The NOAA Climate.gov article Another mild winter? NOAA’s 2018-19 winter outlook by Mike Halpert (10/22/18) discusses the likelihood of El Niño this winter and the impact on temperatures. The discussion of prediction and probabilities can be used in QL and stats courses:
I again remind readers (if this seems repetitive, well, it is) that these forecasts are provided in terms of probabilities (% chance) for below, near, or above average outcomes with the maps showing only the most likely outcome (1). Because the probabilities on these and all CPC outlook maps are less than 100%, there is no guarantee you will see temperature or precipitation departures from normal that match the color on the map. As we’ve explained in earlier blog posts, even when one outcome is more likely than another, there is still always a chance that a less favored outcome will occur. And in fact, for the forecasts to be reliable (a critical part of a probabilistic forecast), less likely outcomes MUST happen from time to time.
There is also interesting material regarding weak, moderate, and strong El Niño events and the graph (copied here) which shows the historic impact of different strength events.
This lack of consistency reflects that a weaker El Niño does not exert a strong push (or forcing) on the U.S. If we have a stronger El Niño, the big push from the vigorous tropical heating sets off a cascade of global impacts, including changes in the strength and position of the jet stream that affects U.S. weather, which tends to dominate over other factors that could impact the outlook. Because of an expected smaller push from El Niño, however, other climate patterns are more likely to play a larger role in shaping the upcoming winter. These patterns, like the Arctic Oscillation and the Madden-Julian Oscillation, can have a profound impact on the character of the winter, but are quite challenging to predict months in advance.
Go to the article if you’d like to see the prediction for this year, but first try providing your own probabilistic estimates for next year. There is similar graph and discussion regarding precipitation.