Well well well.. after an extended period of boring and often dull weather since the middle of December under high pressure it looks like there might be light (and snow) at the end of the tunnel.
A major Sudden Stratospheric Warming has taken place and a further small warming over the coming days will only add to the disruption the polar vortex is likely to see in the coming weeks.
This warming high up in the Stratosphere is predicted to “downwell” into the Troposphere and when this happens we should see a switch up in our weather patterns. Easterly winds downwelling to the surface decrease the chances of a strong jet stream and increase the chances of blocking areas of high pressure.
The extended ECM pressure anomaly chart below shows a signal for high pressure to build Northwards in the Atlantic and across Greenland by around the 20th January whilst a deep trough develops across Scandinavia and Central Europe, this pattern is suggestive of much colder Northerly winds across North-West Europe and indeed the UK.
The GEFS mean tends to agree with the ECM on the colder weather front, below is the GEFS 850hPa Temperature chart showing cold weather across much of Northern Europe and the UK.
This is all likely a result of the Sudden Stratospheric Warming that is currently working it’s way down through the atmosphere and will eventually affect pressure patterns across the Northern Hemisphere.
The GFS 6z ensembles above show the trend towards colder weather in the extended. The further right you go the further into the future you go. The closer the lines are together the more confidence we can have in the forecast, while there is a fair amount of “ensemble spread” as would be expected at that range, the trend is clearly downwards as we go through the forecast period.
Uncertainty exactly how/when our weather will turn colder however confidence is growing for a change in our weather. Snow? With cold comes a possibility of snowfall but given the extended timeframes we’re talking about here, snowfall can’t yet be forecast.