Long range weather forecast for the Western Isles – 25th October 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 29th October until Saturday 7th November.

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 29th October

Some model disagreement for the forecast for Thursday and area of low pressure moves in from the South. The GFS is bring the low pressure system across Scotland with more in the way of rain for the Western Isles. This would result in blustery winds. The EC has a shallower and slower moving an area of low pressure stalling out West of Ireland and this would result in more fine dry and settled conditions for us. Some rain at times but mainly dry.

Friday 30th October

Good model agreement with Fridays forecast with blustery winds and rain. As low pressure systems feed up from the South. Heavy rain at times with winds gusting 30 to 40 mph. Heaviest of the rain for the Uists and Barra as high pressure builds to our South and allows low pressure systems and rain to feed in from the South East.

Saturday 31st October

Good model agreement of a wet start to the day on Saturday. High pressure builds in briefly. This will calm things down and bring lighter winds and dry conditions. Eyes turn to the West for later in the day. Low pressure out in the Atlantic. The EC has it to our West 947 mb and the GFS has it more to our South West and further out to sea.

Sunday 1st November

EC suggests the low pressure system mentioned above moves in and would bring us some heavy rain across the Western Isles for much of the day. Showery rain once the rain clears away and we would see strong winds as the low pressure system scoots past us. The GFS suggests a double whammy. The first area of low pressure our far west and associated fronts bringing strongs winds and rain. This clears away. Before the next area of low pressure system moves in bringing more in the way of wind and rain as we go overnight into Monday.

Monday 2nd November

Once again model differences with the EC suggesting a blustery Westerly and South Westerly airflow with rain and showers. These would be heavy and from this you would see some snow over higher ground on the mainland. The GFS indicates an area of low pressure deepening close to Ireland and we would see heavy rain and strengthening winds and as the area of low pressure deepened and moved Northwards.

Tuesday 3rd November

Again further model differences with the EC suggesting a showery airflow across the Western Isles. Heavy showers and blustery winds. The GFS continues with the above mentioned area of low pressure Sweeping past the Western Isles it would bring us heavy rain and strong winds.

4th, 5th, 6th and 7th November

Now this really the long range. So really is take it with a large amount of salt and is the silly range. At this long range the GFS a mixed pattern is highlighted with some further spells of rain but less frequent then in the previous time frames and there are some hints that high pressure may move in and settle things down for a time.

Thanks for reading any feedback is always welcomed.

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