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Southern Oregon meteorologists use data to study lightning behavior

Lightning tells a story, and two Rogue Valley meteorologists have been working to decipher it.

And they may have a decent guess on what it will say later.

The work of forecasters Shad Keene and Charles Smith has become a new tool on the National Weather Service Medford website. Called “experimental lightning climatology,” the feature captures when and where lightning occurs most and least in areas across the country, including here in Jackson County.

To accomplish the task, Smith and Keene had to collect data on quite a few cloud-to-ground strikes: more than 850 million over a 30-year period for the continental U.S. They fed that information into a database that Keene says is “geographically aware” and can pinpoint where the bolts struck. That data is then extracted and used to create graphics and other digital representations.

“Our goal is just to help people make better decisions regarding thunderstorms,” Keene says. “Specifically for our fire season. We know that about 90% of wildfire acres burned in our forecast area — that’s the nine counties we’re responsible for — are lightning-caused.”

The Oregon Department of Forestry declared fire season May 1 for Jackson and Josephine counties, among the earliest start dates for the area in more than half a century. Keene hopes the lightning data can be an aid to wildland firefighters.

“Because fire season has such a large impact on our area — economically and safety-wise for fire crews, and also, health-wise — the more we learn about lightning in our area and how to better predict it and communicate it ... just doing that hopefully aligns with our mission of the Weather Service: to help save lives and property,” Keene says.

The endeavor started about five years ago, with the two exploring ways they could better document lightning data, showing its impacts in a broader, historical context.

“We had a lot of requests for it from the media,” Keene says. “And also from land management agencies like the Forest Service and BLM. And from the public in general.”

They began to store lightning data locally; more recent numbers first that could show how many cloud-to-ground strikes peppered individual counties in Southern Oregon and Northern California. That vision eventually covered the entire country. They documented 850 million or so flashes, where they struck, what times of year and what time of day.

The data were taken between 1988 and 2017 for the country, but the information has been refined for local studies, looking at the period between 1995 and 2018. During that time, the nine-county region saw 433,950 cloud-to-ground strikes, data show.

The probability of lightning in the region starts to ramp up in May and June before peaking in July. It drops a bit in August then sees a sharp decline in September, the historical data show. Spots in the nine-county area that have seen the most strikes include northern Klamath County and central Siskiyou County.

A separate area of interest is the Kalmiopsis Wilderness, where cloud-to-ground strikes are much more likely during the night. It’s not among the most-struck areas, but Keene says it’s still a notable location, as it has been the site of some of the most significant wildfires southwest Oregon has experienced over the past two decades.

“The Chetco Bar, the Klondike, the Biscuit,” Keene says. “All those were lightning-caused.”

There’s some understanding about why northern Klamath County and central Siskiyou County are hit the hardest. Thunderstorms are more likely to form over higher terrain, such as the Southern Cascade range, Keene says, and typical wind flow during the summer months is southwest to northeast.

“What happens is these storms build, and then they drift off,” Keene says of northern Klamath County. “That’s probably why most of our lightning is over there.”

For central Siskiyou County, Keene points to a “sea breeze” that comes in off the ocean to at least the Siskiyou Mountains.

“We have a little boundary that helps trigger storms in that area,” Keene says. “Afternoon northwest winds can collide with southerly winds in that area.”

Thursday night’s lightning storm appears to have kept up with historical appearances, with 235 strikes recorded in Klamath County and 100 or so in Siskiyou County, Smith says.

“The storms kind of intensified overnight,” he says.

The likelihood of nighttime storm formations in the Kalmiopsis Wilderness has different mechanisms at play, too.

“Storms don’t form at the surface at night. They can form above the surface, and that makes it harder to predict, really,” Keene says. “And that’s why learning about these patterns is so important. We can identify these anomalous areas and learn about them.”

Reach web editor Ryan Pfeil at 541-776-4468 or rpfeil@rosebudmedia.com. Follow him on Twitter @RyanPfeil.

Lightning bolts light up the sky over Medford. The probability of lightning in Southern Oregon starts to ramp up in May and June before peaking in July.Mail Tribune file photo