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Dr. Daniel Swain Profile picture
Dr. Daniel Swain
@Weather_West
Climate scientist-communicator focused on extreme events like floods, droughts, & wildfires on a warming planet.
13 subscribers
Nov 18 • 7 tweets • 3 min read
A strong, prolonged, very moist, and relatively warm #AtmosphericRiver event, in conjunction with rapidly-strengthening #BombCyclone (yes, that's the term!), will bring major rain (and, locally, wind) impacts to OR/NorCal this week. Flooding is likely. #CAwx #ORwx #CAwater [1/6] Snapshot of 3-day accumulated IVT (integrated vapor transport) along the West Coast of North America from the GFS model. It depicts extremely high 72-hr accumulated IVT values aimed at far northern California coast. First, a low pressure system west of OR and WA will undergo explosive deepening (rapid strengthening, known as "bombogenesis") over the next 2 days. It may become one of the strongest low pressure systems on record in this region. (~940mb) #CAwx #ORwx #CAwater [2/6] A map plot depicting the relative anomalousness of surface pressures over the northeastern Pacific Ocean later this week. There is a region of red west of WA and OR, indicating that the upcoming storm may bring some of the lowest surface pressures on record in this region.
Nov 16 • 6 tweets • 3 min read
Signs of some "big time" weather for TBD portions of U.S. West coast over next 10 days. A major #AtmosphericRiver, & perhaps a short sequence of very wet ARs, will affect some section of coast between NorCal & WA--perhaps bringing very heavy rain accumulations. #CAwx #ORwx [1/6] Map of ECMWF ensemble average precipitation accumulated over the next 10 days in the U.S. West. Heavy accumulations are depicted from far NorCal into Oregon and Washington. First, it's important to consider the broader context. This autumn to date has been very (anomalously) dry across most of CA (except for far northern parts of state), but much less so in PacNW. It has also been broadly warmer than average across the West. #CAwx #ORwx [2/6] Map of temperature anomalies for the past 60 days across the U.S. from climatetoolbox.org. Nearly all areas are depicted as being warmer than average.
Map of precipitation anomalies for the past 60 days across the U.S. from climatetoolbox.org. Nearly all areas in California are depicted as being drier than average except for the northenrmost part of the state.
Oct 8 • 9 tweets • 2 min read
We are witnessing a genuinely extraordinary, and regionally quite deadly and destructive, period for extreme #weather in the United States. And, quite frankly, the fingerprints of #ClimateChange are all over what has transpired in recent weeks and may yet occur in coming days. An incredible, ongoing, & increasingly record-shattering heatwave has plagued much of Southwestern U.S. for *weeks* now. Phoenix has now seen *2 consecutive weeks* with record temperatures *every day.* Many other locations have set new Oct and/or "heat streak" records.#CAwx #AZwx
Sep 28 • 19 tweets • 3 min read
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]
Aug 19 • 4 tweets • 2 min read
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.
Apr 7 • 23 tweets • 4 min read
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]
Feb 5 • 10 tweets • 4 min read
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
Dec 5, 2023 • 13 tweets • 3 min read
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]
Nov 7, 2023 • 7 tweets • 2 min read
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.
Sep 20, 2023 • 13 tweets • 4 min read
Some additional thoughts regarding the still strengthening #ElNiño and its implications for western U.S. hydroclimate during winter 2023-24. (Brief thread!) #CAwx #ORwx #WAwx #HIwx #CAwater #CAfire Global map of sea surface temperature anomalies. Multiple areas with +3-5C anomalies are present in addition to the warm anomalies associated with El Nino in the eastern tropical Pacific. International dynamical models ensemble is now unanimous in predicting strong to very strong #ElNiño event that will peak sometime this winter. This is a remarkably strong signal, so I'm reasonably confident that the oceanic signature of a strong EN will actually occur. Time series chart showing Nino3.4 region SST anomalies over the next several months from various coupled ocean-atmosphere models. All depicted models show a strong or very strong EN event, denoted by N3.4 values of +1.5 or +2 C, respectively.
Aug 10, 2023 • 15 tweets • 3 min read
Confirmed human toll from wildland-urban interface #MauiFires is terrible (already second deadliest wildfire in modern American history), but grim reports from residents on the ground suggest actual toll is even greater & that there is still minimal outside assistance. #MauiFire As previously discussed: #Lahaina was town that was unfortunately quite vulnerable to a wind-driven fire from precisely the direction in which this one originated (due to surrounding extensive grasslands and brush, prevalence of wood structures, & relatively isolated location).
Mar 21, 2023 • 5 tweets • 1 min read
One thing I keep reflecting on, especially in context of recent events (CA's winter storm onslaught & dramatic increasingly dramatic hydroclimate whiplash), is how high societal need is for scientist-communicators & others who offer critical context as events unfold in real-time. There is much public demand for such roles, but there continues to be a (frankly) bewildering refusal by institutions (academic, public, private, and otherwise) support these kinds of roles in any broad sense.
