We are usually far from average when it comes to Missouri winters and end up with big fluctuations from year to year. In order to make a seasonal forecast, we look at weather pattern trends to give an idea where we will stand this year as compared to average.
Let's start with a familiar term used in most seasonal forecasts: El Nino Southern Oscillation.
This refers to the water temperature in the equatorial Pacific Ocean and the weather patterns that produces. If water temperatures are above average, an El Nino pattern develops, but if they are colder than normal, a La Nina weather pattern dominates.
Overall, the setup of this winter's weather pattern won't be influenced by either El Nino or La Nina. Instead, neutral conditions, which currently exist in the tropical Pacific, are forecast to continue into spring 2014.
Therefore, we will look at other factors that could drive our winter weather. Some researchers have found that the more ground covered by snow in northern Europe and Asia, the greater the chance of arctic air spilling into the United States.
This past fall, snow cover was running above average in Siberia, which could lead to colder temperatures for us this winter.
Although there are several weather pattern indices we use to make a seasonal forecast, the one to focus on here is the Arctic Oscillation. This is an index which refers to the pressure difference between the Arctic and the northern middle latitudes.
When the Arctic Oscillation is positive, cold air stays bottled up to the north and our temperatures are warmer. In a negative phase, colder air moves south, and our temperatures tend to be colder.
In the winter of 2009-2010, the Arctic Oscillation had a record negative phase and Mid-Missouri had the coldest winter in nine years. This winter, we expect a negative phase more often, resulting in occasional hits of arctic air, leading to the overall winter temperature coming in below average.
We expect the polar jet stream to dive south from Canada most of the winter, bringing frequent hits of arctic air to the Midwest. This will send quick-moving storms systems through, producing numerous small snowfalls this winter with at least a couple moderate snows.
We expect snowfall to come in slightly above average. Freezing rain will be a concern again this winter as we will be sometimes be caught between cold air to the north and warm, moist air to the south, giving us a chance of sleet or ice.
Comparing this year to previous years, we have had two very cold winters followed by two warmer winters. Our forecast puts us colder this winter with an average temperature of 31 degrees.
Snowfall amounts have been all over the place in the past few years, from 53 inches in 2010-2011, which is the second snowiest season since 1890, to only 6.6 inches the following year, which is the sixth least snowiest season since records began.
Last year, we ended up with 35 inches thanks to three late-season winter storms. This winter, we expect to fall between 19-23 inches for the season.
Here is a summary of the ABC 17 Stormtrack winter forecast for 2013-2014:
Temperatures will come in slightly below average for the winter as a whole, with
many hits of arctic air and brief mild spells. The new year will start off with a moderate snowfall, followed by bitter cold air, which will be felt much of the month.
Another decent snow will occur in the second or third week of February before warmer air returns by the end the month.
Several small snow events throughout the winter coupled with a few moderate snows will bring our winter total up to 19-23 inches. We'll also see a few small freezing rain events this winter.