Category 6 mulled for mega-hurricane era

In 1973, the National Hurricane Center introduced the Saffir-Simpson scale, a five-category rating system that classified hurricanes by wind intensity.

At the bottom of the scale was Category 1, for storms with sustained winds of 74 to 95 mph. At the top was Category 5, for disasters with winds of 157 mph or more.

In the half-century since the scale’s debut, land and ocean temperatures have steadily risen as a result of greenhouse gas emissions. Hurricanes have become more intense, with stronger winds and heavier rainfall. This week a research team at the University of Pennsylvania led by climate scientist Michael Mann predicted that the North Atlantic will see an unprecedented 33 named tropical cyclones from June 1 to Nov. 30.

With catastrophic storms regularly blowing past the 157-mph threshold, some scientists argue, the Saffir-Simpson scale no longer adequately conveys the threat the biggest hurricanes present.

Earlier this year, two climate scientists published a paper that compared historical storm activity to a hypothetical version of the Saffir-Simpson scale that included a Category 6, for storms with sustained winds of 192 mph or more.

Of the 197 hurricanes classified as Category 5 from 1980 to 2021, five fit the description of a hypothetical Category 6 hurricane.

In their paper, which was published in the Proceedings of the National Academy of

Sciences, Michael F. Wehner, a senior scientist at the Lawrence Berkeley National Laboratory, and co-author James P. Kossin of the University of Wisconsin–Madison did not explicitly call for the adoption of a Category 6, primarily because the scale is quickly being supplanted by other measurement tools that more accurately gauge the hazard of a specific storm.

“The Saffir-Simpson scale is not all that good for warning the public of the impending danger of a storm,” said Wehner.

The category scale measures only sustained wind speeds, which is just one of the threats a major storm presents.

The Saffir-Simpson scale is a relic of an earlier age in forecasting, Brennan said.