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Dr. Daniel Swain Profile picture
@Weather_West
Aug 8, 2022 • 8 tweets • 7 min read • Read on X
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New research on dry lightning events in California, led by @wx_statman, and including co-authors @climate_guy, @NickyNaus, @Weather_West, @danielletouma, & @ClimateChirper, is out today in @IOPenvironment (open access!). #CAwx #CAfire (1/n) iopscience.iop.org/article/10.108…
We assess regional-scale atmospheric conditions favorable for dry lightning in central & northern California (N&C CA), as well as seasonality. We find that nearly half of all lightning strikes in N&C CA are "dry" (accompanied by <0.10 in. of rain). (2/n) iopscience.iop.org/article/10.108… Image
In some locations, including most of the San Francisco Bay Area, North Coast, and portions of Southern Sierra, fully 60-80% of May-Oct cloud-to-ground lightning strikes occur as dry lightning! Major implications for wildfire risk. (3/n) #CAwx #CAfire iopscience.iop.org/article/10.108… Image
Overall, dry lightning events are most common mid-summer (Jul-Aug), but single largest events historically have actually occurred in shoulder seasons (Jun&Sep). Late-season (Sep-Oct) events preferentially occur in low elev/coastal areas.#CAwx #CAfire (4/n) iopscience.iop.org/article/10.108… Image
We find that environmental conditions favorable for N&C CA dry lightning events include unusually moist & unstable conditions at mid levels atop dry & unusually hot low levels. High total column moisture does not preclude dry lightning (see:Aug 2020)!(5/n) iopscience.iop.org/article/10.108… Image
From a regional atmospheric circulation perspective, we find 4 patterns that are broadly conducive to N&C CA dry lightning. All feature high pressure ridging centered to east of CA over continental interior, & 2 of 4 also feature an offshore trough/closed low.#CAwx #CAfire (6/n) Image
We hope this work will contribute to understanding & predicting dry lightning events in CA given their large implications for wildfire risk, since lightning ignitions often occur in large volume and spread widely across remote areas. #CAwx #CAfire (7/n) iopscience.iop.org/article/10.108…
This is especially true in a warming climate, which is likely increasing the probability of ignition from lightning strikes by causing long-term drying of vegetation and amplifying the potential consequences of those fires that do ignite. (8/8) iopscience.iop.org/article/10.108…

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More from @Weather_West

Dr. Daniel Swain Profile picture
Sep 28
The images and stories just beginning to emerge from eastern TN and western NC in the aftermath of widespread catastrophic flooding wrought by #Helene are genuinely horrifying, and the full scale of the disaster is likely as yet untold. #TNwx #NCwx [Thread: 1/n]
20-30 inches--and perhaps locally 40+ inches--of rain fell along highest ridges of the Southern Appalachians due to 1-2 punch consisting of extreme "predecessor rain event" (PRE) that was historic in its own right followed by further extreme rain directly from #Helene. [2/n]
This was, by far, the most extreme rain event in observed record across much/most of the region, where reliable records date back over 100 yrs. Unsurprisingly, the flooding which resulted has also been widespread, historic, and generally catastrophic across a broad region. [3/n]
Read 19 tweets
Dr. Daniel Swain Profile picture
Aug 19
For the first time since June in many parts of California and the broader Southwest, *cooler* than average temperatures can be expected for the next week, thanks in part to arrival of a *second* anomalously deep August low pressure system over NorCal Thu/Fri. #CAwx [1/4] ECMWF weather model depiction of anomalously low GPH near California later this week, representing an unusually deep summer low pressure center.
Another round of widespread rain & possible t-storms will occur in western WA & OR. In far NorCal, esp. northern mtns (Shasta region), some decent showers & t-storms are possible. Few showers/isolated thunder may reach farther south than last event--locally to I-80 corridor. #ORwx #WAwx #CAwx [2/4]ECMWF weather model depiction of cumulative precipitation across the American West this week, which shows a widespread wetting rainfall across the Pacific Northwest with more limited precipitation across portions of the northern third of California.
All of this will be fortuitous for fire season in western Washington and Oregon--mainly west of Cascades. While active fires will continue to east of Cascades, this may be season-ending precip (or close to it) for western WA and NW OR. #ORwx #WAwx [3/4]
Read 4 tweets
Dr. Daniel Swain Profile picture
Apr 7
For folks in Colorado wondering what the heck is going on with #Xcel's large-scale pre-emptive power line de-energization to avoid wildfire ignitions during high wind events, I wanted to share a some thoughts as a scientist who studies climate/weather/wildfire. #COwx [1/n]
The first utility-scale "Public Safety Power Shut-offs" (#PSPS) in response to fire risk of which I'm aware began in 2010s in California in response to catastrophic wildfire events in urban interface sparked by power infrastructure during extreme fire weather/wind events. [2/n]
Such fires occur when energized lines fall to ground or trees fall onto live wires (igniting vegetation). They tend to be preferentially dangerous precisely because they occur under "worst case" conditions, when weather favors rapid spread & fire suppression is ineffective. [3/n]
Read 23 tweets
Dr. Daniel Swain Profile picture
Feb 5
I wanted to reiterate some recent findings from our own research specifically addressing extreme #AtmosphericRiver storms in a warming climate.

1) CA will more extreme ARs in a warming climate, mainly (~80%) due water vapor increases. #CAwx #CAwater science.org/doi/10.1126/sc…
Image
2) Extreme CA ARs in a warming climate will not only be more intense, but they may also have preferentially more southerly (deep subtropical) origins (like present one!). #CAwx #CAwater science.org/doi/10.1126/sc…
Image
3) Integrated vapor transport, a measure of AR intensity, may increase at a "super Clausius-Clapeyron" rate (>>7%/C), especially over Southern California! #CAwx #CAwater science.org/doi/10.1126/sc…
Image
Read 10 tweets
Dr. Daniel Swain Profile picture
Dec 5, 2023
Scientific institutions must create--and sustain--new kinds of roles so that researchers can provide the deep public engagement necessary to respond effectively to the escalating impacts of #climate change. The status quo isn't working. [Thread: 1/n] nature.com/articles/d4158…
My own role as a climate scientist-communicator is highly unusual in the academic world: I'm a practicing scientist who spends a large fraction (now over half) of my time engaging the public, and the rest of my time actually conducting research and writing papers. [2]
That engagement takes many forms. This year, I've given over 200 news interviews & worked with outlets behind the scenes to develop their coverage. I also work with state/federal agencies, brief members of state/national legislatures, and more. [3]
Read 13 tweets
Dr. Daniel Swain Profile picture
Nov 7, 2023
If you've been wondering why I've been somewhat less visible here, that's partly because of the "shifting winds" of social media. But also, I've been spending much effort scrambling to find some way to support my climate scientist-communicator role moving forward.
Thus far, I have not yet been successful in these efforts--& if nothing changes, the time left in my current role may unfortunately be limited. A great number of individuals & organizations have voiced support--and I'm hugely grateful for that!--but ultimately a large gap looms.
I'm still optimistic that something will arise in the coming months! But operating in this kind of highly public-facing climate science role unfortunately seems to fall between the cracks of existing institutions and funders. And ultimately, the status quo is not sustainable.
Read 7 tweets

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