Long range weather forecast for the Western Isles – 26th November 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 Monday 30th November until Wednesday 9th 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.

Monday 30th November

Some model disagreements with Monday the EC gives us heavy rain and blustery winds across the Western Isles. High pressure still dominates across the UK. The GFS gives us some rain in the morning but then the rain clears away. It should be mainly dry once the rain clears away. It would be a fairly windy day as we are once again stuck between high pressure to the SW and low pressure to our North West.

Tuesday 1st December

Again differences for next Tuesday which highlights the uncertainties in the forecast even in the next 5 days. High pressure over the UK and strong blustery winds for the Western Isles which would gust 50 mph. The EC keeps us mainly dry with some patchy rain. The GFS brings some heavier rain across the Western Isles.

Wednesday 2nd December

Some model agreement with next Wednesday with both the GFS and the EC bringing an area of shallow low pressure close to the Western Isles. This would bring outbreaks of rain which will be heavy at times. Brisk winds once again but not quite as strong as on Tuesday. High pressure would decline back towards Europe.

Thursday 3rd December

Again some differences. The EC brings an area of low pressure to our South West and would bring spells of rain heavy at times. Snow over the higher ground of Scotland. Along with blustery winds. The GFS brings the area of low pressure much further South and high pressure developing over us in the Western Isles. Some morning rain clearing away to allow fine dry weather with breezy conditions.

Friday 4th December

Huge model differences with next Friday and this will no doubt change. The EC develops and extremely vigorous area of low pressure down to 951 mb. This would bring extremely strong winds for Wales, England and Ireland with winds rain and snow. It would be windy in the Western Isles with outbreaks of rain. This will probably change in the next model run. The GFS on the other hand high pressure over the Northern UK and settled conditions across the Western Isles. Low pressure not as strong as the EC over the South of the UK.

Saturday 5th December

Again model disagreement the EC keeps the deep area of low pressure across Ireland at 969 mb strong winds and heavy rain here. It would bring strong winds to the Western Isles. The GFS has high pressure in charge for most of the UK but rain moving into the Western Isles. So again lot of uncertainty.

6th, 7th, 8th and 9th December

Now this is the really long range. So take it with a large amount of salt and is the silly range. The GFS has high pressure in charge with brisk winds and mainly dry conditions for the first two days. The final two days the GFS brings rain across the Western Isles. Which would be heavy at times.

Thanks for reading any feedback is always welcomed.

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