It’s Time To Talk Snow: 2012-2013 Winter Outlook

More-so than any other seasonal outlook I get questions about what the forecast is for the upcoming winter. I don’t know if it is a regional thing or if the winter outlook curiosity is matched across the entire country, but there is no doubt that winter piques the interest of many.

Before I get into what I see for the 2012-2013 winter season I have to note that seasonal forecasting is subject to a lot of error. This is due to the fact that some of the factors that influence large-scale/long-term patterns simply cannot be forecasted accurately beyond a couple of weeks. This may sound like an excuse, but it is simply a limitation that forecasters are faced with when constructing their outlooks. That being said there are some influences on winter weather, such as El Nino and La Nina, that are a little easier to forecast and track.

NORTH ATLANTIC OSCILLATION:

So, let’s start with the short term indicator that, while difficult to forecast long range, plays a large role in the type of winter we will experience here in the Triad. This influence is called the North Atlantic Oscillation (NAO). The NAO is a phenomenon in the North Atlantic Ocean which is defined by fluctuations in the difference of pressure between the Icelandic low and the Azores high. The relative difference between these two pressure systems has a huge influence on winter weather. The NAO is a naturally occurring large-scale climate mode in the North Atlantic that influences not just North America, but also Europe and much of northern Asia.

It is the fluctuations in the strength of the Icelandic low and the Azores high that greatly alters the location of the jet stream which ultimately dictates temperature and precipitation schemes. There are two phases of the NAO; positive and negative. And it looks like we are going to be in the negative phase of the NAO this winter.

The negative phase of the NAO, among other things, opens up the freezer to the north and presents the East Coast with an increase in cold air outbreaks resulting in a better chance for snow. This occurs as the jet stream buckles and drops south in the eastern U.S. due to the blocking Azores high pressure system in the North Atlantic.

A prime recent example of this was during the 2009-2010 winter when the NAO index reached record negative phase levels. This resulted in an abnormally snowy winter in the Triad where we picked up more 16.6 inches of snow. This total nearly doubled the 9 inches of snow that the Triad can expect to see in an average winter.

As I mentioned earlier, the forecast accuracy of the NAO does not really extend much beyond a couple of weeks. So, while forecast models indicate that it will remain in the negative phase, there is always an element of caution when considering long-term trends.

The image below displays the observed and forecast phase of the NAO. The line in the middle represents a neutral phase and the area below the ’0′ line indicates the negative phase. As you can see the NAO has recently been negative for a majority of the time which suggests a continuation into winter.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gifImage Source: NOAA, Climate Prediction Center

EL NINO-SOUTHERN OSCILLATION:

Another, and more well-known, influence on our winter is the El Nino-Southern Oscillation (ENSO). Like the NAO, the ENSO has two phases; positive (El Nino) and negative (La Nina). El Nino is characterized as when the surface ocean water along the equator in the eastern pacific undergoes a warming trend. La Nina, conversely, is characterized as the cooling of the ocean water in the eastern pacific along the equator. This naturally occurring change in climate off the west coast of South America has a large impact on weather/climate around the world.

During an El Nino winter the southern United States can expect to experience wetter and slightly cooler than normal conditions. Whereas, parts of the northern United States tend to be more mild.

http://www.pmel.noaa.gov/tao/elnino/gif/fst-temp-us-big.gif

Anomalies of winter temperature during El Niño. Image Source: NOAA, TAO

http://www.pmel.noaa.gov/tao/elnino/gif/fst-precip-us-big.gif

Anomalies of winter precipitation during El Niño. Image Source: NOAA, TAO

Forecasting for El Nino and La Nina contains a little more skill as fluctuations in temperature trends in the eastern Pacific as well as other global ENSO indicators can be more easily monitored. In that same breath, however, atmospheric/climate science is not perfect and conditions can change without much notice. We are seeing that occur right now as just a couple of months ago it appeared we were headed into a moderate El Nino pattern. Just recently it became evident that El Nino may not be as strong this winter as we initially thought. The latest forecast models now suggest that El Nino will be relatively weak this winter with a trend to a more neutral phase toward spring . A weak El Nino will result in the typical impacts of an El Nino winter to be less apparent.

