Forecasting the Winter Forecast

Note: FORECASTGMU's own Winter Forecast is included at the bottom of this article! 

So I have received these questions immensely in the past couple of weeks. And rather me just answer them individually giving the same lengthy explanation that which I will attempt to give here. I just said, “Wait until I put up my explanation on the ‘Winter Forecast 2014-2015’ and your questions will probably be answered.” So without further ado, I want to apologize for the delay for this article. I was debating on whether I should just do the article right when networks, experts and the almanac decided to give their full winter synopsis, or wait and see if the recent fall weather would further influence their overriding opinion. Their overriding opinion was that this winter was going to be one of the worst within recent history. Temperatures several degrees below average on a consistent basis and more of the heavy snowfall. For winter and snow lovers, this is paradise and music to many meteorologists’ ears (hey we love to track these storms too!) Where are they getting this information from though? How can they just say that?

To be honest there has been many times that I have thought a long range forecast involves a lot of hope and not a lot of visual and quantitative analysis using longer range climatological models. I cannot even count on my hand the amount of times that the line “This winter is going to be one of the snowiest ever.” And there be no snow or a lame excuse for a snowstorm once in mid to late February where the snow melts before midday. Though the opposite of that has been the case as well, mostly due to the fact a 2-3 foot blizzard had occurred that year.

Back to the original question: where do they get the information to produce their season long climatological forecast?

We will start with the most obscure…Farmer’s Almanac (pictured below): This North American periodical has been a mainstay for people’s perception on how the year is going to be seasonally. Though it contains many different other elements to it, such as topics on conservation, gardening and even a bit of humor and trivia, people’s real lull to it is the weather prediction section. They claim that their system of prediction produces 80-90 percent accuracy, though independent samples do not have them to be that accurate. How they actually go about this prediction is mostly a secret sadly. They are actually kept in a secret box in New Hampshire. The main founder of the almanac though, Robert B. Thomas, claims that it is solar activity and sunspots that has the largest influence on our weather.  Over the years though, this theory has been since refined to fit the meteorological discoveries of the day, along with historical weather data. They maintain though that their main source of information is solar observations.

The Old Farmer's Almanac

Other winter forecasts from weather networks and websites, both on a regional and national level use a completely different method. Starting months in advance, upper air motions and atmospheric levels can be analyzed, quantified and therefore ran in complex computer models. These predictions also take into account things like the area’s climatology, meaning the typical weather expected for that area on a yearly basis based off of observed results from years before. These ‘analog forecasts’ as they are called lines up patterns dating back more than 100 years back. This might seem like it works really well…but weather is so chaotic and unpredictable statistically that this would definitely not suffice.

Want to know more about analog forecasting? Click here!! 

 

A great visual example of an analog forecast for temperature anomalies

 What also needs to be taken into account is the sea surface temperature. This of course varies along the cycle of warmth and cooling in the Southern Pacific called ENSO. The water temperature distribution is a key look into how we will predict the forecast values such as temperature anomaly and snowfall amount compared to the average. In an El Nino winter, which this winter is starting to look more and more like according to the readings, there has been higher level snowfall amounts in the Midwest, Northeast and Mid-Atlantic respectively. Also El Nino winters are not warm as people might expect, they are much colder on average (see last winter) and produce wetter conditions in the East, and drier conditions in the West. So far the models are in agreement that the El Nino is supposed to strengthen in the next couple of months to produce said conditions, though this could be subject to change.

What this winter could look like with weather patterns

Want to know more about ENSO? Check out the Climate Prediction Center's site

Though ENSO seems like the only way that long term forecasts can be evaluated, this is surely not the case. Other oceanic oscillations play in important role in climatic predictions. There is also the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) that play major roles in how the winter forecast is formed. Currently the PDO is in a highly positive phase. This warming of the waters has produced above average temperatures for western Canada along with Alaska. This accompanied by a stronger El Nino event could act as a booster to create even warmer and more above average conditions in the North and West and more below average conditions in the Midwest and East. To fully observe this, we can take a look at statistics from last winter. 

A look at last winter's temperature pattern

The Atlantic Multidecadal Oscillation is a long term variation of changes in the sea surface temperature in the North Atlantic Ocean. This pattern has been a huge indicator in global air temperature anomalies, or deviation from the average temperature. Positive AMO’s are a sign of high overall temperatures. For example in 1998 the highest AMO of 0.402 was recorded. This coincided with the warmest year ever recorded globally. Within the years 1995-2008, this value remained fairly positive. This has not been the case though within the last 5 years. The values have declined and gone almost negative, which has historically been a sign of cooler winters for the Northern Hemisphere. The problem is, is that the climatological models are very inaccurate in predicting the patterns within the AMO, so a correlation could be proven null.

