Long range weather forecast for the Western Isles – 1st August 2021

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 covering from Thursday 5th August until Saturday 14th August.

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 ( European Centre for medium range weather forecasts) which is based in Reading and the GFS (Global forecasting system) 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 5th August

Some model differences for next Thursday. The EC has a shallow area of low pressure moving into the UK. We are likely to see some heavy and persistent rain moving into the Western Isles with the cloud dominating. Showers into the evening as the heaviest rain clearing away with some brisk winds. The GFS has low pressure broader and deeping running across Northern England and Southern Scotland. This would bring brisk winds and sunshine and showers for us in the Western Isles.

Friday 6th August

Some model differences again for next Friday. The EC has the above area of low pressure moving away before the next broad area of low pressure moves in from the South West of Ireland. For us in Western isles we would see a day of sunshine and showers along with lighter winds. The GFS on the other hand brings the low pressure pivoting across Northern Scotland bringing rain and showers to the Western Isles with brisk winds.

Saturday 7th August

Again model differences for next Saturday as the low pressure system on the EC moves across the whole of the UK expanding as it goes. This will bring rain and showers to the Western Isles but plenty of dry periods the cloud will dominate. Winds will be brisk. The GFS keeps the low pressure to our north bringing a day of sunshine and showers these will be heavy at times.

Sunday 8th August

Again not much model agreement for next Sunday. The EC brings the low pressure system across the centre of the UK with rain and showers these heavy at times with some sunny spells. Winds easing as the day goes on. The GFS builds in high pressure across the South East of the UK with a South Westerly wind for us in the Western Isles feeding in bands of rain and showers across the Western Isles which would be heavy at times with some decent dry spells in between.

Monday 9th August

A rinse and repeat for next Monday. The EC has low pressure to the North of the UK which will feed and rain and showers across the Western Isles with sunshine and drier conditions in between. Again the GFS has high pressure to the South East of the UK with a brisk South Westerly wind feeding bands of rain and showers across the Western Isles.

Tuesday 10th August

Big model differences for next Tuesday. The EC persists with low pressure close to Northern Scotland this would once again feed rain and showers across the islands. Along with brisk winds. The GFS on the other hand settles things right down with high pressure building across Scotland with a fine dry and sunny day with light winds.

11th, 12th, 13th and 14th August

Now this is the really long range. So take it with a large amount of salt and is the silly range. So the GFS is suggesting that high pressure will keep conditions fine dry and sunny with light winds before a band of rain moves in to the islands later on the 13th but weakening before high pressure builds back in once again later on the 14th.

Thanks for reading any feedback is welcome our feature photo comes from Achmore taken by Susanne Erbida

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