Storm Update 31st - 2nd Jan
Unfortunately we now have growing confidence of a very unsettled pattern developing over the UK over the New Year Period, with the likelihood of two deep depressions crossing the UK. There are however still sig. mismatches between the Models handling of upstream upper troughs/ Jet Patterns emanating over the Davis Strait which will impact our weather over the period.

1) A deepening area of low pressure will cross Scotland during New Year Eve, Multi Hazard low with heavy snow developing over the North Of Scotland & Gales developing to the South, Gusts to 70mph possibly slightly higher over N Ireland, Southern & Central Scotland. Perhaps gusts to 80mph NW Ireland. Models are in fair to good agreement on this first low, though there is still some doubt over the exact depth of the low.

2) The 2nd low crossing the UK on NYD is still causing forecasting major headaches due to the lack of agreement on the shape & depth of the shortwave 300-700mb trough which is swinging SE from the Davis Strait which will pick up a wave depression in the mid Atlantic developing on the cold front as it tries to move SE. The ECMWF insists that this upper trough will be sharper than the flatter more E/W trough that the GFS suggests. Study of the GFS Ensembles suggest that the model has about the right depth, but slightly too far south. The ECMWF Control a tiny bit too far north. The 30 GFS Ensemble + the 51 memnber ECMWF ensemble suggest the Control is a little too far to the North.
The UKMET Global would seem to represent a good multi model and multi ensemble compromise on a track across Ireland, across the Northern Irish Sea towards the Borders as best track i could suggest at this time.

This will likely be a multi hazard storm event, with gales or Severe Gales likely to develop across the South with gusts likely to 85mph+ around coasts and hills in the West, 70-75mph over parts of Ireland, 65mph+ across many Southern parts of the UK., Heavy snow will develop to the North of the storm centre as it sweeps east with 30-40cm across Southern Scotland, Far North England, though again on track , slightly further south and the snow risk increases markedly for major population centers as shown by the 00Z GFS .

The ECMWF Precip Phase ensemble suggests a nearly 100% chance of rain falling from the Low across the Midlands, which strongly backs up my suggestion of a track further north as discussed.

A lot of uncertainty in the detail remains which i will keep on top of over the next couple of days as we get more data on the crucial upper trough coming SE across the Atlantic from the Davis Straight. However I can say with increasing confidence that the risk of a multi hazard storm or storms over the New Year is increasing and we should all be prepared for the potential for some significant disruptive weather across the UK.
EDIT - 06Z GFS coming in further north as i suggested with a track across Ireland, the Borders with a very deep solution of 960mbs with blizzards to the North and 80-90mph gusts (potentially more) around the coasts of West Wales, Irish Sea. (upper trough is correcting towards ECMWF solution)

Paul - 28th December 2024
(Diagrams in the replies below)

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