When one reads about the potential for Northwest and California wildfires, the media and others tend to dwell on temperature and moisture.
Surely, warm temperatures, lack of precipitation, and dry fuels contribute to wildfire (although excessive precipitation during a preceding period can lead to bountiful fuels and wildfire).
But there is another critical parameter for wildfire initiation and growth: strong winds. And in the western U.S., strong easterly (from the east) winds descending regional terrain are of particular importance.
Wind plays a central role in Northwest wildfires, with nearly all of the major events associated with strong winds or rapid wind shifts.
The wind is critical for a number of reasons. Strong winds provide bountiful oxygen for fires. It pushes embers, firebrands, and superheated gases ahead of the flame front, facilitating rapid spread. Wind helps dry surface fuels, such as grasses, and range vegetation. Strong winds can initiate fires, such as when winds damage electrical infrastructure causing sparks and flames (e.g., branches falling on powerlines). Rapid wind shifts can kill firefighters, particularly if they are in canyons or valleys.
Wind is as important as other well-known factors modulating wildfire, such as temperature and precipitation. It turns out that virtually all large wildfires west of the Cascade crest are associated with powerful easterly winds. The largest wildfires in eastern Washington are associated with strong winds.
Consider the deadliest fires in the Pacific Northwest since 1900 (see table below). The Yacoult Burn of 1902 was the biggest killer (65+) and was associated with powerful easterly winds. The famous Big Burn of 1910 resulted in 38 deaths and was accompanied by strong winds associated with at a cold front (which Tim Egan in his book termed a Palouse Wind).
The Beachie Creek fire in 2020 killed five as extremely strong easterly winds accelerated down the western slopes of the Cascades. The Thirty Mile Fire killed four firefighters as the winds shifted rapidly, while they were on the front fire lines. Same with the Twisp River Fire.
I could go on, but you get the message. Virtually all fatal fires in Washington State were associated with very strong winds or a very sharp/rapid wind shift.
What about the largest Northwest fires (see below)?
All were associated with strong winds. The big fires in western Washington and Oregon are all connected with powerful easterly winds. The big fires east of the Cascades are accompanied by strong winds but can be a bit weaker when the fire is over grass or rangeland.
A key message: don't underestimate the critical role of winds in initiating and spreading Northwest wildfires.
So if winds are so important for wildfire, how has climate change altered Northwest winds? And how will critical easterly winds change as the planet warms?
My group and others have been working on this issue, and one of my graduate students is examining wind trends. At this point, it appears that the historical trend in winds has been relatively small over the past 50 years, and that strong easterly winds will weaken (and thus be less likely to support western wildfires) as the earth warms (see plot from a regional climate model simulations below for a location near the crest of the central Washington Cascades).
Thus, a major contributor to NW wildfires may well lessen under global warming, another example of the nuances associated with wildfires.
Finally a climate person talking sensibly about this key variable. Draught/heat have seemed like a red herring that have been overly emphasized as main drivers of worsening wildfires. Why is this variable never mentioned? Certain activist scientists are loud and proud that climate change is making wild fires worse, yet they have failed to address the fact that during the peak of the latest CA drought (last summer) CA had one of the most benign fire seasons of the last decade or longer. Winds are never discussed to this end.
ReplyDeleteSaturday, a 2019 Ford truck pulling a trailer on I-90 near the Horse Monument caught fire. The driver pulled to the side of the road and caught the grass on fire. 100 acres. This happens frequently. July 2018 had a fire near the Ryegrass Rest area. Same deal. More wind. Bigger fire.
ReplyDeleteStop the ignition. Stop in the middle of the road.
Eastern Washington is often windy, warm, and dry.
When I lived outside of Aspen, a few fires were started by dirt bikes off - roading the wilderness areas. Exhaust manifolds get extremely hot in a short amount of time.
DeleteI worked for the US Forest Service on the Wind River Ranger District on the Gifford Pinchot National Forest in the early 1970s. The Yacolt burn is on that district. In 1974 I found a Letter in an archive Box in the Fire ware house written by a fire crew boss to the Forest Supervisor explaining how a member of his crew died on that fire.
ReplyDeleteHe said the smoke was so thick that they became lost. They couldn't see the sun and wandered through the burn for seven days. The only light was from snags burning in the interior. Early on they had spent the night in a mine shaft that was cold and damp. The crew member caught pneumonia and died a few days later.
Here's couple Strong East Wind anecdotal storys from the Wind River Ranger District.
ReplyDeleteThe east winds seem to peak in the fall being especial pesky to prescribe burning of clear cut units in October. There was an escaped Rx burn on one timber sale at night. There hadn't been smoke detected in the unit for a week after it was mopped up. A Forest Service Night watchman was assigned to watch the unit one night due to a forecast for strong east winds. He called on the radio in the middle of the night to report that the unit began burning and had escaped.
The next day the Red Mountain Lookout On the Crest of the Cascades told me that an air attack plane, a Cessna 180 working on the fire, had stopped and hovered outside her Lookout window on his way to the fire from Trout lake.
