Category 5 has become part of the world’s lexicon to describe a disaster of monumental proportion.
Now, thanks to climate change, a pair of scientists don’t think that is a dire enough level to describe hurricanes. They raise the possibility, on a “hypothetical” basis, for a Category 6.
Global warming has increased the energy available for storms to grow stronger, according to a paper by Michael Wehner, senior scientist at the Lawrence Berkeley National Lab, and James Kossin, climate and atmospheric professor at the University of Wisconsin. Their work was published in Proceedings of the National Academy of Sciences of the US.
The scientists make a case for adjusting the five-step, Saffir-Simpson Hurricane Wind Scale, which is used to describe hurricane power. A Category 5 is assigned when storm winds reach 157 miles per hour, and today that goes up to the limit of physics. Wehner and Kossin suggest considering anything over 192 mph a Category 6.
From 1980 to 2021, there have been 197 tropical cyclones worldwide that have been classified as Category 5. Of those, five would have reached the hypothetical Category 6 level, and all of those occurred in the last nine years of the period covered.
Still, there are a couple of issues with their suggestion. One is this theoretical exercise risks getting confused with an official change in weather communication.
Communicating weather risk to the public is something that keeps forecasters, politicians and emergency crews up at night. Hours have been spent tinkering with the wording in messages, the colors used to convey risk and strategies on how to head off false alarms, hysteria and bad information.
While this is no fault of the researchers, now that the idea of a Category 6 is out there, it won’t be long before a storm reaches the threshold and we will probably see social media attention-getters, or maybe even some mainstream news outlets, proclaim: It’s a Category 6!
In the Western Hemisphere the public will turn to the US National Hurricane Center for what a Category 6 means and they won’t find anything. Those meteorologists, politicians and emergency crews mentioned earlier don’t love it when the public they are trying to protect is confused by a threat.
There is also another problem. The Saffir-Simpson scale was a great start when it was created in the 1970s by Herbert Saffir, an engineer, and Robert Simpson, a meteorologist.
Over time, however, it has shown its limitations and drawbacks. First off, it is a wind scale — it doesn’t convey flood risks from rain or storm surge, the wall of water that rolls in like a bulldozer when a cyclone crashes the shorelines.
Surge kills 49% of people who die in hurricanes and rain kills 27%. Wind deaths only account for about 8%.
Also, it can lead to a false sense of security among people in the path of a storm, which was made clear during Hurricane Florence in September 2018.
Florence roared toward the North Carolina coast as a Category 4 hurricane, but as it neared landfall its top winds fell and it became a Category 1. Many people living across the Carolinas thought this meant the storm had weakened and wouldn’t be so bad, and they said so after the fact.
Florence became the wettest storm on record to hit the region and the land was devastated by deadly flooding that carried off houses and businesses as well.
This is a problem meteorologists the world over face, whether they are forecasting hurricanes, typhoons, or cyclones, which are all just different names for the same kind of storm. The public gets fixated on wind speed.
This year the US National Hurricane Center will roll out a new forecast tool that emphasizes other risks as well. Recently it has been painting its maps with storm surge warnings and watches, as well as wind-speed advisories. In August, it is going to revamp the vaunted “cone of uncertainty’’ that outlines a hurricane track to make sure that people up and down a coastline see if they are at risk for being swept away from a flood, even if they are far from the storm’s center.
The world gets stuck on landfall, but these storms are huge, often hundreds of miles across, and people living many miles from where an eye crosses a beach can find themselves in deep trouble – just ask the residents of New Orleans, who suffered dearly after Katrina. Katrina came ashore for the final time near the mouth of the Pearl River on the border of Louisiana and Mississippi, 35 miles from the French Quarter in New Orleans.
To the 1,800 or so who died, the category didn’t matter.
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