New insights into the Ridiculously Resilient Ridge & North American Winter Dipole

Filed in Uncategorized by on December 4, 2017 2,732 Comments

A timely example: Persistent Western ridge, Eastern trough next 2+ weeks

A pronounced example of the “Warm West/Cool East” temperature dipole pattern will develop over North America in the coming days. (NCEP via tropicaltidbits.com)

In the coming days, a remarkably persistent weather pattern will begin to develop across North America and adjacent ocean regions. Characterized by strong high pressure near the West Coast and low pressure over the Eastern Seaboard, this “quasi-stationary,” high-amplitude atmospheric wave pattern will essentially become locked in place for at least the next 2 weeks. Patterns like this have a tendency to become self-reinforcing, lasting for much longer than more typical transient weather patterns and leading to prolonged stretches of unusual weather. This particular event will be no exception: California (and much of the West Coast) will almost certainly experience an extended, multi-week warm and dry spell, while much of the East Coast shivers through repeated blasts of cold, Arctic air.

As it turns out, these upcoming anomalous conditions provide a timely example of several atmospheric phenomena my colleagues and I have been studying over the past few years. In this post, I’ll explore the broader climate context of recent North American weather extremes, with a focus on insights gleaned from two recent scientific papers published by my colleagues and me.

A remarkably persistent, quasi-stationary atmospheric wave pattern will develop across much of the Northern Hemisphere, persisting for multiple weeks. (NCEP via tropicaltidbits.com)

 

Recap: Origins of the “Triple R” and California’s severe drought

In 2013, a curious feature began to emerge on the weather maps: a region of unusually high atmospheric pressure (known as a “ridge” in meteorological circles) was consistently pushing the Pacific jet stream to the north of California, resulting in very dry conditions. At the time, I (somewhat jokingly) termed this anomalous high pressure zone the “Ridiculously Resilient Ridge” due to its implausible longevity, assuming that it would most likely recede by the subsequent blog post. Instead, the “Triple R” held strong straight through the entire winter—and then recurred, in slightly modified form, throughout the winters of 2014-2015 and 2015-2016.

Average position of the “Ridiculously Resilient Ridge” over the course of the 2012-2015 portion of the California drought. (Adapted from Swain 2015)

The multi-year persistence of this anomalous atmospheric ridge was nothing short of extraordinary. The co-occurrence of record low precipitation and record high temperatures associated with the Triple R ultimately yielded California’s most severe multi-year drought on record. I previously discussed the rise of the Ridiculously Resilient Ridge—and associated drought impacts—in an earlier post, which summarized findings from our initial scientific investigations (#1 and #2). Two key points arose from these early papers:

 

1) Atmospheric pressure patterns similar to the Triple R are now occurring more frequently than they did in previous decades.

2) The unprecedented magnitude and persistence of recent West Coast ridging can be traced (at least in part) to regionally-accentuated warming of the lower atmosphere.

As is often the case in scientific endeavors, these early findings raised more questions than answers. These lingering questions motivated us to continue our analyses, which resulted in the two new scientific papers discussed below. (And additional work remains in progress.)

 

A “standing wave” in the atmosphere: Warm in the west, cool in the east

Composite middle atmospheric pressure anomaly map corresponding to extreme North American temperature dipole days (compare to current forecast map above!). (Adapted from Singh et al. 2016)

Global wind and pressure patterns are not uniformly distributed across the Earth’s surface. Even at a given latitude, prevailing climate conditions can vary greatly from place to place (compare, for example, the winter climates of mild San Francisco and often snowy Washington, D.C., which are both located near coastlines around 38°N). These spatial variations in climate are a direct consequence of the physical geography of our planet: the exact position of our continents, ocean basins, and major mountain ranges dictate prevailing atmospheric conditions on a global scale.

