Wildfire Outlook Update

Last week, the Bootleg Fire, a 400,000 acre conflagration that is still only 40% contained, made headlines when it tripped off a set of high-voltage transmission lines known as the California-Oregon Intertie that transmit electricity between the Pacific Northwest and California. At the time, California was experiencing an extreme heat wave and very high electricity usage, so the combination of above-average energy usage and the limited ability to import electricity from the Pacific Northwest meant that California had limited supply during a period of very high demand.

The California Independent System Operator, which is responsible for operating California’s electric grid by doing things like balancing supply and demand, ensuring transmission availability, and economically dispatching electricity from power plants to member utilities’ balancing authority areas, issued several “Flex Alerts,” asking people to reduce power usage to reduce the risk of rolling blackouts.

A #FlexAlert is in effect today, July 12, from 4 p.m. to 9 p.m. pic.twitter.com/ulKwo6LAk1

— California ISO (@California_ISO) July 12, 2021

The Bootleg Fire has seen extreme fire activity as strong winds push it through dry timber. It has even caused “pyrocumulonimbus” clouds, which are clouds that are created as the hot air from the fire rises and cools until it reaches saturation. Some of these clouds exceeded 44,000 feet and were associated with thunder and lightning.

But it’s not just the Bootleg Fire that is burning. As of 7/18, Northwest Interagency Coordination Center counts 16 “large fires” (>100 acres in timber or >300 in grass/brush). I thought my Twitter post labeling the fires visible from space would just take me a few minutes but it turned out to be a project in itself.

Fires across the Western US this afternoon as seen from GOES-17. Fire danger east of the Cascades/Sierras will increase tomorrow and Friday as an upper-level trough approaches and onshore flow strengthens. #wawx #orwx #CAwx #FireSeason2021 pic.twitter.com/1xASjyiuSg

— Charlie Phillips (@GeoduckChuck) July 15, 2021

So far, the 2021 fire season has dwarfed the 2020 fire season year-to-date in terms of acres burnt over Washington and Oregon. And this has occurred without any major dry lightning outbreaks over Washington or Oregon. Fuels are just so dry right now that all it takes is a spark to begin a wildfire, and we’ve had persistent moderate-to-strong onshore flow over Central and Eastern Washington and Oregon that has helped these fires continue to grow.

What a difference a year makes…
2020 — 13 fires (23,966 acres) ↗️ 2021 — 43 fires (558,383 acres).

🔥NWCC Blog: https://t.co/5gEciPMiTV
🔥NWCC Website: https://t.co/3YwvyNPyCe pic.twitter.com/QZLEYNFY1R

— Northwest Interagency Coordination Center (@NWCCInfo) July 18, 2021

With the extreme fire activity already witnessed east of the Cascades, the record-dry spring over much of Oregon and California and record drought over much of the Western US, and the cataclysmic 2020 fire season still very fresh in people’s minds, there is understandably a lot of anxiety as we approach the peak fire season west of the Cascades, which is approximately from mid-August through September but can extend into October, depending on when the first rains of autumn arrive.

I’ll start this blog off with an outlook for the rest of the 2021 Pacific Northwest fire season. The second part of this blog will review the two major fire weather events in 2020 – the mid-August California lightning fires and the catastrophic Labor Day windstorm/firestorm throughout Washington, Oregon, and California. I never really got a chance to blog about these last year since I was so busy with fires for work, but they definitely deserve a little discussion.

And unfortunately, the forecast through early September calls for continued warmer and drier-than-average weather, with worsening drought conditions. I suspect the “Extreme Drought” currently over the Northern Willamette Valley will spread to Portland by the first or second week of August.

From now through September, the primary fire threat for areas east of the Cascade Crest is a dry lightning outbreak. With fuels as dry as they are, the probability of a lightning strike resulting in a successful fire start is well above-average, and a prodigious dry lightning outbreak would create an extreme amount of new fires. Lightning of any sort is not expected for the next 7 days, but it bears extremely close watching.

West of the Cascades, the primary wildfire threat is from strong, dry offshore winds. These winds are most common after mid-August, with September being the highest risk month. By October, fuels are generally too wet, but there have been Octobers with extreme fire danger west of the Cascades. October 1991 was one such month; the video below shows the 1991 Falls Fire racing through the Columbia River Gorge.

