El Nino Impacts along with other Climate Factors That May Influence our Winter Weather

El Nino conditions likely to persist
into 2015-2016 winter season

These graphics show the increased risk of experiencing extreme warm or cold temperatures during El Nino events across the country, averaged over 3 month periods. The northern tier of the U.S. has an increased risk of extreme warmth, but the odds decrease as you head into the latter part of winter and early spring. For the southern U.S, the risk of extreme cold increases and spreads northward heading into late winter and spring (Feb thru April timeframe). Here in our area the odds are fairly neutral for most of the period until we get into March and April when there is an increased risk of colder temperatures.

These graphics show the increased risk of experiencing wetter or drier extremes across the country during El Nino events, averaged over 3 month periods. The southern states from California and Arizona to Florida have an increased risk of experiencing wetter conditions compared to normal as storm systems tend to track repeatedly across these locations. The Ohio Valley and northern states from Montana into upstate New York have an increased risk of drier than normal conditions. This is especially true for the 3 month time period centered on February and again on April.

A Look at Past Strong El Nino Winters - Temperatures

A Look at Past Strong El Nino Winters - Precipitation

A Look at Past Strong El Nino Winters - Snowfall

There have been a lot of comparisons being made between the strong El Nino winter of 1997-1998 and this coming winter. So let's take a look at how that winter panned out for our area:

However, before we get carried away and believe this winter will be a carbon copy of the 97-98 winter, we need to take a look at the bigger picture. A key factor is the current sea surface temperature anomalies, not only along the Equator but in the Atlantic and Pacific Oceans off the United States coasts. These two images show the observed sea surface temperature anomalies across the globe. Yellows and reds correspond to abnormally warm waters while blues are associated with abnormally cold waters.The 1st one shows early November of 1997 while the 2nd one shows early November of 2015:

As you can see by the red circles areas, there are two distinct difference between them. Back in 1997 there was a pool of abnormally cold sea surface temperatures located in the North Central and Eastern Pacific Ocean off the west coast of the United States. In 2015, we have abnormally warm sea surface temperatures located in this same area, which has been the case the last several winters. In fact this area of abnormally warm water off the west coast of the U.S. actually has its own nickname now, termed "The Blob". Also in 1997, the western Atlantic Ocean off the U.S. east coast saw below normal water temperatures while currently we have above normal water temperatures there. This makes it hard to directly compare this year to the 97-98 event.

Unlike El Nino, there are several other key variables that aren't as predictable on a seasonal timescale. Factors such as the North Atlantic Oscillation, the Arctic Oscillation, and even the Pacific North American Pattern will come in to play. It is challenging to anticipate how the final outcome of competing forcings from the tropics and the high latitudes will influence our weather. Here is a quick look at some of these other factors:

Unfortunately, the phase of the AO is hard to predict more than 1 to 2 weeks in advance. If one phase were to dominate the 2015-2016 winter season, it could alter the pattern seen during a typical El Nino.

The official winter outlook is based strongly on the impacts of El Nino. However, as discussed there are several other variables that could potentially alter the pattern seen during a typical El Nino winter. Since these other variables are less predictable on the seasonal time scale, the best route is to side with El Nino.