Hurricane Irma battered the Turks and Caicos Islands early Friday and Cuba evacuated tourists from beachside resorts as the fearsome storm continued a rampage through the Caribbean that has killed at least 16 people, with Florida in its sights.

Waves as high as 20 feet were expected in the Turks and Caicos. Communications went down as the storm slammed into the islands, and the extent of the devastation was unclear.

The first hurricane warnings were issued for parts of southern Florida as the state braced for what could be a catastrophic hit over the weekend. Following in Irma’s wake was Hurricane Jose, with some of the islands hit hardest by Irma in its expected path. 

Irma weakened to a still-powerful Category 4 storm early Friday. The U.S. National Hurricane Center said Irma’s maximum sustained winds decreased to about 150 mph. The center said some fluctuations in strength are likely over the next day or two, but Irma is expected to stay a Category 4 storm.

At 8 a.m. ET Friday, the hurricane’s center was about 80 miles northeast of Cabo Lucrecia, Cuba, and about 450 miles southeast of Miami and was moving west-northwest at 16 mph.

On the forecast track, the hurricane center said, Irma’s eye should continue to move westward, away from the Turks and Caicos Islands, toward the southeastern Bahamas Friday morning. The storm’s core will then move between the northern coast of Cuba and the Bahamas Friday or Saturday, and be near the Florida Keys and southern Florida Peninsula Sunday morning.

Forecasters warned Irma could slam headlong into the Miami metropolitan area of 6 million people and punish the entire length of the state’s Atlantic coast before moving into Georgia and South Carolina.

More than a half-million people in Miami-Dade County were ordered to leave as Irma closed in.

“Take it seriously, because this is the real deal,” said Maj. Jeremy DeHart, a U.S. Air Force Reserve weather officer who flew through the eye of Irma at 10,000 feet.

The U.S. Consulate General in Curacao said it believes about 6,000 Americans are stranded on St. Martin. It said it was working with the U.S. and other governments to try to figure out how to get the Americans off the island either by air or boat. Frantic Americans were calling home to relatives to try to get them off the island ahead of Hurricane Jose, which had some of the islands hit hardest by Irma in its expected path.