From 1 to 5, the numbers we use to categorize hurricanes are ingrained in the minds of millions of Americans from Texas to Maine.
But that famed Saffir-Simpson hurricane scale, which only measures wind speed, is not the best way to gauge a storm’s ferocity, according to a study released Wednesday.
“Sandy is the classic example,” said Dan Chavas, an atmospheric scientist at Purdue University who led the study. “It was a very big storm, but in terms of maximum wind speed it was arguably not a hurricane.”
A better way involves barometric pressure, the study said. Specifically, it’s the difference in pressure between the center of the storm and outside it, which is officially known as the “central pressure deficit.”
“If you looked at the central pressure deficit, you would have expected Sandy to cause a lot of damage,” said Chavas. “But if you used maximum wind speed, as people usually do, you wouldn’t expect it to do the damage that it did.”
Sandy killed more than 150 people and caused $70.2 billion damage in the U.S., NOAA said.
Economic damages are better predicted by variations in central pressure than by peak storm wind speed since the central pressure combines both wind speed and storm size, the study found. The size of the storm is a critical factor in damage potential, particularly due to storm surge.
The limitations of the Saffir-Simpson scale have recently come under scrutiny. Wind speed is often only an estimate, and it’s also highly localized because it depends on a speed sustained for a short time in one location. However, it’s popular with the public and media because of its simplicity.
New ways of categorizing hurricanes have been proposed by many groups over the years, including the Hurricane Severity Index, the Cyclone Damage Potential Index and the Integrated Kinetic Energy Index. All take into account factors other than wind speed, the idea being that more variables make a scale more valuable. None have caught on yet.
The study appeared in the peer-reviewed British journal Nature Communications.