A University of South Florida researcher and a team from the Netherlands are proposing a new way to measure hurricane severity.
Jennifer Collins had been studying evacuation patterns when she saw people would not leave high-risk areas unless the storm was a major hurricane – a Category 3 or higher.
“There’s an underestimate, in my opinion, of the dangers, particularly of these lower category storms, by simply focusing on wind rather than the very deadly threat of flooding,” Collins said.
In her August paper, Collins and her team proposed a storm ranking scale that would consider storm surge and rainfall in addition to wind speed.
The Saffir-Simpson Hurricane Wind Scale, widely used by forecasters, ranks storms based on wind speed from Category 1 to 5.
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But Collins said wind speed only accounts for 10% of fatalities.
Instead of the Saffir-Simpson scale, she is proposing the Tropical Cyclone Severity Scale:
- It would consider the three factors on a Category 1 to 5 scale.
- The storm's ranking would be at least equal to the ranking of the most dangerous factor.
- If two of the factors were a Category 3 or higher, the total ranking would increase by one. For example, if wind speed and storm surge are a 3 and rainfall is a 4, the storm’s severity would be a 5.
- As a result, storms can be as high as a Category 6.
Collins said Hurricane Ian, which made landfall in Florida as a Category 4 in 2022, actually would have been a Cat 6 based on her scale.
“So I think that's really important that people were able to better identify the main hazard and had high evacuation intent when they were looking at those situations where the category on our scale was at least two higher than the Saffir-Simpson Hurricane Wind Scale,” Collins said.
The National Hurricane Center does consider several risk factors, but spokesperson Maria Torres said they would be difficult to capture in one scale.
“Our products and services focus on the specifics of individual hazards, including storm surge, wind, rainfall, tornadoes and rip currents, instead of the particular category of the storm,” Torres said.
If adopted, Collins hopes the new scale will make people more informed about the risks they are facing from a storm and potentially save lives.
For example, Hurricane Debby was a Category 1 on the current wind-based scale. The slow-moving storm caused widespread flooding across parts of Florida. With Collins’ Tropical Cyclone Severity Scale, it would have been a major hurricane at a Category 3.
In the meantime, Collins encourages people to check all of the National Hurricane Center’s measures when determining if they should evacuate ahead of a storm.
