Weather updates from site founder Brian Gaze that keep you in the know.
Posted 7th September, 09:06
The weather during the coming days will be mixed. Tomorrow temperatures rise and in southern and central regions 26C (78F) is a possibility locally. In the north and west it remains more unsettled with rain at times. There are signs of a change taking place this weekend and early next week with the chance of a very warm period.
This morning's GEFS 00z model update illustrates things well. The chart below shows forecast 850hPa (about 1500m above sea level) temperatures and precipitation for London.
In the short term 850hPa values are above the 30 year average but then they dip for a time. However, look what happens during the middle of the month. Most of the individual runs in the model show values rising markedly with a mean of close to 15C by the 14th September. That's close to 10C above the average for the time of year.
What does that mean for temperatures we experience down at the surface? The plot below shows the GEFS 00z forecast 2m temperature spread for London.
In the short term values rise to the mid 20Cs before dipping again later in the working week. However, by day 6 they start to rise significantly and a minority of the model runs show values approaching 30C (86F). Most look to peak at around 26C to 28C on day 7 which is next Monday.
The GEFS often undershoots 2m temperatures by a couple of Celsius so if it has a good handle on the general pattern we can't rule out 30C being hit again this year. It's definitely something to keep an eye on as we head through this week.
Technically it's not an Indian Summer because there hasn't been a widespread frost. Nonetheless, I'm not precious about the technicalities of the term and think it conveys a meaning of late season warmth to many people. In that case "Indian summer" it will be, should it happen.
The warmth looks like hanging around a while, although temperatures do show a decline after day 8. It's also worth noting the warm up looks less marked the further north and west you ahead. It fits in nicely with the pattern of high pressure becoming centred over continental Europe and a southerly air stream feeding up across the UK. Parts of the north west remain more prone to a cooler Atlantic influence.
Computer models are suggesting the possibility of it turning very warm by the end of this week. There is still time for things to change but currently it looks as though temperatures in the south may be hitting the upper 20Cs and even a sneaky 30C isn't out of the equation.
If you've packed away the barbecue it could be time to think about bringing it back for one last hurrah! The nights are rapidly pulling in but the warmth may not be done with us yet.
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