September 18, 2011

Giant hailstones better recorded in social media

The radar map looked like a textbook setup for a stormy day in May, but this was mid-September.

The radar map looked like a textbook setup for a stormy day in May, but this was mid-September.

Supercell thunderstorms fired up west of Wichita, then slid southeast. The storms produced a couple of short-lived tornadoes and huge hailstones.

So large, in fact, that a record for the largest hailstone in state history was set: a stone that fell in southwest Wichita had a diameter of 7.75 inches, shattering the existing record by more than 2 inches.

But Scott Blair, a meteorologist with the Topeka branch of the National Weather Service, came across something startling as he researched the Sept. 15, 2010, storm. Checking local media websites, he found photos of one massive hailstone after another.

By the time he was done, he had found eight hailstones that were larger than the previous state record hailstone, which fell in Coffeyville in 1970.

“I’m sure there was a lot more that didn’t get documented,” Blair said. “That alone shows the impressive nature of the storm.”

Thanks to social media, the storm could become a turning point in how data on severe storms is collected and in researchers’ grasp of what hailstorms can do, Blair and other experts say.

Weather service officials knew of only one potentially record-setting hailstone in the immediate aftermath of the storm, Blair said. The other stones surfaced as a result of social media.

Facebook, Twitter and camera phones could do for hailstorm documentation what the advent of easy-to-use video cameras in the early 1990s did for documenting tornadoes, Blair said.

Until then, it was actually pretty hard to find decent tornado footage, Blair said.

But the Hesston tornado of 1990 and the Andover tornado of 1991 became so well-known in part because there is abundant video footage of them, he said.

It’s no coincidence, Blair said, that the five largest hailstones on record in the U.S. have all fallen since 2003.

It’s not that thunderstorms are producing larger hail than they used to, he said, it’s that people are in position to notice — and properly record — the stones when they fall.

“Hail is a bit more finicky of a thing to document” than tornadoes, Blair said. “You either have to come across it or be hit with it.”

As smartphones have proliferated, he said, it has made it even easier for people to quickly snap a photo of hail that has fallen in their yard or neighborhood. And it’s common for them to share the images with friends and family via Facebook, Twitter, or the websites of local media organizations.

That makes documenting where and when large hail fell easier than ever, Blair said.

“If social media didn’t exist . . . it’s possible that we would have never known about any of these stones that exceeded the state hailstone record size,” he said.

This new era of severe weather documentation is blossoming just as dual-polarization radar is being rolled out on a national scale by the National Oceanic and Atmospheric Administration. The new radar will enable forecasters to more clearly see how much rain — and hail — is falling from a thunderstorm.

The photos, tweets and Facebook posts about hail and storm damage that are becoming commonplace are valuable, Blair said, because they provide confirmation — or what meteorologists call “ground truth” — of what’s actually happening.

Meteorologists can take that information and compare it with what the dual polarization radar indicated, Blair and others say.

As they gathered data on last year’s storm, Blair said, he and fellow meteorologist Jared Leighton found 387 reports from social media. Of that number, 90 percent of those reports had photos to go with them.

The stones were commonly placed next to another object to offer perspective.

For researchers used to getting a handful of reports of large hail from a given storm, to have nearly 400 reports was almost too good to be true.

In that regard, Blair said, last September’s storm is among the most heavily documented large-hail events on record.

Perhaps the most remarkable aspect of the thunderstorm that produced so many record-setting hailstones, forecasters say, is that it was similar to hundreds of thunderstorms any given year.

“It’s not that it was a massive storm,” said Robb Lawson, a meteorologist with the Wichita branch of the weather service. “What made it the most unique was the time of year.”

The relatively common setup of the thunderstorm raises the possibility that large hail falls far more often than realized, Blair said. The convergence of dual-polarization radar and social media should make it easier to confirm that.

“The probability is certainly higher that in the next five to 10 years, we’ll see more and more reports of these of hailstones” because people have the technology and the awareness to document the stones after they fall, Blair said.

“The more we can get individuals to safely provide this type of information, eventually the quality of warnings will improve,” he said.

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