El Niño remains among strongest ever recorded, but California impacts (so far) a bit different than anticipated

Filed in Uncategorized by on February 1, 2016 4,809 Comments

Reminder: when it comes to El Niño, strength matters.

The prospect of an El Niño event in the Pacific Ocean always generates quite a bit of interest in California. This attention largely stems from the fact that two of California’s wettest years on record—1982-1983 and 1997-1998—occurred during the strongest El Niño years in living memory. The popular perception that El Niño always brings a lot of water to the Golden State, though, is not particularly accurate.  The reality is a bit more nuanced: particularly strong El Niño events exert a powerful influence upon the atmosphere over the northeastern Pacific Ocean, and really do have a tendency to enhance the storm track in a way that favors greatly enhanced precipitation across the entire state of California. But more middling weak to moderate events don’t have nearly as pronounced an effect, and in many cases don’t meaningfully affect the odds of seeing wetter or drier than average conditions in California. The main reason for this nonlinear effect is that other periodic oceanic and atmosphere oscillations (other than El Niño) still play a major role in California’s winter weather, and unless El Niño is powerful enough to consistently outweigh all of them, the net effect can swing either way. The key message here: strong El Niño events are the ones to watch out for from a California weather perspective, and it’s reasonable to expect that such events greatly increase the odds of wet conditions throughout the state.

1.Subtropical ridging between Hawaii and California has been more prominent so far during 2015-2016 than during the 82/83 or 97/98 events. (NCEP via ESRL)

Subtropical ridging between Hawaii and California has been more prominent so far during 2015-2016 than during the 82/83 or 97/98 events. (NCEP via ESRL)

 

How is the present El Niño different from other big ones in the past 40 years?

Given that climatologists and meteorologists know to look out for strong El Niño events as uniquely strong predictors of California seasonal precipitation, how does the present event compare to other major historical events? Well, depending on the exact metric, the present El Niño is either the strongest or among the strongest events in the observed record going back to at least 1950. Ocean temperatures in the eastern equatorial Pacific Ocean—the most traditional measure of El Niño’s amplitude—have been at or above their record highest values for at least several months now. So despite assertions to the contrary, the 2015-2016 El Niño is not “a bust” by any means.

But absolute sea surface temperatures don’t always tell the whole story. While the present El Niño is indeed among the strongest ever recorded, the atmospheric response to the warm ocean temperatures this year has been a bit different than we have observed during other big historical events. Over the northeastern Pacific, El Niño acts to deepen the semi-permanent Gulf of Alaska low while simultaneously strengthening (and, literally, straightening) the jet stream over the eastern Pacific Ocean. This enhanced and “more zonal” (i.e. more west-to-east) jet stream is what tends to bring increased winter precipitation to California (and, sometimes, even the Pacific Northwest) during strong El Niño years.

These atmospheric effects occur due to a fairly complex chain of events that link the tropics to the mid-latitude atmosphere. Warmer than usual ocean temperatures in the eastern tropical Pacific increase thunderstorm activity there, which pumps vast quantities of heat into the upper atmosphere. This tropically warm air at upper levels eventually flows northward and descends back toward the surface of the Earth in the subtropics (at a latitude roughly equivalent to that of Hawaii). This enhanced “Hadley circulation” during El Niño years increases the temperature differential between the warm tropics and cool Gulf of Alaska, which is what causes the jet stream to strengthen over the East Pacific.

2.Tropical convection associated with the 2015-2016 El Niño has been centered further north than in previous big events, with subsidence (downward motion) occurring closer to California on its northern flank. (NCEP via ESRL)

Tropical convection associated with the 2015-2016 El Niño has been centered further north than in previous big events, with subsidence (downward motion; yellow/red colors) occurring closer to California on its northern flank. (NCEP via ESRL)

In late 2015 and early 2016, the atmosphere has indeed responded to the ongoing powerful El Niño much in the way that meteorologists have come to expect. The Pacific warmed; tropical thunderstorms increased; the Hadley cell strengthened; the Pacific jet began to roar. But this year, the Hadley cell has actually strengthened a bit more than expected. The descending air on its northern side has occurred closer to California, which means that the enhanced temperature differential is occurring farther to the north than during previous big El Niño events. Subtropical ridging between Hawaii and California has been more pronounced, and the El Niño-strengthened jet stream has set up shop primarily across Northern California and even the Pacific Northwest, rather than Southern California. From a global climate perspective, this is a relatively minor detail; if you happen to live in Los Angeles, though, it makes all the difference in the world.

