ECHO Storm Team: Winter 2014-15 Final Forecast
To be able to project events in the future, we have to study the past. As entirely cliché as this sounds, the past gives us a solid understanding of what we need to look out for as we head into the future. The exact same methodology is used when producing a winter forecast. As we look at the magnitude of winter experienced across much of the nation last year, we can’t help but to speculate if such a winter will occur again.
Last winter left a historic footprint across much of the eastern US. From record-setting cold across the northern states to record ice and snowstorms across the southeast, last winter made a page of its own in the record books. Looking at all of this, the question then becomes, “Will we see a repeat of last winter or will Mother Nature back down a little?” While I’d like to think we will be given a chance to catch our breaths this winter, there are indications that would suggest, perhaps not a repeat of last winter, but a very similar winter in its own regard. There will be different variables that will drive this winter, compared to last winter, however, I do believe that we will arrive at a similar product.
The driving force behind our weather all year round are the waters of the Pacific and Atlantic Oceans. How they behave spells out the various weather patterns we experience through the year. The indices we pay particularly close attention to are oscillations/teleconnections and their trends.
AO (Arctic Oscillation):
The AO recently went negative over the final days of October into the first few days of November. This negative phase in the AO was responsible for the recent surge of colder air temperatures across the eastern US. The AO is expected to go negative and with the increasing snowpack across Siberia this early in the year, this is likely to propel the AO into a sustained negative phase. A negative AO will lead to increased episodes of cold, Arctic air across the eastern US and even parts of the central US.
NAO (North Atlantic Oscillation):
As with the AO, the NAO will produce a very storm winter pattern across the eastern US if it trends negatively. If the NAO flirts between a neutral and negative phase, this is when we get our active winter weather in terms of snowstorms spanning from the Midwest to Eastern US. As has been the trend recently, there is reason to believe that the NAO will flirt with neutral and negative phases as we move forward.
PDO (Pacific Decadal Oscillation)/PNA (Pacific/North American) pattern:
We are trending into positive PDO which would garner the idea of a ridge building in the western US and a subsequent trough in the central and eastern US. If a positive PDO can be sustained throughout the winter which I believe will, this would translate into an active winter across the Mid-Atlantic and East Coast and increase the confidence in a positive PNA
To have another active weather pattern across the southeast US much like last winter, we are looking for a weak El Nino. If we have too intense of an El Nino, this would bring a warmer winter to across the southeast, which I’m almost certain, not too many would complain over a mild winter. Model guidance is, in fact, heavily favoring a weak El Nino which would support another active winter pattern across the southeast states.
Siberia is currently experience an extensive amount of early season snowfall with much more on the way. SAI (Siberian/Alaskan Index) could very well set records this year with such an extensive and increasing snowpack. The SAI is an index that measures atmospheric circulation responsible for ice cover variations in the Bering Sea from year to year. The snowpack across Siberia is likely to play a critical role in the influence of a negative AO and negative NAO throughout the winter.
WHAT CAN BE EXPECTED THIS WINTER:
As winter comes upon us, as is the case every year, we need to be ready for anything and everything will decide to throw at us. At this point, the best we can do is try to predict what these products will be based on the data we have available. I have a strong feeling that we will experience a similar winter to last year, but for different reasons as mentioned above. My thinking is that last year’s cold, Arctic spells could be rivaled again this year, especially across the central and eastern US.
One of the biggest challenges when forecasting winter weather events is how much or how little lake-effect snow will play apart in overall snowfall totals. While lake-effect snow will play a part in the overall snowfall totals, contrary to last year, I don’t see lake-effect snows playing nearly as big a role this winter as it did last winter. There were a series of such exceptionally cold, Arctic air over the Great Lakes last winter that Lake Erie experiences record ice-cover. As a result, the lake water temperatures remain below average which could hinder the lake-effect snow machine from really cranking up some serious snowfall amounts. Not saying that lake-effect snow won’t be a factor, because it will, just not as prominent of a factor as last winter.
As I did in my mid-October article, taking a look at long-range model output and that same pocket of above average, warm waters still resides in the western Pacific. This would allow ridging to build in the west and troughing in the central and eastern US which would result in prime opportunities for cold, Arctic air to nosedive the US through this resulting dip in the jet stream.
So we talked about the cold, but who get’s the snow? I believe that the eastern US will be dealing with an active winter with several opportunities of seeing snow. I would include the Midwest, the Great Lakes, the Northeast, New England, the mid-Atlantic and, yes, dare I say it… my thinking is that the Southeast could see more snow and ice this year again with model guidance heavily favoring a weak El Nino this winter. Of these regions, I would pay particularly close attention to the Northeast, New England, Mid-Atlantic and Southeast as these regions could see an especially active winter in terms of snow and ice events.
Across the central US, average snowfall will likely be the story. The reason I say this is because I have a strong feeling that a lot of the coldest air could be blanketed over the central parts of the country at times. If you have too much, cold, dry air, this will void much of the moisture needed to produce snowfall. Not saying that this part of the country won’t see any snow, rather an average winter snowfall.
Across the west, much of these regions are likely to see continued dry weather with sporadic precipitation opportunities. However, the Pacific southwest could experience some much-needed rainfall.
As I’ve mentioned several times, winter forecasts are extremely challenging to produce as every variable, even the smallest, could have a large impact on the overall forecast, especially over a 3-month outlook. Based on the current and projected data mentioned in this article, I believe that this winter will again be similar to last winter. That same dynamics that resulted in last winter may not be the same as the driving force behind the upcoming winter, but I feel that the end product will be very similar.
I will continue to post updates as I always do, especially throughout the remainder of Fall and through the upcoming winter months. If anything changes or occurs, I will let you know. While this article does say “final” thoughts, this winter forecast, as with every winter forecast is not set in stone with so many variables to be analyzed on a monthly, weekly and daily basis. I hope this article gives you an early idea of what we could expect based on the current data available. As always, stay safe and stay well this winter season…
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