December 2023 ended up being a mobile month with the jet stream for much of it south shifted, which made it more cyclonic than normal, and hence a rather windy month too with four named storms. The LWTLWT Lamb Weather Types are often used in UK-based analyses, with individual weather patterns based on the eight primary cardinal directions (N, NE, E, SE, S, SW, W, NW) plus cyclonic (C), anticyclonic (A) and unclassified (U) types. zonal index was negative for the first week or more, but went positive in a big way from the second week onward. Quite a few classic analyses from the UKMOUKMO The Meteorological Office is the United Kingdom's national weather service. It is an executive agency and trading fund of the Department for Business, Energy and Industrial Strategy during the month ranging from a plethora (thanks CK) of troughs on the 1st & 2nd to multiple occlusions on the 31st (thanks Mr Occlusion).