The current pattern of the PDO

Current pattern for the AMO

Learn more about the AMO here 

Other oscillations that play a major role in winter forecasting are the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). The Arctic Oscillation is pattern of pressure shifting in the higher latitudes. The higher the pressure in the Arctic, or when the oscillation is in a negative phase. This also means that the mid-latitudes have lower overall pressure and they receive more cold, stormy weather than normal. In a positive phase this is reversed. Storms move into higher altitudes while warmer drier weather stays to the south. The record low or negative phase was observed in 2009, which coincided with heavy blizzards and snowfall. We are looking at another year with a negative phase Arctic Oscillation this winter. 

The NAO is also a shift in pressure. It is the going back and forth between the subtropical high and the polar low. Phases for the NAO tend to last several years. A positive phase means a stronger subtropical high and warmer, wetter winters for the Eastern US. A negative phase means a weak subtropical high and Icelandic low. This means there is a weaker pressure gradient and results in colder temperatures to settle into the Eastern US, making them more susceptible to snowstorms.

The NAO's positive and negative modes

There are also upper level wave patterns that have great influence over long-term weather forecasts for the Northern Hemisphere. These polar waves as they are called can be easily detected as they circumvent the upper latitudes.  Rossby waves as they are known in the field help move cold air equator-ward and warm air pole-ward in large wave-like patterns. What has been detected within these long waves that is noteworthy is the large meandering and looping patterns that they seem to be producing along with the slowing velocity which has caused droughts in the west, floods in Europe, and cold winters here in the Eastern US. They are said to have less zonal flow (west to east) and more meridonal (north to south) flow, which means more energy is being transferred and higher west to east temperature variations.

What are Rossby waves and how do they influence weather? Click here 

Sea Ice loss is a strong influence of upper level waves. During the summer with well above average temperatures globally warming Arctic Ocean waters disproportionally, there are increased amounts of sea ice melt. Now along with the positive feedback of the sea ice melt, with the now more exposed ocean waters, more and more solar energy is absorbed by the ocean. In a study done in 2012 by the American Meteorological Society, they studied whether or not a warming Arctic really meant harsher winters for the Eastern US. There may be more than just a subtle connection between higher energy storms in the mid-latitudes, which in the case for winter is regarding heavier snowfall events such as blizzards, and the increase of sea ice melt. This also means that there will be an increase in something known as Arctic Amplification, which can be best explained as the increase in amplitude of upper level atmospheric waves. This will cause larger troughs and ridges to propagate and sustain for large periods of times over one area as the air moves slower with higher amplitude. As we saw with last winter, extreme cold temperatures can be ‘blocked’ in for weeks at a time in a process known as Arctic Amplification. This winter could prove to be no different.

A visual look at Sea Ice Melt

What is Arctic Amplification? Find out here 

There are many other factors that could be game-changers this winter. The one's that I have listed above are just the main few that can be attributed to within a longer seasonal forecast. 

FORECAST GMU's Forecast

Here is our forecast for the winter for the DC region specifically:

Overall temperatures: slightly below the climatological average, but warmer than last year. With a stretch, most likely in the timeframe of middle of January-early February, there could produce some extremely cold temperatures. 

Snowstorms: 3-5 with no large one truly taking hold of the region, though an ice storm could prove just as dangerous. 

Total snowfall predictions: 18-24 inches regionally with variations higher to our west and lower to our east. 

How long will this winter be: This winter will also be much shorter than last winter with an early start to Spring beginning in March, there may be some cold spells after, but not consistent enough to cause any concern.

On a larger scale, I think this winter will be a bit different than last winter. To start I think that the Western US (especially California) will receive more rain this last year with a revitalized Pineapple Express pumping in warm moist air from the South and West due to an active El Nino. The jet stream dip and patterns could play a large role in how and when storms form and what path they will take.  Many have compared this winter to the winter of 2009-2010 and 1977/78 due to the presence of a weak El-Nino system. These years were highlighted by heavy snowstorms/blizzards and slightly below average temperatures. 

Of course, I have a firm belief that the climate system on the whole is merely impossible to accurately fit into a model and the models that we currently have running are just a best guess given the information that we have. Not to say that they are complete rubbish, but the amount of variables that go into one forecast is one thing. This does not account to all the variables that now being added to the equation due to human interaction with the atmosphere and ocean.

Also this article has a bunch of things I can imagine are unfamiliar with all of you. If you have a question about what things are or how they work on a simpler scale, please let me know. I have provided links after paragraphs to help explain topics that I covered within this article. Also I attached videos below attached which I have found to be great source points even for my own education within forecasting. 

How climate change and humans interact

A look inside a forecast (if you are interested, watch more of his videos)