Sunday, March 20, 2016

Still Waiting for El Nino in the Southwest

Chris Farley always delivered, but even if all other "tropical storms" bow before El Nino, as he suggests above, the 2015/16 "Super" El Nino continues to be a bust for the southwest United States.

Let's go back to a few months ago when we knew a strong El Nino was likely for this winter.  At that time, one could find all sorts of graphics like the one below showing the "typical" wintertime pattern associated with El Nino, including the wet southwest.
Source: NWS
Forecasts from the Climate Prediction Center showed the dice loaded for above average precipitation in the southwest.

Source CPC
The fact that this El Nino was going to be strong led some people to believe that the odds of a wet southwest were high, especially since the last two strong events, 82/83 and 98/99 were fairly wet in the southwest.

Let's fast forward to today.  The percent of average precipitation below covers the past 90 days (roughly since just before Christmas).  Northern California has done quite well, which is why reservoirs there have recovered, but most of the southwest has been below average during this period.

If we look at snowpack the numbers in the far southwest are really dismal, but even southern Utah, southern Colorado, and northern New Mexico are slipping below average.
Source: NRCS
And, if we look at forecasts for the next 10 days, they continue to skunk the southwest.  Below for example is the 10-day accumulated precipitation forecast from the GFS.  Plenty of action in the north, but little in the south.  Rather than El Nino, this looks like a good La Nina pattern.

Source: NCEP
It's time to face facts.  First, the skill and utility of seasonal outlooks, whether they show weighting of the odds or pick an outcome (e.g., below average, average, or above average), remains limited for many applications.  I suspect we will see improvement in coming years and decades, but where we are in seasonal prediction today is about where we were in weather forecasting in the 1960s and 70s.  The models are crude and we're relying too much on past analogs and human intuition.  Ultimately, these outlooks are going to improve, but even then, we must guard against converting those probabilities in to deterministic outcomes (e.g., increased odds of above average precipitation equals above average precipitation).  Second, we need to be more cautious about pushing analogs based on past events too far.  A few months ago, many people were using the past two super El Ninos as analogs for this coming winter.  A sample size of two is simply too small.

Finally, if you are skiing in northern Utah, you should just stop looking at seasonal forecasts altogether.  SEASONAL OUTLOOKS ARE UTTERLY AND TOTALLY VALUELESS FOR ANTICIPATING WHAT KIND OF SKI SEASON WE ARE GOING TO HAVE IN NORTHERN UTAH.  Next October, don't waste your time on this stuff.  Wax your skis and be happy.


  1. FWIW, Joe Bastardi called this El Nino very well. He argued (pre-season) that the El Nino blob was in a totally different position this year than past events, and would result in a totally different outcome as a result. Nailed it.

  2. You can count this meteorologist as part of the minority that was never onboard with the "epic" winter forecast in the southwest. I was politely ignored.

    I noted back in the early Fall that there are several important differences between this Very Strong El Nino and others. Most notable is where the warmest waters in the tropical Pacific developed. The maximum temperature anomaly is substantially farther west than in previous events.

    I also tried to point out that since we have had only two Very Strong El Nino's in the modern recorded era, it would be statistically foolish to assume that another would behave in the same way.

    I wish it would have been epic. I was ready to have a great year of skiing.

    1. What is your name? Nice work if you called for below normal precipitation for the winter of 2015/2016 in the southwest but lets see the proof.

  3. With all due respect to other opinions, I'm not sure I can agree with the assertion that the max temperature anomalies were further west than the 1982-83 El Nino. The structure for both was very similar. What was different, was the lack of significantly cooler than normal water just north of the warm El Nino anomalies. To strengthen the elongated W-E Pacific jet and bring it all the way thru onshore across the SW US you need that thermal gradient, and the lingering "warm blob" near Baja might have impeded that.

    Not sure if this has to do with the overall warming we've seen across the Nrn Pacific the past decade, that coincides with the rapid loss of Arctic ice, but there have been lots of papers published recently on how the late Summer/Fall Arctic ice reduction has led to an overly amplified Pacific Ridge that tele-connects from near the equator all the way to the Arctic, and its effect on West Coast drought over the past 7 years.

    No doubt there should be some interesting papers coming out in the near future on why some areas (Srn CA-AZ-Srn UT) missed out, while other areas (Central-Nrn CA and New Mexico thru Florida) did in fact get the normally wet El Nino Scenario.

  4. Your 90-day precipitation graphic is interesting. Can you supply a URL for that?


    1. Click through the options.