The latest EC46 is out and it paints a rather settled picture across the UK for the next two weeks with high pressure close to the UK or over it.
To end December the EC46 has high pressure sitting to the West of the UK bringing a period of settled weather, we’d likely see colder air getting into the flow bringing some overnight fog and frost.
Week 3 sees largely the same pattern, high pressure sinks Southwards a little but generally things remain largely settled, perhaps a little less cold.
By week 4 high pressure has moved away and has been replaced by lower pressure to the East of the UK and higher pressure towards Greenland, this is suggestive of a colder North/North-Westerly flow across the UK.
So perhaps a sign of things becoming more blocked and colder as we move towards the middle of January, but there is a caveat with these models and that is developments in the Stratosphere above the Arctic.
The below three charts require some explanation…
This shows predicted temperatures in the Stratosphere, the circled line shows a sudden and rapid warming which is the likely Sudden Stratospheric Warming expected to occur at the end of the month.
The second chart is a cross section of the Atmosphere from the ECMWF model, the part of interest is the red blob in the bottom left showing the Stratospheric Warming.
The third chart is the GEFS ensembles for mean zonal winds. The top half of the chart indicates positive zonal winds, so the usual normal Westerly flow. The bottom half is a negative zonal flow, a reversal to Easterly winds and this is expected to occur in response to the Sudden Stratospheric Warming.
So whilst the EC46 can be used as a guide, it has to be used with caution because models are likely to be quite volatile until they can resolve what happens once the SSW has taken place.
Want more? Our Winter Model output discussion is now open.
We’ll have more for you on Friday 😉