Just picture this – it’s a warm afternoon and a thunderstorm starts to roll overhead. You head indoors and hear rain begin to fall. As the cracks of thunder get louder, you peek out the window to see large chunks of ice on the ground…
If you really think about it, rain makes sense to fall from a storm – But large pieces of ice?
“Hail is one of those things that we don’t really know how it forms,” says Sean Waugh, a research scientist at NOAA’s Severe Storms Laboratory.
We do know some of the basics… Strong thunderstorms have strong updrafts – think like a vacuum cleaner that’s able to lift moisture high up into the atmosphere. It’s cold up there, so that water freezes into a small stone. It collects more water, refreezes as it cycles through the storm – more water, refreezes… you get the idea.
Eventually, the hailstone gets too heavy and tumbles to the earth below. Waugh says wind speed, direction and moisture in the air also play a part in hailstorm development.
We also know hail can be expensive…
“In any given year, it’s 60-80% of the damage that comes from severe thunderstorms," says Ian Giammanco – a meteorologist at the Insurance Institute for Business and Home Safety. He says we’re just getting more hailstorms these days.
“Rewind the clock all the way back to 2008 – every year since then, we’ve had over $10 billion in damage from hail. This has crept up now to a $20-30 billion problem.”
Giammanco says that’s why research like what Sean Waugh is doing is so important – finding out what hail looks like before it hits the ground.
“All of our observations basically as long as we’ve been doing hail research is post-impact – meaning that the stone falls and you collect it maybe 20 minutes later, 30 minutes later after it’s had a chance to melt," Waugh says. "We don’t know what broke when it landed, how much of that mass, or size or shape have we lost between when it fell and when we find it, right? I’ve seen six-inch diameter stones melt before I can get out of the car to pick them up, so we know this is occurring,” he explains.
There are other questions, too: how fast does hail fall? Does it fall in a specific orientation? Does the stone melt while it’s falling to the earth below?
“These are all really, really important questions if you’re trying to ascertain what hail looks like to a radar. And that’s a really critical piece of knowledge if you’re trying to warn for hail in real time, which is obviously the goal! Most people want to know if there’s going to be golf balls falling at their house or softballs,” Waugh says.” “There’s a very big difference between those.”
Waugh and his team have built a complex rig that observes hail in free fall and in real time. They head out from Oklahoma – typically to the Southern Plains – to get the system in front of a storm producing large hail.
The rig has high speed and high-quality cameras, and Waugh says there’s another key component…
"But we need a lot of light to do that. Otherwise, the image would just be dark,” he explains. “So, the LED array I have on the back of the truck produces about 30% more light than the sun! You actually need eclipse glasses standing behind the vehicle to look at it.”
Waugh says the project is already producing some incredible results, as you can see here:
Right now, Waugh is working on getting his system onto more trucks because it’s hard to get in just the right place at the right time to capture large hail.
“We can use that knowledge to improve our forecasts of what storms are likely going to produce hail days in advance. By understanding the type of hail that different storms produce, that increases our ability to model it properly and then forecast that in the future,” Waugh says. “And that way people can take appropriate action to protect life and property.”
You can find more information about all of the life and property saving research that NOAA and the National Severe Storms Laboratory are working on here.
