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 – Monday 20th September to Saturday 25th September
The EC is suggesting for the Monday that high pressure dominates as low pressure moves past to the North West. For us in the Western Isles we will see brisk winds with sunshine and scattered showers. Winds gusting 20 to 40 mph.
Into Tuesday and the EC is showing a deep area of low pressure moving to our North West which would bring fairly strong winds to the Western isles gusting 40 to 50 mph. A dry start but a band of heavy rain would push in later in the day.
For Wednesday the EC is showing another day of brisk winds with rain and showers for the Western Isles as brisk airflow sets up across Scotland. Winds wouldn’t be as strong as on Tuesday but gusting 20 to 40 mph. Some sunny spells but a largely overcast day. High pressure sits across the South of the UK.
Thursday and the next area of low pressure comes rolling across Scotland. This would bring some heavy rain to the Western isles and strong winds. The strongest of the winds would remain slight further south according to this run of the computer model but we would still see winds gusting 40 to 50 mph. Rain and showers with sunny spells after the heaviest of the rain has cleared away.
Friday a long way off as yet but the area of low pressure mentioned above would bring further strong winds and showers as it cleared away into the North Sea. Behind it dragging down some cooler air from the North. A brief ridge of high pressure would build in to end the day introducing sunshine and cloud with lighter winds. However the next weather system lines up from the West….
Saturday now this is a long way off as yet but the EC has a deep an vigorous area of low pressure moving into Scotland which would bring heavy rain and gales if it where to happen. Like I said a long way off as yet and plenty of uncertainty. The previous model run has an area of low pressure moving over Scotland but less. It is 8 days out so very much a watch this space.
GFS – Monday September to the Wednesday 29th September
So the GFS for the Monday is suggesting that high pressure will dominate across most of the UK with sunshine and cloud for us in the Western Isles. Brisk winds with a few isolated showers.
Into the Tuesday and again high pressure dominates across the South East and brisk winds for the North West of the UK. For us in the Western isles once again it will be a day of sunshine and cloud with winds gusting 20 to 40 mph. Light rain and drizzle is expected later in the day.
Wednesday high pressure across the South of the UK and low pressure to the North of the UK. For us in the Western Isles we would see an overcast day with rain and showers. It also has the potential to be a windy day with winds gusting 40 to 50 mph. Possibly slightly stronger.
Thursday high pressure again from the South with low pressure moving down from the North this would bring brisk winds and showers to the Western Isles with winds gusting 20 to 40 mph.
Friday – A brisk airflow sets up across the UK on Friday we would see rain and showers across the Western isles which would be heavy at times. Some sunny spells. Winds gusting 20 to 40 mph and feeling cooler in the wind direction coming from the North West.
Saturday – A showery start to the day. Low pressure will slide down from the North past Norway bringing further rain and showers to the Western Isles. Some sunny spells in between. Winds would be brisk. Again not the deep area of low pressure that the EC is indicating.
The final 4 days of the time period and we are likely to see rain and showers heavy at times. Some sunny spells in between. A chance of a deeper area of low pressure moving in for the Wednesday bringing in heavy rain. But a long way off as yet.
Thanks for reading any feedback is welcome, our featured photo is Nicholas Leach of Barra lifeboat and the relief lifeboat.