and a Category 4 hurricane with maximum sustained winds of 130 mph over the weekend. A major hurricane is a Category 3 or stronger, with maximum sustained winds of at least 111 mph.

Erin’s sustained winds increased to 70 mph, just 4 mph shy of hurricane strength. The hurricane center said Erin should continue to strengthen through the weekend, when it should be moving near or north of the Leeward Islands, according to the official forecast path.

Over the weekend, Erin is expected to rapidly intensify all the way to a Category 3 hurricane. By Monday, as the storm steers away from the Caribbean and toward Bermuda, it's now forecast to hit Category 4 with 130 mph sustained winds. Some long-term computer models suggest it could get even stronger and hit Category 5 in the open ocean.