‘Hot towers’ focus of hurricane intensification

The eye of Hurricane Charley spins in a 2004 photograph by the crew of the International Space Station.

Relatively warmer seas off South Carolina now mean any tropical cyclone that forms could strengthen rapidly as it approaches the coast. If ones does, its eye will be flaring “hot towers.”

The towers are rain clouds that rise to the top of the cyclone eye, pushed by heat generated in the spinning eye wall like plumes from a fire. They tend to flare up from six to 12 hours before a storm gets stronger.

And that’s the next nut for forecasters to crack.

The tendency for storms to strengthen abruptly as they close in on a coast, called “sudden intensification,” has been a big struggle for computer models and forecasters to predict. For example, devastating Hurricane Hugo caught everyone short when it strengthened to a Category 4 storm with 135 mph winds 12 hours before it made landfall in Charleston in 1989.

The towers the eye walls plume have been theorized for more than a half-century, roughly verified by aircraft observations and now more keenly by satellite observations.

The Global Precipitation Mission satellite earlier this month picked them up before Tropical Storm Frank strengthened in the Pacific.

The problem is, exactly where the clouds rise in the eye wall is as important as when, and researchers are honing in on that with every observation. Experimental computer programs already incorporate the findings for test runs.

Whether the storm gets worse appears to depend on how close towers form to the its center and the spots where the winds are strongest, said Robert Rogers, research meteorologist with National Oceanic and Atmospheric Administration’s hurricane research division.

“We think that plays an important role. It’s an important ‘building block’ to sudden intensification. I think we’re getting close, with some of the new tools coming online,” he said.

Aircraft and satellite readings soon will be supplemented by a few hundred “CubeSats,” miniature satellites being deployed to provide near constant, real-time coverage.

“Although satellite and aircraft data give us a fairly good picture of the environment around the storm, we still suffer from limited information about the inner workings of the storm,” said Jason Dunion, NOAA meteorologist. “The last piece of the rapid intensification forecast challenge is that a good intensity forecast relies on a good track forecast. If the track is off, then the predictors that we’re using to forecast rapid intensification might be off as well.”

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