The Climate Prediction Center (the branch of NOAA that handles long term forecasts) recently issued their forecast for this upcoming winter. Whether you are a “snow lover”, or a “snow hater”, there is not much to get excited about. That’s because the forecast calls for equal chances of below or above normal precipitation. The NOAA forecast map for this December, January, and February is below:
The “EC” stands for equal chances, and one of those EC’s is sitting right over the northeast. The green shaded areas with the A represent locations which have slightly better odds to receive above normal precipitation, and the orange shaded areas with the B represent locations which have slightly better odds to receive below normal precipitation. Precipitation includes rain as well as snow, but it still can be used as guide for making long term snow forecasts.
There is a lot of analysis that goes into making a long term forecast, and there are many different methods that can be used. Several private forecasting firms have also come out with winter forecasts and the outlooks vary. While I don’t know everything that went into the forecast from the Climate Prediction Center, it’s likely that they based some of it on El Nino, which has a better than 50% chance of developing by this winter.
El Nino is characterized by the warm waters in the equatorial Pacific; this can affect the position of the jet stream and long term weather patterns. During El Nino periods, the Pacific jet stream tends to cut across the southern part of the United States.
This brings a lot of moisture and lift to this region, which is why El Nino often brings soaking rain from central/southern California to the southeastern United States. But history has shown there is NO strong signal for the northeast; that is likely one of the reasons for the “equal chances” forecast by NOAA for our area.
For the sake of curiosity, I decided to look at a few of the past El Nino winters and a possible snowfall trend. Here is a breakdown; the snowfall data comes from TF Green Airport (source: Northeastern Regional Climate Center)
El Nino Winter Snowfall
With the normal TF Green snowfall being 33.8 inches, you can see that 2 El Nino winters had above normal snowfall, and 2 El Nino winters had below normal snowfall. This includes a very snowy winter in 2004-2005 with 72 inches, and a very wimpy winter in 2006-2007 with just 15.1 inches. Because there are only four years listed above, we can’t draw any scientific conclusions from this data. However, it is interesting that the these four years support the idea that El Nino doesn’t really tell us anything about the upcoming winter in the northeast. It can snow a lot, it can snow about average, and it might not snow that much at all!
Of course, we should be able to give a few more specifics as we get closer to winter. Enjoy the beginning of autumn! -Pete Mangione