CASCADING DISASTERSWestern Wildfires Spark Stronger Storms in Downwind States

Published 26 October 2022

When wildfires burn in the west, their heat and airborne particles inflict stronger rain and larger hail upon central states. In some cases, the heavier rains have causes flash flooding in states like Colorado, Wyoming, Nebraska, Kansas, Oklahoma, and the Dakotas.

A new study shows for the first time that wildfires burning in West Coast states can strengthen storms in downwind states. Heat and tiny airborne particles produced by western wildfires distantly intensify severe storms, in some cases bringing baseball-sized hail, heavier rain and flash flooding to states like Colorado, Wyoming, Nebraska, Kansas, Oklahoma, and the Dakotas.

Typically, western wildfires and storms in the Central U.S. are separated by seasons. As blazes begin earlier each year, however, the two events now strike closer together.

Earth scientist Jiwen Fan, a Laboratory Fellow at the Department of Energy’s Pacific Northwest National Laboratory, began investigating a relationship between the two phenomena when she noticed that the west’s 2018 wildfires overlapped with storms in the Central U.S. She found that both events occurred simultaneously for a week. Looking further, Fan found it was the first time these storms and wildfires had concurred in 20 years where storms lasted over four days.

“I thought, maybe there’s some kind of connection there,” said Fan, who led the new study. Her team used data describing the storms’ hailstones and rain levels, as well as the fires and smoke plumes, to explore a possible mechanism behind the connection. The group used weather models that track heat and smoke particles to explore how the fires could remotely influence weather. 

“We need to be careful and informed,” said Fan. “The more we understand about the contributing factors behind storms like this, which cause massive property loss, 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,” Fan added. “Therefore, it is reasonable to expect that these co-occurring events would happen more frequently, and the impact of western wildfires on central storms may become increasingly important in the future.” 

The paper was published in the journal Proceedings of the National Academy of Sciences.

Smoky Skies, Stronger Storms 
What’s behind the relationship? Let’s begin with fires raging in the Western U.S. As they burn, these fires release incredible levels of heat. Some of the blazes, for example, warmed the fire area 10–40 times hotter than typical background temperatures in July. They also release billowing smoke particles, called aerosols.