In North America, these underlying geographical constraints yield a semi-permanent wintertime “wave” pattern in atmospheric pressure (in a two-dimensional map sense), which is characterized by generally higher pressure in the west and lower pressure in the east. This pre-existing wave pattern is not always easy to discern on surface weather maps, but becomes more apparent when considering pressure patterns at higher altitudes (often quantified as “geopotential height” (GPH)). This typical “western ridge/eastern trough” set-up predisposes the eastern U.S. to experience far colder winter temperatures than the West, as relatively mild southwest winds (originating over the Pacific Ocean) blow across the West Coast but harsher northwest winds (originating over the cold Canadian interior) blow across the East—producing a longitudinal temperature dipole. This “standing” (i.e. stationary) wave pattern is also the reason why California can be highly susceptible to long dry spells, even during the winter rainy season. More often than not, rain-bearing storms tend to veer northward just before reaching the West Coast due to the angled southwest-to-northeast trajectory of the jet stream as it approaches the west side of the semi-permanent Western ridge.

 

“Warm West/Cool East” extremes have become more common in recent years

Quite a few recent winters have featured not only extremely dry (and warm) conditions across much of California, but also numerous outbreaks of very cold, Arctic air across the eastern U.S. The Eastern Seaboard, in particular, has suffered through a number of regionally-crippling (and superlatively-named) “Snowmadeggon” and “Snowpocalypse” snowstorms. In most cases, these opposing extremes have occurred simultaneously due to an extreme amplification of this pre-existing “western ridge, eastern trough” configuration. Altogether, this recent flurry of wintertime extremes across North America raises the question: has there really been a sustained trend toward an increasingly pronounced winter temperature dipole?

 

Observed trends in the frequency of occurrence of extreme North American temperature dipole days (different colors represent different definitions of what constitutes a dipole). (Adapted from Singh et al. 2016)

Our recent work (led by Deepti Singh) answers this question affirmatively: there has indeed been an increase in the number of days each winter characterized by simultaneously very warm temperatures across the American West and very cold temperatures across the East. We found that there has been a substantial increase in the propensity for extreme ridge/trough sequences to produce especially severe temperature contrasts across the U.S., and (to a lesser extent) an increase in the frequency of the relevant atmospheric “western ridge/eastern trough” pressure patterns themselves. Using climate model simulations, we further found that an increase in extreme temperature dipole days like those we’ve observed in recent years is considerably more likely in a climate with rising greenhouse gas concentrations than in a hypothetical climate without human influence.

Intriguingly, this increase in contrasting dipole extremes appears to be caused primarily by the increased rate of warming in the western U.S. relative to the eastern U.S. While the eastern U.S. has indeed experienced a recent string of remarkable Arctic outbreaks, there hasn’t been a sustained trend toward cooler temperatures. In fact, when we estimated future changes using climate model simulations assuming continued growth in atmospheric greenhouse gas concentrations, we found that the occurrence of these extreme temperature dipole days will soon start to decrease as winter warming accelerates across the entire United States—making it more difficult to achieve extreme thermal contrasts between the East and West.

One question we weren’t able to assess in this study was how the atmospheric pressure patterns conducive to extreme dipole events might themselves change in the future. But in a separate paper, we have now taken a closer look at the “Western Ridge” half of the equation—and I’ll discuss those results below.

 

Oceanic links to North Pacific winter ridging

Statistical relationships between ocean temperatures in different regions (black boxes) and middle atmospheric pressure patterns (i.e. GPH anomalies), plus long-term trends in ocean temperatures (right). (Adapted from Swain et al. 2017)

There has been a tremendous amount of interest—not just within the scientific community, but more broadly among weather-watchers and other drought-weary Californians—in understanding the causes and longevity of the Ridiculously Resilient Ridge. And that turns out to be a genuinely challenging question to answer, despite several years of formal study by quite a few scientists. To date, the strongest evidence appears to implicate unusually warm ocean waters in the tropical western Pacific, which can trigger a hemisphere-scale wave pattern favoring an enhanced subtropical ridge near California. Other work has suggested that unusually warm ocean conditions in the “extratropical” Pacific (i.e. the so-called “Warm Blob” in the Gulf of Alaska) may also be linked to the persistent ridge—though there’s considerable evidence that the atmospheric Triple R caused the oceanic Blob, rather than the reverse. Still others have wondered whether the striking loss of Arctic sea ice in recent years may have played a role, though the evidence supporting this connection remains sparse. Finally, it has also been shown that random variations in the atmosphere can occasionally produce an extremely persistent North Pacific ridge. In other words: the Triple R may be at least partially attributable to “bad luck.”

