Your meaningless winter 2020-2021 forecast

Welcome to the point of the summer when we are all simply too hot and we start to think about fall and winter! With that in mind, I wanted to give a meaningless mid-July forecast for winter 2020-2021. Meteorologists often attempt to predict if it will be a snowy or cold winter well in advance of the start of winter, but in my opinion, this is simply too hard to do (especially now, when it starts getting done). That said, I'm going to share some insight anyway. **If you don't feel like reading information that is essentially meaningless, close your webpage now**

To begin, the Climate Prediction Center (CPC) issued a La Niña watch on July 9. According to the CPC, while ENSO-Neutral conditions are favored to remain through the end of the summer, there is a 50-55% chance of La Niña conditions developing in fall 2020 and continuing through winter 2021. Let me unpack all this for you. The El Niño-Southern Oscillation (ENSO) is an oscillating climate pattern that involves changing surface water temperatures in the central and eastern Pacific Ocean near the equator. The 3 stages of ENSO are El Niño, ENSO-Neutral, and La Niña. Meteorologists like to track ENSO because it can have important implications on the jet stream, which can in turn affect temperatures and precipitation. Right now, we are in an ENSO-Neutral phase of the cycle, meaning that Pacific Ocean temperatures are not particularly hot nor cold. The CPC is tracking the possibility of a La Niña developing this fall and continuing into the winter, which would have a setup like this in the pacific ocean:

Sea surface temperatures during La Niña (Wikipedia)

The large swath of blue near the equator in the eastern Pacific Ocean indicates that Pacific sea surface temperatures (SSTs) are lower than average. What does this oceanic configuration mean for our winter weather in New England? Generally during La Niña we see about average temperatures with above average precipitation.

Typical winter pattern (NWS)

So on the basis of La Niña forming (which the CPC says has ~ a 50% chance of happening), we can expect a snowy winter with fairly typical temperatures. Note that this does not always happen during La Niña winters. We certainly can experience a dry and cold winter when there is a La Niña in place. And if you've made it this far, note again that all of this information is practically meaningless, as it's so difficult to forecast for the winter this far out.

Here is what the CPC thinks for temperature probabilities during December 2020 - February 2021.

Three-Month temperature outlook for Dec 2020 - Jan 2021 (CPC)

Probabilistically, the CPC calls for approximately a 55% chance that we'll see above average temperatures during that three month period. And for the same period, the CPC is stating that there is a 50/50 chance that we'll se above normal precipitation.

Three-Month precipitation outlook for Dec 2020 - Jan 2021 (CPC)

The above map shows a typical La Niña pattern: dry in southern areas, and wet in northern areas.

To recap, it looks like there is a chance that La Niña will develop as we head into the winter. Historically, this would mean that we'd expect average temperatures and slightly above normal precipitation, but this is certainly not always the case. As I've maintained throughout this post, all of this information is more or less meaningless - it's simply too hard to forecast for the winter in the middle of July. We'll simply need to wait until December to know what winter will be like. Until then, it's more heat and humidity for us.