UK and London Weather 30/07/2012 – 05/08/2012

UK Met Office Synoptic analysis for 00 UTC on the 2nd of August 2012

This week saw a change towards much more unsettled conditions, due to the retreat of prevailing high pressure conditions, allowing low pressure systems to push in from the north atlantic (see synoptic chart above). There were showers in London and much of the UK throughout the week between partly cloudy skies, with only southern coastal areas of England remaining relatively sunny.

Both Monday the 30th and Tuesday the 31st saw some overcast and rainy conditions in London. It became somewhat drier overnight on Tuesday, but the cloud and occasional rain continued on Wednesday, with temperatures in Greeater London dropping to around 13 degrees C.

Wednesday the 1st of August started out with bright and Sunny spells across much of the UK, including in London, but there was further clouding over and some heavy showers as a cold frontal system pushed in towards England from the west. Winds were quite breezey but during the sunny periods temperatures peaked to a warm 24 degrees C. This was followed by a largely dry night in London with only some showers reaching into western England. Friday the 3rd had similar conditions – bright sunny spells in the morning followed by some intermittent heavy showers in the afternoon. This eventually peetered out to a dry night with temperatures dropping to 13 once again. Throughout the working week winds were light to breezey, predominantly from the southewest across London.

Some heavy rain showers were observed in London during the mornings of Saturday the 4th and Sunday the 5th, with winds from the SSW up to 20 kmph. This later cleared to dry but overcast conditions towards evening, with temperatures peaking at 20 and 22 degrees C on Saturday and Sunday respectively.

Given the unsettled conditions compared to the high pollution events forecast and observed during the hotter weather in the previous week, it was perhaps not surprising to see that the Met Office forecast uniformly low air quality pollution index levels this week, with no particular peaks being forecast, but we should wait and see what the chemistry observations were. Showers, which were common this past week, can be a particular limitation on dispersion of pollution, since they promote deposition of particulate matter and inhibit convective mixing through the boundary layer.

The forecast for the upoming week is looking even drearier. The skies will be largely overcast with rain showers building up to heavy rain on the Thursday, with further showers predicted through the weekend. Temperatures will be cooler too, likely not pushing past 17 degrees C after today. Winds are going to remain light and predominantly from the Southwest.

I’ll be taking a closer look at some of the lidar observations from the first week of the IOP (when a potential case study was identified) in an upcoming blog post in the next few days, so watch this space for further updates.

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