In our latest paper, we set out to explore all of these hypotheses using a unified framework. Using a combination of real-world assimilated observations climate model simulations, we asked the following overarching question: are there traceable linkages between tropical/extratropical ocean temperatures, Arctic sea ice, and the occurrence of seasonally-persistent ridging along the West Coast?

 

Tropical Pacific may offer early warning of “Triple R”-like patterns

Observed middle atmospheric pressure pattern anomalies during the 2012-2016 (left) vs. predicted pressure pattern anomalies using the methods in our study (right). (Adapted from Swain et al. 2017)

Ultimately, we found that there do indeed appear to be strong relationships between Pacific Ocean temperatures and persistent West Coast ridges conducive to dry conditions in California. Especially prominent are the links to western tropical Pacific Ocean warmth. These connections appear several months in advance, which not only suggests a causal linkage but also hints that it may be possible to predict the occurrence of “Triple R”-like ridges several months in advance. This result agrees with previous work by other scientists suggesting that displaced tropical precipitation associated with West Pacific warming can generate a trans-Pacific atmospheric “wave train,” favoring an enhanced subtropical ridge near California. We also reproduced the already well-known connection between cool “La Niña” conditions in the eastern tropical Pacific and broader high pressure in the Gulf of Alaska, which can also lead to dry conditions in California.

Importantly, the West Pacific relationship exists independently of the El Niño/La Niña (ENSO) cycle: that is, warm conditions in the western tropics can be sufficient to cause a California ridge entirely on their own. Of even greater interest: recent warming of this particular portion of the Pacific Ocean has coincided with a considerable uptick in the frequency of persistent winter ridging near California. This latter point offers further circumstantial evidence that at least some portion of the recent California drought may have origins in the warming tropics.

What about “The Blob?” Well, we did find a strong statistical linkage between warm ocean conditions in the North Pacific and West Coast ridging—similar to that which occurred during the recent drought. In this case, though, the “chicken or egg” issue rears its head once again: while a time-lagged relationship between autumn ocean temperature and winter ridging did exist in observations, only an contemporaneous relationship existed in climate model simulations. We posed two possible reasons for this divergence: either the persistent ridging itself caused the subsequent ocean warmth (rather than the reverse), or climate models may be underestimating the role that warm North Pacific SSTs can play in ridge-building. Additionally, it’s still plausible that warm ocean temperatures in this region, once in place, can enhance the persistence of ridging via self-reinforcement (i.e. high pressure causes the warm ocean in the first place, which then favors more high pressure, thus causing an even warmer ocean).

Observational analysis suggests a possible link between sea ice loss and West Coast ridging (here, blue represents ridging when sea ice decreases). Climate model simulations, however, do not support this relationship. (Adapted from Swain et al. 2017)

And how about the sea ice hypothesis? Well, the link between Arctic sea ice anomalies and West Coast ridging remains…unclear. Our observational analysis hinted at a possible relationship, but climate model simulations disagreed. As my co-authors and I have previously emphasized, however, a scientific “absence of evidence” is not necessarily equivalent to an “evidence of absence.” That is to say: just because we didn’t find strong evidence of a connection doesn’t mean one doesn’t exist in the real world. The Arctic is now warming more than twice as fast as the rest of the world, and sea ice has been disappearing at a greater rate than had projected by climate models—a rapid rate of change that has complicated scientific investigations into high-latitude linkages. Indeed, the relationship between “Arctic amplification”/sea ice loss and mid-latitude climate remains the subject of a vigorous and ongoing debate in atmospheric and polar science circles. While it’s increasingly clear that these profound shifts in the Arctic have the potential to alter mid-latitude weather, it still is not clear precisely where, when, and to what degree. Thus, while our work does not obviously implicate sea ice loss in recent California extremes, it’s still plausible that stronger evidence could emerge using more sophisticated modeling tools or new observational approaches in the future.

