It’s hard to believe how fast summer is flying by after the bitter cold winter of 2013/2014 and it’s already starting to feel like autumn here in Bozeman Montana. Now it’s time for our 2014/2015 winter weather forecast. It looks like the roller coaster I mentioned last year continued in 2013-2014 with some pretty good results in snow cover and cold temperatures. In fact, last winter hit the record books as the coldest winter in 30 years. We set quite a few all-time records for below average temperatures particularly in the upper Midwest where the all-to-famous ‘Polar Vortex’ hit which, by its self, isn’t unusual but the persistence and duration of these polar bursts made it one for the record books.
Let’s take a look at the state of the NAO since it has been the big player over the last couple winters. Currently the NAO is negative and trending into the positive direction. However, compared to the last few years, the NAO is in near neutral territory and models are showing little variation from this. So I expect the NAO to take a bench this winter and let the other factors play.
The next big factor to look at is the state of the ENSO (El Nino Southern Oscillation). Some experts are predicting a 60%-70% chance of a weak to moderate El Nino this winter which would pretty much dictate the weather across the US. However, I’m seeing something different. The chart below shows the El Nino forecast through June 2015. The grey highlighted area shows the winter 2014-2015 months. An El Nino event usually happens when the sea surface temperature anomalies exceed 1 degree Celsius indicated by the upper red line. The lower red line shows the boundary for a La Nina event. The bulk of the models and the averages are all below the El Nino boundary. My prediction is a 30% chance of a weak El Nino. Just because we may not hit an official El Nino, the waters will still be slightly warmer than usual and this can lead to mild ‘El Nino-like’ effects. I am however seeing some high pressure blocking beginning to predominate in the Alaskan gulf so we’ll talk about that further down. With NAO and ENSO playing weak roles this winter we’ll need to take a look at more factors than usual for this winter’s forecast.
Let’s take a look at a few more things like AO and PNA. The AO (Arctic Oscillation) determines the stability of the cold air over the North Pole. When the AO is in a positive state the air wraps tightly over the north pole pulling it away from the lower 48 but in a negative state the air mass becomes unstable and starts to plunge south into southern Canada and sometimes as far as the US. Last year the famous “Polar Vortex” can be clearly seen in the chart below when the AO suddenly plunged into negative territory and didn’t really start to recover into positive territory until early spring. So far this summer the AO has been negative which can help explain the cooler than average temperatures and early snowfall recently across the Rocky Mountains. Currently the AO is negative and forecasts are predicting it will stay negative through September. My preliminary prediction is that the AO will stay mostly negative at least through the beginning of winter so we can expect a cold autumn and a fashionably early winter.
The PNA (Pacific North American Teleconnection) is tightly connected with, and or affected by, the state of El Nino. These two factors could play together to induce a stronger than predicted El Nino event but could also potentially cancel out a weak El Nino. The PNA stayed negative for a really long time from late winter 2012 and just started spiking into positive territory this last summer which is probably correlated with the predictions of a weak El Nino. Typically this means warmer temperatures for the West coast and colder temperatures for the Southeast with lots of snow around the Gulf of Alaska down into the Pacific Northwest and low snow totals in the Midwest.
So what’s the bottom line? I must warn you that it’s still pretty early to predict the entire winter accurately and with variables such as El Nino lurking around, anything could ultimately end up happening. But for now here is what I predict. The Northeast will see plenty of snow with average temperatures. Southeast will be cold and wet (look out for potential ice storms). It will be pretty cold this winter, maybe not as bad as last winter but pretty close, for the Midwest and the Montana, Wyoming, Colorado, and Utah areas. Those areas should also expect around average snowfall, which for some of you can still be a lot of snow. The south central USA and southwest will be cold and wet with a high probability of ice storms particularly in the eastern south central. If you live anywhere along the west coast or the Pacific Northwest you’re in for lots of rain in the south and lots of wet snow in the north. If you’re looking for a good ski getaway I would checkout Alaska, they should be getting a good deal of snow this winter.
As I said before it’s still early for making any kind of accurate winter forecasts so use this as a guideline but don’t put too much money on it. And as always, I’ve included a trusty copy of the Farmer’s Almanac winter forecast for you to cross-reference.