New hur­ri­cane scale might change how storms are mea­sured

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

Sun Sentinel Palm Beach Edition - - LOCAL - By Brett Clark­son

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.

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