 

Some conclusions, and thoughts about the present winter

Ocean temperatures have been cool in the eastern tropical Pacific and warm in the western tropical Pacific since early autumn. (NOAA via tropicaltidbits.com)

Ultimately, we confirm that unusual ocean temperatures are linked to seasonally-persistent West Coast winter ridging similar to the Triple R. Tropical warmth (in the West Pacific) and coolness (in the East Pacific) are both linked to different patterns of North Pacific winter ridging, and may offer an early warning of seasons with an elevated risk of dry conditions in California. Interestingly, tropical Pacific Ocean temperatures during autumn 2017 were warm in the west and cool in the east amidst a modest (and ongoing) La Niña event—a combination that suggests a substantially elevated likelihood of West Coast ridging this winter. To date, Southern California has experienced one of its driest starts to the Water Year on record, and strikingly persistent West Coast ridging is now expected to last at least two weeks. It will certainly be interesting to see how this winter plays out in the context of these new research findings.

 

This blog post focuses on peer-reviewed research from two separate papers published in scientific journals (Singh et al. 2016 and Swain et al. 2017). While most Weather West articles are primarily based upon my own informal thoughts and analysis, this piece is directly informed by formal investigations by a team of scientists. I would like to thank my collaborators in this work—Deepti Singh, Daniel Horton, Justin Mankin, Tristan Ballard, Leif Thomas, Bala Rajaratnam, and Noah Diffenbaugh—for their invaluable support and ongoing insights.

I am happy to provide a personal copy of any paper mentioned above (on which I am an author) upon email request.

Want to learn more? Follow climate scientists on Twitter!
Daniel Swain, Deepti Singh, Daniel Horton, Justin Mankin

 

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  • molbiol

    All the disclaimers apply here and this is just for fun mainly. Taking a look at 1000-850mb thickness values on the 12Z GFS (attached image), it looks like those values will be around 1310M over the LA Basin down into San Diego. Immediately inland, values approach 1290M and even lower across the high deserts. In this pattern, snow down to sea level is not likely unless strong convection or very heavy precip rates occur. This is due to higher thickness values over the ocean and moderation due to warmer ocean temps. However, inland areas would stand a better chance with snow levels. Across the PacNW, similar thickness values would put the snow level at 500ft during the day and 0-200 ft during the night or if heavy showers occur.

    https://uploads.disquscdn.com/images/8525b539a7eaefc3b7cc53d7a34faaf5a5c0f7d35a592f10e46f8126237c8e73.png

    • weathergeek100

      Regardless, it is going to get downright chilly. This will be a shock for LA and SD that have been seeing endless 80s for the past several weeks.

      • RunningSprings6250

        You mean months lol

        • weathergeek100

          Seriously, right???

    • SoCalWXwatcher

      Based on past experience, under that scenario with 540dm making it down to San Diego it would mean snow levels near 3,000ft in the San Gabriels & San Bernardino Mts, & lower than that if there are lingering showers in the post-frontal cold air. That would be very welcome indeed!

      • SoCal Al (El Monte-SGV)

        From fire to snow……..if this happens, what in gods almighty earth is next?

        • SoCalWXwatcher

          Well, we’ve got the San Andreas Fault on standby.

        • thlnk3r

          Unprecedented RECORD shattering snow may fall on the Inland Empire. MULTI extreme weather! Sell your couch and TV…MOVE TO A BUNKER.

        • Taz & Storm Master

          EF 5 tornados hiting LA CA roads under water in new york and big super storms that would drop the air teamps down too -150 that would be next

  • ThomTissy

    It has consistently been 28-30 degrees at 7am in the Santa Cruz Mountains and heats up very quickly thereafter.

    • janky

      Where do you live in the Santa Cruz Mountains? I live off Skyline in Los Gatos (2750′) and it was 62 degrees at 7am. I drove down to Highway 17 and it was 36 degrees. Insane.

  • Bob G (Gustine)
  • 82/83 El Nino baby (San Jose)

    Jim Cantore would go nuts for this given his excitement level for thunder snow: https://twitter.com/mikeseidel/status/940607662877761537

    • I saw several smaller snownados than that one at heavenly, 2016? Maybe a third the size? Snow conditions have to be just right, if there is light powder dust it’s easier

  • Apollo

    Here in Santa Paula we have a very strong static charge with the winds and single digits humidity and I’m getting sapped on everything. The static can also be a traject accident waiting to happen when people are filling up there cars with gas and not thinking about the spark that can be produced and ignite the fumes coming from nozzle. I hope there thinking about it.

