After pummeling Louisiana on Sunday as a Category 4 storm, Hurricane Ida is spinning its way through Alabama and Tennessee toward the East Coast, where it is forecast to spread yet more severe weather in the form of rain and tornado-generating winds.
In its wake Ida left millions of people in and around New Orleans without power—possibly for weeks. Damage in the state was a result of wind gusts of up to 185 miles per hour, storm surges reported to be seven feet or more, and torrential rainfall.
The storm grew in a matter of hours from virtually nothing into a beastly storm, nourished by pockets of extremely warm waters in the Gulf of Mexico that currently measure about 85 degrees Fahrenheit, several degrees warmer than average.
“There’s so much energy stored there that once you get a hurricane to form you can feed it more energy and create a monster,” says Louisiana State Climatologist Barry Keim.
Experts say Hurricane Ida is an example of what storms could look like on a warming planet. It strikes the Gulf Coast on the heels of a major United Nations report finding strong evidence that climate change will make hurricanes rainier, slower, and more capable of explosive growth.
“Ida is another example of a changing face of hurricane intensity,” says Jill Trepanier, an expert in extreme weather at Louisiana State University.
Not since last year’s Hurricane Laura and an unnamed storm from 1856 has a storm with such strong winds hit the state. Damage and economic losses from the storm could amount to as much as $80 billion, according to early estimates by AccuWeather.
More powerful storms in the future?
To determine the exact influence climate change may have had on Hurricane Ida, scientists will have to perform what are called attribution studies. In those, computer models re-run forecasts under atmospheric and oceanic conditions as they would have existed with and without greenhouse gas emissions. Such studies have proven that climate change contributed substantially to the intensity of the recent Pacific Northwest heat wave, Hurricane Harvey in 2017, and Hurricane Florence in 2018. But they can take months to complete.
Absent those more precise studies, scientists recognize several links between climate change and Hurricane Ida, pointing to certain characteristics consistent with warmer air and oceans.
One of the most eye-popping aspects of Ida was how quickly it grew from a blip on the radar to a major hurricane.
“Just a few days ago it didn’t really exist,” says Daniel Horton, an extreme weather expert at Northwestern University. Three days before the storm hit, “if you had looked at a map you wouldn’t have seen a hurricane in the Gulf.”
That type of fast-forward growth is what meteorologists call rapid intensification—defined as a 35 mile-per-hour increase in under 24 hours. Ida, however, far surpassed that criterion, increasing by 65 miles per hour in half that time.
Ida spun up out of a tropical depression in the southern Caribbean, a common place for storms to begin during the peak of hurricane season. On Saturday afternoon it was a Category 1 hurricane, with winds measuring 103 miles per hour. But then it passed over Cuba and encountered what’s called the Loop Current, hot Caribbean water that curls into the Gulf of Mexico.
“This exceptionally warm water basically created this warm-water superhighway for this storm. It fed the storm energy and allowed that storm to blossom into a Cat 4,” says Keim.
A study published in 2019 in the journal Nature Communications found early evidence that climate change has likely made rapid intensification more common. In recent years, some of the most damaging hurricanes resulted from rapid intensification—Hurricane Laura in 2020, Hurricane Michael in 2018, and Hurricane Harvey in 2017. And while the ocean undergoes periods of natural warming that can supply hurricanes with more fuel, the study found an increase in rapid intensification surpassing those natural fluctuations, says lead author Kieran Bhatia.
Unlike records rainfall or drought, records of storms rapidly intensifying only stretch back about 40 years, Bhatia says. But scientists are urgently trying to figure out the phenomenon and how climate change affects it.
“Rapid intensification is a phenomenon that turns a storm from a predictable natural disaster, one that can be forecasted five to six days in advance, to an unpredictable one,” he says.
Faced with such a sudden storm, Louisiana struggled to prepare. New Orleans didn’t have time to implement a mandatory evacuation. While meteorologists are experts at predicting where and when a storm will hit, forecasting intensity is challenging, and rapid intensification makes it more difficult.
In the future, scientists don’t expect to see more hurricanes, but they do expect more powerful ones. Over the 20th century, ocean temperatures have been steadily rising, not only at the surface, but also into great depths. Hurricanes that may have once been restrained by cooler ocean water beneath the surface can now access a vast supply of the warm water they use as fuel.
“The ones we get are likely to be stronger, which means we’ll probably have more storms in the major hurricane classes—Category 3, 4, or 5,” Keim says.
Slow, rainy storms
While the exact future of rapid intensification remains under investigation, scientists can confidently say warmer temperatures will make hurricanes rainier and slower moving: For every degree Celsius the atmosphere warms, it can hold 7 percent more moisture—and thus more rain—and because the poles are warming faster than the tropics, the winds that move hurricanes forward are expected to weaken.
As Hurricane Ida made landfall, its advance slowed to about 10 miles per hour—not the slowest storm in recent years, but enough to expose New Orleans to nearly 15 inches of rain and strong winds for longer. For comparison, last year Hurricane Laura moved over southeast Louisiana at 20 miles per hour.
In addition, Louisiana’s topography played a role in Ida’s sluggish movement. Storms rely on warm ocean water as fuel, and when the hurricane made landfall in Port Fourchon, the marshes and swamps continued to feed it energy l and keep it intact. Those same wetlands, however, also help absorb one of the deadliest impacts of hurricanes—walls of water surging in from the sea. Hurricane Ida was forecast to produce a surge as high as 16 feet, but early reports indicate the surge was half that. Forecasters intentionally warn about worst-case scenarios to encourage those in harm’s way to evacuate.
As Hurricane Ida crawled over land at a pace slower than the average long-distance runner, it dumped enough rain to cause levee failures in Plaquemines Parish and flooding in low-lying areas south of New Orleans. Part of that flooding was brought on by a storm surge high enough to inundate coastal towns. And because Louisiana loses its wetlands at the rate of a football field every hour, it will increasingly lose protection against surging ocean waters.
As climate change makes storms more extreme, it means coastal communities will have to adapt to more dangerous weather.
“The takeaway has got to be that if you’re relying on plans, whether they be evacuation plans or infrastructure or design, and it’s not based on what I would call the new normal—that climate change has altered the frequency and intensity of extreme events—then it’s time to update them,” says Northwestern’s Horton.