The news looks grim for Floridians as Hurricane Irma makes its way across the Caribbean. Forecasters now predict that Irma, possibly the most powerful storm ever recorded in the Atlantic, will take a sharp turn shortly right into Florida in the next few days. The news is especially bad for the Keys, which could wind up under water for the storm’s duration:

Hurricane Irma is expected to make a sharp turn toward Florida this weekend. Hurricane Wilma, 12 years ago, was the last big storm to hit Florida head-on. That Category 3 hurricane killed 23 people and caused around $20 billion in damage.While Irma is threatening all of the state, the low-lying islands of the Florida Keys could be swamped by a catastrophic storm surge. …

Florida Gov. Rick Scott also issued several urgent warnings Tuesday.

“Storm surge and extreme winds are the biggest concern right now,” Scott said.

Storm surge is especially a concern in the Keys, which are, on average, about six feet above sea level. The surge during Hurricane Irma has potential to be more than nine feet high.

“We could be looking at wave heights that could literally put the ocean over the islands,” Senterfitt warned.

Authorities in both the Keys and in Miami-Dade county have the same message for those still around — get out now. The word went out for the Florida Keys late yesterday. Evacuation of tourists began this morning, and residents will have to start moving out by 7 pm tonight:

Evacuation orders are being given in the Florida Keys as Monroe County emergency managers prepare for Hurricane Irma.

Key West International Airport will close Wednesday night, cancelling all commercial flights until further notice. …

“For the Florida Keys, if you were to create the worst case scenario that is what we are looking at,” said Monroe Co. Emergency Operations Center Director Martin Senterfitt.

The grim outlook prompted Senterfitt to order mandatory evacuations.

“We’re emphatically telling people you must evacuate, you can not afford to stay on an island with a Category 5 hurricane coming at you. Most of this island chain is only three to five feet above sea level. With the surges we’re expecting this is not the place to be,” said Senterfitt.

In Miami-Dade County, the orders to evacuate have not yet been issued, but Miami mayor Carlos Gimenez has been told they are coming. The beach areas will go first, but they won’t be alone. The evacuation orders will eventually impact more than 400,000 Floridians and the bulk of the area’s tourist capacity:

“This is a powerful storm which poses a serious threat to our area. We will be taking some extraordinary actions to ensure that the residents of Miami-Dade County are safe,” Gimenez said at an afternoon press briefing Tuesday. “I would rather inconvenience our residents on this occasion than suffer any unnecessary loss of life if we are hit by Hurricane Irma.”

The planned instructions to flee the county’s A and B evacuation zones — A covers coastal areas in southern Dade, Key Biscayne and a pocket north of Miami, while B encompasses Brickell Avenue, more inland areas and Miami Beach and other cities along the ocean — represent the most dramatic example of Miami-Dade’s efforts to clear out in advance of a hurricane that reached Category 5 status on Tuesday. Miami-Dade’s schools chief canceled classes Thursday and Friday, and most governments and colleges announced similar shutdown plans for an already shortened holiday week. …

Triggering an evacuation of Zone B also strikes at the heart of Miami-Dade’s hotel industry, with Miami Beach home to the county’s largest concentration of hotel rooms. Gimenez on Tuesday addressed his remarks to visitors, urging tourists to consider “cutting your vacations short.”

Miami Beach mayor Philip Levine didn’t wait to get the orders. “I’m personally recommending to our residents that you consider leaving the city of Miami Beach,” Levine said at a press conference yesterday, “in advance of the evacuation order that we anticipate will be coming from the county mayor.” That’s good advice; in previous evacuations from urban centers, the traffic jams made evac impossible for many. In Texas, Hurricane Rita got most of its victims in those traffic jams, which is why Houston’s mayor was reluctant to order evacuations ahead of Harvey. A head start now would be a very good idea.

County officials told the Herald that mandatory evacuation orders do not include criminal penalties for defiance. However, it does mean that emergency services will not necessarily respond, and anyone who stays will have to fend for themselves. After seeing the destructive power of Harvey last week, that prospect should have every Floridian in Irma’s path looking for the exits.

Update: Here’s a glimpse of the destruction wreaked by Irma in Saint Martin:

Batten down the hatches.