3.While nearly all of California is expected to be above average in terms of season-to-date precipitation after this weekend’s Southern California storm, only the northern 2/3 of the state is above average for the full season to date. (NOAA via WRCC)

While nearly all of California is expected to be above average in terms of season-to-date precipitation after this weekend’s Southern California storm, only the northern 2/3 of the state is above average for the full season to date. (NOAA via WRCC)

The net effect so far in 2015-2016: Northern California and the Pacific Northwest have gotten soaked, while Southern California has been left pretty dry (with a few notable exceptions). While a veritable “parade of storms” has indeed inundated the northern reaches of the state with very heavy precipitation, bringing the best Sierra Nevada snowpack in years, leading to huge inflows to large reservoirs in critical watersheds, and even causing some minor flooding at times, many of California’s most populous cities haven’t witnessed an especially remarkable winter to date. The San Francisco Bay Area and Sacramento region have seen “Water Year” precipitation to date that is pretty close to the long-term average (which, decidedly, seems like a lot relative to the extremely dry years witnessed as of late). The densely populated greater Los Angeles region, on the other hand, is well below average for the season to date (though with significant precipitation this past weekend, its January total may well end up near or above average). From a long-term drought relief perspective, the season to date looks pretty good—precipitation is near or above average in most of California’s largest watersheds, and the water stored in the critical Sierra Nevada snowpack is uniformly above average. So far, though, this isn’t quite the blockbuster year that many had hoped for (especially in the south).

 

What does the near-term future hold?

So what are our prospects for the rest of the season? Well, El Niño is certainly still with us, and it’s still a top-tier event. For that reason, the good money’s still on a wetter than average season for California (yes, even now). This is especially true since the precipitation during strong El Niño years is often heavily “back weighted,” with an unusually large fraction of seasonal totals occurring during the second half of the rainy season from February-April. What is less clear, at this point, is whether the northerly-shifted atmospheric response to this El Niño will persist—and whether Southern California will start to make up for lost time. It’s certainly possible that a sudden transition to a much wetter pattern will occur, and it’s easy to forget that a surprisingly large fraction of precipitation in the Southland occurs during a handful of intense storms each year (even in strong El Niño years). From a statewide perspective, some substantial drought relief has already occurred this year, but there remain large regions in the southern part of the state that are still extremely dry. The refrain from earlier in the autumn is now more relevant than ever: while El Niño is likely to bring some degree of drought relief, California will likely still be facing long-term drought conditions by the coming summer.

 

Some thoughts regarding the bigger picture

Finally, there has been considerable discussion lately regarding why the atmospheric response to El Niño this year has been different than historically observed (and also than foreseen by some of the flagship seasonal forecast models). It’s impossible to ignore the fact that global temperatures in late 2015 and early 2016 have reached their highest levels in recorded human history. Part of this very recent warming is likely due to our record El Niño event, but the rest is pretty clearly attributable to the long-term warming trend associated the with human emission of greenhouse gases. While global mean temperature doesn’t directly affect El Niño teleconnections, per se, the Earth hasn’t been warming in a spatially uniform way. This year in particular, the subtropics and the polar regions have been especially warm relative to other parts of the world. It is possible that this spatial pattern of warming may be playing a role in the particular atmospheric configuration that has resulted from the 2015-2016 El Niño event.

2015 was the warmest year on record globally, but warmth has not been evenly distributed throughout the Northern Hemisphere. (NASA Scientific Visualization Studio)

Unfortunately, it is virtually impossible to say more than that in the present blog post. The pace of climate change attribution science is much slower than that of the atmosphere itself, and it’s hard to make causal inferences from observations alone. Climate models are often the best tool available for climate scientists to test the counterfactual reality: what would this year have looked like without global warming? But such experiments take a considerable amount of time to do the right way, so we’ll probably have to wait a while to find out more. I’m planning to write a series of posts on Weather West (beginning this coming summer) discussing the latest scientific evidence regarding how California’s climate will change in the future. Until then, though, hopefully El Niño will bring more uniformly distributed California drought relief in the coming months. Stay tuned.

 

© 2016 WEATHER WEST

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  • PrimeMover

    4.8 quake in Bishop 20 min. ago.

    72 and sunny also

  • Thunderstorm

    Barometer has been falling all day. Winds are coming. Now for those of you that remember Harry Geise from the 1970’s, he said that there is a major weather change every 72 days. Last one was December 19th and we indeed had good rains for 6 days. So February 29 the RAINS RETURN, hopefully for the entire month of March. Don’t believe it, you will come March.

    • Charlie B

      Harry was a fixture on my living room TV when I was a kid. Almost to the point of being a family member. “Harry has gained a few pounds” my Mon would comment when his suits got a little tight. He fed my early interest in the weather, and I am sure I am not alone. I have to wonder what he would be thinking about now….

    • jstrahl

      My barometer is down to 29.91 at 4:25PM, lowest it’s been in a LONG while. (central Berkeley).

