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Three days before Hurricane Ida hit Louisiana in August 2021, the storm was expected to peak as a Category 2. The New Orleans Saints thought they might be able to host a pre-season game in the meantime.

By the next day, Ida was spinning up so fast that forecasters were warning of a monster Category 4 hurricane – and New Orleans’ mayor said it was too late to order a mandatory evacuation. In the end, Ida delivered a gut-punch west of New Orleans while sparing the city the worst.

Along the way, Ida provided a sober lesson for the rest of America’s Gulf Coast. When a storm gains steam quickly and without warning, cities could run out of time to evacuate everyone.

Houston is one of the cities most at risk for a hurricane that intensifies just before landfall, according to a 2017 study. Some experts argue the problem could get worse with climate change, with storms ballooning at a moment’s notice more often.

In the Houston area, emergency managers say they are preparing for an era of storms that ramp up fast. They may narrow the list of people asked to evacuate to avoid clogging the roads. Meanwhile, they may host some residents in “shelters of last resort.”

It is yet another shift for a region that hit the reset button after the fatally flawed Hurricane Rita evacuation in 2005. Some experts say preparing for rapid intensification is critical.

“It’s one of the biggest concerns as a forecaster that you have,”said Eric Berger, a meteorologist who co-founded Space City Weather. “With the rapidly intensifying storms, especially near land, it just gives planners very little time to deal with them.”

When a famed meteorologist set out to model how climate change would affect hurricanes, he ran 22,000 simulations of how tropical storms interact with warming waters. One run bore a grim lesson for Houston:

The date is September 9, 2086. A hurricane cutting west across the Atlantic hits Florida as a Category 1, lashing Orlando with winds and rain. By the time it reaches the middle of the Gulf on Sept. 11, it has dissipated into a tropical storm.

Meteorologists know the weakened storm is tracking toward Houston, but even the Ike Dike cannot save the city from what happens next. In less than 24 hours, the storm’s winds speed up by 120 mph. The storm makes landfall on Galveston Island on the night of September 12 as a catastrophic, Category 5.

Kerry Emanuel, the Massachusetts Institute of Technology professor who conducted the study, wrote that rapid intensification on such a massive scale was “essentially nonexistent in the late 20th-century climate.”

In an era of global warming, he said, such monster explosions are set to become 100-year storms. Lesser, but still dangerous, intensifications of 70 mph in the 24 hours before landfall could happen once every five or 10 years on average.

For Emanuel, the lessons of the study were twofold. First, forecasters need to do a much better job improving their predictions of the intensity of storms, which has proven to be more difficult than predicting their track. Second, residents need to be prepared to react at a moment’s notice to a huge hurricane.

Scientists have mixed opinions on whether climate change will translate into more or fewer hurricanes, according to the Center for Climate and Energy Solutions. There is a consensus, however, that warming waters, which serve as the fuel for hurricanes, will translate into faster wind speeds. Rising sea levels also have the potential to make flooding worse.

Not every expert agrees that climate change will make rapid intensification more common – even so, there is plenty of evidence that planners need to take the phenomenon seriously. The deadliest hurricane in modern times, Hurricane Katrina, followed a slow, plodding path and lost strength shortly before landfall.

Katrina was an exception. In fact, about 80 percent of major hurricanes on record underwent rapid intensification. All four Category 5 storms to make landfall in the U.S. intensified rapidly in the last two to three days, according to the National Hurricane Center.

Gulf Coast cities like Houston are particularly vulnerable, experts believe.

“The ones that form off the Yucatan – and they can intensify rapidly – you don't have as long to plan,” said Phil Bedient, a professor at Rice University who studies hydrology and disaster management. “If that water is really hot out there … those things can very quickly become a Category 4 storm or a Category 5.”

Contraflow in question

One month after Katrina, as Hurricane Rita bore down on the Texas coast, Houstonians far outside storm surge zones who were prompted by dire warnings from officials hit the road en masse.

The storm is best remembered for the disastrous evacuation that accompanied it. Millions of drivers turned southeast Texas highways into a vast parking lot. Twenty-three nursing home residents died when their bus caught fire south of Dallas. Dozens more died from heat exposure during the evacuation.

In the wake of Rita, evacuation planners went back to the drawing board. One key new measure was contraflow, in which the highway lanes heading into the Houston area would be reversed to act as a second set of exits.

While contraflow can save crucial hours for motorists, it also is a cumbersome process that requires “every single cone and barrel you can find,” said Jeff Kaufman, a research scientist at the Texas A&M Transportation Institute.

