Why so grey in Reigate? Anticyclonic gloom explained…

March 1, 2013 — Leave a comment

HIGH pressure means air sinks, warms up as it descends and dries out: this should mean less cloud… right? Unfortunately not always. Reigate has seen very little sunshine in the last few weeks despite a persistent HIGH pressure. Stratocumulus cloud and stratus cloud has hung low over the North Downs. This low cloud has been trapped by a temperature inversion at 1000m, where temperatures rise with height putting a “lid” on the weather. Any rising air will hit this inversion and convection will stop. Clouds forming beneath the inversion will simply spread out, join up and cover the sky: creating overcast dull gloomy conditions. Once the cloud forms it is difficult to shift because, whilst the sunshines above the cloud warming the air, the cold air persists below exacerbating the inversion. A stronger breeze or drier air or a shift in the position of the HIGH will release us from this weather underworld. The good news is the weekend looks brighter with winds less likely to be blowing from a cool, damp North Sea. Sunday looks the brightest with temperatures reaching 9 or 10C by the afternoon: almost spring like. The rest of the week from Wednesday will become more unsettled, feeling warmer but wetter as the HIGH at last moves away to the south east allowing Atlantic westerlies back for a breath of wet air!

To Spring… early forecast models suggest wetter conditions with slightly below average temps for the south of England with possible frequent easterly winds as LOWS track to the south; and drier, warmer and slightly above average conditions in the north of the country.  Essentially HIGH to the north and LOW / jet stream to the south of the country which will keep the south cooler and unsettled with the north enjoying better weather.  In short, more of what we had in late winter, just a warmer version?! Updates later.

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