Daniel Swain Profile picture
Mar 27 12 tweets 5 min read
Now that activity on the #NCARFire in Boulder, CO has calmed down significantly, a majority of the evacuation orders have been lifted, and the risk of property loss moving forward appears low, I wanted to share a few related thoughts. (All photos from yesterday, 3/26/22.) #COwx Image
1) NCAR Fire is an example of a relatively small fire posing disproportionately high risk to homes in wildland-urban interface. Should an ignition have occurred exactly the same place during one of Boulder's infamous downslope windstorms, it could have been a catastrophic event. Image
2) Emergency comms during this event were...not good. There was little info during first 1.5 hrs, which would have been critical had conditions been worse. Then, suddenly, a startlingly wide evacuation was ordered for ~15-20k people well *upwind* of fire,causing traffic gridlock.
3a) With this & other recent fires, there has been some handwaving regarding supposed non-influence of climate change. Obviously, climate change is never singular cause of *any* fire. But making an accurate assessment requires deeper consideration of underlying factors... Image
3b) Here, it's true that Jan-Mar period was very wet in portions of the Front Range. But it's also true that conditions yesterday were record/near record warm (prior to spring green-up),& the region experienced an all-time record warm/dry period from last summer into autumn.#COwx ImageImageImage
3c) The prolonged, multi-month period of record high aridity & evaporative demand last year caused 1,000 and 10,000 hour fuels (i.e., dense dead/down vegetation w/large diameters that respond slowly to climate conditions on timescales of ~1-10 months) to become exceptionally dry.
3d) Grass is a 1-10 hr fuel, meaning that is responds quickly to ambient conditions (like record warm/very dry & windy conditions yesterday). But 1-10k hr fuels, plus living but severely drought-stressed trees, were all burning in NCAR Fire, in addition to grass.
3e) To summarize point 3: this is not a formal analysis of potential links between climate change & this specific fire. But I do want to illustrate how important to think critically about these links between climate & wildfire--it's not just about weather the day of the event.
4) Finally, a silver lining! Assuming that current reports are correct (no homes lost/no injuries as a result of NCAR Fire), it may ultimately serve as an unplanned "prescribed burn" that could help improve ecosystem health & protect parts of South Boulder during future fires. Image
(P.S.) I authored a perspective piece in @outsidemagazine on broader context of the (much more devastating) Marshall Fire--which also hit close to home just <3 months ago. Circumstances were somewhat different, but much of the discussion remains relevant. outsideonline.com/outdoor-advent…
(P.P.S.) One additional thing that I forgot to mention is elevated potential for post-fire flash flood/debris flows that might arise in both Marshall Fire & NCAR fire footprints (esp. South Boulder Creek and Bear Creek watersheds) during upcoming spring/summer flash flood season.

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More from @Weather_West

Feb 19
Some mixed news on CA weather front over next couple of weeks. First, by Monday, another "inside slider" system will bring another burst of cooler & winder conditions statewide. Once again, some Sierra snow showers are possible, but most places stay dry. #CAwx #CAwater
Midweek, however, an even colder airmass and associated low pressure center will slide down the coast slightly farther to the west. This system, although still quite dry, stands a better chance of bringing convective activity (scattered showers/isolated thunder) statewide. #CAWx
The biggest impact from this mid-week system, outside of some additional modest Sierra snow accumulations and a few pockets of accumulating small hail showers at lower elevations (like last week in SoCal), will be a dramatic shift toward much colder temperatures. #CAwx
Read 6 tweets
Feb 19
Very compelling and timely new analysis out in @Nature led by @DrBalch and featuring co-authors including @climate_guy, @_mikoontz, and @peedublya on how #climate warming is weakening the global barrier to nighttime fire. nature.com/articles/s4158…
They find a strong trend toward increased nighttime fire activity across most regions globally, driven primarily by increases in overnight vapor pressure deficit (VPD). In western U.S., number of flammable nights have increased by 45% in past 4 decades! nature.com/articles/s4158…
These quantitative findings strongly corroborate widespread anecdotes from wildland firefighters, who have reported remarkable increases in nighttime burning activity that seriously challenge historical fire management strategies--which assume fires usually "lie down" at night.
Read 6 tweets
Feb 7
Folks with self-described severe climate anxiety now reach out to me (& other climate scientists I know) essentially every week. It is often hard to know how to respond, since climate scientists are not trained clinical psychologists. (1/12)
The nature and volume of these requests can become overwhelming for those not professionally equipped to help people in that way. This is especially frustrating since many of these folks have actually sought professional help, yet those practitioners have been dismissive...(2/12)
...telling people that climate change won't affect them personally, or that it's "not as bad as you read about in the news," or that there's nothing they can do about it, so you need to "let it go." Well, as many folks who are paying attention realize, none of this is true.(3/12)
Read 13 tweets
Jan 5
Our new study on co-occurring air pollution extremes (ozone & PM2.5), led by @wx_statman & w/co-authors including @ClimateChirper, @climate_guy, & @Weather_West, is out today in @ScienceAdvances. We find large increases in co-occurrences in U.S. West.(1/n) science.org/doi/full/10.11…
Increasing air pollution co-occurrence trends are widespread across the U.S. West over the last ~20 years, and encompass almost all of the West's major population centers from the Rocky Mountain Front Range to the Pacific Coast. (2/n) science.org/doi/full/10.11…
This increasing trend in co-occurring high levels of two key classes of air pollutants, ozone (photochemical pollution; think smog) & PM2.5 (fine particulate matter; think smoke) is almost entirely due to increasing frequency of extreme PM2.5 events. science.org/doi/full/10.11… (3/n)
Read 14 tweets
Dec 31, 2021
Some photos, footage, and commentary from yesterday's devastating #MarshallFire in Boulder County. All photos and videos taken at various points along South Boulder Road (north side of the fire, looking south, on 12/30/21). Winds were gusting around 90mph at the time. #COwx (1/4)
Fire behavior was as you'd expect in grass/brush amid extreme wind & drought conditions: rapid rates of spread, continuous spotting and periodic sheeting fire. Fire jumped 6-lane Hwy 36 like it was nothing, and there was a 2+ mile long active fireline. #MarshallFire #COwx (2/4)
Behavior and dynamics of the fire plume were fascinating...and scary. A nearly horizontal plume, tilted by extreme westerly downslope winds, transitioned into a shallow pyroCu plume at the top of a hydraulic jump within a pronounced mountain wave. #MarshallFire #COwx (3/4)
Read 5 tweets
Dec 30, 2021
Conditions along South Boulder Road right now. #marshallfire #COwx
Unfortunately can confirm that numerous structures are now burning, many of them homes. This is an extreme/dangerous wildland-urban interface fire. Mainly Superior/Louisville. Gusts in excess of 80mph continue.
Read 4 tweets

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