Winter Forecast Headlines:
Overall over December, January and February the 3 months of meteorological winter, temperatures are forecast to be colder than average to 1991-2020 long-term average.
Drier than average winter, however, snowfall above average especially in southern UK. The risk of disruptive snowfall is higher this winter than perhaps we seen since 2012/13 winter, and potential the most significant cold patterns since 2018: Beast from the East.
Above average frequency of northerly and easterly winds: potential for severe cold coming from near continent. The mid-winter period could be particularly challenging. This will also put the grid under significant strain. An emergency footing might be necessary this winter given the already present difficulties securing energy, with French electricity imports weakened. As many nuclear plants are under maintenance. A cold and low wind scenario is the worst scenario and I have concern for this winter.
Continue reading for a more detailed breakdown and explanation of the factors involved which were used to construct this rather eyebrow-raising winter forecast. I will immediately add the caveat I am not a professional meteorologist, just a very big weather enthusiast who has built up his knowledge over years on the Internet. Therefore, forecasts from people like myself should be taken extra cautiously as I can afford to be bolder, I do not have clients like professional organisations such as Met Office.
ENSO (El Nino Southern Oscillation) and recent winters
This upcoming winter will be the third consecutive winter with La Nina conditions. Such long-duration events are extremely unusual; since 1950 there have only been two other incidences, the first in 1973-1975 and the most recent 1998-2001.
This gives context to the unusualness of complex global weather patterns resulting from variations in ocean temperature in equatorial Pacific. La Nina is identified by a colder equatorial Pacific. Historically more colder winters have been seen during La Nina (cold ENSO), and there does seem to be a greater tendency for cold spells earlier in winter with more blocked patterns. Than warm equivalent, El Nino, indeed 2016 was Earth's hottest year on record in midst of a strong warm ENSO event. Weaker Nina events have the most striking correlation with colder winters in northwest Europe including UK.
If we remind ourselves winter 2020/21 was a quite seasonal winter the January was coldest January since 2010, and early February brought a spell of very cold easterly winds even in London daytime temps were subzero, but, away from coasts of East Anglia and Kent snowfall was not widespread or significant. It was a winter where the wind direction aligned to deliver cold to very cold weather, however, what was noteworthy during this winter was lack of deep cold air. Particular frustration for example was from rainy January easterly. This led to many blaming climate warming on lack of deliverance it was a likely handicap.
Winter 2021/22 on the other hand had very little in way of cold weather, indeed for many late November brought only wintry weather that winter. The winter was milder than average, despite other promising background signals this was entirely drowned out by a very strong stratospheric polar vortex. This is a spiny low-pressure intense area of upper westerlies which typically sits in the Arctic, normally a strong stratospheric vortex has a strong influence on the troposphere lower area of the atmosphere, where weather happens, for example, reinvigorating the jet stream. This often results in stormy and mild weather in NW Europe the last winter suffered greatly from an enormously strong polar vortex much stronger than normal. It is really quite unlikely we see a repeat of that this winter.
Moving back to state of ENSO this winter La Nina conditions are expected to persist throughout the winter but then transition to neutral-ENSO in spring 2023.
The cold SST (sea surface temperature) anomalies are greatest in the east of basin. There are different types of La Nina events, sometimes it is basin-wide Central Pacific (CP) La Nina where cold ocean temperatures are equally distributed. In this upcoming winter, we are seeing an Eastern Pacific (EP) La Nina. This can give different responses to the tropical atmosphere, what happens in the tropics, does not stay in tropics! Studies have shown EP La Nina are most favourable to cold winters in Europe compared to CP La Nina.
My takeaway from ENSO this winter and the type of La Nina is that it is really quite favourable for cold weather patterns in Europe.
Historically it has served us well, a Nina which is declining in strength through the winter and is east based is an interesting trajectory. Which could mean unlike in the 2010 winter, which featured a strong La Nina event after experiencing coldest December since 1890 the winter really burnt out. Cold and blocked weather patterns are perhaps more likely to sustain in a weakening La Nina winter. Therefore, cold weather patterns which are expected this December are more likely to continue into January and beyond.
Sea surface temperatures (SST)
Sea temps surrounding NW Europe and UK to north and east are noticeably warmer than average, by as much as 2C in the southern North Sea beside SE England. Immediately this is not a positive factor as east and north winds are likely to be more moderated and hence brings a higher risk of temperatures insufficient for snowfall. However, if a very cold polar continental air mass was to travel over these relatively warm seas, the snowfall rates could be quite something to behold in eastern England and Scotland.
Looking at the wider North Atlantic there is quite a dipole frequent cold westerly winds from Canada has resulted in significant cooling in mid Atlantic a significant change from a month ago when the map was entirely red. Therefore, westerly winds potentially quite a cool direction which is a change from earlier thinking.
