New hurricane scale might change how storms are measured

Takes into account flooding, storm surge and the potential for economic damage

AccuWeather says it has created a new way of rating hurricanes that goes beyond the long-used method of categorizing storms based solely on wind strength — and its forecasters are hoping it catches on.

The Pennsylvania-based weather data, forecasting and media company announced on Wednesday what it calls its AccuWeather RealImpact Scale for Hurricanes.

Under the new system, last year’s Category 1 Hurricane Florence, a relatively weak hurricane in terms of wind strength, would be a 4 because of the catastrophic flooding and storm surge it unleashed on the Carolinas — a threat that forecasters emphasized as the storm neared land.

Hurricane Harvey, which was a still formidable Category 4 that put much of Houston under water, would be a 5 under AccuWeather’s system.

Whether the new scale would see widespread use beyond AccuWeather or be embraced by the general public isn’t yet known.

The U.S. government’s official hurricane monitoring agency, the National Hurricane Center based in Miami, generally sets the tone for the rest of the American meteorological community when it comes to hurricane forecasting. It uses the Saffir-Simpson Scale, or the method of describing a storm as a Category 1, 2, 3, 4 or 5.

Under the Saffir-Simpson breakdown, there are five categories of hurricane. A Category 1 hurricane is the least strong type of hurricane based on wind speed, while a Category 5 is the strongest.

But the center, which says that water, not wind, is historically the biggest risk to life and property during a hurricane, is also cognizant of the challenges posed by the wind-based scale and in recent years has ramped up its efforts to convey the threat posed by water.

For its part, AccuWeather says its new scale categorizes storms from 1 to 5 but in addition to wind strength also takes into account flooding, storm surge and the potential for economic damage.

Also, the scale uses a “Less Than 1” designation, which aims to communicate that even if a storm’s winds are not technically strong enough to be called a hurricane, the storm could have hurricane-like impacts.

In recent years there’s been an ongoing discussion among forecasters and in the weather media about how best to effectively communicate that wind alone doesn’t make for an accurate description of a storm’s threat — especially after the catastrophic water damage unleashed by storms like Katrina in 2005, Sandy in 2012, Harvey and Maria in 2017, and Florence in 2018.

Forecasters express concern about whether the Saffir-Simpson system, developed in the 1970s, gives residents in a storm’s path a false sense of security if the category is one of the lower numbers.

“According to AccuWeather, this low rating on the Saffir-Simpson scale may have impeded some people’s understanding of the need to evacuate or take other necessary precautions despite the threat of disastrous inland flooding and storm surge along the coast,” AccuWeather’s announcement stated.

Whether the National Hurricane Center was also considering changes to how it classifies storms ahead of the 2019 Atlantic storm season wasn’t yet clear. A spokesman wasn’t available to comment because of the federal government’s partial shutdown.