How Hurricane Idalia Snuck Up on Florida

Some 20 million Americans woke up on Monday to the news that they have just one full day to prepare for Tropical Storm Idalia, which is expected to strengthen into the first major U.S. hurricane of the season this week. The “nasty” weather is likely to begin in Florida on Tuesday night, ahead of landfall on Wednesday morning.

Though meteorologists had been carefully watching Idalia — née Invest 93L — since at least Wednesday, the storm’s rapid intensification has taken even forecasters by surprise. Idalia had grown into a tropical depression by Saturday, fully a day or two ahead of schedule, only for a NOAA reconnaissance flight on Sunday to discover it was already gusting at 65-mile-per-hour — enough for it to promptly be given status as a named tropical storm. Newly minted Idalia then intensified even further overnight on Sunday. New models show it will grow from a Category 1 hurricane on Monday night into a full-blown Category 3 hurricane “just 24 hours later.”

Needless to say, Idalia has everyone jumpy. Part of that is superstition: Storms with names that start with the letter "I" are the most frequently retired. But it also looks like Idalia is the real deal: “The number one rule of this column is not to pull the fire alarm unless there is a fire,” meteorologist Ryan Truchelut wrote for his newsletter WeatherTigeron Sunday. “Idalia is a fire. I’m pulling the alarm.” Florida Governor Ron DeSantis stressed similar urgency in an early morning news conference on Monday: “This is going to be a major hurricane,” he said, adding, “Floridians, you need to be executing your plans now. Late Tuesday, early Wednesday, it’s going to start to get really nasty.”

In an age of sophisticated weather modeling, the rapid intensification of Idalia feels like the hurricane snuck up on us. Sure enough, conditions like the record-warm Gulf of Mexico water temperatures — which Axiosdescribes as “the equivalent of a powder keg for hurricane energy” — have some experts cautioning we might not have exhausted all of Idalia’s surprises just yet.

Here are some of the most concerning variables as the storm approaches the coast.

The water temperature

The biggest reason to watch Idalia carefully is that it’s churning over some seriously deep warm water. The Gulf of Mexico has averaged a temperature of about 88 degrees Fahrenheit this month, which is 2.6 degrees above normal. For context, just a 1-degree rise in ocean temperature can bump up a hurricane’s winds by 15 to 20 miles per hour, meaning Idalia is essentially running on “rocket fuel,” Yale Climate Connections warns.

So we know Idalia will have ample fuel, but we don’t quite know what that means yet, since “storm intensity forecasts are notoriously hard to make, especially more than a day in advance,” as Andrew Freedman writes for Axios. But deadly Hurricanes Ian and Michael also rapidly intensified over warm waters, and “Idalia is likely to encounter waters even hotter” than they did.

Though climate change caused by human activities doesn’t increase the frequency of hurricanes, warmer oceans mean the ones that form tend to be more intense, slow, and destructive. Earlier this month, the National Hurricane Center updated its 2023 outlook from a “near-normal” season to an “above-normal” season, anticipating two to five major hurricanes. Oh, and in case you were wondering: The Atlantic, where Hurricane Franklin is chugging toward Bermuda, is really hot, too.

The tides

The biggest threat to life from to-be Hurricane Idalia looks like it will be from the storm surge. Though conditions can still worsen — particularly with a storm as seemingly unpredictable and rapidly intensifying as this one — emergency officials aren’t suggesting people in the storm’s path flee altogether, just that they get to higher grounds ASAP. “Evacuate tens of miles, not hundreds of miles,” the Executive Director of the Florida Division of Emergency Management Kevin Guthrie said.

One reason for the storm surge danger is because of the region’s “bathymetry,” meteorologist Matthew Cappucci tweeted. That is to say, the slope of the sea floor can lead to water “piling” up against the coast and being pushed inland. On top of that, emergency officials are closely watching the tides; as Florida Today notes, this week’s supermoon is making high tides even higher.

The trajectory

Hurricanes that approach the west coast of Florida can be “notoriously challenging” to track because of their angle, Yale Climate Connections writes. “[O]nly a slight nudge in trajectory to the right or left can change the landfall location by 50 or 100 miles.”

Idalia’s trajectory will become increasingly clear as it moves closer and closer to shore, but in the meantime, emergency officials are urging everyone both within and without the cone to be prepared for the storm. Notably, the storm surge in particular will impact areas outside of where Idalia directly hits:

Foiled emergency preparations

One rule of thumb for hurricane season is to always keep half a tank of gas in your car. But on Sunday afternoon, Florida reported contaminated gasoline and diesel had been sold from at least 29 stations in the state in a corridor potentially stretching from Brooksville south to Fort Myers.

The contaminated gas could “increase the chances of drivers getting stranded” while “generators used in the case of storm-related power outages could also be affected,” The Washington Post reports.

All the more reason to know your zone and leave early if necessary, follow evacuation orders promptly (and arrange alternative travel if you’re concerned about your car), and be prepared for flooding.