    • RunningSprings6250

      It’s been extremely ‘staticky’ here and the winds just ramped up again after being calm yesterday…..

    • happ [Los Angeles]

      I can’t even touch my pets without giving the critters a shock

  • MakeSoCalWetAgain (SMX)

    Reached a low of 33 at SMX this morning. Didn’t expect it to be this cold.

  • CHeden

    BTW, logged 22 Geminids and 8 sporadics last night between 9-11p.m. including 3 fireballs and 8 earthgrazers that each lasted 1-2 seconds. A great start…and tonight and tomorrow should be even better (skies permitting).

    • Thor

      “Geminids and 8 sporadics” – How can you tell the difference?

      • matthew

        Point of origin.

        • CHeden

          Correct. If you trace an imaginary line parallel to the tracks of the meteors, they all converge at a single point. Those meteors that follow a different path are either part of another shower going on at the same time, or are “random” meteors which we call sporadics.

          • Thor

            Thanks!

          • CHeden

            If u can, check them out tonight and let me know how you did? Look mostly ENE about 45 degrees above the horizon.
            The Geminids are often quite bright, so you should see at least a few even in moderate light pollution.

          • Dan the Weatherman

            I live in Orange County where light pollution is high, but I am more toward the eastern edge of the populated areas where it is a little darker than most areas and I have seen Geminids in past years.

    • Dan the Weatherman

      I almost forgot about the Geminids. Thanks for reminding me as I didn’t even go out to look last night! I will certainly look tonight, as it should be clear enough. I have been seeing a few of these in recent years ever since I have become aware of this shower.

  • Fairweathercactus
    • SoCalWXwatcher

      Where?

    • AlTahoe

      1962 and 1974 keep popping on the Analog list. I think your area did well in 1974 correct?

      • Fairweathercactus

        74-75 was right at average. A lot of old timers will say Whittier got a trace of snow around that time.

      • Hardcort

        74-75, the Sierra got crumbs all the way through mid-jam and then it snowed through April with no long breaks in between storms

  • Here’s January 1962 snowstorm in San Jose NH setup and TT NH for around Christmas. Similar in some ways. We’ll see.
    https://uploads.disquscdn.com/images/712605edc35521f9504eb30cf7385c4979f5f2071912f0cdefc61c81921d7e6b.jpg

  • Fairweathercactus

    I asked some people on facebook part of the Whittier group. People are saying they remember sometime in the late 70s a very light dusting of snow early in the morning for the Whittier area but it melted shortly after the sun rose. Trying to get more information.

    People also remember a more accumulating snow in 1969.

    • SoCal Al (El Monte-SGV)

      I was told by an elderly neighbor that he recalls a dusting of snow atop Rose Hills in the late-60’s and snow over the local foothill locations around the SGV.

    • SoCalWXwatcher

      That may have been December ’76.

      • Fairweathercactus

        I think it was December of 76

        • SoCalWXwatcher

          I recorded a low of 27°F in Downey at dawn on December 17 1976, if memory serves. (I was 11 years old, some of this stuff is a blur now) I recall the Eastern US got brutalized with cold & snow during the remainder of the season, while we continued our 3rd year of drought, which would get busted by an epic rainy season in 77/78.

          I was 11 years old, so I took the garden hose and wet down the driveway & sidewalk just to watch it freeze.

          Edit: That 27° low temp stood as the record low in my area until 2007.

    • BP (Ventura)

      My dad told me it snowed on the beach here in Ventura in Jan or Feb of 1969. Not sure which month. Wasn’t born until summer of 70′ so no personal knowledge of this one…

      • Dan the Weatherman

        I wasn’t born yet, either, so I don’t know if the Orange area got any snow in 1969 or not. I know there was some flooding in parts of Orange County in the winter of 1969 and there was a road in Orange that went across Santiago Creek that washed out that year and that particular part of the road was never rebuilt.

  • Rainmaker (San Jose)

    weather depression should be an illness. A chronic illness for us in California!

