Included is a basic overview of the medium-long term modelling, and a deeper analysis into climatic patterns afterwards.
The EC Weeklies have a -NAO block over Greenland, that is reacted to downstream by a trough over Europe, which should help snowfall and cold over the European continent. It should also help bring some cold for the UK from the Arctic. GEFS shows a similar look.
We see the pattern on EC become more zonal, but the trough is still over Europe, and the -NAO is intact. This should aid cold to continue over the continent, support snowfall in the Alps and Southern Europe, and possibly the UK. Extended GEFS is showing the low further out towards the UK at this stage.
We still see decent potential for the Southern Alps/Europe in terms of snowfall, but the pattern is shifting towards favouring the North. The pattern gets more zonal again and the trough shifts closer to the Atlantic, making it less fruitful for UK snowfall as it gets deeper into mid-Feb. Extended GEFS shows the trough weaker and further out into the Atlantic with a more zonal look.
So we have are at the peak of the actual Sudden Stratospheric Warming that has occurred in recent weeks, and we are now seeing the stratospheric polar vortex gain its strength again in the near future. GFS suggests in its long term prognosis in the last few days of Jan into the first week of Feb, that we may see this occur rather fast and in connection to a more positive AO for early Feb:
EC Weeklies (below) show us currently at the peak of the reversal of stratospheric zonal winds, and that we are going to climb rather fast over the next 10 days, that could hint at a more +AO pattern to follow in early Feb.
It means that after the next two weeks, snowfall prospects for the UK and for Southern Europe and the Alps are going to weaken. And eventually as we head into February, it would signal signs of a more zonal +NAO pattern in the Atlantic, that would bring mild conditions to the UK and Southern Europe, but more snowfall for the Northern Alps.
On the other hand, the NAO is forecasted by some long term model ensembles to remain negative as far as March:
So the NAO and AO is a little up in the air, but are possibly heading towards positive as early as the last few days of January, and probably in the first two weeks of February.
The MJO is currently in Phase 3, which when you add a 10 day lag corresponds to a more +NAO outlook (good for snow in the Northern Alps, not so much for Southern Alps/Europe and the UK). Possibly heading towards Phase 6/7 in the first week of February per the GFS projection below, which would correspond to a -NAO with the opposite effect.
The Pacific and global momentum, despite forecast +EAMTs underdelivered, leaving us with a mildly -AAM currently and a medium term period of us being in the Nina-esque base state.
Fortunately for Southern Alps/Europe snowfall and the UK, these GWO phases 1-3 are beneficial for a -NAO bringing cold air down to these places from the Arctic. But the phases 4-6 are correlated with the escalation of a more zonal +NAO pattern, and given the MJO forecast and observed positive frictional torques, it is possible that we see the GWO move into these phases less positive for Southern Europe/UK snowfall in early February. Or we may stay in the negative phases longer term.
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Disclaimer: There is lower skill asssociated with using long range model forecasts to find snow systems.
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