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 Monday 17th May until Wednesday 26th May
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.
Monday 17th May
Some slight model differences for next Monday. The EC has low pressure close to the Western Isles and low pressure dominating the weather across the UK. For us in the Western Isles we will stay fine and dry apart from the odd scattered shower. Feeling on the cool side. Now the GFS suggests that low pressure is also close by to the Western Isles but this would be weaker and less in the way of rain. For us in the Western Isles it suggests a fine and dry day with sunshine and cloud with light winds.
Tuesday 18th May
Some good model agreement for next Tuesday. The EC sets up a cold airflow across the UK. We are going to see rain and showers moving down across the Western Isles. Brisk winds with some sunny spells. Now the GFS also sets up a cold airflow moving down across the Western Isles but it expected to be fine and dry with sunshine and cloud. Before rain moving in later in the day. Feeling cold.
Wednesday 19th May
Again some model agreement. The EC still the cold airflow across the Western Isles with rain and showers moving down from the North. Some decent spells of sunshine before high pressure builds across the North West later in the day with sunshine. The GFS also has the colder air flow coming down from the North with plenty of sunshine and a few scattered showers but mainly dry.
Thursday 20th May
Model differences for next Thursday. The EC moves in an area of low pressure across the UK. This would bring blustery winds and spells of rain which will be heavy at times across the Western isles with some sunny spells. The GFS on the other hand brings spells of rain across the UK. For us in the Western Isles we should see fine and dry conditions with some sunshine and cloud.
Friday 21st May
Again more model differences for next Friday. The EC keeps low pressure across the UK with spells of rain and showers for the Western Isles with brisk winds. These showers would be heavy at times. The GFS keeps a colder airflow across the UK. For us in the Western isles we should see mainly fine and dry conditions with sunshine and cloud. A few scattered showers.
Saturday 22nd May
Again model differences for next Saturday. The EC has rain and showers across the UK. These across the Western Isles will be heavy at times with blustery winds and spells of sunshine. The GFS has a slack airflow across the UK with sunshine and cloud and a few scattered showers across the Western Isles. Winds will be lighter according to the GFS.
23rd, 24th, 25th and 26th May
Now this is the really long range. So take it with a large amount of salt and is the silly range. So with the GFS for the final four days of this period that further areas of low pressure systems will move across the Western Isles and this would bring further rain and blustery winds.
The featured photo is Eoligarry taken by Frances Buchanan