Forecasters didn’t even anticipate Otis would become a hurricane. Then it broke all-time records.
When residents of Acapulco, Mexico, went to bed on Monday, Wednesday’s forecast called for gusty winds and some downpours. Otis, a run-of-the-mill tropical storm, was expected to only “gradually strengthen” en route to the coast. Instead, Otis intensified faster than any other eastern Pacific storm on record Tuesday and became the strongest hurricane to ever strike Mexico slamming Acapulco as a “potentially catastrophic Category 5.”
As winds catapulted to Category 5 strength Tuesday evening, shocked forecasters at the National Hurricane Center described the storm’s extreme intensification as a “nightmare scenario” and “extremely dangerous situation.” Nobody saw it coming — but with human-caused climate change warming the planet’s oceans, this situation could become more frequent.
On Monday night, most computer models only simulated Otis’s top winds reaching 60 mph (these forecasts increased some on Tuesday as the storm showed signs of rapidly gaining strength). Instead, Otis came ashore near Acapulco with 165 mph winds, surely catching most of the city of 1 million off guard.
On X, formerly Twitter, meteorologists described the forecast as “an almost incomprehensible miss,” “a fail of epic proportions” and “just a catastrophic failure.”
Hurricane warnings weren’t issued for southern Mexico’s western coast until 2 a.m. local time Tuesday, about 24 hours before landfall — and, even then, the forecast was for a Category 1. The 9 a.m. Hurricane Center forecast on Tuesday — about 15 hours before landfall — still called for a Category 1. Not until 3 p.m., less than 12 hours before landfall, did the forecast increase to a Category 4.
While hurricanes can surprise meteorologists, a wind forecast error of nearly 100 mph is highly unusual. But some climate scientists have warned that extreme rapid intensification, made more likely by the effects of human-caused climate change and warming oceans, will lead to more unpredictable storms.
In 2017, MIT hurricane scientist Kerry Emanuel published a paper titled “Will Global Warming Make Hurricane Forecasting More Difficult?” In it, he argued that instances of extreme rapid intensification could be up to 20 times more common by the end of the 21st century.
Otis careened from a tropical storm to Category 5 strength in 12 hours, and its peak winds increased 115 mph in 24 hours. That’s around a threshold that Emanuel wrote was “essentially nonexistent in the late twentieth-century climate” but increasingly probable in the current warming climate.
Just this week, a study documented substantial increases in rapidly intensifying Atlantic storms over the past several decades. “The increased likelihood for hurricanes to transition from weak storms into major hurricanes in 24 hours or less was particularly striking,” Andra Garner, the study’s author, told The Washington Post.
Strongest landfalling Pacific hurricane on record
On Monday night, most computer models only simulated Otis’s top winds reaching 60 mph (these forecasts increased some on Tuesday as the storm showed signs of rapidly gaining strength). Instead, Otis came ashore near Acapulco with 165 mph winds, surely catching most of the city of 1 million off guard.
On X, formerly Twitter, meteorologists described the forecast as “an almost incomprehensible miss,” “a fail of epic proportions” and “just a catastrophic failure.”
Hurricane warnings weren’t issued for southern Mexico’s western coast until 2 a.m. local time Tuesday, about 24 hours before landfall — and, even then, the forecast was for a Category 1. The 9 a.m. Hurricane Center forecast on Tuesday — about 15 hours before landfall — still called for a Category 1. Not until 3 p.m., less than 12 hours before landfall, did the forecast increase to a Category 4.
While hurricanes can surprise meteorologists, a wind forecast error of nearly 100 mph is highly unusual. But some climate scientists have warned that extreme rapid intensification, made more likely by the effects of human-caused climate change and warming oceans, will lead to more unpredictable storms.
In 2017, MIT hurricane scientist Kerry Emanuel published a paper titled “Will Global Warming Make Hurricane Forecasting More Difficult?” In it, he argued that instances of extreme rapid intensification could be up to 20 times more common by the end of the 21st century.
Otis careened from a tropical storm to Category 5 strength in 12 hours, and its peak winds increased 115 mph in 24 hours. That’s around a threshold that Emanuel wrote was “essentially nonexistent in the late twentieth-century climate” but increasingly probable in the current warming climate.
Just this week, a study documented substantial increases in rapidly intensifying Atlantic storms over the past several decades. “The increased likelihood for hurricanes to transition from weak storms into major hurricanes in 24 hours or less was particularly striking,” Andra Garner, the study’s author, told The Washington Post.
Strongest landfalling Pacific hurricane on record
Otis’s Category 5 landfall is a first for Mexico, as well as for the entire Pacific coastline of North or South America. While the west coast of Mexico regularly experiences hurricanes, and Otis is the fourth storm to make landfall in Mexico in a month, many of them exhibit a weakening trend before landfall. Otis strengthened up until the very last moment.
It appears that high-altitude winds relaxed more than originally intensified, offering Otis an undisturbed and untapped environment within which to intensify at breakneck pace. It took advantage of bathlike water temperatures around 88 degrees.
Otis’s entire formation came about as an “accident” of sorts; instead of beginning its life as a preexisting tropical wave, it instead was caused when northerly Gulf of Mexico winds were funneled through a gap in between mountain ranges on Mexico’s Isthmus of Tehuantepec. That created a spurt of winds that curled in on itself upon exiting into the Pacific, leading to a small lobe of spin, or vorticity, that began producing thunderstorms.
One of the reasons Otis was so difficult to forecast was its size. As a relatively compact storm, it was particularly sensitive to very localized environmental conditions and prone to rapid fluctuations in strength.
Although hurricane intensity forecasts have improved substantially in recent years, models still have a difficult time predicting rapid changes that can occur in smaller storms.
How does Otis compare to other storms?
Otis’s winds leaped 90 mph in 12 hours, a record for the eastern Pacific. However, its 24-hour intensification falls just shy of Hurricane Patricia in 2015; that storm’s peak winds leaped a record 120 mph in strength in 24 hours. It eventually made landfall as a 150 mph Category 4, weakening as it approached land. But it had become the strongest hurricane on record over the ocean with 215 mph winds.
Aside from Patricia, half a dozen other hurricanes made landfall on Mexico’s west coast as Category 4s since the 1960s.
It first became clear that Otis was undergoing extreme rapid intensification on Tuesday afternoon, when a Hurricane Hunter flight found staggeringly different conditions inside the storm within two consecutive passes through the eye. Within 80 minutes, the storm’s central air pressure dropped by 10 millibars. In other words, there was 1 percent less air in the middle of the storm. That may not sound like much, but it signaled an extreme “vacuum” effect within the storm, causing the winds near the ground to accelerate to dangerous levels.
Matt Lanza, a meteorologist who runs The Eyewall, a hurricane commentary website, wrote the forecast for Otis was unacceptable.
“Otis will be studied in the coming months and years to understand why it blew up so quickly, and so powerfully, in such a short period of time,” he said. “In moments like these, forecasters utterly failed the people of Southern Mexico. We must do better.”
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