As we are starting to transition into Autumn, those chionophiles among us can’t but help to think about the coming winter. For those of you that have met me in person and discussed my beliefs on the matter, will know I have a theory.
Based on nothing more than my own experience, it goes that our winters tend to fluctuate on a three or four year cycle. We will have a good year, as far as the snow conditions are concerned. Which will then diminish slightly each year for two or three years, until we have another good year. The worst year in the cycle preceding the best year. With the better years being after three preceding declining years.
I bring this up now as the forecast for this winter looks like it is supporting my theory. 2021 was the last good year, with the snow in January being some of the best for decades. Unfortunately not many of you could get out to enjoy it as we were all shut up at home. But don’t worry for those of us that were in the mountains we made the most of it on your behalf. Conditions were epic and with so few folk about we had days of riding certain areas just with our little crew. Was a definite silver lining to what was an otherwise a pretty cloudy time.
Some nice snowy pictures from January 2021
Not wanting to digress from the point, we have since then had three diminishing snow years, with last year being in some ways the worst for a long time. Don’t get me wrong we had good days, but below 15oo meters the snow never really arrived. So by my reckoning we are due for good season.
So as usual I have been trying to compile a load of information from numerous forecasts and put together my understanding of what the major weather systems will be doing and how that will affect us this winter.
So to quickly recap on the weather systems we need to be aware of up here in our part of the world.
The Jet Stream is the circulation of air that runs westerly around the top of the planet and has the most direct influence on the weather we experience in northern Europe. It can vary in form as it weakens and strengthens and gets pushed north and south.
Two of the major influences on the Jet Stream are the North Atlantic Oscillation (NAO) and the Polar Vortex. The Nao is the circulation of air between Iceland and the Azores and will vary its direction and strength depending on the difference in temperature between those two areas.
The Polar Vortex is a strong cold wind that circulates around the north pole (there’s one in the south too) up in the stratosphere. A strong or stable Polar Vortex keeps the Jet Stream stable and further north. A weak or disrupted Polar Vortex, weakens the Jet Stream and it becomes wavy and moves further south.
Knowing our local weather systems is one thing, working out what they are going to do in the future is another. To work that out we look at all the other systems in the global weather pattern and compare their trending habits to times in the past when things were the same as or close to what we have going on in the present.
Which is.
We are coming in to a new La Nina event. La Nina being the cold cycle of the El Nino Southern Oscillation (ENSO). Although it doesn’t often affect us directly up in Europe, as it’s main influence is in the Pacific region, it does influence some of the systems that do affect us.
La Nina is expected to develop in the Eastern Pacific, which is usually a clear signal for a negative NAO and a resultingly more southerly running Jet Stream. La Nina also give a higher chance (60-75% chance) of a stratospheric warming event. Stratospheric warming weakens the Polar Vortex and in some cases can cause a collapse (or reversing) of the PV, allowing cold polar air to flow further south as well as more low pressure events (or storms as we’d call them). Up in the Stratosphere we also have the Quasi-Biennial Oscillation (QBO), which circulates around the equator. The QBO shifts between an easterly or westerly direction very year and half or so. Again not necessarily a direct influence in its self but the QBO plays a big role in how other system indirectly influence or communicate with each other. The QBO is currently in a new westerly phase which in conjunction with LA Nina historically indicates a negative NAO.
Below is the influence on temperature and precipitation from a Negative NAO.
So we already have a bunch of indicators for a negative NAO and a weak PV, both resulting in a weak and wavy Jet Stream, more cold polar air moving south and more storms.
The last piece in the puzzle to mention this year is the Solar cycle. This is the 11 years cycling of the Suns magnetic field. This is supposedly quite easy to observe (if you have the right kit) in the number of sunspots visible on the surface of the sun. As the QBO is so high in the tropical atmosphere it is strongly influenced by the solar output, it’s amplitude cycling in turn with the sun. We are currently heading towards a solar maximum that is stronger than originally forecast, which previous studies have shown is all favourable for a disrupted Polar vortex.
The last couple of times this happened was early in 2018 and 2021. Both good snow years but especially in late Jan and early Feb .
Having said all that the weather is the weather and if one things seems truer every year it’s that its gets harder to predict and having just read back over previous years predictions I do tend towards the optimistic. Though this year I am genuinely excited about this outlook.
If you would like to have look for yourself I get my info from gavsweathervids.com, severe-weather.eu, metoffice.gov.uk and ecmwf.int
Some nice snowy pictures from January 2018
