Weather updates from site founder Brian Gaze that keep you in the know.
Summer has gone missing with unsettled and cool weather dominating through late June and the start of July. Will things change in the next few weeks? After all this is often the hottest time of the year.
During the next week or so it looks quite mixed. Showers or longer spells of rain are likely in all regions, but particularly the north. The UK remains under an Atlantic flow but at times ridges of high pressure build from the Azores to bring drier and warmer conditions to southern and central areas.
The ECM 00z chart below shows forecast 850hPa temperatures and mean surface level pressure for Saturday 11th July. Oranges and reds indicate a warm air mass at this time of year with greens and blues showing cooler upper level air. The UK is covered by green shading and it stretches down over much of France. The the heat is bottled up in the Mediterranean.
It's quite a common pattern but in recent years we have become accustomed to the west European heat dome pushing northwards out of southern Europe and into the UK. Even last summer brought several hot Spanish Plume (or blowtorch) periods despite being mixed overall. This June brought a similar, albeit short lived, spell of heat during the second half of the month. Therefore, we could see a repeat this year but at the moment things are looking more average and typical. Having said that there are signs of a change during the second half of the month.
The London GEFS 06z ensemble chart below shows forecast 850hPa temperatures and rainfall for the next 16 days. It now takes us past the halfway mark in the meteorological summer. Not sure if anyone else thinks the same but time is flying by even faster this year due to the lockdown and corona virus pandemic! Automated White Christmas updates are scheduled to start on TWO in less than 2 weeks.
I've annotated the plot to make things clearer (spot the typo if you can). The key points are:
1) Upper level air temperatures are forecast to be below the 30 year average for much of the period between now and July 15th
2) It's not looking particularly wet but there is a risk of rain at times and later on things become quite uncertain. Note: Comparable plots for locations farther north and west suggest more rain.
3) There is a weak signal for upper air temperatures to rise between July 15th and 19th. I'd like to see that repeated in subsequent updates before becoming confident about it materialising.
Therefore, there are tentative indications of it turning warmer after mid-month but it is far from certain. The other point is it may not be very settled. On the rainfall part of the plot I've put question marks from July 14th onwards because there are spikes appearing. We could find areas of low pressure approaching from the south or southwest with high pressure building to the north of the UK. That pattern would increase the potential for heavy showers and thunderstorms.
The next week or so look changeable. Next Wednesday or Thursday could see it warming up in the south but the general theme is a rather cool one. During the second half of the month there is a weak signal for it to warm up. However, it may not be particularly settled with a risk of low pressure areas bringing heavy showers or thunderstorms up from the south or southwest.
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