WAVE 3 News Winter Forecast 2021-2022
A look back at the 2020-2021 season...
Last winter was all about February. While we got a nice teaser to make for a borderline White Christmas, we didn’t see much wintry weather after that until February. It was near Valentine’s Day that we ramped up the cold attacks and added a southern storm track into the mix. We ended up with multiple systems over a 2 week period that brought freezing rain, sleet and snow. It was a messy period for travel as well with the lack of warm-ups during that time that kept the ice around. The winter chill lasted a while and even brought us an April snowfall which doesn’t happen too often. While the winter months’ snowfall (December-Februrary) was 17.5″, the April snowfall and a small dose in November of 2020 brought our snowfall total to 19.4″ for the entire 2020-2021 season. So overall the warm and cold balance was a bit colder that forecast. Snowfall was solidly above normal thanks to February and April. The normal snowfall for Louisville was 12.5″ until now. The climate records shift each decade so now the normal for temperatures and precipitation are based on events from 1991-2020. That has now shifted the normal snowfall for Louisville from 12.5″ to 13.4″.
FACTORS AT PLAY THIS SEASON:
This is the cooling of the Eastern Pacific Ocean. It is the opposite event of El Niño which is the warming of the ocean waters.
The typical pattern for La Niña favors more of a trough into the Central US with an active southern jet stream (your moisture provider) also in our area.
We have picked up some big snow events with these type of winters but it comes with a big risk. An increase in moisture means warm air is involved as well. We face usually one or the other but to get both to line up is gold if you love snow. The signal this winter is for a La Niña but unclear just how strong it will be as it will likely be weakening in terms of a significant winter factor by the time we get to the second half of winter. But it no doubt will be a player on the field for this season to monitor and will be given some weight to the overall outlook.
Arctic Sea Ice
This part has been interesting. We have been witnessing a dramatic decrease in the sea ice in the Arctic for the past decade especially. And that is significant to the winter climate trends, wildlife and shipping. However, this year, we actually have had an increase due to the lag in winter into spring and the constant jet stream blocking for colder attacks especially on the eastern side of the view in the graphic. That puts us very closer to what 2017 trends were.
If you were to just take this factor alone, it would indicate a later winter vs early. However, I think it will mean the opposite this year with more cold attacks in November and December compared to previous years. More on that down below.
There are several teleconnections we look at to help tell the storyline for about 2 weeks out. And these are fantastic indicators that certainly help when creating the 10 Day Outlook. Having said that, we do notice some elements taking place that give some signals that a teleconnection is likely to trend a certain way beyond the 2 week window. It is a risk element to a winter forecast as the skill level on that drops off quite a bit.
Given the blocking pattern that has been locked in for some time and is likely to persist, along with ridging over the Rockies that is going to really fight the jet stream this winter...a negative North Atlantic Oscillation looks highly probable. And for us, it means slower low pressures that move in from the south and could even get “cut-off” from the flow at times...lingering through our area. We have already witnessed that several times the past few weeks alone. The ridging over Greenland is a big player in that going negative and I am more confident on that section of the jet. Less confident for the jet around Alaska and Western Canada. That makes a different on whether you get the air flow from the Pacific (mild) or from the Arctic (cold). This factor is going to be a big element for the winter outlook trends.
No, not that Poehler Vortex.
This Polar Vortex...
This has always been around but gained much attention around 2013 with its major “disruption” that lead to severe cold in the Plains. It can be a complex factor to explain but I will try. This involves the stratosphere over the Arctic. The main thing we watch for this circulation is when it warms aloft, cold air is driven toward the surface and a disruption takes place. This can be a completely displacement into Asia or even North America. And sometimes it can split and be in both locations. Just like the NAO, it has its limits in long term forecasting and is limited to about a 30 day window. Anytime we see the stratospheric warming take place, it gets our attention. The cold air is on the move. But to where? That is where the NAO and jet stream setup comes into place. If the gates are open for our area, it will flow in. But sometimes the gates are closed and it misses us. It is a love/hate relationship as we get to get step 1 (the warming aloft) but still have to figure out step 2 (where it will go). For this winter, it is showing signs of warming already into November which would likely mean cold attacks for us as a negative NAO is looking liking. However, after November there are some hints the PV will return back home and recharge. So the December/January outlook for this risk is much more unclear.
WINTER FORECAST THEMES
Given the idea that there Polar Vortex will has some disruptions, NAO stands a good chance at going negative for significant periods of time and La Niña on the field, the Plains and Great Lakes stand the higher chances for going below normal with the temperatures overall for the season. Current thinking is while we could get off to a wintry start before winter officially begins, the jet stream is not always going to line up in our favor for cold/snow and could even mean a couple warm surges with severe t-storms. That should leave us fairly close to normal for the overall highs and lows for the season. Keep in mind, that doesn’t mean there won’t be some impressive cold, that part does looks higher than normal, it just means there will be a few warm periods that will help balance out the sheets in the end.
Potential for winter storms
This graphic is more just for fun. The pattern looks like it will be busy so that is the main driver for the data here and when you combine that with some decent cold attacks, it helps in looking at how active the winter storm portion will be. Of course the skill level in this type of forecast is poor. So again, just for fun. A “winter storm” for our area is a combination of significant ice/snow and/or 4″ or more of snow in 12 hours or 6″+ in 24 hours.
WINTER FORECAST 2021-2022
The list above is a look at the main players on the field for this winter. There are others that will be there but they don’t look to be big drivers at this time. The plan is to experience temperatures that will balance out close to normal or even slightly below. Snowfall looks to be above normal with the risk for slow-moving low pressures/storms and several southern tracking systems. Again, what is not listed here that is on the table will be a couple of severe t-storms events as the Polar Vortex is likely to settle back north and recharge. It looks to be an exciting winter with lots of changes that will be painful for snow-lovers at times. But it only takes one storm to bring smiles to those that love snow. And “blockbuster” snow events can happen with this pattern.
What is interesting about winter forecasting as we see the elements at play, but usually one ends up as the MVP when winter is over. We just have to figure out which one. So it is for that reason there will be TWO winter forecast updates this season. The next one will come out on Christmas Day! It will be a much more detailed look at the winter, week by week. It will be something new for our outlooks that should be exciting to track.
And just for fun, the team took a stab at the date of our first 1″ snowfall at Ali International (official reporting station)
What is your guess for the first 1″?? Let us know!
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And...BOTS! (Bring On The Snow)
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