  • PrimeMover

    An aftershock right now 2.8

  • low snow levels

    dont even look at the 18z GFS turst me you wont be happy with it if you looked

    • Tyler Price (Van Nuys)

      I think it looks good.. Still showing a definite pattern change in the LR, pinning down the exact date is one thing, but the screaming message is that there is most likely a significant pattern change coming..

      • weatherwhisperer

        doubt it. seriously doubt this

        • jstrahl

          bigB makes a good case, right above.

    • xeren

      looks good to me, not much different in the 10 day from 12z or 6z

    • Wyomg

      i know you said don’t, but what website could we find these “runs” everyone keeps checking and analyzing… thanks.

      • jstrahl

        See here, for instance, look at first line of first table, under different runs ( arranged per global time)/ He’s wrong, look right above at the post by “bigB.”

    • mosedart (SF)

      You put way too much stock in fantasyland. Anything beyond 8-10 days is literally a fantasy. They should put a warning on the GFS models that “anything beyond 240 hours is for research and entertainment purposes only”.

      • Bandini

        Without those GFS runs this comnent section would lose 50% of it’s traffic. The good news is that if you attach the caveat that “this is fantasy land” along with the pretty colors on your model run it makes everything OK.

  • bigB

    The GFS 18z run also suggests a favorable precip pattern for CA by late Feb/early March. Note the low pressure systems (blue colors) moving under high pressure (red colors) displaced over Northwestern US/Canada. That’s consistent with a +PNA and +ENSO set-up. If the MJO propagates through phases 7-8, it will only reinforce this pattern.

    NOTE: Try not to focus on specific details this far out, just note the overall pattern being suggested. Again, if the PNA and MJO develop as advertised, one
    can bet that this is what the pattern will look like.

    As for the upcoming storm, can’t wait. Need the rain and a break from the heat. It’s also generating a nice little short period WNW swell. An added bonus for those of us that surf.

    • jstrahl

      Thanks, highly appreciate this thoughtful analytical post!

      • The ECMWF Ensemble also verifies drying weather after this storm. But Fantasyland is Fantasyland after all.

        • jstrahl

          This isn’t what the forecast above says.

          • Quick question if I may. Is that really a forecast? Or is it what the models most favor in terms of possibilities based on current patterns and expected developments based on these patterns. I ask, because I was under the impression that forecasts are what you get in the short term from the NWS/NOAA and the bobbing heads on TV. I may have been misunderstanding what models are all this time.

          • jstrahl

            What’s above is an analysis of what models are saying, three of them, based not on current patterns per se as much as on current conditions and principles derived from the laws of physics applied to the atmosphere and oceans.. Since it’s an analysis of model run outcomes, which involves more than one model, i regard it as more of a forecast, trying to put together information received from the models, which provide guidance.

          • Thanks for educating me. I have not been viewing the model runs as forecast and I guess I should be. I learn things here every day.

          • jstrahl

            That’s NOT what i said. Model runs are not forecasts, what bigB wrote is effectively a forecast, which requires more than just calculations, requires looking at different model runs, seeing trends, etc. requires THINKING, which model runs don’t do.

          • GFS are forecasts up to 16 days.
            CFS is what yenlard posted above and that one can forecast out beyond the time when our sun turns into a red giant.
            The NWS uses models from all over the world to make short term forecasts.

        • The subject is trend. The Eu is trending in the same direction. Same fantasy only with more players

          • Ian

            That’s sounds like a good time!

    • SlashTurn (Santa Barbara)

      Yes, agree…good trends… good swell.

    • Unbiased Observer

      Wow, look at the positive height anomaly over the arctic, that’s nuts!

  • DML

    Local forecasts still trending down, 20% now for the high desert. Might get a little mist but that’s probably about it.

  • Looks like Shasta and all of Sierra getting some much needed snow. This is the very optimistic forecast for snow, but this might jive with the NAM and it’s good hit in the So. Sierra.

    • SoCalWXwatcher

      Looks like Santa Barbara gets a boost from favorable orographics this time around. Also looks like LA Metro area and points South will see a drizzle-fest.

      There’s a lot of dry air in the lower levels of the atmosphere around here thanks to several days of Santa Ana Winds, so hopefully things moisten up quickly so that our drizzle-fest doesn’t end up being a virga-fest. 😉

      • yenlard

        Oxnard saying .25 inch. We’ll take it.

        • SoCalWXwatcher

          Looks like Santa Barbara could get around 3/4″ according the latest estimates from NWS Oxnard.

      • IDK (Santa Barbara)

        Here’s 0z NAM. Looks like no more drizzle-fest for LA if this pans out.

      • Dan the Weatherman

        That probably means my area here in Orange will hardly get a drop. I hope I am wrong, though!

