June 09, 2009

El Nino Returns

Some major changes have been occurring in the tropical Pacific. Most of the last winter was characterized by La Nina conditions in which the surface temperatures of the central/eastern tropical Pacific were cooler than normal. But recently there has been a shift to the opposite, El Nino, where the water in that region is warmer than normal. The plot below shows sea surface temperature for several areas in the tropical Pacific..the Nino 3.4 region is the one of most interest. There is a cycle between El Nino and La Nina called ENSO (El Nino Southern Oscillation) that has a period of roughly 3-7 years.

My profession has a variety of ways to predict the future of El Nino and La Nina, the two main ways being dynamical (full physics) and statistical models. The results of these models is shown below (Note that positive is El Nino side). Most models are going for warming (El Nino), although some (mainly the statistical models) are going for a neutral (near zero temperature anomoly from normal)...also called La Nada years.

So why do we care about El Nino and La Nina? Because there is a modest correlation with our weather, particularly during the winter. La Nina years tend to have more cold and snow (like last year!), while El Nino years tend to be drier, with less snow in the lowland and mountains, and weaker storms. I would hesitate to buy an annual ski pass at Snoqualmie Summit if the El Nino strengthens (but don't tell them I said that). And one more thing...during El Nino years southern CA tends to be much wetter than normal.


  1. Cliff,
    Does El Nino change anything for the summer? Vegetable gardeners want to know... it seems like we have already been warmer and drier than normal over the past month.

  2. Cliff: To what extent do you expect the current-but-early cold-phase Pacific Decadal Oscillation to alter any El Nino that we may get? As I understand it, we don't entirely know whether PDO drives ENSO or vice versa. I suppose if NASA's GMAO model is correct it might not matter. Any thoughts?

  3. Cliff said Back on December 27th 2008
    "Remember...this is a neutral year...neither El Nino nor La Nina...and the most severe snow and wind events..."

    Then in February.......and this is a La Nina year

    and now.....El Nino Returns. I wouldn't call it a year. Back in the days yes a "year".

    Maybe a "period" or something. It seems like this oscillation is oscillating pretty fast...

    Maybe we should call it something else. Like "La Nino"...

  4. JewwlyaZ
    No...there isn't much correlation between El Nino and summer weather.
    My vegetables are finally doing well, though...cliff

  5. From a farmer's perspective, this spring has been very warm here in Western Washington. My vineyard is loving the heat. In my research (mainly around grape growing) El Nino years have been hotter and drier in the Summer and Fall, something I look forward too!

  6. 3 of the 4 regions show above average temps last year in the summer, including region 3.4, followed by cooling in the fall and winter. Couldn't that happen again this year?

  7. There is a listing of the Oceanic Nino index here:

    I see La Nina conditions in 1968 gave way to a moderate El Nino in 1969. And from the xmACIS data...
    22" of snowfall for Sea Tac in December 1968, followed by 45" in January 1969 (while the ONI was +1).

    This gives me hope that someday a winter like '68-69 will repeat when we least expect it.

  8. I would gladly take a '68-'69 redux.

  9. Cliff,
    Does anyone know why we are getting such a great start of warm and dry weather to our year, most potential storms seem to miss the Puget Sound and we have mostly sunny days in late may and June like it is July and August. What is different this year that could be driving this current pattern. Even in May almost all of our rain seemed to come in one big storm. Everyone is happy about this weather, except for the meteorologists who may find it boring, but there must be something interesting to talk about.

  10. One thing is for sure: this is the year of the tomato. How often can that be said of the region?

  11. I think the E Wa cherry crop is done for again this year. They have been on the leading edge of thunderstorms and hail. Tonight, more are expected to roll in.

  12. Bill Nye was explaining the first cloud type nomination since 1951 on the Rachel Maddow show tonight. The cloud appreciation society.

  13. britten_clark, not everyone is happy about this weather. Just so you know.

    any particular reason the record stretches of days without precipitation are so much longer than the record stretches of days with precipitation, yet people say it rains here all the time? we're going on 25 straight days of no rain and I haven't even heard talk about how big of a deal it is, like the near-record rain stretch a few years back.

  14. The NOAA CFS forecast (which updates daily as opposed to the IRI ensembles, which contain models that are up to a month out of date) has been showing a return to El Nino for over a month, and now it's actually turning into a strong El Nino prediction (http://tinyurl.com/n2crsm)
    The CFS model led the pack in predicting last winter's La Nina, so on that very short track record, I would probably skip the season ski pass next year.

    Good questions in the comments about the last month's unusual dryness -- I too would like to know if any group was forecasting that, and what the physical drivers were. Not really a weather question, but not far from it.

  15. Hi, I was wondering if there's been an update in winter weather predictions with the El Nino ENSO?

    I was thinking about buying a ski pass to hone the new skis but wouldn't do it if the prediction is for warm, wet weather.

    I've heard that ENSO could also bring warm dry weather? Thanks for posting links and your always informative blog.



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