My single biggest worry from now through the end of fire season is an offshore wind event over critically dry fuels, particularly after mid/late-August. As I’ll explain in part two of this blog, the probability of us seeing a September 2020-style event is small due to the rarity of such an event. However, a “garden variety” east wind event, like the fire above or the Eagle Creek Fire from September 4-5, 2017, would still result in extraordinarily high fire danger. Click here to read the post I wrote back in 2017 on the Eagle Creek Fire.

I’ll end with this: it’s not a matter of if we will see offshore flow or dry thunderstorms for the remainder of the year, it’s a question of when and how strong. The below fire prevention tips are more important now than ever. Let’s hope for the best, prepare for the worst, and we’ll get through this together.

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Part 2: 2020 Fires Review

The Mid-August 2020 California Lightning Fires

In mid-August 2020, California experienced an unusual pattern, with an extremely strong ridge of high pressure over the Western US and strong southerly flow along the West Coast that brought moisture from the remnants of Hurricane Elida and Tropical Storm Fausto northward.

This combination of very strong ridging and tropical moisture resulted in two things. The first was a record-breaking heatwave with unseasonably humid conditions, resulting in extraordinary heat indices and very little overnight relief in temperatures, as water vapor is a strong greenhouse gas and helps prevent heat loss at night. Demand skyrocketed during the heatwave, and California had to implement rolling blackouts for the first time since the California Electricity Crisis from 2000-2001. But unlike the 2000-2001 energy crisis, which was due to energy traders artificially reducing supply and taking advantage of the increased prices, the 2020 energy crisis was due primarily to extreme temperatures. A fun fact about the 2000-2001 energy crisis: it greatly (and undeservedly) harmed then-Governor Gray Davis’ standing, and a certain Austrian bodybuilder won in a 2003 recall election.

The other main impact of this ridge/tropical moisture combo was unusually strong thunderstorms over the San Francisco Bay area with gusty winds, extremely frequent lightning, and little precipitation. This resulted in numerous fire starts over the Bay Area.

Wild night in the San Francisco Bay Area. This is probably the most widespread and violent summer thunderstorm event in memory for Bay Area, & it’s also one of the hottest nights in years. Convective gusts 60+ mph; enormous amount of (partially dry) lightning. Wow. #CAwx #CAfire pic.twitter.com/Q5AOEQcqR7

— Daniel Swain (@Weather_West) August 16, 2020

Several of these fires eventually became California’s largest wildfires on record. Five of California’s largest wildfires in history occurred in 2020, and four of these (all except the Creek Fire) occurred in August. By the time it was fully contained on November 12. the August Complex alone had scorched 1,032,648 acres, nearly 3.5 times the area of all of Multnomah County.

5 of the largest wildfires in CA history have occurred this year. As we move further into fall we recognize that we still have the potential to experience more large & damaging wildfires so we remain prepared. Make sure you & your family also plan, prepare, & stay aware. pic.twitter.com/blmgo4r52p

— CAL FIRE (@CAL_FIRE) September 30, 2020

Here’s a picture of the Doe Fire on August 17, the largest of all of the individual fires within the August Complex.

Thunderstorms and extreme heat also made it into the Pacific NW. Dry lightning on 8/16 ignited numerous fires across the Oregon Cascades, including the Beachie Creek and Lionshead fires, both of which would grow dramatically during the Labor Day firestorm. Seattle reached a high of 98 degrees on the 17th, while Portland “only” made it to the mid 90s due to smoke from the California fires reducing high temperatures. I was fishing up at Sekiu during that time and escaped the extreme heat, but I was treated to a spectacular nocturnal lightning show that I blogged about here.

The Labor Day 2020 Fires

While the August 2020 fires were caused by lightning, the Labor Day firestorm was due to extraordinarily strong and dry offshore flow that caused new or existing fires to quickly burn out of control. I still get chills looking at the satellite imagery below.

I wasn’t in Portland at the time of the Labor Day fires; I was staying up on Whidbey Island near Puget Sound with my folks. But I still remember how gusty the east winds were on Labor Day and seeing the whitecaps on Puget Sound, which I’d never seen before during easterly winds. And although the smoke was nowhere near as bad over Whidbey as it was over Portland and the Willamette Valley, it was still extraordinarily thick. The persistent smoke created a temperature inversion at the surface, resulting in a thick, damp smog that stuck around for the better half of a week.