  • jstrahl

    High today of 75 deg F in central Berkeley, ties the highest temp i’ve ever measured here, for February this would be starting in ’92. I’ve twice recorded 75. on 2/12/96 and 2/6/11. Pressure has taken a dive since 8 this morning, 30.10 to 29/.91.

  • IDK (Santa Barbara)
  • yenlard

    Oxnard saying this next ridge not as strong or long lasting. Hopefully things start happening soon after.

  • Intljock

    For what it’s worth. Just had a mosquito try to bite me. Mosquitoes. In February. In Los Angeles.

    • SoCalWXwatcher

      The June Bugs should be starting to come out any day now…

      • Tyler Price (Van Nuys)

        June bugs in February?! Muahaha! I’ve never seen them come earlier than May in SoCal before

        • Just checked my porch light and none yet, but with this weather, I’ll probably start seeing them soon. 🙁

    • yenlard

      It only gets worse from here.

    • alanstorm

      Mosquito’s have awoken up here in Mendocino County. Alittle early in the year if you ask me.
      Spring & summer there are hordes of them here

    • 805 Weather (Camarillo)

      Didn’t know they ever went away in the drought?? I’ve been having mosquitoes here in Camarillo since 2012…

  • jptimmons

    The El Nino hype has lived up to its name in North Eastern CA, The Mountain Echo has written that “The Adin Mountain (Sweagert Flat) snow survey was completed on 2/2/16. Snow depth was 48.7 inches compared to the long-term average of 27 inches. This is the highest recorded snow depth at the Adin Mountain snow survey site in the month of February since 1969 (51 inches). Water content was 15.4 inches compared to the long-term average of 8 inches.”

    • Bombillo1

      Went to Surprise Valley in the RV in October. What we got from everyone there was that it was the wettest SUMMER they had ever had. Still chuck holes with water and green in an otherwise “high desert” environment. They seem to be getting something beneficial there from our current set-up.

    • Ventura Highway

      They really need it up there. I love that area. Especially the Devils Garden. I have had some wonderful hunting trips up there. The elk really depend on those water holes.

  • yenlard

    http://www.tropicaltidbits.com/analysis/models/cfs-mon/2016021606/cfs-mon_01_apcpna_month_namer_1.png. I’m going to keep posting this until the whole state turns yellow. When will that be ? Only a week and a half left of February.

    • SlashTurn (Santa Barbara)

      In June.

    • IDK (Santa Barbara)

      How about not.

  • alanstorm

    NOAA satalite image of tomorrow’s storm. Impressive enough.
    Apparently another on for northern areas on Friday as well.
    Both are fast movers, so not a major rain event, but……BETTER THAN NOTHING

  • IDK (Santa Barbara)

    New Update from Daniel:
    http://weatherwest.com/archives/3877

  • Thunderstorm

    Been hearing that this el-nino is a twin in many areas to the 1888-89 el-nino. The 1888-89 el-nino was on steroids during March. Anyone have confirmation on this. Looking for more confirmation on this.

    • Thirsty Nick (Santa Maria)

      If this is true, we could be in for something big next month.

    • AN50

      SB had 7.8″ in March 1889 and 20.4″ for the year. That was in the middle of a 3 wet year run.

  • thebigweasel

    Woke up to thunder at 6:30, hearing intermittent peals every ten minutes or so. Kind of a lackadaisical thunderstorm. 46 out, which is incredibly warm for a February sunrise.

    • As far as precip for this season are you doing okay?

      • thebigweasel

        Yeah. Still got a drought deficit to fill in, but we’re at about 115% of normal right now.

  • Apollo

    Wakey, wakey and eggs and bakey.

  • Apollo

    ..

  • Apollo

    One more.

  • SlashTurn (Santa Barbara)

    Mid level moisture making it to the ground up here…no virga! Thought it would take a while for the lower level to saturate, but an actual steady rain started as soon as it made landfall. Good flow direction and high PWATs make me think I can do well when the main front sags a little later…such a welcome relief.

  • roseland67

    So, it appears from the data exchange that almost 90 million gallons/day, (net gain), is flowing into Shasta now.
    Is that a relatively “good” # based on past history?

  • FishinTuna

    I’ll be completely satisfied with 1 inch from the first storm in socal. With the pattern change in place I think we will get a series of storms in March – April.

  • TruckeeLover

    Now that is the right attitude…well said.

  • Paul

    March 25, 2016
    11.56 inches of rain in Arroyo Grande, CA up to this point and no rain in the forecasts for the central coast (SLO county) we are below “normal still. The local news stations hype up every single rain event around here as if they are El Nino storms, total hype. We have not had a single El Nino storm pattern yet on the central coast and March is just about over. Here’s hoping we have a wet, a really wet April!

  • Davidae58

    Man made high pressure heating the ionosphere.
    https://m.youtube.com/watch?v=3NqPC0R4JpY