Weather updates from site founder Brian Gaze that keep you in the know.
Posted 6th August, 10:04
Southern and central regions can expect a lot of very warm or hot weather in the coming days. In the north it is a more mixed and generally cooler outlook.
How hot could it get and will thundery downpours become an increasing risk?
The London GEFS 00z plot below shows good agreement between the individual runs until about August 14th. It suggests exceptionally warm temperatures at the 850hPa level. The combination of duration and intensity could be approaching record levels.
Will that upper level warmth translate to exceptional heat at the ground level? Various factors come into play. Examples are cloud cover, wind direction and the possibility of rain. At this time of years the days are beginning to shorten quite rapidly, but the temperature record set in 2003 at Brogdale was on August 10th. There is still time for records to tumble this summer!
The lower part of the plot shows the rain forecasts. It suggests a chance of rain (showers or thunderstorms quite possibly) between August 9th to 11th and from the 13th onwards. These forecasts have been moving about quite a lot in recent updates so I wouldn't focus too on the details too much. The key point is the potential for rain.
The plot below is also from today's GEFS 00z update and is for the London area. It shows the 2m temperature (those we experience at the surface) forecasts from all of the individual runs in the model. Generally the GEFS raw data underestimates by a couple of degree.
In the next few days maximum temperatures are around 32C. In reality I'm expecting 35C or even 36C locally from London to East Anglia and the south eastern corner. If I'm right values will be exceptionally hot but a new record is unlikely.
Now look at the second red arrow I've added to the plot. A close inspection shows the maximum temperature forecasts during this period - August 11th to 14th - are actually a little HIGHER. If that turns out to be the case we could get another chance at the UK temperature record even if it isn't set tomorrow or on Saturday.
Due to the shortening days it would be very difficult to imagine the UK temperature record falling during the second half of the month. Although at the moment virtually anything seems possible. 40C? Inevitable sooner or later I think.
Taking all of the above into account I'm not ruling out a new UK maximum temperature record being set in the next 10 days. I still think the most likely outcome is for the existing one, which was set in July 2019 at Cambridge Botanical Gardens, to remain.
A key factor could well be the extent of thundery conditions. The GFS / GEFS model has a tendency to over forecast the extent of precipitation and that could well turn out to be the case this time. In fact some of the other computer models are already showing the storms as being more hit and miss.
Finally, I haven't forgotten those of you in the northern half of the UK. Your weather will be much closer to par, although some warm days are probable.
Exceptional upper level warmth is forecast to remain over the UK for an extended period. At the surface hot days are expected in the southern half of the UK. There is also a growing risk of showers or thunderstorms as we head through next week. Temperatures tomorrow could reach 35C or 36C in the south and even 37C isn't out of the question. Saturday could see similar values to the south and east of London.
Marginally lower temperatures are possible early next week. However, the mercury could then rise again and it's not out of the question that the UK maximum temperature record could be challenged.
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