Winter is almost here and there has been quite the buzz about the expectation for this upcoming season. We’re feeling very confident the upcoming winter will be colder and snowier than last winter, but that isn’t saying too much. Between December 1st 2015 and February 28th 2016, Portland averaged a temperature of 31.2 degrees. It was the 2nd warmest on record at the Jetport. The city received only 41 inches of snow during that time frame which was well below normal.
The driving weather feature behind the warm winter of 2015-16 was the state of the El Nino Southern Ossoliation Index or ENSO. Last winter was an El Nino winter, and was one of the strongest on record in fact. So what is El Nino?
While entertaining, it has nothing to do with Chris Farley on Saturday Night Live, but more to do with an abnormal warming of the Eastern and Central Pacific Ocean.
The warmer sea surface temperatures typically configure the jetstream in a way that provides the northern tier of the country with a warmer than normal winter. That’s exactly what happened winter 2015-16.
ENSO index shifted neutral and then negative over the summer. For a period this summer it appeared we would be heading for a La Nina this winter.
La Nina is just the opposite of El Nino which is a cooling of the Eastern and Central Pacific ocean. Here’s the current Sea Surface Temperature Anomalies for October and you can clearly see the ribbon of cooler than normal ocean temperatures.
It’s becoming more clear however the this winter will be a weak La Nina at most and most likely transitioning toward neutral by late winter and early spring.
This winter should not be a “typical” La Nina winter though as the ENSO numbers suggest weak La Nina early and then most likely becoming neutral by late winter and spring. So what does this all mean for us here in the northeast?
I’m not a huge fan for seasonal forecasts for obvious reasons. Forecasting New England weather is often challenging just several days out, never mind a few months in advance. There are methods though that in my opinion that can give us a general idea of the kind of weather we can expect. This method is a step above educated guess in my book.
Lets first look at all the winter seasons that had a weak La Nina transitioning neutral by late winter or spring going back to 1950. They are.
The temperature and precipitation anomalies for those years between December and February looked like this. The core of the colder than normal temperatures was centered in the Northern Plains and Western Great Lakes. Precipitation was slightly above normal in Northeast but not by much.
Of those winters coming off of an El Nino the previous winter are
Those three seasons looked like this for temperature and precipitation.
Another variable we like to keep an eye on heading into the winter months is the Arctic Oscillation or AO. When the AO is negative, that typically provides northern latitudes with more long wave troughs and ridges.
And is expected to remain negative into the winter.
Finally the winters that were weak La Nina, transitioning neutral, off a previous El Nino Winter, and also had a negative AO were.
Both were big winter’s in the northeast and looked like this.
These analog years would suggest a colder and snowy winter here in the northeast. Lets bring some of the modeling into the picture now. Just like in the analog years above, we’ll look specifically at the three month period of December through February. Both the JMA and CFSv2 hint at a lower heights and “troughing” over the Great Lakes/Northeast and “Ridging” over the west. That type of pattern would likely result in frequent chances of storms in the northeast.
Furthermore, the models are not nearly as cool as the analog years outlined above would suggest. It is worth mentioning, modeling during the cold 2015 winter was warm in the northeast as well. That was the February Portland recorded the coldest on record, not only at the Jetport, but all other observing sites going back to the 1800’s. For what it’s worth, here’s the three month temperature anomalies.
My temperature forecast is based on analog years outlined above combined with the warmer solutions suggested in computer forecast modeling. The coldest part of the nations (relative to normal) is likely to be west of northern New England from the northern Plains through the Great Lakes. New England should see a more normal temperature set up for winter 2016-17.
My precipitation forecast is developed in a similar fashion combining analog years and forecast modeling. Based on that, I anticipate northern New England will experience above normal precipitation and slightly above normal snowfall December through February.
It’s also worth mentioning there’s a strong signal of normal to above normal snowfall in both November and December. 9 out of 12 winters studied (75% ) of them had normal to above normal snow early winter. That combined with current and European model weeklies are giving me higher confidence we’ll get into a snowier early winter than previous years.
Full disclaimer, while there’s nothing I can do to influence the weather (wish I could), I’m advocating a snowy winter for selfish reasons. My family and I enjoy skiing and snowshoeing during the winter months, and we love living in Maine for that reason. We already have our first snowman under our belts. Last weekend we took a ride up to the mountains for that specific reason.
Odds are there there will be many more chances in the coming months. I’d love to see your weather photos and reports this winter. A good way to connect is through social media here. Thanks for reading.