Northern Hemisphere snow cover
Snow extent in the Northern Hemisphere at end of November is very high at about 41 million square kilometres according to NOAA the highest in decades. Russia is entirely blanketed, snow is also covering nearly all of Alaska and Canada. Snow cover increases albedo of which freshly fallen snow can reflect 90% of incoming solar radiation back to space. This allows more heat to be lost, and thus it is colder than absent snow cover. Of course in last decade, we have all seen high snow extent also despite that winters have been mild in NW Europe. While there is no explicit signal to colder winters. In the event the weather patterns do align, for example, winds from Siberia a thick and widespread snow pack is likely to contribute to a colder easterly flow so it is undoubtedly positive to see for cold weather.
NAO (North Atlantic Oscillation)
If you have been watching my tweets lately you might have noticed how I keep yapping on about North Atlantic Oscillation. The NAO is a measure of the atmospheric pressure gradient between the Icelandic Low and the Azores high. The strength of NAO determines the strength of westerlies. A positive NAO is indicative of a stronger than average pressure difference between these two regions. As a result, this thermal gradient north and south creates a strong jet stream and greatly increases risk of milder winters in Europe. However, when in negative phase there is a weaker than average difference between Icelandic Low and Azores High. Consequently, colder winds from north and east are much more frequent as the North Atlantic is effectively blocked off with high pressure to north and west of UK.
An explanatory video on what is the NAO? Courtesy of UK Met Office
Predictability of winter NAO is limited typically only to 2 weeks out, but when NAO is particularly strong or negative often this can last for a prolonged time and really determine how the winter evolves... from an early juncture. Once in a strongly positive NAO phase a time of enhanced westerlies, it is very hard to break out from. Which is why I have been recently emphasising the significance of current forecasts and how rare they are in early winter. A significant -NAO is in forecast in early December this is very unusual indeed.
As previously stated the NAO in negative phase equates to weaker westerlies visiting the UK and northwest Europe and therefore the risk of cold spells is much higher. The more unsettled weather goes to the Mediterranean as the storm track is deflected to our south by high pressure areas in North Atlantic. What is interesting about previous Decembers which featured major blocking which this upcoming December is expected to have.
The majority of January days (62%) also featured -NAO giving a sense of long term control on upper air patterns. Thanks to Ben Noll.
December 2010 was an example of a very cold December with a very powerful -NAO the coldest December since 1890 in UK, but the rest of winter was unremarkable. In contrast to that winter I believe the mid-later winter period will harbour a less destructive environment in the breakdown of -NAO. We do not have a strong La Nina like in 2010 which increases risk of mobile, unsettled weather especially later in winter, indeed by the end of winter the forecasts show Nina conditions as looking weak. Which I have alluded in that it has highest correlation with colder winters in UK. My idea the strong -NAO in early December will serve a template for the rest of the winter, with greater confidence of colder and blocked patterns extending into January. Potentially this could all lead up to January seeing exceptional cold from north or east as the cold accumulates in the Northern Hemisphere at the coldest time of year. Much less confident on February but a blocked Arctic profile is likely to result in a much weaker than average stratospheric polar vortex. As such the chance of SSW (sudden stratospheric warming) is higher given that December is typically a time of rapid intensification.
Final thoughts on upcoming winter
A colder than average winter is favoured by me, potentially much colder than 1991-2020 normal, rainfall below average or near normal.
December is expected to be cold, likely coldest since 2010 - confidence is quite high. An increasing risk of snow near mid month onwards a white Xmas could be worth a flutter this year. It is possible the pattern could briefly relax and turn less cold before turning cold or very cold again late in the month.
January the coldest month of winter or featuring the coldest weather of winter, with highest risk of severe cold in UK/Europe. The cold could be quite extensive in mid lats of Northern Hemisphere something we have not seen in a number of years.
February significant uncertainty, it could be much milder a taste of spring or the cold could persist, a breakdown is likely to occur the transition period could bring snowfall.
So there is my winter forecast for 2022/23, I have not done a forecast like this before. It is worth noting cold and snowy winters are not normal in UK, and never have been really. The average number of cold winters is 1-2 per decade, the maritime climate of northwest Europe makes it very difficult on top of European warming trends.
There is potential this forecast could go spectacularly wrong. I'm sure many will be hoping I am wrong with cost of living backdrop; coming when it is least needed. In some way I am trusting the early December deep polar blocking to leave a scar and imprint on upper air patterns, there is a risk it could collapse swiftly but I am prepared to be brave. As I do not think the risk is insignificant, I think it is worth communicating.
What is noticeable already in Northern Hemisphere is a greater availability of intense cold air, and snow cover is well above average. The Siberian High is also very strong, a cold air factory. The macro situation seems quite dissimilar to what we have seen in last decade which has seen aggressive winter warming in Eurasia, with emergence of a powerful -NAO very soon. In my opinion it is most primed for a cold winter affecting UK since 2010 winter.
Thanks for reading.
Dan
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