Fires in West may intensify storms in Central U.S.

heat, particulate matter lead to more severe weather

Pacific Northwest National Laboratory reports new that heat, aerosols and heightened pressure of wildfires in West states bring heavier rain and flash flooding to Central states.

Published in the journal Proceedings of the National Academy of Sciences, the article states that in some cases, the impact has resulted in “baseball-sized hail, heavier rain, and flash flooding (over) states like Colorado, Wyoming, Nebraska, Kansas, Oklahoma, and the Dakotas.”

Historically, fires in the West and storms in the Midwest have been separated by seasons. However, drought is making fire season nearly year-round, increasing the probability of the phenomena coinciding.

Earth scientist and PNNL fellow, Jiwen Fan and her team used datasets on hailstones, rainfall, fires and smoke plumes as well as weather models to explore a possible mechanism behind the connection.

Fan commented, “The more we understand the contributing factors behind storms like this, the better we’ll be able to prepare for them. And as we look at the future climate, we know wildfires will increase, particularly in the West. Severe storms in the Central U.S. are also projected to increase.”

Fire science

With wildfires, incredible amounts of heat and aerosols area released. As high air pressure near fires build, the surround air moves toward areas of lower pressure like the Central U.S. The air flow intensifies wind that naturally flows west to east.

As winds strengthen, they bring aerosols and atmospheric moisture. The condensation and additional heat can make storms more severe. If the condensed water droplets freeze, hailstones begin to form. Repeated updrafts and more time inside a storm create bigger hailstones.

Local wildfires also strengthened storms in the Central states, but to a lesser extent.

Yuwei Zhang, first author of the study and a postdoc in Fan’s research team added, “If we know that distant wildfires contribute to stronger storms, that information could bring about better projections, which might help avoid some degree of destruction.”

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