Winter is now around the corner and while most people consider the winter months as being December, January and February, it is important to note that November is considered as winter in Bjorli - as is March. For the purposes of this post, winter will refer to the period December - February.
Perhaps some of you have heard about El Niño and La Niña and if so, you may know that the coming winter could be influenced by a strong El Niño.
Every two to seven years, the equatorial Pacific Ocean gets up to 3°C warmer (what we know as an El Niño event) or colder (La Niña) than usual, triggering a cascade of effects felt around the world. This cycle is called the El Niño Southern Oscillation (ENSO) because every El Niño is naturally followed by a La Niña and vice versa, with some months of neutral conditions in between events.
El Niño is a regular and large-scale climate phenomenon that occurs when the sea temperatures near the equator of the central and eastern Pacific Ocean are above average for months at a time. The change in water temperatures reshapes the jet stream and this in turn alters the global weather patterns - of which Europe is affected.
El Niño was declared in July and has strengthened through this autumn. It's expected to strengthen further as we head into winter.
In the main, El Niño winters are said to bring drier and colder winters to the far N of Europe (especially during the second half of winter) while wetter and milder winters are more likely across central and southern parts of Europe. However, it is important to note that this does not always transpire to be the case and the reasons for this are twofold. The first reason is because of other interacting factors and the second reason is because scientists still do not have a complete understanding of the complexities involved in this phenomenon.
So... what are some of the other factors which can impact seasonal weather? The Indian Ocean Dipole can affect weather patterns in the mid-latitudes and the Quasi-Biennial Oscillation (QBO) plays an important role in the seasonal weather patterns at higher latitudes. The QBO is essentially a measure of changing wind anomaly in the tropical Stratosphere and is known to influence the Polar Vortex.
There are numerous other variables in play and many of them are beyond my level of expertise but we do know that models cannot factor in all these variables and so this is worth bearing in mind.
The ECMWF October update shows a +NAO with stronger polar vortex and troughing at high latitudes with high pressure to the south - especially during December and January. This pattern brings cold and snowy weather to N Scandinavia while central areas of Norway can expect more variable temperatures with both mild and cold incursions. Drier and milder than average conditions would prevail over the UK and France.
For Bjorli, this will mean variable temperatures with heavy snowfalls through December and January.
With Low Pressure systems tracking over N Scandinavia, heavy snowfalls can be expected at times in Bjorli with winds often between the SW and NW. However, with High Pressure just to the south, it is also common for the High to exert its influence across mid-Norway from time to time which means plumes of mild air can also be expected as the air comes up from the SW over the top of the ridge. This type of set-up can also bring short periods of rain and sleet in-between any snow. February is predicted to show more troughing over the UK and so this will mean drier and colder weather for much of Norway with most of the snow falling in the S and E of the country owing to more of an E'ly component in the wind.
All models are quite in agreement regarding a westerly-based trough for December. However, this is where the alignment ends because each model shows different outcomes from January onwards.
ECMWF is similar to December with a mean trough to the west while GFS has a mean trough further to the north and the UKMET has it to the south over central Europe. For February, ECMWF has the mean trough over the UK while GFS shows the mean trough being between Iceland and Norway. UKMET shows the trough being over northern Scandinavia with a ridge over southern Europe. C3S has a trough signal close to the UK.
Conclusion
As you may have guessed, the conclusion is pretty inconclusive because there is very little consensus among the top models - with the exception of December. With a zonal pattern most likely for the start of winter, it is fair to say that temperatures will likely be over normal for large parts of N and W Europe with systems moving in from the Atlantic on a SW to NE trajectory. For Bjorli, this will mean periods of rain/sleet and snow. An unsettled and milder-than-average December will generally result in "decent enough" snow cover for Bjorli because there tends to be a net-gain in snow cover from the heavier snowfall which follows the shorter mild interludes.
January and February are obviously tough to call at this time. The UKMET is wanting to build pressure over Scandinavia which will mean very cold but drier weather for Bjorli during January whereas the other models want to keep things more unsettled. February is interesting in that both UKMET and GFS has the trough located to the N which will deliver heavy snowfalls over Bjorli, along with a colder weather pattern with winds between N and W.
Overall, winter 2023-24 is most likely to be milder than average across most of Europe.
Looking at the models and taking into account the ENSO, Sea Surface Temperatures and the NAO, I would be fairly confident in predicting a milder than average winter across most of Europe - including Scandinavia. However, the definition of mild varies from one country to the next and with this in mind, here is my subjective definition of "mild" in Bjorli: A temperature above -5c is relatively mild, close to freezing point is mild and extremely mild is if it were to go above 6-8c. If winter 2023-24 is to turn out milder and more unsettled than average, I wouldn't hesitate in betting on a very snowy winter in Bjorli...
In Bjorli, one thing is certain each winter and that's snow.
While the models may struggle in forming a winter prediction, there is always one thing which is certain. Whether the coming winter in Bjorli is cold, average or mild, Bjorli will always get its fair share of snow. This is a given and so if you are a fan of winter and snow, be rest assured that Bjorli will deliver... as it always does.
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