Hurricane Irma is expected to hit South Florida and the Gulf Coast: What we know

Hurricane Irma is already one for the record books.

Earlier in the week, Irma sustained 185 mph winds for more than 24 hours, a record length of time for a hurricane in the Atlantic. And Irma was a Category 5 storm for around 3 days — which is also nearly a record.

Now, Irma has weakened a bit to a Category 3 storm, slowing over Cuba to 125 mph. But don’t let that fool you: The National Hurricane Center believes that it will speed back up when it leaves Cuba before it makes landfall on the Florida Keys (expected on Sunday morning).

Originally, Miami was expected to bear the brunt of the storm once it hit Florida — but by Saturday morning, the storm’s trajectory had shifted westward, with Tampa, the Gulf Coast, and other parts of South Florida (including the Florida Keys) in line for the worst effects. Mandatory evacuations have been issued for Collier County around Naples, Hillsborough County around Tampa, and the Keys.

Tropical storm and hurricane-strength conditions are expected to begin in Florida around 2 pm on Saturday and continue into Sunday. Roughly 5.6 million have been asked to evacuate their homes in the state due to the storm.

"You need to leave right now — not tonight, not in an hour, now,” Florida Governor Rick Scott said in a Saturday morning presser. “You are running out of time"

The National Hurricane Center projects that Irma will be Category 4 when it hits Florida. That would make it one of the most powerful hurricanes to land in the state. And it could even strengthen back into a Category 5.

But don’t focus so much on the category number, which is determined solely by wind speed: It’s the combination of wind, storm surge, rain, flooding, and even the possibility of tornadoes that are the biggest concern for much of the Florida peninsula. (The greatest threat to loss of life in most hurricanes is storm surge and coastal flooding — not wind.)

The National Hurricane Center has issued a hurricane warning for much of West and South Florida, which means the center believes dangerous conditions are imminent.

NOAA

“There is the danger of life-threatening storm surge inundation in portions of central and southern Florida, including the Florida Keys, during the next 36 hours, where a Storm Surge Warning is in effect,” the National Hurricane Center explained in a Saturday morning update.

There’s also a chance that coastal areas of Gorgia, South Carolina, and North Carolina, will be affected by Irma. “Irma will likely bring periods of heavy rain to much of the Florida Panhandle, Georgia, South Carolina, and western North Carolina early next week, including some mountainous areas which are more prone to flash flooding,” the hurricane center reports.

NOAA

Irma has already devastated several Eastern Caribbean islands

On Wednesday, the fierce storm hit the northeastern Caribbean islands with 185 mph winds, moving through Barbuda and St. Martin. The New York Times reports widespread damage to property, homes, and infrastructure on these and other islands. Gaston Browne, the prime minister of Antigua and Barbuda, told reporters Barbuda “is totally destroyed — 90 percent at least.” Reports indicate at least 19 have died in the Caribbean.

Wednesday night, the storm passed just north of Puerto Rico, and knocked out power for around 1 million people on the island. There are fears the outages could last months. On Thursday, Irma grazed by the north shore of Dominican Republic and Haiti and started to pummel Turks and Caicos and the Southeastern Bahamas. Friday night, the storm hit Cuba.

Evacuations in Florida are underway

Much is still uncertain about how the storm’s impact on Florida. Tiny shifts in its track appear to have steered the worst of Irma away from Miami-Dade and towards Tampa. There are also chances of impacts in Georgia and the Carolinas, depending on which direction the storm movesin the coming days.

Florida has declared a state of emergency, freeing up resources for shelters, evacuations, and deploying National Guard members. Mandatory evacuation orders are underway in the Florida Keys and the Gulf Coast. Officials in Miami-Dade and Broward counties in Florida are ordering evacuations of certain residents in low-lying areas.

Georgia Gov. Nathan Deal has also declared a state of emergency and ordered the evacuations along the coast beginning Saturday. Georgia, with a concave, shallow coast line, is particularly vulnerable to storm surge, Hal Needham, a geographer and storm surge expert says. Even if Irma degrades to a tropical storm by the time it reaches Georgia, “there still can be a 10 to 12 foot storm surge,” Needham says.

NOAA

"We can rebuild your home, but we cannot rebuild your life," Florida Gov. Rick Scott said on CNN Wednesday. "Take what you need, but only what you need."

Don’t just focus on wind speed. Even if Irma downgrades, it’s still a dangerous storm.

Irma is currently churning with sustained 130 mph winds. That kind of wind can destroy homes, uproot trees, and knock out power for months. But scientists caution against focusing on wind speed alone. As we saw with Hurricane Harvey, even a downgraded hurricane or tropical storm can cause massive destruction and chaos. Even if Irma downgrades, it’s still dangerous.

The National Center for Atmospheric Research has a hurricane severity scale that factors in wind speed, hurricane size, and forward speed (whether it stalls or not) to rate the potential destructiveness of a storm 1-to-10 scale. Earlier this week, Irma rated at a 5.3. On this scale, Hurricane Katrina would have scored a 6.6.

Zachary Crockett/Vox

Harvey dumped 50-plus inches of rain over parts of Houston and Louisiana, creating devastating floods (mostly because the storm stalled over the Gulf Coast after it made landfall). Irma, so far, is not expected to be as devastating a rain event.

But the US is still reeling from the impacts of Hurricane Harvey. Parts of Houston are still under water, thousands are still living in shelters, and cleanup efforts have barely begun. Needless to say, another catastrophic storm in a two-week period would add salt to a wound and further strain the disaster relief resources of the federal government and groups like the Red Cross already stretched thin with the response to Harvey.

But wait, there’s more: Hurricane Jose is now a Category 4

As if Irma weren’t enough to worry about there’s another huge storm churning in the seas — Jose.

Hurricane Jose is a Category 4 storm as well; when it and Irma were at their peak strengths earlier this week, it was the first time two hurricanes with 150-plus mph winds have been in the Atlantic at the same time. Jose has slowed somewhat, its winds having come down to 145 mph. Jose is expected to graze by (by not directly strike) some of the very same eastern Caribbean islands devastated by Irma. The entire island of Barbuda, population 1,600, has been evacuated again. After passing by these islands, Jose is expected to travel North and East into the open ocean, and begin to weaken.

NOAA

How to follow Hurricane Irma:

• The National Hurricane Center has a page updating every few hours with the latest watches and warnings for Harvey. Check it out.
• Follow the San Juan branch of the National Weather Service on Twitter. And the Miami, Florida Keys, and Tampa branches as well.
• Follow the Capital Weather Gang’s Twitter account. These folks tend to live-tweet storm updates.
• Here’s a Twitter list of weather experts via meteorologist Eric Holthaus. These experts will give you up-to-the second forecasts and warnings.

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