UK set for a COLD rinse cycle next week!

January 23, 2014 — Leave a comment

(Got pics of “mini-tornado” damage?! Please post them on twitter or send them to me here for a post on the subject to be posted shortly, thanks.)

QUICK UPDATE Sunday: Reigate mixed cool wintry weather this week with always marginal conditions between sleet/snow but mostly rain midweek as the active LOW sinks south and fills and produces some interesting but uncertain possibilities for unstable bands of heavy rain circulating round the LOW in troughs as the week progresses. Convergence at times on the S coast could cause thunderstorms at times.  The coldest air overlying SE is due Sunday-Monday but, given the subtle nature of wind directions from the continent and the uncertainty of models as to how this scenario ends, anything could happen regarding next weekend… heavy Atlantic rain and then cooler could be possible. Watch UKMO warnings carefully for updates regarding Tuesday and Weds rain. 

Temperatures are set to dip next week below the balmy winter conditions we have been used to recently.  Below average temps will arrive for the first time this winter to Reigate.  It has been mild so far this January with CET temps over 6c average, courtesy of an extremely lively east-bound jetstream that has flooded (literally) the UK with mild and moist westerly winds from the Atlantic.  A cold plunge has been on the model-cards for a while but has come to nothing so far. However, a LOW pressure spinning up in the Atlantic on Friday is set to bring stormy conditions especially to the W and NW of the UK this weekend with fronts sweeping some significant rain right across the country, including SE and Reigate on Sunday.  It is the track of this LOW pressure that is likely to cause the dip in temps next week. Whilst significant snow is not likely for the SE it is possible that we might get some wintry mix of sleety/ snowy /rain precipitation on occasions through next week and, as Atlantic fronts possibly push in across the region at the end of the week / next weekend these might bring more significant snow on the leading edge of fronts, possibly for the end of Jan or start of Feb.  This is a way off so not certain at all but a possible interesting outcome to ponder that might bring at least fleetingly proper wintry weather to our winter-starved region.

The cold air is set to be dragged down across the UK as the LOW pressure over NW Scotland moves south and east across the country eventually sitting, cut-off, over the continent through next week.  A cut-off LOW is a cold low with plenty of cold air wrapped up in the circulation (called “cold uppers”: cold air throughout the depth of the atmosphere) that becomes cut-off from direct polar or tropical feeds of air.  It becomes a closed circulation with the cool air gradually sinking down to the surface, chilling things further.  Convective showers are also possible as these lows “warm through” from any surface heating.

When this “cut-off low” or cold pool settles over the near continent by early next week, the winds on the northern back edge of the LOW will pull in cool easterly and NE winds that could be cold enough to produce wintry precipitation on occasions, certainly to the North of the UK and maybe to the SE as well, but this is by no means certain for us and probably remains unlikely at the present time until maybe later in the week.  Whilst the source region for the wind is not as cold as 2013, the continent is nevertheless pretty chilly at this time of year so expect Tmax temps to crawl to just 5 or 6c in Reigate but not much higher.

So, we are set for a “cold rinse cycle” next week as this cut-off low circulates cold air over the SE with resulting change in wind direction from mild westerlies, through cool showery NW and, eventually easterlies with the potential for incursions of even colder air from the continent at times.  This is not a severe winter episode, merely a cool/cold snap with some wintry precipitation possible.

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