PEORIA, Ill. — The 2019-2020 winter season got off to an early start with record-setting snowfalls at the end of October.
From October 30th through the 31st Peoria received 4.2″ of snow, about 18% of our average yearly snowfall, making it the snowiest October on record. Will the trend continue?
- The El Nino Southern Oscillation is in a Neutral Phase and is expected to remain neutral through Spring 2020.
- The end of November and December could be mild but the pattern should turn more volatile with wild temperature swings at the start of 2020.
- Below-average temperatures are favored across Central Illinois.
- Above-average precipitation is favored with near to above-average snowfall possible.
From seasonal model forecasts to regional folklore to secret methods, there are numerous ways people try to get a leg up on the upcoming winter season. When it comes to folklore, the Farmers Almanac has a list of things that point to a hard winter, many of which I’ve heard here in Central Illinois.
No matter what methods are used, seasonal forecasts are difficult and getting the forecast perfect is highly unlikely. That said, there are a few things we can look at that could at least shed some light on what’s to come. Forecasters often rely on current trends, various climate patterns known as teleconnections, and model data. One of the most well-known teleconnections is the El Nino Southern Oscillation.
What is the El Nino Southern Oscillation (ENSO)?
ENSO is one of the most important climate phenomena on Earth and has the ability to change and impact the weather across the globe. It’s often highlighted in seasonal forecasts such as this to help determine how the weather across the U.S. will be impacted. There are three phases to ENSO that are determined by monitoring sea surface temperatures and wind patterns over the Pacific Ocean.
The three phases are:
El Niño – This phase occurs when sea surface temperatures across the central and eastern Pacific are above average. This often results in less rainfall over Indonesia and increased rainfall across the central and eastern Pacific. Shifting winds near the equator will carry tropical moisture north into North America. This typically leads to cooler and wetter seasons across the southern U.S. while warmer and drier seasons occur across the northern U.S.
La Niña – This is the cooling phase of the El Niño Southern Oscillation. In this phase, sea surface temperatures across the central and eastern Pacific are below average and rainfall often increases across Indonesia. The sub-tropical jet stream weakens and polar jet becomes the main driving force for storms across the U.S. and results in dry and warm conditions across the southern U.S. while the northern part of the country sees cooler and wetter seasons.
Neutral – In this phase, sea surface temperatures across the central and eastern Pacific Ocean are near average. While the direct impacts of this phase are often minimal, warm and wet conditions typically prevail in the southeast U.S. while colder conditions linger across the northern U.S.
This winter, ENSO is in a neutral phase which means the impacts from the cycle are most likely going to be minimal across the U.S.
While the El Nino Southern Oscillation may have little to no impact on this upcoming winter season, the Pacific Ocean may still have some answers. Sea surface temperatures across northeastern portions of the Pacific Ocean and the Gulf of Alaska are well above average. This pocket of warm water has been dubbed “The Blob” by researchers and it could have some impact on the overall pattern across the U.S.
How can “The Blob” impact the weather?
It’s not clear what led to this anomalously warm water but the loss of Arctic Sea ice and variations in the Pacific Decadal Oscillation likely play a role. These warm waters often reinforce high pressure which sends the jet stream north over Alaska creating an upper-level ridge over the western U.S. This, in turn, creates a large scale trough east of the Rockies allowing cold air from Canada to be diverted southward.
The impacts from “The Blob” are more often felt west of the Rockies where temperatures will be above average due to an upper-level ridge. Further east the direct impacts are minimal, however, it can work in concert with the Arctic Oscillation to bring reinforcing shots of cold air to Central Illinois.
What is the Arctic Oscillation?
The Arctic Oscillation (AO) is a short term teleconnection that determines how much cold air will impact the eastern U.S. Unlike ENSO, the predictability of the Arctic Oscillation only extends a few weeks out.
The phase of the AO is characterized by the strength of the winds circulating counterclockwise around the north pole, a phenomenon known as the Polar Vortex.
When the AO is in a negative phase, the eastern U.S. can end up seeing significantly cooler temperatures. In Central Illinois, a negative phase of the AO often results in more frequent arctic air masses and increased storminess making for some rather uncomfortable stretches of winter weather.
A positive phase of the AO indicates stronger westerly winds around the Arctic which confines colder air masses to the Arctic Circle. When the AO is negative, westerly winds circulating around the North Pole become weaker and more distorted which then allows the colder air to penetrate southward into lower latitudes.
Other Things Taken into Account
Long-range forecast models can provide some insight as to what could be heading our way in the coming months. The models have been advertising a warmer than normal winter across Central Illinois though these models often seem to carry a bit of a warm bias.
When it comes to precipitation, the forecast are typically less skillful. However, they have been rather consistent in bringing above-average precipitation to the northern U.S.
We are also in the midst of a solar minimum which historically has led to colder winter across the northern U.S. and the Midwest.
My Bold Prediction
Despite the recent stretch of cold and snowy weather this Fall, I think we’ll see a large shift in the pattern towards the end of November that will leave Central Illinois with mild conditions through December. The pattern could then become more volatile at the start of the new year with sharp changes in temperature from week to week as numerous shots of cold air associated with Arctic outbreaks impact the region. While I don’t think it will stay cold all winter, I feel that the stretches of cold weather will outweigh the warm ones. Overall I feel temperatures will end up slightly below average through the cold season.
When it comes to rain and snow, I predict that Central Illinois will experience near to above-average precipitation. There’s no scientific way to predict snow this far out, so this part of the outlook is just a guess. Peoria’s average seasonal snowfall is about 24 inches. With the numerous rounds of cold weather at the start of 2020 and the above-average precipitation, I think the area will see above-average snowfall with Peoria seeing somewhere between 24 and 30 inches of snow.