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Thursday, September 17, 2020  Spokane, Washington  Est. May 19, 1883
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Weathercatch: Multiple incidents of derechos and fire tornadoes this summer

A derecho heading east near Denver International Airport on June 6 was the third ever recorded to form west of the Rocky Mountains.  (Courtesy of William Scherer/Twitter)
A derecho heading east near Denver International Airport on June 6 was the third ever recorded to form west of the Rocky Mountains. (Courtesy of William Scherer/Twitter)
By Nic Loyd and </p><p>Linda Weiford For The Spokesman-Review

Two ominous weather-related conditions that many people had never heard of sprang into public awareness this summer: derechos and fire tornadoes.

Each phenomenon is capable of producing deadly wind speeds, but from completely different origins. One is induced by thunderstorms, the other by raging fire.

Derechos and fire tornadoes are rare occurrences in the United States, which makes it all the more remarkable that they struck multiple times during the warm weather months of 2020.

A derecho (pronounced deh-REY-cho) is a fast-moving line of thunderstorms that generates severe winds along a swath of 400 miles or longer.

Sometimes called “inland hurricanes” due to their hurricane-level winds and rain, an average of one strikes each year in the central or eastern U.S., according to the National Weather Service.

Since early June, three have struck in the U.S., which in itself is unusual. But that one of them occurred in Colorado is an absolute rarity. Only two other derechos have ever been documented to form west of the Rocky Mountains, according to the weather service‘s Storm Prediction Center – the first in May 1994 and another in June 2002.

Both ripped across a region of elevated terrain that included southeast Idaho, Utah and Wyoming. They arrived fast, racing forward at speeds up to 100 mph.

The derecho that slammed Colorado on June 6 moved at an average speed of 60 mph, while peaking at 120 mph.

The biggest head-scratcher about this band of thunderstorms is that it managed to cross the Continental Divide, which typically dismantles storms with its steep topography.

Meanwhile, Iowa residents are still struggling in the aftermath of the fierce derecho that struck parts of the Midwest exactly a month ago. The highest winds recorded during the Aug.10-11 siege reached 140 mph in the city of Cedar Rapids.

The first derecho of the 2020 season barreled through portions of Pennsylvania and New Jersey on June 3, unleashing gusts up to 90 mph and knocking out power to more than a half-million customers.

Not surprisingly, derechos are notorious for toppling power lines, uprooting trees and flattening entire crop fields.

The U.S. has also experienced an unusual occurrence of fire tornadoes this summer.

Extreme wild fires can get so intense that they generate their own weather systems. Occasionally, it’s an ominous twister made of flame and smoke. Not only do these large spinning columns sprint across landscapes at speeds of up to 160 mph, but they burn everything in their path as they go.

Which is just what happened during the explosive Loyalton fire in Northern California that spawned at least five fire tornadoes on Aug. 15.

One was so massive and potentially deadly that it prompted the National Weather Service to issue its first-ever fire tornado warning: “This is an extremely dangerous situation for fire fighters,” the warning read. “Do not go into this area! Life-threatening situation!” it said.

And just last weekend, Doppler radar detected two fire twisters in the Creek fire burning in California’s Sierra National Forest.

Fire tornadoes, like derechos, can form quickly and be difficult to predict. Though they’ve occurred throughout history, 2020 has thrown us a handful. Fortunately, new computational models and meteorological radar advancements are allowing us to detect and track them better.

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