Historically, if La Niña is going to strengthen, this is the time of year it will happen. So, let’s see what it’s up to…

The graphic above shows how La Niña has been behaving since the middle of August. Remember, to be classified a La Niña, that dotted blue line needs to be at or below -0.5 for three consecutive months. Technically, we have briefly achieved that threshold… However, you can see that since the end of October, it has been weakening. As of now, we are barely hanging on to weak La Niña status. Also, we need the atmosphere to respond and couple to the ocean for this La Niña to truly have a meaningful impact. Is that happening? Not yet…

The graphic above is a measure of the Southern Oscillation Index (SOI). When it is around +10 or above, we are in La Niña. You can see back in 2022 how positive it was and we were certainly in a La Niña at that time. Recently, you can see that we briefly went positive in September, but then have been hovering in neutral territory with no major move to positive territory. The big question is…Will that continue? 

The graphic below is a forecast for the next couple of weeks. As I write this (Nov, 18th), there looks to be a major surge in the easterly trade winds along the equator. This shows up as green and blue on the graphic… 

Westerly wind bursts show up as orange and red, and will likely remain confined to the Indian Ocean and far western Pacific. In order for La Niña to start developing again, those easterly trade winds not only have to be strong, but also have to persist. For right now, it looks like that will occur… So, I would expect us to see this weak La Niña intensify a bit. Do I expect this La Niña to become a moderate or strong event? No, I do not…

The graphics below show the various models and how strong and long they think this event will become.

December ENSO Forecast

February ENSO Forecast

April ENSO Forecast

A couple of takeaways…1) NOAA is consistently the strongest with this event and lingers it the longest. NOAA has also been the most inaccurate for the past few months. 2) The BOM and ECMWF models, which are my favorites, are not as strong or long lasting with this event, and have been much more accurate with their forecasts. In fact, they really don’t show much of a La Niña event at all… 3) The BOM and METEO models actually warm the ENSO region to +0.4 during the spring. This would indicate a subtle move toward a possible weak El Niño. I am not discounting that possibility, but the confidence in that happening is pretty low at this time.

What does this mean for the next few months? Well, while I do expect some La Niña impact, which usually means drier than average conditions for many of us, I also expect more pattern variability. Why? Because this La Niña is only going to be a weak event at best. Without a strong La Niña signal to lock us into a long standing dry pattern, we are likely to get more variability in the pattern. While there will still be plenty of dry time, I also expect the frequency of storms to be higher than when a moderate or strong La Niña is present. More on that next month…