“It’s not just time-consuming, it’s potentially dangerous,” Kaufman said. “The process involves what we call ‘flushing the system.’ So, if you think about it, it’s basically stopping all the traffic between Dallas and Houston. What you’re doing is, you’re trying to get all that traffic off the road so you can then put traffic going in the opposite direction down that road.”

Along with widened shoulders known as “evaculanes,” contraflow is a cornerstone of the evacuation plan for the highly car-dependent region. Transportation officials, however, say past a certain point, contraflow is off the table.

“A decision on implementing contraflow must be made by an appointed official within 60 to 48 hours of landfall,” Danny Perez, a Texas Department of Transportation spokesperson, said in a statement. “Getting the necessary equipment and personnel to their designated spots will take approximately 12 hours. Under 48 hours, contraflow is off the table.”

That timeline means that one of the regions most at risk for a rapidly intensifying storm could lose one of its best evacuation tools when it is most needed.

Brian Murray, spokesman for the Harris County Office of Homeland Security and Emergency Management, said that depending on the storm, in the event of a rapidly intensifying hurricane, officials may try to narrow evacuation orders to those most at risk.

“The immediate coastline becomes the only priority for the evacuation, and you’d have a much bigger emphasis on getting people to stay home, stay secure as opposed to trying to get on the roads and trying to get people out,” Murray said.

Changing plans

As Katrina closed in on New Orleans, officials directed residents who did not own cars to a hastily designated shelter of last resort, the Superdome. The harrowing scenes that played out inside the lightless, airless stadium made many residents vow never again to go to such a shelter.

In an era of tighter evacuation timelines, however, emergency managers increasingly expect to rely on shelters close to home. Officials stress that some shelters will be barebones refuges designed to host people for 12 to 24 hours, before they are whisked away.

The quarters will not be comfortable, planners warn. There may not even be electricity.

Harris County officials say they have identified a number of locations that could serve as emergency shelters.

“The idea is that to get people out of the surge zone is ultimately going to be the most important thing, so if that means we don’t get you any further than Tomball, yes, you’re still out of the surge zone. We don’t have to take you all the way to Austin for that,” Murray said.

Houston also is eying refuges of last resort. Emergency officials said they are mostly envisioned for publicly owned facilities such as schools, but they declined to release a list.

“We do not want people going there thinking that they are a full-blown shelter,” Mark Rayne, the city’s deputy emergency management coordinator, said. “So, the refuges of last resort, they are released at the very last minute.”

After a storm, planners hope to get residents out of smaller refuges quickly.

“If their home is safe and they want to go home, they can do that,” Brent Taylor, a spokesperson for Houston’s office of emergency management, said. “If they don't have somewhere, then they would be given the option to go into our evacuation hub, or what would end up being the city shelter system that pops up after the incident.”

Running the buses

When a big hurricane is headed toward Houston, the city has plans for picking up some of its most vulnerable residents, people who do not have cars that would allow them to flee on their own.

That plan involves shuttling residents to a central hub, the George R. Brown Convention Center, where they can catch buses to other parts of the state. It relies on buses and paratransit vehicles provided by METRO.

Both the city and the transit agency say they are ready to tweak their plans for a rapidly intensifying hurricane. In both cases, the city and the Metropolitan Transportation Authority have refused to release their baseline plans in response to public records requests, citing post-9/11 secrecy laws.

If Houston released its plans, a city lawyer wrote, “a terrorist or other criminal element could exploit the requested information in planning mass attacks, in order to incite panic and enhance the likelihood of death among emergency responders and members of the public.”

Other cities around the Gulf Coast, including Beaumont and New Orleans, have made their evacuation plans available in full. New Orleans has a specific, written contingency plan for a rapidly intensifying hurricane.

Neither Houston nor METRO officials provided a drop-dead time for when they no longer could execute the hub plan, but said they were ready to adapt to a rapidly intensifying hurricane.

“We look at, what’s the sustainment of winds, what are the road conditions, are there any high water areas?” Taylor said. “At one point, there are those triggers we can no longer pull anymore, for the safety of our personnel, as well. And those are the hard decisions.”

Editor's note: The story has been updated to correct the attribution of a quote.

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Matt Sledge is the City Hall reporter for the Abdelraoufsinno. Before that, he worked in the same role for the Times-Picayune | New Orleans Advocate and as a national reporter for HuffPost. He’s excited...