Clear signal on the GEFS for colder conditions later this month. A couple of caveats:
1) There are a number of big dippers on the plot but very few runs are staying in the trench for long. That suggests the probability of cold and mild air blocks being close to the UK without one firmly having the upper hand. Without looking at the details, it would typically mean that snow is more likely in the north.
2) The 30 year 850hPa mean ticks up during the middle of June. Someone posted a WZ link and it appears consistent with the TWO plots, so I don't think it is an artefact. The effect is to make the dip in 850s look a little more pronounced than it is.
Despite 1 & 2 the outlook in my view is interesting but I would urge a lot of caution at this stage.
https://www.theweatheroutlook.com/twoforecasts/ensemble-forecast.aspx?location=London
Originally Posted by: Brian Gaze