Why some say the Saffir-Simpson hurricane scale is outdated and should be replaced
As Hurricane Florence’s winds decreased on its September approach to the Carolinas, the anxiety of meteorologists rose.
When the long-lived storm was a fierce Category 4 cyclone with 140 mph winds, people took notice, preparing, evacuating, “freaking out,” as one North Carolina forecaster put it this month at the National Hurricane Conference in New Orleans.
Then Florence faltered, weakening to a Cat 2, then a Cat 1. National Hurricane Center forecasters stopped talking Saffir-Simpson scale and official advisories no longer mentioned wind speeds in the headline. They chose their words carefully, hoping to divert attention away from the category of storm to the risks that hadn’t changed — 30 inches of rain, life-threatening surge, inland flooding for days.
Still, the category is what stuck.
“When Florence weakened from a 4 to a 1, there was a collective sigh of relief from our viewers that they weren’t going to get hit that hard,” said Ed Piotrowski, chief meteorologist for a TV station in Florence, S.C. “This is despite the fact we were communicating the flood risk. People feared the wind, but didn’t take the flood seriously.”
In the wake of Florence, and following 2017′s prolific rain makers Harvey and Irma, discussions about the weaknesses of the decades-old Saffir-Simpson Hurricane Wind Scale resurfaced at the hurricane conference, which drew 1,500 emergency officials and meteorologists from Texas to New York.
Twenty-three people died from the direct effects of Florence, according to a preliminary NHC report. Of those, 17 drowned in fresh-water flooding.
“There were a lot of people who took their eye off the rain when Florence went to a Cat 1,” said Jack Beven, senior hurricane specialist at the NHC.
Hundreds of people also had to be rescued during Florence when the ocean roared 100 miles up the Neuse River piling 11 feet of storm surge into the historic city of New Bern, N.C. — an event well forecast by the NHC.
The hurricane center has emphasized risks over storm category for years, but officials are reluctant to talk about potential changes or alternatives to the Saffir-Simpson scale that considers only wind speed in its determination of storm ferocity. Launched in 1973, the ranking is as ingrained in the consciousness of coastal residents as the dreaded cone of error.
Joel Myers, president and chairman of the Pennsylvania-based AccuWeather, has fewer reservations.
AccuWeather, which Myers founded in 1962, introduced the “Real Impact Category” this year in an effort to communicate a storm’s overall threat of wind, flooding rain, storm surge and economic loss, rather than just wind speed.
Under AccuWeather’s scale, Florence would have been a “Real Impact Cat 4” at landfall, instead of a Cat 1 under the Saffir-Simpson scale.
Hurricane Harvey, which made landfall Aug. 25, 2017, as a Cat 4 storm would have been ranked as a Real Impact Cat 5 under AccuWeather’s scale because of the wind and forecast rainfall. Harvey stalled for four days after landfall, dumping 5 feet of rain over parts of southeastern Texas.
Harvey is responsible for 68 direct deaths, all but three of which were from freshwater flooding.
Myers said the reception of AccuWeather’s scale by the meteorological community has been tepid.
“AccuWeather has always been an innovator, a creator, and some people like it but a lot of people don’t,” Myers said. “As long as we are true to the science and scientific method we are going to do it and the community will say what it wants.”
Some studies have looked at measuring storms by integrated kinetic energy, which considers the size of storm as well as wind speed. In 2013, a paper by researchers at Florida State University and the Florida Climate Institute proposed a measurement that includes size, intensity and duration.
When Hurricane Florence’s winds slowed, the storm expanded in size, meaning its reach was larger. It had also spent two weeks making its way through the Atlantic, building up wave energy along its path.
“Then there are some storms that produce gobs and gobs of tornadoes, so there is no simple way to capture all the risks in one measure,” Beven said.
Myers said Saffir-Simpson is still useful, but people have to take it for what it is — wind only.
The discussion of transferring the hurricane conversation from wind to water permeated the National Hurricane Conference to the point that one speaker suggested redoing the National Hurricane Center’s symbol — a red circle that mimics the wind field of a storm — to something water related.
“It’s time to change the visual folks,” said Leslie Chapman-Henderson, president and CEO of the Federal Alliance for Safe Homes. “We all know it’s about water, but no one else does.”
Sixty-nine percent of deaths during the 2018 hurricane season were water related. In the supercharged 2017 season, 91 percent of deaths were drownings.
Rick Knabb, tropical program manager for The Weather Channel and a former NHC Director, said the cable network made a deliberate effort to steer viewers away from Florence’s wind scale to the risks from storm surge and the belated flooding from torrential rains.
He almost seemed exasperated that the issue of Saffir-Simpson had come up again, saying that ranking storms by any category, even one that combines factors, is a mistake.
“Can you imagine how confused people will be if you blend in all the wind and surge and rainfall hazards,” he said. “I want to get down on my hands and knees and beg, please no more category systems.”
Knabb stressed focusing on impacts. The NHC began issuing storm surge watches and warnings in 2017. There are also inundation maps that show how deep the water may get at different points inland.
But Piotrowski said there are so many watches and warnings now — flood, flash flood, aereal flood, wind, surge — that people can’t decipher them and become “crippled.”
The simplicity of Saffir-Simpson is possibly one reason it’s so embedded.
“People feared the wind, they are terrified of the wind,” Piotrowski said. “The last thing they were thinking about were flood waters.”