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How a 30-minute, dry thunderstorm started the Bighorn Fire

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TUCSON (KVOA) - People who have been following the Bighorn Fire know that the Bighorn Fire was started by a lightning strike during a thunderstorm almost a month ago. But how many strikes of lightning did we see and why was there no rain with that storm?

The Bighorn Fire was started naturally by a dry thunderstorm over Oro Valley that produced more than 25 lightning strikes in under 30 minutes. But no rain poured down in the area that day.

"The reason why they are dry is because the dew point hasn't reached the sweet spot needed to deliver us rain," Chief Meteorologist Matt Brode said.

According to the Tucson National Weather Service, storms like these are common in the weeks leading up to the monsoon.

"We can still get thunderstorm development," Ken Drozd of NWS Tucson said. "But since there is not a lot of lower-level moisture, those storms will not produce a lot of rainfall at the surface."

Brode continued, "We can actually have good thunderstorms. We can have lightning coming out of the clouds. We can have thunder and gusty winds. But if you have very dry lower levels of the atmosphere despite the fact that it might be raining up high, it's just going to evaporate before it reaches the ground."

The west wind Southern Arizona saw and the mountains also contributed to the thunderstorm development.

"During the hot part of the day, you get air to rise," Drozd said. "It's going to be push up going through the valley and against the mountain and lifting upward."

That upward lift also caused more lightning to develop in the storm. Lightning is caused when a storm is so tall that ice crystals start to develop in the clouds.

Those crystals then rub against each other creating static electricity. If you get enough static, that could cause a lightning strike.

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Daniel McFarland

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