Long range weather forecast for the Western Isles – 27th December 2020

Good afternoon and welcome to our long range forecast. This is posted either once or twice a week covering from 4 days ahead to 10 days ahead. In this update coving from Thursday 31st December until Saturday 9th January.

Please note there is not a lot of accuracy for this kind of time frame. Anything beyond 4/5 days out becomes really difficult and subject to change so we will be looking at trends. Mainly take with a large vat of salt. We will be using the main two computer models for this. The ECMWF which is based in Reading and the GFS which is the American based global model.

This comes from the GFS 06z run and ECMWF 00Z run. I will refer to EC to save on typing.

Thursday 31st December

So good model agreement for New Years Eve with a slack airflow across the islands. We are expected to see spells of rain and wintry showers. Winds coming in from the North and North West. Likely to be a cold day with frost and ice. Some of the showers could be squally in nature. Brisk winds.

Friday January 1st

Some model agreement for next Friday with high pressure building. The EC has high pressure building to our West. A cold airstream is still set up with some rain and wintry showers. But we would also see some sunshine. The GFS builds a high pressure system in over Scotland. But it also brings in low pressure down across the Western Isles. A shallow low pressure system this would bring spells of rain to the islands.

Saturday 2nd January

Model disagreements with next Saturday. The EC has High pressure system over the UK. Here in the Western isles we are in a slack airflow still with further spells of rain and wintry showers but plenty of dry conditions. The GFS has the high pressure declining to our North West. An area of low pressure moves down from the South. Not a deep area of low pressure but would bring blustery conditions and rain to the islands.

Sunday 3rd January

Some good model agreement about a week today with the EC bringing some morning spells of rain. Before becoming drier and brighter later with sunshine as high pressure dominates across the Western Isles. The GFS has the slow moving low pressure system mentioned above becoming stalled to the South of the Western isles. This would bring spells of rain to parts of the islands for a time before conditions become drier and brighter later.

Monday 4th January

As ever the further we go out the more the models diverge. The EC builds a firm ride of high pressure system across the Western Isles with spells of sunshine and lighter winds. The GFS strangely still has the area of low pressure mentioned above moving back across the Western Isles bringing rain and snow showers as it deepens slightly.

Tuesday 5th January

Again model differences. The EC declines the area of high pressure to the South West. A deep area of low pressure moves down from the North and it would bring heavy rain, snow at times and strong winds. The GFS brings low pressure over Ireland. We in the Western Isles would stay fine and dry but strong winds which would gust in excess of 50 mph.

6th, 7th, 8th and 9th January

Now this is the really long range. So take it with a large amount of salt and is the silly range. So with the GFS suggests we would see more traditional January weather with multiple areas of low pressure moving across the Islands with strong winds and rain. Worth keeping an eye on.

Thanks for reading any feedback is always welcomed.

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