NW England and the Isle of Man are among the more exposed parts of the UK, being relatively close to the Atlantic and containing large upland areas. The strongest winds are associated with the passage of deep areas of low pressure close to or across the UK. The frequency and strength of these depressions is greatest in the winter half of the year, especially from December to February, and this is when mean speeds and gusts (short duration peak values) are strongest.
The variation in monthly mean speeds (average of a continuous record) and highest gusts ('instantaneous' speed averaged over about 3 seconds) at Ringway is shown below.
Another measure of wind exposure is the number of days when gale force is reached. If the wind reaches a mean speed of 34 knots or more over any ten consecutive minutes, then that day is classed as having a gale. Wind speed is sensitive to altitude and local topographic effects. Over the Isle of Man, the average is around 10-15 days of gale per year while on the mainland gales occur on 5-10 days along the coast but low-lying places inland experience less than 5 gales per year.
There have been several noteworthy gales affecting NW England, accompanied by property damage and disruption to travel and power supplies. Examples include 2 January 1976 when a depression moving eastwards across Scotland to the North Sea brought storm force winds with a gust of 79 knots at Fleetwood (Lancs), the 'Burns Day storm' of 25 January 1990 when gusts of 60-70 knots were recorded widely and 8 January 2005 when a deep depression resulted in a gust of 88 knots at St Bees Head, Cumbria.
The direction of the wind is defined as the direction from which the wind is blowing. As Atlantic depressions pass the UK the wind typically starts to blow from the south or south west, but later comes from the west or north-west as the depression moves away. The range of directions between south and north-west accounts for the majority of occasions and the strongest winds nearly always blow from this range of directions. Spring time tends to have a maximum frequency of winds from the north east, due to a build of high pressure over Scandinavia at this time of year. Summer can have a greater incidence of north-west or west winds associated with sea breezes.
The annual wind roses for Ringway and for Ronaldsway are typical of open, level locations across the region. There is a prevailing south-westerly wind direction through the year, but a high frequency of north to north-east winds in spring. Topography again plays a part in modifying the climate with channelling of winds between areas of high ground. For example, the Pennines and N Wales give a southerly bias to winds over Cheshire and Greater Manchester and the Eden valley gives a SE bias to winds at Carlisle. Easterly winds blowing across the Pennines can result in mountain wave effects when strong winds are brought down to low levels in the lee of upland; a well-known example is the 'Helm wind' associated with Cross Fell (893 metres) in the northern Pennines.