Image Source: International Research Institute For Climate and Society

WHAT DOES THIS TELL US:

Taking into consideration the NAO, the ENSO and a couple other large-scale climate patterns a rough outline of winter begins to take shape. Due to the fact that both the NAO and El Nino do not appear to be particularly strong this winter there cannot be a lot of weight put into either one of their typical impacts. If NAO remains negative into the winter months the Triad can expect to see an increase in systems bringing cold Canadian air in from the northwest. This combined with a weak El Nino which tends to bring us wetter than normal winters could translate into a little more snow than normal.

WINTER TEMPERATURES:

Temperature-wise, I believe that the Triad will experience a near normal winter with cooler than normal temperatures through the deep south and slightly warmer than normal temperatures in the Midwest and northern tier states. The normal high temperature in the Triad during December, January and February is 51, 48 and 53 degrees respectively. The normal low temperatures are 32, 30 and 32 degrees respectively for December, January and February.

http://www.erh.noaa.gov/rah/climate/data/gso_annualclimate.png

Image Credit: RDU National Weather Service Climate Page

WINTER PRECIPITATION:


If one thing is for certain, it doesn’t appear that the Triad will experience a drier than normal winter. Given the setup that we currently have with the NAO I believe that the Triad can expect to have a near normal if not slightly above normal amount of winter precipitation. The setup for an increase in bursts of cold air from the northwest elevates the odds of getting snow, but given the influence of El Nino and a more southerly storm track this could also result in more mixed precipitation events. (i.e. sleet and freezing rain). This pattern also suggests above normal rainfall through the Deep South and Gulf States and normal snowfall through the Midwest and the Nations Heartland.

PREDICTION:

So as I sit here going into the middle of October I would not be surprised if we see anywhere between 8-11 inches of snow during the 2012-2013 winter season. Considering our average snowfall is 9″ this prediction may not seem that out-of-line with a normal winter, but when you compare it to the last five winters it would sit towards the top as one of the snowiest. In fact, if we get more than 10 inches of snow this winter it could be the second snowiest winter in the last 6 years.

Last 5 winter’s snowfall (including 2012-2013 prediction)

1) 2009-2010: 16.6″

2012-2013: 8″-11″

2) 2010-2011: 9.9″

3) 2008-2009: 6.9″

4) 2007-2008: 4.0″

5) 2011-2012: 1.6″

There are a lot of factors that have to fall in to place for this prediction to come to fruition. For all of you snow-lovers out there it appears that this winter may be leaning in your favor, but a number of small fluctuations in the large-scale atmospheric patterns could throw things off. Moreover, individual winter storms are impossible to predict this far out and could greatly alter the outcome and perception of the season.

Basically, what I’m saying is… take this prediction with a grain of salt and with the consideration that winter forecasts tend to have a large margin or error. When all else fails we can always rely on some of those old wives’ tales and the Farmers Almanac to get us through the winter.

Until next time…

Grant

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Posted on October 10, 2012, in Weather and tagged , , . Bookmark the permalink. 6 Comments.

  1. Very informative!

  2. Thank you so much for this NC report! I will pass along on FB!

  3. I agree with Lauren…very informative and I thinking he’s on to something! I’m looking forward to having at least 1 inch of snow here in North Carolina! Come on white winter!:)

  4. I got a feeling us on the east coast are going to get hammered pretty good this winter 2012-2013 with ABOVE normal snowfall, including the mid atlantic

  5. Will the snowfall in Seattle area in the north west have average snowfall above average snowfall or below average snowfall?

  6. “Its Time To Talk Snow: 2012-2013 Winter Outlook Weather Or Not” was definitely enjoyable and
    instructive! In the present day society that is tough to deliver.
    Many thanks, Arlen

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