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 13th September to Saturday 18th September
So the EC has high pressure to the East of the UK on Monday and low pressure close to Ireland. Rain and showers are expected to move northwards into the Western Isles this result in some heavy rain at times. Winds will be mainly light. Into Tuesday the rain and showers stay close to the Western Isles but becoming drier later with a slack airflow across the UK. High pressure moves away to the East. For the Wednesday low pressure forms to the South East of the UK and a slack airflow across most of the UK. For us in the Western Isles the rain and showers will clear away. We are going to see a dry day with some sunshine and a brisk wind. Moving into the Thursday and an area of low pressure moves across the far North of Scotland bringing rain heavy at times across the Western Isles with brisk winds. A ridge of high pressure builds in behind it and a drier end to the day with some sunshine. For the Friday low pressure sits to our far North West and feeds in showers throughout the day. These will be heavy at times the showers will also be accompanied by brisk winds. Some sunshine in between the showers. Into the Saturday and the EC brings in yet another area of low pressure with further bands of rain which would be heavy at times along with brisk winds, possibly reaching gale force. The area of low pressure would stay to our far North West.
GFS –Monday 13th September to the Wednesday 22nd September
So the GFS keeps things fairly settled to start Monday with sunshine and cloud. A developing area of low pressure moves across Ireland and will introduce some rain across the Western Isles later in the day. For Tuesday across the UK low pressure dominates and will bring spells of rain heavy at times to the Western Isles. Despite this winds will remain fairly light. Wednesday will see a ridge of high pressure moving in. This will bring fine dry and settled day with sunshine and cloud along with light winds. Into Thursday the ridge of high pressure moves across the UK and as it does a band of rain heavy at times will move across the UK and this will bring heavy rain to us in the Western Isles along with brisk winds. Moving into Friday and Saturday and we will see a couple of sunshine and showers day. Some decent spells of sunshine at times. Winds will be light however they will become brisk later in the day on Saturday with a slight risk of them becoming gale force. The final 4 days of the time period with brisk winds and sunshine and cloud. Mainly dry but some showers moving in later in the day.
Thanks for reading any feedback is welcome, our featured photo is Vatersay by Floraidh Macleod