Very Brief El Niño Update – End of April 2015

The weekly sea surface temperature anomalies for the four NINO regions across the equatorial Pacific were at or above the +1.0 deg C threshold of a moderate El Niño, based on data for the week centered on April 22, 2015.

Figure 1

The source of the data is the NOAA Monthly Atmospheric & SST Indices webpage, specifically here. The anomaly data are referenced to the WMO-preferred base years of 1981-2010.  NOAA defines a moderate El Niño as an “Episode when the peak Oceanic Niño Index (ONI) is greater than or equal to 1.0°C and less than or equal to 1.4°C.”  See the footnotes in the NOAA ENSO Blog post here.  The NOAA Oceanic NINO Index is based on the sea surface temperature anomalies of the NINO3.4 region.

On the other hand, the 30-day and 90-day averages of the preliminary BOM Southern Oscillation Index are in ENSO-neutral levels, well shy of their El Niño threshold of -8.0.

I’ll provide a more-detailed ENSO update in a few weeks.

About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
This entry was posted in 2015-16 El Nino Series, ENSO Update. Bookmark the permalink.

8 Responses to Very Brief El Niño Update – End of April 2015

  1. Thanks for the good views, Bob.
    The SOI has been negative since March 2015.
    The ENSO Tracker has been upgraded to El Niño ALERT. This means the likelihood of El Niño developing in 2015 is at least 70%.
    Recent warming of the tropical Pacific has primed the ocean for El Niño. International climate models monitored by the Bureau indicate the central Pacific Ocean will continue to warm, with all models indicating El Niño thresholds will be reached or exceeded by mid-year. El Niño increases the chance of a drier than normal winter and spring for eastern Australia.

  2. Hi Bob,
    sometimes it looks like El Niño-Modoki in Nino4 in the central Pacific since NH-summer 2014, doesn’t it…?

  3. Bob Tisdale says:

    schneefan2015, there’s a El Nino Modoki Index (EMI) data page attached to the link you provided. See:
    The EMI turned positive in September, so, you’re right. It was late boreal summer when the switch to positive occurred…though it may not have reached high enough, long enough for it to register as an El Nino Modoki event.

    At present, the sea surface temperatures are probably too high in the eastern tropical Pacific for it to hold that classification.


  4. Sig Silber says:

    It looks like it was a Modoki Type II combined with PDO+ and what the Japanese call the California Nino. Now we have some warm water off of Ecuador and Peru so it looks more like a Traditional El Nino. If there is not another Kelvin Wave this will play out in Nino 3.4 in two months and totally in four. If there is another Kelvin Wave we will have an El Nino this winter Only two of 19 I believe survived for two years for the reasons Bob Tisdale has explained many times namely the spreading out of water to evaporate and cool.

    A Modoki Type II maintains the RRR which is the only form of El Nino that does. That is why California has been dry.

    The Key Question is is there enough warm water to sustain this Warm Event?. I suspect not but we will see.

  5. Sig Silber says:

    Although this article of mine features sunspots, I also each week track this Warm Event.
    I am not sure we have had an El Nino. We may have. The ONI criteria were marginally met and the SOI never confirmed an El Nino which to the extent it occurred was a Modoki Type II.

    Now I see a Kevin Wave which will play out by the end of August. So to have an El Nino in the Fall and Winter of 2015/2016 we need another Kelvin wave.

    Of all people I know, Bob Tisdale has best explained these dynamics mainly the way a Warm Event dissipates heat into the atmosphere and cools the water. So in my mind, the question is the supply of warm water in the Warm Pool to generate a substantial enough impact to get an El Nino going this Fall. I am dubious.

    Also this rise in the PDO Index might be a false signal as it usually happens with an El Nino but if I have it correct did not happen with the 1982 El Nino. And the Pacific now appears to be becoming less PDO+.

    So I think the dynamic here are complex and I do not think that NOAA is on top of the situation.

    But in six months we will know the answer.

  6. Hi Sig,
    the latest MEI is +0,95 for March-April in a clear Nino-value.
    The “borderline El Nino” continues since last year and perhaps ends like last year with a peak in April-May 2014 with +0,93.
    The comparation with similiar situations in the past supports your doubts about NOAA`s ENSO-projections…
    I think we`ll see it more clear after the so called “spring barrier” in June, which makes ENSO-predictions very difficult from February until May.


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