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Research finds big clue to SC threat of suddenly strengthening hurricanes

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Beach walkers look for shells washed ashore by Hurricane Dorian as it tracked away from Folly Beach. While the storm largely spared S.C., Dorian’s rapid intensification and stall over the Bahamas follows the trend of more powerful and slower hurricanes. Matthew Fortner/Staff

The mysterious eye of a whirling hurricane — where winds can rapidly strengthen approaching landfall — is close to giving up a crucial secret.

Researchers are zeroing in on channels where heat flares up in the eyewall, "hot towers" of clouds that rise to the top of the eye, pushed by heat from the ocean surface like plumes from a fire. They tend to flare up from six to 12 hours before a storm suddenly gets much stronger, called rapid intensification.

As a rule, hurricanes tend to weaken just before landfall. But some strengthen and, in recent years, more appear to do so. The intensification has been unpredictable: towers also flare up regularly without spurring it. Now, a research group has found a signal to look for.

That would be a big bonus to hurricane forecasting for South Carolina and the Southeast coast, where warming waters, more powerful and slower-moving storms are making rapid intensification more of a threat.

Forecasting it more accurately could make a life-or-death difference in evacuation zones along the coast. But it's been a big struggle for computer models and forecasters, one of the real headaches in forecasting and a priority of researchers.

Among storms that suddenly intensified was Hurricane Dorian in 2019, which suddenly blew catastrophic 185 mph winds before making landfall in the Bahamas. On the other hand, the winds of Hurricane Florence in 2018 rose some 55 mph overnight to 150 mph, then rapidly weakened before making landfall in North Carolina.

Hurricane Wire is a pop-up newsletter during hurricane season that delivers anyone who lives on the East Coast all the information they need to know as storms brew in the Atlantic and beyond.

A group of Chinese and Australian meteorologists studying Super Typhoon Rammasun in 2014 found the storm — which suddenly became catastrophic just before landfall in China — did it after a tower rose on the backside of the eyewall and spun off a complete ring of thunderstorms that straightened up the eyewall itself.

The synchronization of those three phenomena could be the signal forecasters need to watch for, said Noel Davidson, a research scientist at the Australian Bureau of Meteorology and an author of the study.

Robert Rogers, a meteorologist with National Oceanic and Atmospheric Administration’s hurricane research division, studies rapid intensification. He said the group's finding is consistent with the work NOAA has done and has the potential to improve NOAA forecasts.

"To the extent that we can observe and forecast those conditions and communicate that to the National Hurricane Center in real-time, then we can get better predictions," Rogers said.

"But there are aspects of the physical processes we still don't understand, gaps in our observing systems, and deficiencies in our computer models that make improvements challenging. It's an active area of research for us."

Reach Bo Petersen at @bopete on Twitter or 843-937-5744.

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