Hurricane Milton’s ferocious winds that peaked at 180 mph have people asking yet again—is it time for the National Hurricane Center to add a “Category 6” classification to the Saffir-Simpson Hurricane Wind Scale?
The question will likely take a backseat at the NHC ahead of Milton’s landfall in Florida on Wednesday evening. Once the storm surge recedes and hurricane season comes to a close, however, some researchers want the federal agency to make a change—especially as powerful hurricanes are expected to increase in frequency amid the warming of our oceans.
Among those in favor of adding a new designation is Michael Wehner, a climate scientist at the Lawrence Berkeley National Laboratory. He co-authored a study earlier this year that looked at recent storms that would be worthy of the Category 6 hurricane denomination and determined a new classification would help emphasize a truly catastrophic storm’s potential devastation.
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The current Saffir-Simpson Scale. Some researchers want to see it expanded.
NOAA“Our motivation is to reconsider how the open-endedness of the Saffir-Simpson Scale can lead to underestimation of risk, and, in particular, how this underestimation becomes increasingly problematic in a warming world,” Wehner said.
Calculating a storm’s risk—and communicating it to those in harm’s way—is why we have the NHC. Without the agency, we likely wouldn’t have received word in real time that Milton had strengthen from a Cat 1 storm with winds of 80 mph on Sunday evening to being a Cat 5 cyclone by morning, making it the third fastest-intensifying storm on record in the Atlantic Ocean.
Just as Wehner wants a Cat 6 classification to better protect the public, some prominent researchers, like Jeff Masters of Yale Climate Connections, don’t want to see the Saffir-Simpson Hurricane Wind Scale altered for the same reason.
“People won’t be any more motivated to evacuate from a Cat 6 headed their way compared to a Cat 5,” he said.
Other researchers have made a similar point as Masters, adding that it’s already difficult enough to convince people in coastal communities to evacuate ahead of storms. In that argument a Cat 3 hurricane, considered a major hurricane that’s typically life-threatening, might appear as less of a threat to some since it’d appear as “half” the intensity of that of a Cat 6.
Wehner’s paper suggested that a new Category 6 designation would require a storm to have 193+ mph winds—a high threshold that even Milton would have felt short of at its peak. If the NHC were to make a change, which Masters says he hasn’t heard any rumors of happening, the scientist said he thinks the more appropriate start for Cat 6 should be 190 mph.
The current Saffir-Simpson Hurricane Wind Scale is as follows: Category 1, max sustained winds of 74-95 mph; Category 2, 96-110 mph; Category 3, 111-129 mph; Category 4, 130-156 mph; Category 5, 157 mph or higher.
The Saffir-Simpson only accounts for sustained wind speeds, which are often not the most damaging aspect of hurricanes. Because of this, some researchers, like Phil Klotzbach of Colorado State University, more frequently rely on metrics like “Accumulated Cyclone Energy” to better account for a storm’s destructive power—and for how long it maintained it.
