#Reigate anticyclonic gloom this weekend then hints of cooler

March 13, 2015 — 1 Comment

Pleasant mild sunshine of late looks to give way to some cool drab easterly winds this weekend as high pressure builds over Scandinavia.

Easterlies this time of year are less cold than in winter as the continent warms under stronger Spring sunshine.  In any case, the continent has had a relatively mild winter so there is not much deep icy cold in our continental source regions so we cannot expect much real cold in this easterly episode.  Cool, drab cloudy skies are most likely … called anticyclonic gloom.  This is built when a large scale temperature inversion occurs: a cold cloudy air mass near the surface stays cold while above the air warms in sunshine and prevents convection going higher.  Low level convection, unable to rise, creates low cloud that spreads out as a thick low blanket of stratocumulus often with occasional drizzle. Most unimpressive!

2015-03-12_22-42-21

Further ahead there are hints of a possible colder mid/late March as some models suggest northern blocking: the Greenland high joining in with increasing pressure over the Pole and lower pressure blocked to the south.  This situation can allow polar air to escape into mid-latitudes given the right pressure pattern.   A forecast Arctic Oscillation (below)  diving steeply negative is also an indication that this might be on the cards.  Similarly there is a negative tilting North Atlantic Oscillation too.  Both these show indications of going negative.  The Madden-Julian Oscillation (below) is an indicator of the activity and location of  cyclical tropical convective wave systems that travel east along the Equator.  Different phases of the MJO have been connected with influencing different global weather patterns – including tenuously with European/Atlantic weather. The MJO is moving into Phase 7 and this has been correlated with northern blocking and a negative NAO, at least 50% of the time anyway!

Some of the models are hinting at the idea of some colder weather this month, but it’s a way off so not certain, worth watching though as a possibility of winters last gasp might catch people out.

 

One response to #Reigate anticyclonic gloom this weekend then hints of cooler

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