    • happ [Los Angeles]

      It is and it is called seasonal affective disorder (SAD). Many think only places like Seattle w/ endless clouds/ rain suffer from weather-related depression. I can assure you many in SoCal suffer from endless sun/ no rain a.k.a. S.A.D.

      • Nathan

        I don’t think that’s necessarily what he means.

  • fr94114
    • Dan the Weatherman

      It also snowed in Orange in January 1949. I have seen a picture of what was the front of Orange High School at the time, now Chapman University, in which there was snow on the lawn and the students were playing in the snow.

      I have lived in the Orange area my entire life and I have not ever seen it snow in my neighborhood.

    • AlTahoe

      That’s so cool!

      My grandparent’s have a picture from the mid to late 50’s in Madera California and there was 5- 7″ of snow on the ground. They built a 5′ tall snow man and apparently the snow stayed on the ground for about a week at their farm.

    • fr94114

      Nearly 70 years later both trees are still alive and kicking – taller of course. My grandfather planted them himself.

  • http://wx.graphics/models/ecmwf/2017121212/southerncalifornia/ecmwf_t_precip_southerncalifornia_240.png
    Final Frames of Euro picking up on SoCal magic, more details in a moment.

  • So, here’s the deal. Euro needs another run. HOWEVER. Preliminary fun for this bun:

    //s.imgur.com/min/embed.js

  • Fixed – Euro needs another run to get the rest of the Magic under its Johnson.
    https://uploads.disquscdn.com/images/7b8174164f8e26eb347c05b75b628591582f76193c2a9c7abb822eb583fb79fe.gif

  • MakeSoCalWetAgain (SMX)

    Next person who says models for drier weather from December 20-31st gets thrown into the Thomas Fire.

  • Bob G (Gustine)
    • Nope, Win7 Chrome or Android 5.1.1 Chrome working fine. I made a embed that broke but that was only 1 comment, refresh?

      • Thanks that restored all of you.
        I needed to adjust my filters then after I refreshed I decided to revert.

      • Taz & Storm Master

        if you are runing android 5.1.1 i say get a new phone with at lest android 7.0 on it

        • You will never pry my Galaxy Alpha Exynos with my own homebaked debloated rom and 14 removable batteries from my cold dead hands.

    • Bob G (Gustine)

      Yes, what did you do? 🙂

    • SoCalWXwatcher

      CrashingOut is a problem? 😉

  • Speaking of fires – Skirball has a cause now. Homeless encampment fire:
    http://beta.latimes.com/local/lanow/la-me-skirball-fire-cause-20171212-story.html

  • Bob G (Gustine)
  • Well, those sure are some interesting model solutions coming out in the very long range at the moment. Upcoming pattern does appear to be conducive to a major West Coast cold outbreak, but exact trajectory will dictate its extremity. Simulated sea level snow on day 14 (yes, that 12z run did show that) is quite unlikely. But this should be a very interesting pattern to watch evolve in the coming days.

    • SoCalWXwatcher

      The cold will be a refreshing break from the warm weather but It will be worry time for citrus growers.

      • Bob G (Gustine)

        Gotta break the fans out and get the irrigation systems running

        • Thunderstorm

          Next record to fall this year will be record cold, possibly all time record cold. Have had 5 all time records this year where I live, SF bay area by Fremont. 21F is the coldest all time here close to the bay where i live.

          • Bob G (Gustine)

            Yikes. We were at 29 degrees this morning at 7:30AM. I remember in the late 90s at a friend’s ranch in the foothills west of Patterson the temp was 16 degrees at daybreak

    • Taz & Storm Master

      YAY for the West Coast

      heh heh heh for the E coast the E coast is on my Naughty list for taking are fun away

  • Taz & Storm Master

    seems like the Canadian
    model is a out liner right now

  • Taz & Storm Master

    whats see what the 18z brings

    • RunningSprings6250

      Yes whats. Can’t wait.

    • edge of seat time, it’s at 180 hours rendered and the action is not long after that, 30 mins?

  • Matthew Nelson

    In the spirit of one-upsman-ship here is my place (4 miles West of Temecula) on the last day of 2014. Right about 7 inches of snow. Absolutely demolished my farm, have never recovered. So I hope this does not happen again.

    https://uploads.disquscdn.com/images/d677c2eebf27283275cba661a5600a2382e2b18e89c5745a194df50d267c6356.jpg

    • The architecture on the building upper right corner is hilariously out of place. Like seeing an igloo on fire or something.

