“This insight could help forecasters provide more accurate predictions of hail size, helping those in the path of the storm be safe and prepared.”
– Rick Smith, Warning Coordination Meteorologist – NWS Norman
High speed cameras encased in bullet-resistant polycarbonate. LED lights 30 percent brighter than the sun. All mounted to the back of a diesel pickup truck wrapped in a metal cage. That’s the latest innovation in hail storm science from the NOAA National Severe Storms Laboratory (NSSL).
Each year hail causes billions of dollars worth of damage to homes, vehicles, crops and infrastructure in the United States. Yet despite its frequent and costly impacts, the challenges of studying hail in real-time make it one of the least understood severe weather hazards.
“It’s very, very difficult to study hail,” said NSSL Researcher Sean Waugh. “It moves quickly. It breaks everything it hits. All our observations are post impact, so we really need a way to see it in freefall.”
Developed by NSSL researchers, the new hail camera is part of an inventive effort to collect detailed, real-time, pre-impact observations of hail events. The system uses high-speed, high-resolution imaging to record hailstones in free fall.
“This is a camera based system that shoots 4K footage at 330 frames a second,” said Waugh. “With those two cameras, we can actually calculate the depth and size of the hail stones. We can track it from one frame to the next to get velocity in all three dimensions. We’re getting an incredible one-of-a-kind look at hail.”
The system itself, which is mounted on the back of a diesel pick up truck, is built for deployment during field research campaigns and includes weather-hardened housing, on-board computing power, and an incredible array of LED lights.
“The challenge with running a camera that fast is that each frame is only exposed for 75 microseconds, which means we need a lot of light in order to illuminate those objects,” said Waugh. “The LED array on the back of this truck produces about 30 percent more light than the sun on the surface of the Earth. It’s definitely not something you want to stand behind when it’s on, but it is incredible to see and the images we’re getting are fascinating.”
HELP FROM A NEIGHBOR
Once hailstones are captured on video, researchers can measure their size and speed frame by frame, but as with any new invention, testing was needed to ensure the captured data was accurate. In order to test its capabilities and calibrate the computation of the images being recorded, Waugh went for a little help from a neighbor.
Waugh partnered with The University of Oklahoma Athletics to take the hail camera just across the street from NSSL headquarters to be tested by athletes from the OU baseball and softball teams. Pitchers threw balls through the frame, allowing Waugh to test the machine’s performance in capturing motion as well as the in-house algorithms it uses to do analysis.
“Those pitchers threw objects of a known-size and speed through the camera frame,” said Waugh “The baseball was about traveling at 94 miles an hour. Softball was about 55 to 60 miles an hour. Knowing those object sizes and speeds, we could compare it to the velocity the camera system calculated and ensure it matched. That gave us confidence the data we’re collecting are accurate and representative of reality.
With the help of those student-athletes the hail camera was tested, calibrated and ready for the field.
HAIL MAKES AN IMPACT
The hail camera has already been deployed with the Low-Level Internal Flows in Tornadoes (LIFT) project, a collaboration with Cooperative Institute for Severe and High-Impact Weather Research and Operations (CIWRO), to great results.
“Recently we were able to watch almost three-inch diameter stones falling, watching them impact with the bed of the truck and how they shatter, or don’t,” said Waugh. “We’re actually seeing results from this system that are challenging some of the ways that we’re going to look at hail going forward.”
Innovative tools like the hail camera are bringing researchers closer to understanding one of nature’s most damaging phenomena. The data being collected with this system, not only this year but in the years to come, is going to drastically improve our understanding of hail and how it impacts our living environment.
“The knowledge gained from this research will ultimately help meteorologists improve our warnings by giving us a better understanding of hail production in severe storms,” said Rick Smith, Warning Coordination Meteorologist with NOAA’s National Weather Service Norman Forecast Office. “This insight could help forecasters provide more accurate predictions of hail size, helping those in the path of the storm be safe and prepared.”
For the latest forecasts of hail and other severe weather, please go to Weather.gov
