When Hurricane Melissa hits Jamaica On October 28, it showed just how destructive a Category 5 hurricane can be—and more.
It will be several weeks before experts can truly assess How badly did Hurricane Melissa devastate Jamaica? and nearby islands. But scientists are already confident that climate change contributed to the storm's terrifying strength, which pushed wind gusts above the minimum required for a Category 5. And Melissa could revive the debate revolving around whether the five categories meet the Saffir-Simpson hurricane wind scale. enough to describe the monster storms that climate change can cause..
READ MORE: How Hurricane Melissa became one of the most powerful Atlantic storms on record
LEARN MORE: Pictures of Hurricane Melissa show a monstrous storm entering the Book of Records
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What will a Category 6 storm look like?
The Saffir-Simpson scale breaks hurricanes into numbered categories based solely on peak sustained wind speeds. At this scale, a storm with sustained maximum wind speeds of 74 to 95 mph is a Category 1 hurricane. When wind speeds reach 181 mph, it becomes a Category 3, which is also the official designation of a “major hurricane.” The most severe classification on the Saffir-Simpson scale, Category 5, designates hurricanes with sustained peak wind speeds of 157 mph or higher.
But last year, hurricane scientists suggested that this “open” nature of the Saffir-Simpson scale is no longer sufficient to capture the reality of modern hurricanes. They proposed to create category 6which will begin with maximum sustained winds of 192 mph.
Five storms have so far reached this terrifying milestone, all of them years after 2010, the researchers noted. These storms were Hurricane Patricia in the eastern Pacific and four traditionally uncategorized typhoons in the western Pacific: Haiyan, Goni, Meranti and Surige.
Hurricane Melissa didn't quite meet the proposed Category 6 boundary, with initial measurements showing maximum sustained winds of 185 mph. This ties it with several other major storms—the Labor Day Hurricane in 1935 and Hurricanes Gilbert, Wilma and Dorian in 1988, 2005 and 2019, respectively—as the second-highest peak sustained wind speed in the Atlantic Ocean.
The strongest sustained wind speeds in the Atlantic on record occurred during Hurricane Allen in the 1980s, which reached 190 mph, nearly hitting the researchers' proposed Category 6.
However, some scientists argue that expanding the Saffir-Simpson scale is not necessary. This argument is based on the fact that the scale not only includes category numbers and wind speeds, but also indicates what kind of damage can be expected from those winds. Indeed, Herbert Saffir, one of the scientists behind these scales, was a civil engineer who studied wind damage.
Category 3 is described by the National Hurricane Center as causing “devastating damage”: Even well-built homes could lose their roofs, and the affected region could experience loss of water and power for days. Both categories 4 and 5 are described as causing “catastrophic damage”: “Much of the area will be uninhabitable for weeks or months,” the rubric says. At this point, Category 6 opponents argue, there is no point in making any further distinctions about how dire the situation will be.
Some are concerned that the additional category could have the opposite effect than intended. “This could inflate the scale so much that destructive storms assigned to lower categories will receive even less attention than they currently do,” wrote University of Arizona atmospheric scientist Kim Wood. on Bluesky.
Climate change and monster storms
The shocking winds of Hurricane Allen in 1980, before there was a noticeable trend of increasing hurricane intensity, are an important reminder that climate change does not directly affect cause monstrous hurricanes. Scientists prefer to describe climate change as “loading the dice” or increasing the severity of severe storms.
And scientists have already concluded that climate change did contribute to the strength of Hurricane Melissa. An analysis by the nonprofit research organization Climate Central estimated that the waters Melissa passed through as a Category 5 storm as it approached Jamaica were more than one full degree Celsius (two full degrees Fahrenheit) hotter than normal—a circumstance that climate change has made more than 700 times more likely.
A second rapid analysis by ClimaMeter found that climate change has boosted Melissa's winds and rainfall by about 10 percent compared to how the storm would have played out without humans adding heat-trapping greenhouse gases to the atmosphere. In the coming days and weeks, the researchers will publish more similar “attribution analyses,” as the studies are called.
In general, however, scientists know that hurricanes are becoming more severe as climate change accelerates. Warmer ocean water causes stronger winds, and warmer air holds more water, which can then turn into precipitation. Meanwhile, rising sea levels make coastal regions more vulnerable to storm surge. Research has shown that as climate change continues, an increasing share of hurricanes reach Category 3 status, while other data shows that even tropical storms and weak hurricanes are also strengthening.
But the initial analysis also points to the weakness of the Category 6 idea and the inherent weakness of the Saffir-Simpson score as a risk communication tool: The scale only takes into account wind speed, but storm surge and precipitation from hurricanes can be just as dangerous.if not more.
READ MORE: Hurricane categories do not reflect all of the storm's true dangers
Many of the most destructive hurricanes in recent years have caused untold destruction, although they were much weaker than a Category 5 hurricane. Take, for example, 2005's Hurricane Katrina, which made landfall as a Category 3 hurricane but produced a massive storm surge and killed more than 1,800 people. More recently, Hurricane Harvey made landfall as a Category 4 storm in 2017, but its most dangerous hazard was heavy rain, not wind.
Hurricane scientists have long been frustrated by the limitations and shortcomings of the Saffir-Simpson scale as a communication tool for the general public, and many are looking for another metric that is just as easy for people to understand but better captures the complex threats of any given storm.
This is a difficult task. “It's impossible to boil down the threat of a hurricane to one number,” said Brian McNoldy, a hurricane researcher at the University of Miami. Scientific American at the start of last year's hurricane season.
The difficult truth is that hurricanes are complex beasts and are inherently difficult to boil down to a single number. Hurricane Melissa's devastation is a terrible alchemy created by the unique combination of unstoppable wind gusts, seawater rushing inland, and deluge pouring from the sky, all interacting with the landscape and human lives the storm encountered along its path.
