Extreme wildfires make their own dangerous weather

And climate change is making it even worse.

 

Extreme wildfires can fuel tornadoes, creating erratic and dangerous conditions for firefighters, like this one on Rabbit Mountain during the Douglas Complex fires of 2013.

This article was originally published by The Conversation and is republished with permission.

It might sound like a bad movie, but extreme wildfires can create their own weather – including fire tornadoes.

It happened in California as a heat wave helped to fuel hundreds of wildfires across the region, many of them sparked by lightning. One fiery funnel cloud on Aug. 15 was so powerful, the National Weather Service issued what’s believed to be its first fire tornado warning.

So, what has to happen for a wildfire to get so extreme that it spins off tornadoes?

As professors who study wildfires and weather, we can offer some insights.

How extreme fire conditions form

Fires have three basic elements: heat, fuel and oxygen.

In a wildland fire, a heat source ignites the fire. Sometimes that ignition source is a car or power line or, as the West saw in mid-August, lightning strikes. Oxygen then reacts with dry vegetation to produce heat, ash and gases. How dry the landscape is determines whether the fire starts, how fast it burns and how hot the fire can get. It’s almost as important as wind.

Fire weather conditions get extreme when high temperatures, low humidity and strong winds combine with dead and live vegetation to produce difficult-to-fight, fast-spreading wildfires.

That combination is exactly what the West has been seeing. A wet winter fed the growth of grasses that now cover large areas of wildland in the western U.S. Most of this grass is now dead from the summer heat. Combined with other types of vegetation, that leaves lots of fuel for the wildfires to burn.

The remnants of Hurricane Elida also played a role. The storm increased moisture and instability in the atmosphere, which triggered thunderstorms further north. The atmosphere over land was pretty dry by then, and even when rain formed at the base of these clouds, it mostly evaporated due to the excessive heat. This led to “dry lightning” that ignited wildfires.

Wildfires can fuel thunderstorms

Fires can also cause convection – hot air rises, and it moves water vapor, gases and aerosols upward.

Wildfires with turbulent plumes can produce a “cumulus” type of cloud, known as pyrocumulus or pyrocumulonimbus. Pyrocumulus clouds are similar to the cumulus clouds people are used to seeing. They develop when hot air carries moisture from plants, soil and air upward, where it cools and condenses. The centers of these “pyroclouds” have strong rising air.

It’s pretty common, and it’s a warning sign that firefighters could be facing erratic and dangerous conditions on the ground from the indraft of air toward the center of the blaze.

In some cases, the pyroclouds can reach 30,000 feet and produce lightning. There is evidence that pyrocumulus lightning may have ignited new blazes during the devastating fire storm in Australia in 2009 known as “Black Friday.”

Where do fire tornadoes come from?

Similar to the way cumulonimbus clouds produce tornadoes, these pyroclouds can produce fire‐generated vortices of ash, smoke and often flames that can get destructive.

A vortex can form because of the intense heat of the fire in an environment with strong winds. This is similar to a strong river flow passing through a depression. The sudden change in the speed of the flow will force the flow to rotate. Similarly, the heat generated by the fire creates a low pressure, and in an environment with strong winds, this process results in the formation of a vortex.

One fire tornado, or fire whirl, that developed during the deadly 2018 Carr Fire devastated parts of Redding, California, with winds clocked at over 143 miles per hour.

These vortices can also increase the severity of the fires themselves by sucking air rich in oxygen toward the center of the vortex. The hotter the fire, the higher the probability of stronger updrafts and stronger and larger vortices.

Persistent heat waves that dry out the land and vegetation have increased the potential of wildfires to be more violent and widespread.

Is extreme fire weather becoming more common?

Global warming has modified the Earth’s climate in ways that profoundly affect the behavior of wildfires.

The frequency of California’s extreme fire weather days in the autumn fire season had more than doubled since the early 1980s.

Scientific evidence suggests that the severity of prolonged droughts and heat waves has been exacerbated not only by rising temperatures but also by changes in atmospheric circulation patterns associated with recent climate change. These changes can enhance extreme fire-weather behavior.

Firefighters and people living in wildfire-prone areas, meanwhile, need to be prepared for more extreme wildfires in the coming years.The ConversationA study published Aug. 20 found that the frequency of California’s extreme fire weather days in the autumn fire season had more than doubled since the early 1980s. Over that four-decade period, autumn temperatures in the state rose by about 1.8 degrees Fahrenheit and autumn precipitation decreased by about 30%.

