From 1 to 5 years, the numbers we use to classify hurricanes are rooted in the minds of millions of Americans, from Texas to Maine.

But the famous 47-year-old Saffir-Simpson wind scale, which measures only wind speed, may not be the best way to measure the ferocity of a storm.

Last week, the powerful hurricane Florence was reduced from category 4 to category 2 and finally to category 1 because of its landing – which may have contributed to creating a false sense of security.

"The concept of saying 'degraded' or 'weakened' should be permanently banned," Professor of Meteorology at the University of Georgia Marshall Shepherd I said. "With Florence, I felt that it was more dangerous after being lowered to category 2."

This is because water, whether it's a sea wave or driving rain, often ends up being a lot more deadly and destructive than the wind of a hurricane.

When the Florence winds weakened and fell into the storm category, "we have made it clear that this will not reduce the flood and flood impacts," said Bill Lapenta, director of the national centers for flood control. NOAA. Environmental Prediction.

The storm has killed more than 30 people and will likely cost several billion dollars worth of damage.

Other storms like Harvey, Ike and Sandy were also much more destructive than their category might suggest.

A study published last year in the British journal Nature Communications indicated that barometric pressure could be a better indicator of a storm's ability to inflict damage.

"Sandy is the classic example," said Dan Chavas, an atmospheric scientist at Purdue University and senior author of the study. "It was a very big storm, but in terms of maximum wind speed, it was probably not a hurricane."

A better way involves barometric pressure, according to the study. Specifically, it is the pressure difference between the storm center and the outside, officially called "central pressure deficit".

"If you look at the central pressure deficit, you would have expected Sandy to do a lot of damage," Chavas said. "But if you use the maximum wind speed, as people usually do, you would not expect to suffer the damage it caused."

Sandy has killed more than 150 people and caused $ 70.2 billion in damage to the United States, the National Oceanic and Atmospheric Administration said.

Property damage is better predicted by changes in central pressure than by maximum wind speed, because the central pressure combines both wind speed and storm size.

The magnitude of the storm is a critical factor in the potential for damage, especially because of the storm surge.

The limits of the Saffir-Simpson scale have been examined in recent years. Wind speed is often only an estimate, and it is also very localized as it depends on a sustained speed for a short time in one place. However, it is popular with the public and the media because of its simplicity.

Susan Cutter of the University of South Carolina said the hurricane center and the national meteorological service "have not done a good job of communicating the risks associated with tropical systems beyond the winds".

Many groups have proposed new methods of categorizing hurricanes over the years, including Hurricane severity index, cyclone damage potential index and integrated kinetic energy index.

All take into account factors other than wind speed, the idea being that more variables make a balance more useful. But none of these scales has yet made its way.

Contributor: Associated Press

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