It's been a real scorcher of a week this week, and it's not going to to stop there with temperatures expected to rise to 32 or 33 Celsius today!
But will it last through the weekend or will it come crashing to an end? Laura Tobin has all the details in her blog...
The heat wave will come crashing to an end!
Dramatically! It's been quite a week of weather. We started with rain for northern areas and sunny spells elsewhere with temperatures rising day on day, thanks to a warm southerly flow developing bringing warm air up from Spain and France. Peaking at 29.4C on thursday at Hampton water works making it the warmest day of the year so far, which is sure to be smashed on Friday (a targeted AMBER is possible today.) As the heat and humidity build we'll all feel the need fora storm and they will arrive in dramatic style on Saturday with some spectacular light displays, however with dry ground and so much rain in a small space of time we could see flash flooding.
St Swithens day
Tuesday was St Swithens day and folk law says that the weather you have on St Swithens day we'll have for 40 days and 40 nights. While this has never been true, it's though that the position on the jet stream in mid July often remains unchanged through the rest of summer, so the thinking is this is an indication of what is to come.
Friday sees some of the hottest weather we have seen since August last year, with temperatures set to reach 32 or 33 Celsius, 90 Fahrenheit, in and around London. This is thanks to a plume of very warm air moving up from the near continent. However, the heat will also be accompanied with increased humidity so although many will enjoy the sunshine for some it will feel quite uncomfortable. In fact parts of the UK today will be hotter than the Mediterranean, the Caribbean and even Egypt!
On Saturday this hot and humid air will bring the risk of some severe thunderstorms - enough for a weather warning to be in place for much of the UK. We can expect torrential downpours in many places, frequent thunder and lightning, and some hail. It will stay hot and humid too, especially in the east of England. The first area of heavy thundery rain during the early hours of Saturday could give 50-75 mm in 3 hours, although most places will see much less. The showers then following have the potential for isolated 50 mm plus in an hour (!) with the most likely zone from the Southwest through Wales, the Midlands and into northern England. The detail will be difficult to pin down until almost the time of the event due to the nature of shower development.
That sort of rainfall is above the month's average for many places. England typically sees 62 mm in July, the Southeast only 52 mm.
Thankfully things should quieten down for Sunday with fresher conditions trying to spread in from the west. A scattering of showers is likely but not to the same extent as Saturday, and there will be some sunshine.
So where is all this heat, humidity and severe weather coming from? It’s all to do with a complex set of conditions which establish themselves across northwest Europe and is called a “Spanish Plume”. There are several ingredients which are needed for this to happen, chief among which are an area of high pressure to the southeast of the UK and low pressure to the northwest. With this pressure pattern in place, warm and humid air from the Spanish plateau flows northwards to the UK and meets colder air from the Atlantic. As these two types of air meet the warm air is forced to rise rapidly and give rise to severe thunderstorms.
The following week looks a little more typical for the time of year with a northwest-southeast split developing. Atlantic weather systems will move in from the northwest but weaken as they spread southeastwards, meaning that much of central, southern and eastern Britain should see the best of the dry weather. It will stay hot at times though, especially in the southeast, but generally not as humid.