Charles Jones is a professor of atmospheric science at the University of California, Santa Barbara and Leila Carvalho is a professor of meteorology and climatology at the University of California, Santa BarbaraEmail High Country News at [email protected] or submit a letter to the editor.

High Country News Classifieds
  • CONSERVATIONIST? IRRIGABLE LAND?
    Stellar seed-saving NGO is available to serious partner. Package must include financial support. Details: http://seeds.ojaidigital.net.
  • EXPERT LAND STEWART
    Available for site conservator, property manager. View resume at http://skills.ojadigital.net.
  • ANCESTRAL LANDS ADMINISTRATIVE MANAGER
    Starting Salary: Grade C, $19.00 to 24.00 per/hour Location: Albuquerque or Gallup, NM Status: Full-Time, Non-Exempt Benefit Eligible: Full Benefits Eligible per Personnel Policies Program...
  • GRAND CANYON DIRECTOR
    The Grand Canyon director, with the Grand Canyon manager, conservation director, and other staff, envisions, prioritizes, and implements strategies for the Grand Canyon Trust's work...
  • ADMINISTRATIVE ASSISTANT
    Great Old Broads for Wilderness seeks a part-time Administrative Assistant to support the organization's general operations. This includes phone and email communications, office correspondence and...
  • HISTORIC LODGE AND RESTAURANT - FULLY EQUIPPED
    Built in 1901, The Crazy Mountain Inn has 11 guest rooms in a town-center building on 7 city lots (.58 acres). The inn and restaurant...
  • ONE WILL: THREE WIVES
    by Edith Tarbescu. "One Will: Three Wives" is packed with a large array of interesting suspects, all of whom could be a murderer ... a...
  • PROGRAM DIRECTOR, SALAZAR CENTER FOR NORTH AMERICAN CONSERVATION
    The Program Director will oversee the programmatic initiatives of The Salazar Center, working closely with the Center's Director and staff to engage the world's leading...
  • WILDEARTH GUARDIANS - WILD PLACES PROGRAM DIRECTOR
    Salary Range: $70,000-$80,000. Location: Denver, CO, Portland, OR, Seattle, WA, Missoula, MT or potentially elsewhere for the right person. Application Review: on a rolling basis....
  • RIVER EDUCATOR/GUIDE + TRIP LEADER
    Position Description: Full-time seasonal positions (mid-March through October) Organizational Background: Colorado Canyons Association (CCA) is a 10 year old nonprofit organization fostering community stewardship of...
  • BOOKKEEPER/ADMINISTRATIVE ASSISTANT
    Position Description: Part-time, year-round bookkeeping and administration position (12 - 16 hours/week) $16 - $18/hour DOE Organizational Background: Colorado Canyons Association (CCA) is a 10...
  • LAND STEWARD
    San Isabel Land Protection Trust seeks a full-time Land Steward to manage and oversee its conservation easement monitoring and stewardship program for 42,437 acres in...
  • EXECUTIVE DIRECTOR
    Ventana Wilderness Alliance is seeking an experienced forward-facing public land conservation leader to serve as its Executive Director. The mission of the Ventana Wilderness Alliance...
  • COMMUNICATIONS AND DEVELOPMENT DIRECTOR
    The Quivira Coalition (www.quiviracoaltion.org) is a Santa Fe-based nonprofit that builds resilience on arid working lands. We foster ecological, economic, and social health through education,...
  • GRANT WRITER
    "We all love this place we call Montana. We believe that land and water and air are not ours to despoil, but ours to steward...
  • DEVELOPMENT DIRECTOR
    The Development Director is responsible for organizing and launching a coherent set of development activities to build support for the Natural History Institute's programs and...
  • WILDLIFE PROJECT COORDINATOR
    Founded in 1936, the National Wildlife Federation (NWF or Federation) is America's largest and most trusted grassroots conservation organization with 53 state/territorial affiliates and more...
  • EXECUTIVE DIRECTOR
    The Cinnabar Foundation helps protect and conserve water, wildlife and wild lands in Montana and the Greater Yellowstone Ecosystem by supporting organizations and people who...
  • OLIVERBRANCH CONSULTING
    Non-Profit Management Professional specializing in Transitional Leadership, Strategic Collaborations, Communications and Grant Management/Writing.
  • GREAT VIEWS, SMALL FOOTPRINT
    Close to town but with a secluded feel, this eco-friendly home includes solar panels, a graywater reuse system, tankless hot water, solar tubes, and rainwater...