      • Nathan

        If palm trees could talk:

        “FML.”

  • Jon Bartel

    I hope it snows below sea level.

    • SoCalWXwatcher

      Snow on top of the salt flats in Death Valley?

      • Well yeah! When it does melt it makes an extremely rare and expensive brine for pickling all types of edible cacti. This is the “Beluga of Brine”.
        Speaking of rare snow events: In Monterrey, melted snow is transported to Jalisco to water blue agave. The rarest of the rare are exclusively watered only with melted snow from Monterrey in small plots that contain the richest volcanic soil.

        • SoCalWXwatcher

          That’s got to be very rare indeed. They most certainly wouldn’t be able to make a batch every Winter.

  • honzik

    I remember growing up in San Jose when the rain turned into snow around 7 in the morning while I was delivering newspapers on my bike. I also remember how surprised I was, because a few days before – on the Winter Solstice if I’m correct – the high on that hazy day was 73 degrees. I’m thinking is was either 1975 or 1976. Can anyone back me up on that?

    • February 1976 and January 1962 are only times I’ve seen snow stick and accumulate San Jose.

      • honzik

        I think the snow didn’t stick for very long – on the orders of hours – but it was an unmistakable experience to watch the rain turn into snow.

    • Bob G (Gustine)

      I wasn’t in San Jose but just north of there and yes it stuck. I remember the playing in the street and having snowfights at school. The school ballpark was covered in snow and it stuck all day. We went home and our street was covered in snow

  • Taz & Storm Master

    the 18z has a cold snap then a nic storm too follow for all of CA but will need too watch the timeing on that storm if there any cold air trap we could be looking at vary low snow levels at the start of the storm

  • Taz & Storm Master

    18z was fun

    • ThomTissy

      Yeah, some would even say sexual (not me of course), but some.

  • Sumster
  • AlTahoe

    Newest GFS shows the first storm for next week holding together better than previous runs with cold air. Then the storm after takes the path that last winters storms did, where moisture undercuts the block with a rainier and warmer pattern. It’s going to be a fun battle on future runs to see if undercutting can take place or not.

  • Great Winter of 2017 (SMC)

    18z is fantastic

  • Fairweathercactus

    All aboard the hype train. The doors will be left often for the first bad model run. https://uploads.disquscdn.com/images/164671688dc5850bb04e14c2cbbac1d96789fa0655ddd5d1ab1986f1694924bb.png

  • For those in the wondering what the smoke is doing today, I was in Concord working this morning with lots of haze and likely smoke low to the ground however now, well, picture is an interesting one:
    https://uploads.disquscdn.com/images/c9ea02743850fa0dce2acb84684349086208c8cd9e9d9f9218371756bb108327.jpg https://uploads.disquscdn.com/images/d3609f1fd2d77c82b0c004ec722f91cec36ce4097a7e0cb137a6ac14dcecbaec.jpg

  • Great Winter of 2017 (SMC)

    12z GEFS mean snowfall to 384 hours has snow in coastal SoCal and Central Valley. GFS ain’t the only one.http://climate.cod.edu/data/forecast/GEFS/2017121212/US/GEFSUS_prec_meansnacc_384.png

    • Great Winter of 2017 (SMC)

      And 18z within 252 hours.

  • Sumster

    Maybe a silly question…..bit I will throw it out anyway. Is it possible that the smoke from the recent fires has produced enough volume to reflect enough sunlight/heat
    to have an affect on coastal SST’s, wind patterns and ultimately 500MB contours? At least in the short to mid-term time frame.

    • Bob G (Gustine)

      I am going to take a guess here and say no.

  • MakeSoCalWetAgain (SMX)

    December 21st looks like the next storm day, according to WU. We’re overdue for one. Fingers crossed, toes crossed, arms and legs crossed.

  • Darin

    NPR article about arctic melt and long term effects. Deep links provide some finer details
    https://www.npr.org/sections/thetwo-way/2017/12/12/570119468/arctics-temperature-continues-to-run-hot-latest-report-card-shows