UK and London Weather 06/02/2012-12/02/2012

Temperatures have stayed low this past week, with an intense ridge of high pressure remaining of eastern Europe. On Monday the 6th there were widespread patches of snow on the ground, which were conducive to the formation of extensive fog across England. The west of the UK was a little warmer than the east thanks to the presence of a frontal system which brought heavier cloud. On this day London saw widepsread mist and low cloud, and outbreaks of wintry showers had left the urban surfaces icy in places with maximum temperatures around 3C. Monday night was also dry in London with further mist and fog, though some clear spells also crept in and temperatures dropped to -3C.

The Met Office UKV model outputs were predicting shallow boundary layers across the majority of the IOP sites on Tuesday the 7th – between 200 and 800m through the morning, and the sensibe heat fluxes were predicted to peak around 100-120W/m2 that afternoon, likely due to the clearing conditions that had been forecast. The high pressure ridge over Europe was still inhibiting the progress of Atlantic weather systems across the country, and it was in the morning that the wintry weather started to die down around North London, leaving only heavy cloud cover. Temperatures droped to bitterly cold that night, around -7C to -8C, leaving a harsh frost as well.

Temperatures were remaining low on Wednesday the 8th as well, with many places in the UK remaining only at or below freezing during the day and dropping to -4 in the evening with only light winds. As such the turbulence and surface radiation measurements from the BT tower were relatively steady throughout the day with only some variation.

London was still clear and cold with temperatures fluctuating between -1C and 1C under partly cloudy skies for much of Thursday the 9th. At 7pm there were snow flurries observed in the capital that lead to some light accumulations. The conditions for the snowfall can be seen in the figure of the  Met Office’s synoptic forecast below, where a very slow-moving warm front is progressing southeastwards.

By the 10th the synoptic situation affecting the UK had becomea little more active. The mild air that had been pushing in from the Altantic against the persistent blocking high was now affecting the Northern and Western UK, and between the two airmasses there had been outbreaks of sleet, snow and even freezing rain which causes numerous road accidents in Cumbria:

Meanwhile London was experiencing cold and icy but otherwise dry conditions with very little wind. This will likely have lead to another shallow, stable boundary layer with the potential for accumulating moderate-level concentrations of pollutants in the urban area. These cold and dry conditions remained in place across London into the 11th, where the maximum temperatures again barely rose above 1C. The winds remained quite light – even 190m up at the BT tower the observed winds only peaked at slighly above 14kmph, while at the surface they were variable at between 5 and 8 kmph.

Sunday the 12th saw the formation of mist and fog in London during the morning, with the visibility styaing hazy into the afternoon with some light rain being observed at 11.50. The observed relative humidity at the BT tower was in the 90%’s, with a negative sensible heat and a positive latent heat flux from the early morning to early afternoon, reflecting the misty conditions. Then temperatures began to rise under the cloudier conditions, to 3-4C. Although temperatures are now on the rise as of today, strengthening winds are still making it feel quite cool in London.

The Met Office 12 UTC Synoptic Chart for the 9th of February 2012


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