Another time I got a call from an insurance adjuster. He wanted to know if we had any records of wind speed for the previous weekend. He had a client that was working on a snag falling contract in the Yacolt Burn and had gone home for the weekend. His travel trailer had been parked on a ridge. Re returned to find that the wind had blown the trailer off the ridge into the drainage below.
I called the Red Mountain Lookout and held the phone up to the radio. I asked her what the wind speed had been. She said "It was calm Friday night, Saturday morning it was 50 mph, at noon it was 70 and by 3 pm it was 90". The insurance adjuster said "Okay, I've herd enough, thank you".
In December 2006 strong winds blew the roof off the Red Mountain Lookout.
Link of info and photos of Red Mountain Lookout. http://www.firelookout.com/wa/redmtn.html
Tom Jones
Wind is the main factor in spreading large grass fires and also in the large east wind fires west of the Cascades. Most of our fire loss in Washington has been east of the Cascades where strong winds from the west are the main driver. These strong westerly winds are a frequent summertime occurrence compared to the east winds of Western Washington but do not aways result in large forest fires, even when fire may be present. It is when these winds are preceded and accompanied by warm, dry weather that they become a big factor. Often strong westerly winds in Eastern Washington are accompanied by cool, more moist air or come during periods of cool, damper weather so are not dangerous. Most of the historical fires you listed were preceded and accompanied by a period of warm, dry weather. The Thirty Mile fire near Winthrop in 2001 that claimed four lives was an example of a sudden blow up of a fire that had been smoldering in the valley bottom in cooler, more humid air below a strong temperature inversion. Above the inversion was very, warm, dry air and when this inversion broke later in the day, mixing this warm, dry air down into the valley bottom, the fire suddenly blew up and spread rapidly in a very dry forest, up the narrow valley in winds largely created by the fire. This condition, when fires are burning under a strong inversion that breaks, has happened on other fires and is especially dangerous because it is not directly felt or easily measured by firefighters, like temperature, humidity and wind.
ReplyDeleteFinally, much appreciation to you and the researchers at the UW for developing the forecast models that have greatly assisted us forecasters, especially in frost and fire weather predictions.
In general, leeside events are not associated with inversions. Previous warm days are associated with a deep, well mixed boundary layer. Then cool air moves into western WA, the result is greatly enhanced downslope westerly flow, which can rev up fires. This flow is often cooler than the preceding air.mass.
DeleteAnd as you have mentioned in the past, accurate local wind (now)casts will greatly improve the electric grid as we build more wind power.
ReplyDeleteHi Cliff! There was a fairly large and active storm that formed around 3am last night. Frequent cloud to ground lightning woke me up through double ear plugs as I presume it struck somewhere around Cle Elum ridge. I have noticed that storms seem to form frequently between 410 and I-90 south of Cle Elum lake. Is there something special about this area that is favorable to thunderstorms?
ReplyDeleteHi Jimmy, I'd be interested in your best guess as to how many T-storms per year form in your area (I gather that you live in Cle Elum). Here in the western valley, we're lucky to get one decent T-storm per year. I am from the East coast and I miss watching them.
ReplyDeleteI have noticed the same over the last month or so. The area from Mt Rainier to the Stampede/Snoqualmie pass have seemed to be the bullseye area. Any ideas Cliff?
DeleteThere is probably not a good climatology of the number of thunderstorms per year in the Cle Elum area, but a study of thunderstorm frequency using observations from fire lookouts from the 1930s and 1940s came up with an average of 10 to 15 thunderstorm days for the Wenatchee NF for the summer period June thru September. Since there is usually a greater frequency of storms in the eastern and northern sections of the Wenatchee NF, the frequency of storms is probably less than this for the Cle Elum area.
DeleteHi Cliff. Thanks for taking the time to make weather accessible for your readers. :-) The same is true with winds in the SE corner of Australia which likewise has big fires some years (our death tolls are somewhat higher sadly, e.g. the 2009 Black Saturday bushfires). Living surrounded by tall Eucalyptus Obliqua forest, and as a former volunteer rural fire fighter myself, kind of makes you consider forest fires as a serious risk. The last big fires down under have all been accompanied by strong winds as well. It's particularly hazardous because the initial hot winds will drive a long narrow fire front. The front can extend for kilometres in a single narrow direction. But when the wind change sweeps through, even if it is cooler and contains more moisture, the fire front will then extend outwards along the entire line of the active fire narrow front which pushes the fire an entirely new direction, but now with a massively wide fire front. Those types of fires are rare, but they do happen and are awfully hard to extinguish. Cheers. Chris
ReplyDeleteVideo of fire marshal at the Mcewan fire: we were shocked at how rapidly the fire spread without wind. He was explaining why they did not warn homeowners earlier to evacuate.
ReplyDeletethe fire is only 232 acres. Not a large fire. Contained.
DeleteI really enjoyed Eagan's "Fever in the Heartland" and was looking for another book of his that struck my interest. I assume the "Palouse Wind" is from "The Big Burn"? Have you read it? If so, would you recommend?
ReplyDelete