A remarkable week of weather across the UK

  • Evolution of the temperature at Heathrow on the 1st of July (Green Line)

    Sunbathers enjoy the warm weather on the beach in Brighton, East Sussex. Credit: Lauren Hurley/PA Wire/Press Association Images

    Satellite imagery shows the active front with thundery rain on the 4th of July.

    Lightning strikes on the 4th of July in/around the UK on the 4th of July.

  • A remarkable week of weather across the UK
    04.07.2015 14:03

    Last week, the weather across the UK filled the headlines due to Wednesday's record breaking temperatures and huge thunderstorms that followed. Let’s summarise what happened day by day.

    Nothing really special on Monday in the UK but the heat was exceptional in Iberia. The scorching conditions in parts of Spain with near 44C in Jaen, Andalucia triggered a rare red warning for extreme temperatures by the Spanish Weather Service. The jet stream over the Atlantic started to push this very hot air mass northwards but instead of this, the air mass curved further east passing across France. This meant the air mass avoided the cooling effect of the Cantabrian sea and allowed the air mass to stay very hot in its journey towards the south of England. The highest temperature for the UK was 27C at Gravesend, Kent.

    Temperatures had a sudden rise across much of the UK, of more than 6C in places. The maximum temperature was recorded at St. Helier, Channel Islands with 33C and 31C at Northolt, London. Even northern areas of Scotland, such as Tain Range reached 25.7C and 26.6C at Lossiemouth. In addition to this heat, a very humid plume of air began to join the hot air mass. This was the fuel thunderstorms needed to break out.

    The hot temperatures on Wednesday meant the hashtag #hottestdayoftheyear was a trending topic on Twitter. Actually, not only was Wednesday the hottest day of year so far for the UK, but also some previous records were breached. At Heathrow airport, a scorching 36.7C was reached, overtaking the previous 36.5 °C on 19 July 2006 in Wisley, Surrey. Nine weather stations across Lancashire, Nottinghamshire, Cleveland, West and North Yorkshire, Cambridgeshire and Cumbria obtained new all time records. Scotland also reached their highest temperature of the year so far of 27.4C at Achnagart.

    Shortly after the highest temperatures were reached, some supercells broke out in northern England, bringing heavy downpours, frequent lighting, strong winds and large hail, for instance, at Swaledale, Yorkshire Dales. A supercell is a violent storm that develops when these several ideal factors converge: An unstable atmosphere, hot temperatures, plenty of moisture, an inversion at middle levels of the troposphere and wind shear.

    It was a much cooler day across the UK due to fresher westerly winds. The maximum temperature across the UK was 28C in Santon Dowham, Norfolk which was a decrease of about 10C in places compared with Wednesday. However, thundery showers moved eastwards, giving 18mm at Exeter, Devon

    Friday to Saturday
    It was generally a warmer day than Thursday and largely dry. Overnight, a massive area of instability with plenty of moisture triggered active thunderstorms and showers with heavy rain, hail and frequent lightning that pushed north across the UK. According to Meteogroup Lightning Tracker, in the 12 hrs up until 08:30 on Saturday morning there were around 50,000 lightning strikes recorded across or around the UK.

    The forecast next week
    On Monday, rain will clear from northern Scotland whilst cloud will thicken from the southwest of Britain, bringing heavy rain to north Wales, northern England and southern Scotland. However, the south-east of England and northern Scotland will stay dry with sunny spells. Temperatures in the mid twenties in the south-east of England.

    On Tuesday, much of the UK will be unsettled and breezy with showers or longer spells of rain with a risk of thunder. Highs of 25C are possible in East Anglia. Windy on Wednesday with cloudy skies and rain in the north. A cooler day across the UK with max temperatures of 20-22C.

    A warmer day on Thursday with temperatures possibly exceeding 25C in the London area and the south-east. However, there will be rain in northern Scotland but it will be dry and fine elsewhere. Warm and sunny for most on Friday but with rain in Northern Ireland. Current indications suggest a very warm day in the south of England.

    By: Mario Cuellar