Long range weather forecast for the Western Isles – 26th September 2021

Welcome to the our long range forecast for the Western Isles. This is our twice weekly update covering up to two ahead. We look at trends and patterns. Usually posted on a Thursday and Sunday.

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.

EC – Thursday 30th September – Tuesday 5th October

So the EC is suggesting that an area of low pressure system will bring heavy rain and brisk winds across Scotland and to us in the Western Isles. It would become drier and brighter to end the day. Onto the Friday the next area of low pressure will move into Ireland and then scoot up towards the Western isles this would not be a deep area of low pressure but would bring bands of rain which would be heavy at times. Along with brisk winds. For the Saturday and Sunday the low pressure system would be slow moving bringing bands of rain and showers across the Western Isles which would be heavy at times. Becoming drier and brighter for the Sunday evening. For the final two days of the time period the Monday and Tuesday two shallow areas of low pressure move across the UK for us in the Western Isles it should be mainly fine and dry with sunshine and cloud. Winds would be lighter.

GFS – Thursday 30th September – Saturday 9th October

The GFS is suggesting that low pressure will sit to the North West of the UK feeding in rain and showers for the Thursday across the showers will be heavy at times across the Western isles with some sunny spells and brisk winds. Into the Friday and little chang with low pressure still to the North West feeding in rain and showers along with brisk winds. For the Saturday a messy synoptic set up with multiple areas of low pressure close to the UK feeding in rain and showers. For us in the Western Isles we will see spells of heavy rain and blustery winds. Into the Sunday and conditions will be mainly fine and dry as the areas of low pressure clear away. Another small area of low pressure pops up later in the day which would bring rain and showers to the Western Isles. For the Monday and Tuesday low pressure moves to the North of Scotland bringing in colder air down from the North bringing rain and showers across the Western Isles. For the Wednesday, Thursday and Friday mainly light winds and mainly dry conditions with occasional showers. But an extremely deep and vigorous area low pressure moves in for the Sunday which would bring strong winds and rain but a very long way off as yet.

A lot of uncertainty with the long range forecasts due to activity in the tropics.

Thanks for reading any feedback is welcome, our featured photo comes from Loch Crabhadail taken by Rowanne Posy Griffiths

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