Mar 16, 2023 • 4 tweets • 3 min read
Brief thoughts on likely return to active weather pattern in CA after a much-needed several day break right now. There is *high* confidence that wet and cool conditions will return next week, but right now there is *low* confidence in strength of storms. #CAwx #CAwater (1/4) Time series plot from ECMWF... Ensembles suggest that there is very high likelihood that unsettled and occasionally stormy conditions return to most of CA by early next wk. But vast majority of ensemble members suggest this will involve series of weak to moderate systems vs. major storms. #CAwx #CAwater (2/4)
Mar 12, 2023 • 8 tweets • 5 min read
Brief thread about...snow. As of this weekend, the Southern Sierra now appears to have largest snowpack in recorded history (as measured by snow water equivalent, or SWE). Not just for the calendar date, but for *any* date! #CAwx #CAwater [1/n] SWE time series trace from DWR for the major California Sier As I earlier noted was plausible, the "warm" atmospheric river storm on Fri actually *increased* net watershed SWE substantially--partly because it still snowed at high elevations, but also because lower elevation snowpack absorbed a lot of rainwater! #CAwx #CAwater [2/n]
Mar 9, 2023 • 5 tweets • 3 min read
A few storm updates following my session Wed PM:
Event still largely on track, but two modest shifts that could affect impacts:
1) Storm may not be quite as warm across central & northern Sierra; could see some very heavy snowfalls above 6,500 ft once again.
#CAwx #CAwater [1/5] 2) Rainfall may be a bit heavier and more concentrated across the northern portion of central CA (but slightly less to north). This means flood risk in Monterey County (including Big Sur Coast), as well as southern Sierra & foothills, has increased somewhat. #CAwx [2/5]
Feb 16, 2023 • 7 tweets • 3 min read
Lot of hype right now regarding supposed potential for widespread "sea level snowfall" later next week NorCal.

That almost certainly isn't going to happen (for variety of reasons). But some unusually low elevation snowfall (to 1000-1,500 feet or so) is certainly possible. #CAwx Yes, I know that the coarse-resolution ensemble models are showing accumulating sea level snowfall for SF/Sacramento. They are very likely wrong--and the same models' *own thermal profiles* are not supportive of snow in these areas with this pattern! #CAwx
Jan 11, 2023 • 4 tweets • 3 min read
Additional widespread precipitation is likely over the next 8-9 days over the northern 2/3 of CA, and it will be heavy at times (especially northern third of CA). Strongest storm, with some more heavy rain, wind, and thunderstorms, is due in on Sat. #CAwx #CAwater [1/4] Projected precipitation map from ECMWF ensemble depicting wi However, these are primarily areas that have not been nearly as wet as central CA recently. Also, these will generally be colder storm systems, bringing a greater balance of snow (vs rain) in mountains & somewhat limiting higher elevation runoff. #CAwx #CAwater [2/4]
Jan 2, 2023 • 17 tweets • 10 min read
Okay, folks. Starting to look like it's going to be a rough 10+ days from a flood risk perspective in Northern California, with a series of very wet & high-impact storms. Brief thread now; blog post late this PM; YouTube live Q&A Tue. [1/n] #CAwx #CAwater The next inbound storm looks like it will be quite strong. A rapidly deepening surface low (i.e., meteorological "bomb cyclone") will remain well offshore, but the associated warm and cold fronts will bring widespread heavy rain and strong winds to NorCal later Wed. #CAwx [2/n] Map showing ECMWF model representation of "bomb cyclone
Dec 29, 2022 • 8 tweets • 6 min read
Some thoughts on impacts from ongoing and likely prolonged very wet spell in NorCal. (Short thread). TL;DR: widespread heavy precipitation is likely, with mostly minor flood issues becoming more widespread this weekend & *possibly* more significant next week. [1/n] #CAwx #CAwater Lighter precipitation continues today, but the next significant storm will be this weekend. This will come in the form of a moderately strong low pressure system coupled with a robust, warm, and relatively slow-moving atmospheric river. #CAwx #CAwater [2/n] Image
Dec 20, 2022 • 5 tweets • 2 min read
Still not seeing many images of damage, but based on anecdotes from folks in quake zone it does sound like there was damage to some structures & especially to infrastructure. I suspect that ongoing widespread regional power outages are reason we haven't heard more yet.#earthquake This points to an emerging paradox in media reporting on disasters that's become really apparent in recent years: the more severe the damage, the less news initially makes it out (because power is out and telecoms are down) and the less coverage they receive.
Dec 20, 2022 • 4 tweets • 3 min read
To @JFrancisClimate's point, there has been some interesting recent work suggesting that amplified Arctic warming may be causing the *stratospheric* polar vortex to become disrupted more often in winter. But this is still the topic of very active research. science.org/doi/10.1126/sc… And there's further evidence that Arctic warming may be associated w/jet stream patterns favorable for warm season weather extremes. So my view is that there is something going on! It just doesn't appear to be manifesting as colder winter extremes. science.org/doi/10.1126/sc…