New 'Category 6' designation needed for hurricanes, study says

(NewsNation) — Hurricanes are rated on a scale of one to five based on their wind speeds, and it may be time to add a sixth category, according to scientists.

In a paper published Monday in the Proceedings of the National Academy of Sciences, researchers Michael F. Wehner and James P. Kossin lay out their case for the expansion of the Saffir–Simpson scale. Established in the 1970s, the scale separates hurricanes into five different categories, with 158 mph or greater storms at the top of Category 5.

But as climate change worsens severe weather, Wehner and Kossin say an open-ended scale has become inadequate for assessing the risk posed by a storm.

“We find that a number of recent storms have already achieved this hypothetical category 6 intensity and based on multiple independent lines of evidence examining the highest simulated and potential peak wind speeds, more such storms are projected as the climate continues to warm,” they wrote in the paper.

Wehner and Kossin propose Category 5 storms be classified as those reaching 157 to 192 miles per hour, and a new Category 6 include storms with wind speeds greater than 192 mph, NPR reported.

Under the new model, Category 6 storms would be exceedingly rare. However, Wehner and Kossin identify multiple storms that would have already been classified as such: Typhoon Haiyan in 2013, Hurricane Patricia in 2015, Typhoon Meranti in 2016, Typhoon Goni in 2020 and Typhoon Surigae in 2021.

Patricia was the most powerful tropical cyclone on record in the Western Hemisphere, reaching speeds of up to 215 mph. It made landfall in Mexico and resulted in two direct deaths, according to the National Hurricane Center.

After Haiyan hit the Philippines in 2013 with 195 mph winds, scientists in Taiwan argued it necessitated an update to the Saffir-Simpson scale.

“We expected that climate change was going to make the winds of the most intense storms stronger,” Wehner, an extreme weather researcher at Lawrence Berkeley National Laboratory, told the news ou t let Grist. “What we’ve demonstrated here is that, yeah, it’s already happening. We tried to put numbers on how much worse it’ll get.”

While the new category would do little to convey to convey the danger from storms that produce major flooding and storm surge, “it could raise awareness about the perils of the increased risk of major (storms) due to global warming,” the researchers write.