On September 1, 2019, Hurricane Dorian made landfall 190 miles east of Miami on Abaco Island in the Bahamas as a Category 5 storm – the highest echelon in the Hurricane Saffir-Simpson Wind Scale, which the National Hurricane Center uses to classify hurricanes based on their maximum sustained wind speed. Any storm with maximum sustained winds of 74 mph or more is considered a hurricane and then assigned a category, starting at 1 and then increasing in levels approximately every 15 to 25 mph until it reaches 5, the category that officially encompasses all storms with maximum sustained winds of 156 mph or greater.
But Hurricane Dorian, with maximum sustained winds of 185 mph and gusts of up to 220 mph, seemed too powerful to be considered a Category 5. After all, when Hurricane Andrew hit South Florida in 1992 as a Category 5, her maximum sustained winds were an alarming 165 mph but still considerably less than Dorian’s. Based on the progression between each level, it was speculated that the hypothetical Category 6 rating would begin at sustained wind speeds of 182 mph.
“Dorian was the tipping point for me. I kept saying to myself, ‘This is different from a Category 5,'” said Richard Olson, director of Florida International University’s Extreme Events Institute ( FIU). new times. “My God, when you’re in the 180 to 200 [mph of sustained wind speeds] – that, to me, has to be another category.”
After Hurricane Patricia’s maximum sustained winds reached 215 mph off the Pacific coast of Mexico in 2015 and then Dorian’s 185 mph in 2019, Olson realized the need to prepare for what he and his team called internally “Category 6” storms, although no such designation exists on the current Saffir-Simpson scale. In 2012, the FIU launched its wind wall, a 12-fan, 8,400-horsepower hurricane simulator that is currently the largest and most powerful university research facility of its kind. The only problem is that its wind speeds peak at around 160 mph and, as the oceans continue to warm, scientists predict a dramatic increase in the frequency of ultra-intense megastorms like Patricia and Dorian from occurring once every eight years in the late 20th century to about one megastorm per year by 2081.
“We have to get ahead of what nature throws at us,” says Olson. “We have to move on. I don’t want my kids and grandkids to say, ‘You knew that. Why didn’t you do anything? Why didn’t you research this problem when you have you had the chance?'”
The good news is that Olson and his team at the Extreme Events Institute have been recently awarded a $12.8 million grant from the US National Science Foundation to design a large-scale test “Cat 6 prototype facility” with wind speed capabilities of up to 200 mph. Olson estimates it will be four times larger than the Wind Wall and comparable in size to a small football stadium. The project is still in its initial design and planning phase, with CRF’s Department of Civil and Environmental Engineering leading a multidisciplinary team of researchers from eight other schools, including Stanford University, the Georgia Institute of Technology and the University of Florida. The proposal has yet to be approved, but Olson believes the new facility could be operational by 2030.
The biggest improvement, however, is not the facility’s wind speed, but its water basin, Olson explains. For the first time, researchers and engineers will be able to test not only how buildings and infrastructure respond to extreme winds, but also the combined effects of extreme winds, storm surges, waves and flooding.
“We’re trying to get all the components of a hurricane under control — not just wind and rain, but understanding how wind interacts with water,” Olson said. “Frankly, it is the component of water that is most dangerous to human beings.”
The Saffir-Simpson scale was developed in the early 1970s by Coral Gables structural engineer Herb Saffir and then-National Hurricane Center director Robert Simpson. It has since become the predominant measure among meteorologists for describing hurricane strength. But after Hurricane Dorian, there were growing calls for the hurricane center to change its ranking system or abandon it altogether.
“Don’t be fooled by the storm’s Saffir-Simpson scale. It has several issues,” said Jeff Masters, meteorologist for Yale Climate Connectionsrecount new times. “First, it’s just a wind scale. So it doesn’t take into account the threat of storm surge or freshwater flooding from heavy rain.”
This may lead the public to underestimate the threat of larger storms with lower wind speeds, which tend to rank lower on the Saffir-Simpson scale but still carry substantial risk due to surges. storms and inland flooding. This is particularly dangerous given that a 2014 study by Edward Rappaport, assistant director of the hurricane center, found that 90% of all hurricane deaths are water-relatedmost people drowning in flooding caused by storm surges or freshwater flooding and mudslides caused by precipitation.
Hurricane Sandy, for example, was a Category 1 storm when it made landfall near Atlantic City, New Jersey, in 2012. But as one of the biggest hurricanes on record, it caused heavy rains and floods: 72 people died in the United States and there. $70.2 billion in damages. In 2008, 113 people died in the United States as a result of Hurricane Ike, even though it was a Category 2 storm when it made landfall in Galveston, Texas.
“A lot of people are caught off guard because they’ve been like, ‘Oh, that’s just Category 2,'” Masters says. “The take home message is that you don’t need a Cat 5 [hurricane] suffer catastrophic damage. »
The National Hurricane Center currently issues storm surge watches and warnings separate from its Saffir-Simpson scale. But Masters has long considered other ways to more accurately portray the threat of coming storms to the public. He thought of creating two additional Saffir-Simpson-type scales in addition to wind speed: one for storm surge threat and another for freshwater flooding.
“But maybe it’s too complicated,” he admits.
He also wondered about the European medium-term forecasting model, which emits a simple yellow, orange or red color-coded threat based on the combined effects of winds, storm surges, flooding and other variables. There is also something called the Integrated Kinetic Energy (IKE) metric, which accounts for the intensity and size of the storm and is said “more representative of his destructiveness.”
“The oceans are warming and hurricanes get their power from the heat of the water,” notes Masters. “There’s been a 10% increase in major hurricanes around the world, and the strongest storms are definitely getting stronger around the world.”
It’s only a matter of time before one of these megastorms makes landfall in the United States. Masters sees the CRF’s prototype Category 6 facility as an integral part of preparing for storms of this magnitude.
“We have to do this job,” he says. “If we know in advance what these storms are capable of, we can design a response to the threat, get people out of harm’s way, protect our infrastructure as best we can before the storm hits, and maybe change some of our practices so that we don’t build in harmful ways to the degree that we do now.”