Analysis: Storm chaos was all down to deepening low pressure area in Atlantic

THE stormy conditions that have been battering Scotland have been caused by a deepening area of low pressure that moved in from the Atlantic over the previous 24 hours.

It has been travelling across Scotland through yesterday afternoon and last night.

Low pressure systems move across the Atlantic and deepen as they get towards land. This one has deepened very dramatically. In addition, there is high pressure to the south of Britain and low pressure to the north, leading to a very steep pressure gradient across the country.

Wind speed is determined by a number of factors, a key one of which is the pressure gradient. Wind flows from high to low pressure areas to balance out the difference. In basic terms, this means the greater the variation, the stronger the wind blows.

The whole of Scotland and northern England has been hit, with the strongest winds just to the south of central Scotland. The winds have been gusting at more than 80mph in Glasgow and Edinburgh, which is obviously where most people live, so it makes it very noticeable. If you went on to higher ground, it would be even windier, with gusts of well over 100mph being recorded. These are well in excess of gale force – they are storm force.

This type of weather is not common, but it tends to occur more in Scotland than in England. It probably happens once every couple of years, but the really stormy conditions are often restricted to areas where fewer people live, such as the Scottish Highlands. The impact of this storm has been particularly severe because some of the strongest winds have affected the big population centres and coincided with the early-evening rush hour. Schools closing and the level of disruption seen across Scotland is quite rare.

There is also the possibility of sleet and snow showers over the next 24 hours, which could add to the disruption. It’s very difficult to pinpoint exact locations for these because showery precipitation can fall in one place and bypass another completely.

It has to be said this was pretty well forecast by the computer models over the past few days. Hopefully this should mean people have had a chance to prepare. Lots of schools have closed and there will have been large amounts of travel disruption, which will be worse if its snows and turns icy. However, temperatures are not exceptional, and it is certainly a lot less cold than it was last December.

The peak of the storms should have happened through yesterday afternoon and overnight. Once we get through today and into the weekend, it should be a lot calmer. Until then, people should check the weather forecast before travelling, and be prepared.

• Brian Gaze is a weather forecaster and founder of the WeatherOutlook agency.