Hurricane Otis went from a mild hurricane to a massive hurricane in record time, and scientists are struggling to figure out how — and why they didn’t see it coming.
Typically, reliable computer models and the meteorologists who use them failed to predict Otis’ explosive intensification, leading to a nightmare scenario of an unexpectedly strong storm overnight. Acapulco was expected to be a tropical storm just below hurricane strength, but 24 hours later Otis barreled toward the Mexican coast with winds of 165 mph (266 km/h), the strongest landfall of any Eastern Pacific hurricane.
In just 12 hours, Otis doubled in strength from 70 mph (113 km/h) winds to 160 mph (257 km/h) – also a record as it approached the coast. And it got even stronger before it struck. Typically, storms gain or lose a few mph in 12 hours, although some outliers reach 30 to 50 mph (48 to 80 km/h) in a day.
People receive assistance crossing a highway blocked by a landslide triggered by Hurricane Otis near Acapulco, Mexico, Wednesday, Oct. 25, 2023. (AP Photo/Marco Ugarte)
“What happened to Otis was just crazy,” said University of Miami hurricane researcher Brian McNoldy. But it falls in line with a documented trend Scientists said hurricanes have intensified rapidly in recent decades due to warmer waters linked to climate change.
Five different hurricane experts told The Associated Press they weren’t entirely sure what triggered Otis and why it wasn’t forecast, especially as forecasters have dramatically improved their intensity forecasts in recent years.
“The models completely screwed up,” said Massachusetts Institute of Technology (MIT) atmospheric sciences professor Kerry Emanuel, a hurricane expert.
Experts point out that there is a lack of data about the storm and its surroundings and that there is simply no full understanding of why a storm behaves like it is on steroids.
And that’s really important because in the case of Otis, the storm was just about to come ashore when it intensified.
“It’s one thing for a Category 5 hurricane to make landfall somewhere when you expect it to,” McNoldy said. “But it happens when you don’t expect something to happen, it’s really a nightmare.”
For example, McNoldy, who lives in Miami, said that the forecast of a tropical storm would prompt him to “do something like put some light furniture in there, take down wind chimes, things like that.” That’s all. They are not preparing for a Category 5 hurricane.”
Michael Brennan, director of the National Hurricane Center, said: “This is a very dire scenario, a populated area, rapid intensification just before landfall, a change in expectations of impacts occurring in a time frame that doesn’t mean much to people There is time to react.” .”
Brennan said Otis’ unforeseen increase was because “it found a much more favorable environment than we expected.” He said part was warm water, but part was that the winds – moving in the right direction and at the right height – allowed a somewhat harsh storm to quickly develop structure and strengthen.
McNoldy said there may be a mystery ingredient that scientists don’t currently know about, but water is the key.
Warm water is fuel for hurricanes. Hot, deep water is like an all-you-can-eat buffet.
Tourists swim in Acapulco, Mexico, October 24, 2023. (AP Photo/Bernardino Hernandez)
Globally, the world’s oceans have been recording monthly surface heat records since April. Surface water off the Mexican coast was warm, but “not insanely warm,” said atmospheric scientist Kristen Corbosiero of the University at Albany. Bennan and McNoldy said the water temperature was perhaps 1 or 2 degrees above normal.
Below, the water was much hotter than usual, “and there’s a lot of fuel out there right now,” McNoldy said. Still, the storm did not persist or strengthen, as would be expected if it intensified rapidly, Brennan said.
The heat content in the deeper ocean has increased worldwide Breaking records. According to McNoldy and other scientists, this is due to human-caused climate change, as the oceans act like a sponge, absorbing much of the excess heat created by burning coal, oil and gas.
Otis and two other historically explosive cases of rapid intensification – Patricia in 2015 and Wilma in 2005 – all occurred during the same period in mid- to late October, when the heat content of deeper water and oceans was at its highest, McNoldy said.
Numerous studies around the world have shown that there are more cases of rapid hurricane intensification than before. An official definition of rapid intensification is a strength increase of 35 miles per hour (56 km/h) in 24 hours. Six storms in 2020 intensified rapidly, many shortly before making landfall. In 2017, two devastating hurricanes, Harvey and Maria, rapidly intensified. Last month, Hurricane Lee rapidly strengthened in the Atlantic from 80 mph (129 km/h) to 155 mph (249 km/h) but made no impact.
“We’re seeing so many more cases of these just amazing rapid intensification events,” said former hurricane and climate scientist Jim Kossin of the National Oceanic and Atmospheric Administration, now at the First Street Foundation.
Kossin said there is evidence that what is happening around the world over a longer period of time is partly due to human-caused climate change, but that is difficult to say about a single storm.
But he added: “This is exactly what we would expect as the climate warms.”
Trucks sit idle on a highway blocked by a landslide triggered by Hurricane Otis near Acapulco, Mexico, Wednesday, Oct. 25, 2023. (AP Photo/Marco Ugarte)
MIT’s Emanuel said it could be more than just the temperature of the water, but also its low salinity. The water in the area is fresher at the surface this time of year due to heavy rainfall, and that changes the mix of water temperatures, he said. Typically, a hurricane mixes the warm water on the surface with cooler water below. But when the surface water is fresher, a storm pulls even more hot water up from the bottom, feeding the storm even more “and before you know it, you’re in hot water,” Emanuel said.
An important test of this theory is whether Otis leaves warm water behind. Typically, hurricanes leave behind cold water. Emanuel hopes satellite images will show it, but it’s not certain they will provide the right picture.
Another factor Brennan and others mention is that forecasters may have underestimated Otis’ initial strength. That would mean that it hasn’t intensified as much as it seems because it was stronger to begin with.
“The Eastern Pacific is a huge data deficit in many ways,” Brennan said. “There are no buoys. There are very few land observations. There are no radars on the west coast of Mexico. So we rely almost exclusively on satellite images.”
And sometimes satellites looking at a storm from above can’t get an accurate picture of what’s going on.
Think of it like a puzzle where forecasters sometimes only have 10% of the pieces, Brennan said.
Forecasters have many more tools to see what happens during storms in the Atlantic, he said.
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