About 10 days ago, the CPC ended their El Niño watch after conditions declined into the ENSO-neutral category. Coming out of La Niña last Winter, most forecasts expected El Niño conditions to develop for this year’s Winter. In fact, El Niño conditions did occur earlier in the Fall, but then the warm temperature anomaly in the central Pacific Ocean associated with El Niño cooled, leading to neutral conditions. (For reference, the temperature anomaly must be above 0.5 degrees Celsius to meet El Niño conditions. I believe this is once again the case, but the CPC references the wind field as their reason for why they think ENSO-neutral conditions will be the norm during Winter.)
So, why does this matter? For starters, the El Niño Southern Oscillation (ENSO) is the driving force behind a lot of the large scale patterns around the globe when it is positive or negative. In neutral conditions, other ocean oscillations become more dominant. El Niño gets it’s name for the time of year it usually develops and is well-defined – Christmas. Thus, ENSO conditions usually play a large role in determining weather patterns in the US during Winter. In other words, those forecasters that like to put out Winter Outlooks/Forecasts usually rely strongly on ENSO conditions to help determine there long-range outlooks. If ENSO isn’t strong one way or the other, it may make Winter forecasting a problem.
Accuweather plans to update (and I assume finalize) their Winter outlook tomorrow. NOAA has already issued their Winter Outlook and has updated it in recent days (sort of). My plan is to share these during the early part of this week, but keep in mind how ENSO-neutral conditions may make forecasting this Winter an issue.