New tool boosts warnings for hazardous pulse storms

ST. LOUIS – They hit fast, and they can hit hard. Pop-up storms, sometimes called “pulse storms,” can unleash powerful downburst winds with little if any advance warning. They’ve been a common theme around St. Louis this summer. New research may help forecasters get ahead of these sudden and often difficult to predict weather events.

Bridgeton resident Gary Linke and his wife witnessed the power of these freak storms. Their home was crushed by a falling tree, brought down by small downburst near St. Louis Airport on Aug. 17.

“I could hear some banging and the wind blowing and some rain a little bit, then I heard this crash,” Linke said. “I came upstairs, and I couldn’t get the door open from all the junk that’s come down.”

Charles Kuster, a research meteorologist with the National Severe Storms Laboratory, is leading the charge to give forecasters better tools to warn about these fast-hitting bursts of wind.

“When you hear the term microburst, you're talking about a really small downburst –
only a couple miles wide or so. That’s actually really difficult to detect with radar,” he said.

Kuster’s research focuses on a specialized radar product called specific differential phase (KDP). This product can identify areas where melting hail and heavy rain is causing rapid cooling in the storm clouds. These KDP cores are thought to trigger strong storm downbursts.

“KDP adds to reflectivity, because you may have a really high descending reflectivity core, but it may be full of dry hail,” Kuster said. “Maybe there's not that melting going on.”

Kuster’s team studied nearly 90 downbursts and found a KDP core preceded nearly every one of them.

“If you see a KDP core, there's going to be a downburst in the next 10 to 15 minutes or so,” he said.

Which is exactly what happened with the Aug. 17 storm. A KDP core appeared over the airport. Moments later, the downburst hit. Wind gusts at the airport reached nearly 60 miles per hour. Those same winds brought down the tree that crushed Gary Linke's home in Bridgeton.

“We're starting to hear success stories from the operational community saying, ‘Hey, I saw this KDP core — and then a downburst occurred,’” Kuster said.

It’s another tool that should improve severe thunderstorm warnings in the future.