Long range weather forecast for the Western Isles – 6th 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 10th December until Saturday 19th December.

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 10th December

Some good model agreement about next Thursday. The EC brings rain across the Western Isles. Heavy at times with blustery winds. An area of low pressure to the North West of Scotland will bring further spells of heavy rain and winds later in the day. The GFS also bring further spells of rain which would be heavy at times but keeps the low pressure further out in the Atlantic which would mean the winds would not be as strong.

Friday 11th December

Some model differences for next friday with blustery winds and spells of rain heavy at times with a brisk airlow. The GFS brings the area of low pressure mentioned yesterday close into the Western isles and this would bring outbreaks of rain and strong winds across the islands which would gust to 50 mph. Before clearing away as the evening goes on.

Saturday 12th December

Some model agreements again about next Saturday with the EC having early rain but this clearing for a dry day with high pressure briefly building across the Western Isles before rain arrives later in the day. The same situation for the GFS with rain in the early morning a more fleeting ridge of high pressure but this moving as a new area of low pressure pushes across the Western Isles bringing strong winds and rain. Nothing to significant but a blustery evening.

Sunday 13th December

Good model agreement for next Sunday with low pressure sitting out in the Atlantic according to the EC this would bring heavy rain and brisk winds across the Western Isles. The GFS has an area of low pressure out in the Atlantic and this would bring heavy rain across the Western Isles. It also develops a secondary low pressure system which would bring in further spells of heavy rain and likely gales.

Monday 14th December

Again good model agreement between the EC and the GFS with spells of showery rain which would be heavy in places. It would be windy throughout the day as low pressure sits out in the Atlantic but no significant winds. A slack airflow across the rest of the UK and snow over the higher grounds of Scotland.

Tuesday 15th December

Some model disagreements for next Tuesday. The EC brings spells of rain heavy in places for the morning but clearing away as high pressure builds things in. The GFS keeps fairly strong winds across the Western Isles with spells of rain which would be heavy at times but finally clearing away later in the day.

16th,17th,18th and 19th December

Now this is the really long range. So take it with a large amount of salt and is the silly range.  The GFS settles things right down across the UK. High pressure firmly in charge with light winds and sunshine. It would be cold and frosty if this came off.

Thanks for reading any feedback is always welcomed.

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