WINTER 2017-2018 REVIEW
Before we dive into this year’s winter forecast, let’s quickly review recent history here in the Youngstown area.
Snowier-than-average winters have been common in recent years, including the last 5 of the last 7:
5 of the last 7 winters have also been on the mild side:
The winter of 2017-2018 was an interesting one. The season got off to a fast start with a cold and, at times, snowy December and early January. February turned remarkably warm for the 2nd straight year. And once again we paid the price in March, which ended up colder than February.
The final numbers looked like this. Despite colder-than-average months of December and January, February’s warmth tipped the balance of meteorological winter toward the warm side. Plenty of snow in March (and April!) made the season appear pretty snowy (almost 20″ above average), even though the heart of winter wasn’t especially snowy at all.
HOW DO YOU MAKE A WINTER FORECAST?
Putting together a seasonal outlook, especially an outlook for winter, is much different than putting together a daily 7-day forecast. The standard forecast I work on every day is heavily reliant on analyzing the current weather and interpreting the output from a host of computer models. Long-range models are an ingredient in our winter forecast “cake” but the main ingredient (the “batter” if you will) is actually a process that involves looking at the PAST. We look for years that are an “analog” to this year; years that had similar conditions in the atmosphere and the oceans as this year. Then we take a look at what happened those winters…..how much snow? How were temperatures compared to average?
MOST IMPORTANT FACTORS FOR THE 2018-2019 WINTER FORECAST
I’m going to walk through some of the key factors this year. This is pretty science-y stuff but hey this is a science blog and it’s important to note that this isn’t “throwing darts at dartboard” stuff. The forecast is science-based and takes many, many hours of work to come up with.
1) It’s an El Nino winter, but not a “typical” El Nino winter
Arguably the most important driver of weather patterns across the northern hemisphere in the cold weather season is the ENSO, or El Nino-Southern Oscillation. When a pool of warmer-than-average water forms in the central and eastern Pacific, it’s El Nino. The opposite is La Nina. In a standard El Nino, the warmest water is banked up against South America. But sometimes, the warmest water is centered much farther west, in the central Pacific. The water near South America is sometimes even cooler-than-average. This is called a “Modoki” El Nino.
Why does all this matter? Well the oceans and the atmosphere are really joined at the hip. The oceans can influence the behavior of the atmosphere above. Warm (or cool) water in this important region can alter weather patterns over North America, especially in the winter. The strength of the El Nino/La Nina is also quite important. The stronger it is, the higher the correlation to the “flavor” of the winter here. We are expecting a weak to moderate El Nino this season. Notice the average of all these models is around a 1.0, near what is considered to be the border of weak/moderate.
2) The Quasi-Biennial Oscillation is making a u-turn
Say what? The “QBO” refers to a ribbon of air VERY high in the atmosphere, almost at the edge of outer space. When it’s blowing in one direction (easterly), it’s been shown to tickle the upper atmosphere in a way that increases the odds of a cold winter in the eastern United States. The opposite is true when it’s westerly.
Well the QBO is trending from VERY negative last winter, spring and summer to weakly positive this winter. Studies have shown that the transition from one phase to the other sometimes helps to provoke a dislodging of the polar vortex from over the North Pole to either Asia or North America. If it wobbles down into North America, surges of arctic air come south.
3) Very warm water in the northern Pacific
This winter we are likely to see a pool of warm water continuing to build in the northern Pacific, south of Alaska. Again…so? Well warm water in this location tends to favor a ridge of high pressure in the atmosphere over the west coast of Canada and the US. Just like waves on the ocean, every crest is accompanied by a downstream trough. And that trough often sets up over the Midwest and Northeast. This allows cold arctic and Canadian air to be pushed south.
This map shows the warm water in the El Nino region and the northern Pacific early in November:
4) The Sun is quiet. Very quiet….
What does that mean? Well we are in a “solar minimum” right now, which means there’s almost no sunspot activity. This occurs every roughly 9-10 years. Studies have shown that there is an atmospheric response to solar minimums and it can be easier for “blocking patterns” to form over Greenland and the northern Atlantic during solar minimums. These ridges of high pressure can aid in “locking in” cold air over eastern North America.
5) Autumn snow cover over Eurasia
Yet another thing that my raise some eyebrows. Who cares about the snow over Siberia in October? Well, studies have shown that a rapid increase in snow cover during October in parts of Europe and Asia can provoke at atmospheric response that leads to more blocking over the same area mentioned above. It’s effect on weather patterns is especially pronounced when the El Nino/Nina signal is neutral or weak.
This season’s snow cover got off to a slow start but increased rapidly late in October.
THIS SEASON’S ANALOGS
Ok, so all that being said, what years were most like this one? Well it was hard to find many exact matches. I looked for years that featured a weak to moderate Modoki El Nino with a QBO trending into the westerly phase (after being strongly easterly), with a solar minimum and with a warm blob over the northern Pacific. Really hard to find exact matches. But here’s the closest matches and the results in our area:
-More winters were cold than mild and there are a couple of very cold ones on there (1977-78 and 2002-03).
-5 out of the 7 years had above-average snow (average at the airport is about 62″).
-1994-95 was a very snow-less winter and is an outlier on the list.
Average together the years and the national map looks like this for temperatures:
Precipitation (all, not just snow):
You can see the active storm track that often results from this type of El Nino, which results in a wet winter across the southern tier of states and the East Coast. Drier conditions are favored in the Northwest and the Midwest.
So, based on the analog information shown above, computer model forecasts and my intuition/gut feeling…..here’s the forecast.
I do not expect December to be as cold as last year and the month will likely start out rather mild. Shots of colder air later in the month will probably balance out the warm start and lead to a near-average month overall.
This is the month I had the hardest time with. We will probably see a transition into a colder pattern in January and I have the month ending up as somewhat colder than average locally. Recent runs of the European seasonal model paint a warmer picture in January but I lean toward the colder analogs for now.
This is likely to be the month that packs the most punch. It will be the coldest month of the winter and a HUGE change from the last 2 years. There is strong agreement both on the models and in the analogs on this.
The forecast is for a colder-than-average winter and the coldest winter since 2014-2015. The forecast is highly dependent on February being a very cold month compared to average and January being colder than average. If January ends up warmer than expected, the overall forecast may be too cold.
I am expecting more snow in the “heart” of winter this year, rather than on the fringes (November, March, April). Lake-effect will, as usual, jack up the numbers in parts of Mercer and Trumbull counties. A bounty of East Coast storms, especially during the 2nd half of winter, may lead to higher numbers in our eastern viewing area. Overall the forecast is for a near to somewhat above-average year although somewhat less than last year.
THE BOTTOM LINE
I will have an update to the forecast in a little less than a month. Right now I would place my overall confidence in the forecast at a “medium”. I am bullish on February being a nasty month but am unsure how the mid-winter transition to that pattern plays out.