UK meteorology

Those midges might get a touch chilly over the weekend, Johnny!:D;)
Here's the 72 hour discussion from the usual member:
Today sees a complex area of low pressure cover the UK and eastern Atlantic with lows over Ireland and the North Sea and a front moving south over Scotland thus some rain and snow on the high ground whilst further south the odd heavy rain shower. Further to the west in the Atlantic the high pressure is ridging north, then north east,whilst a low forms between Greenland and Iceland.



By midday tomorrow the pattern change is well under way with the ridge progressing south towards Scotland thus also pushing the upper tough south into western Europe. This initiates a much colder north easterly surface wind over of the UK This process is facilitated by the aforementioned Greenland/Iceland low tracking east with the associated front marking the boundary between the much colder air to the north. Max temps 5-6C in England and Wales but 2-3C further north and quite breezy in the south.



Over the next 24 hours the high cell continues to slip south over Scotland but at the same time it's starting to adjust to a more NW/SE orientation. This process completely alters the airflow over the UK, cutting off the north easterly and initiating quite a strong easterly in the south which is being squeezed by the low pressure over Spain. Indeed the airmass in the far south of England could well be sourced in north Africa. As can also be seen the Iceland low is now tracking across Scandinavia taking the front and cold air boundary with it. Max temps on Sunday around the 4-6C apart from northern Scotland where they might struggle to get above 2C.



The coal face awaits but that's for another day



The ecm closely follows the gfs.
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Today's post:
Today sees the Atlantic ridge continue to expand north east between Iceland and Scotland whilst the upper trough deconstructs with the main area being forced south into France/Iberia. Thus on the surface a cold north easterly wind sets in behind an old occlusion which is slowly moving south. Ergo clear behind the front with some showers in the east but cloudy with patchy rain further south in the vicinity of the front.



By Sunday at 06 the high cell is over the north of the UK, and consequently there is quite severe frost, with temps down to minus 10C and more in places. But as the day progresses the ridge/high cell is coming under increasing pressure from upstream energy pushing east and by 00 Monday the upper trough to the north west, with a strong low level jet delineating the boundary between the cold/warm air, has forced a realignment of the high cell which is now NW>SE over the eastern North Sea and thus cutting off the north easterly surface wind. Albeit it does create a strong easterly in the south which id squeezed between the low pressure.



This in fact heralds the start of the battle between the high pressure, which now starts to get organized to the east and Atlantic lows and frontal systems driven by the aforementioned energy with the UK at the coal face. This is clearly illustrated through Monday



From this point, and after a quick glance at the T84 chart, one could be forgiven for thinking that the Atlantic breakthrough is inevitable but this is only partially correct and what happens is quite intriguing but outside of the remit of this thread.



This according to the gfs of course.
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Count of Undolpho said:
Ooh cha! Nesh this morning!
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It's cold here as well, Colum. I'm afraid my posts have been short of recent due to my anxiety being bad, but I'm still going to quoe the usual chap from Netweather at minimum. He hasn't posted much this morning, as another senior member, who was a Met Office forecaster, was describing the rather uninteresting set up for the next 2-3 days yesterday. What he did say was this:
As John mentioned yesterday not much new to report in this time frame but perhaps worth a quick mention of something we have seen a fair bit of this winter and that is rapid cyclogenesis.

Yesterday evening a wave formed away to the south west and over the next 24 hours it is set track rapidly north east along a baroclinic zone to be SSW of Iceland 967mb by 1800 tonight with the associated front orientated N/S at 20W.





This ultimately redirects the energy and pushes the aforementioned front east to traverse the UK

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Some practice readng charts (as always with the usual chap's posts, click on the charts to view):
Midnight Thursday with the upper ridge to the west disrupting the trough



Which 24 hours later pretty much leaves the UK and the area to the east becalmed as the next roughs and the energy and more troughs pile up in the Atlantic



By T102 a broad area of high pressure to the east with the upper trough over Ireland and a good illustration of the two energy flows

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Today's view, as drizzle and low cloud again conspire to make South Norfolk drab and grey yet again:

Today there is a slow moving front traversing the country as a small wave forms to the south west which tracks north east to be near Cornwall by 1800 before ducking south east into Biscay as the HP to the west ridges north east.



Over the next 24 hours or so (Friday 00) the ridge continues to move east over the UK as the cut off upper low is relegated to the Mediterranean and the next trough promulgated by the Canadian vortex arrives in mid Atlantic. The result of this is the UK is in a very slack pressure gradient over Thursday/Friday.



But there are some very powerful forces at play here with high pressure block to the east and the energy flowing east around the southern tip of Greenland so the Trough follows a familiar route and deconstructs with one segment tracking SSE just to the west of the UK. Thus the surface front stalls over Ireland and begins to lose it's identity by 00 Saturday and the UK slips into a light southerly flow. The light rain associated with the front will thus peter out.



The result of all of this is the UK is once again plunged into a col scenario between the two fores but there is only one winner here, Note where the colder air is.

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Further out from Netweather's chief forecaster:

Atlantic making inroads by Monday now into the reliable timeframe, so a spell of cold zonality next week likely. Although the N and NW of the UK favoured for snow, perhaps to lower elevations for Scotland and with elevation further south during the day, one or two secondary waves embedded in the NW flow could bring snow further south and perhaps transitory to lower levels.

Although last night's 18z and now 06z GFS op offers some eye candy synoptic-wise, I'm trying not to fall into the trap of having knee-jerk reactions to each 6 hourly update. There appears to be some discontinuity growing between EPS and GEFS with the northern and southern extent of the lobe of the tropospheric PV extending SE across Atlantic into Europe later next week onwards, and this seems to be tied in with the strength and expanse of the high latitude ridge modelled from Barents Sea across Svalbard and into Greenland. From the 00z day 10 ens below you can see the EPS mean further north with the trough than GEFS (which is stronger with the high latitude ridge too) :

EPS mean day 10

GEFS mean day 10

The 06z GFS op has the ideal combination of amplification developing from upstream over the Atlantic from days 8-9 which combines with the high lat ridge over Greenland/Svalbard to disrupt the Atlantic trough and push a cut-off low into Europe.

But until there's agreement between GFS and EC on how to evolve the placement and shape of the upper trough extending SE into Europe next week and also modelling any amplification working downstream over the Atlantic plus strength / effect of ridging over Svalbard, then I won't be jumping in bed with the better looking 18z and 06z GFS just yet.
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Just a warning regarding the west of the UK on Saturday - as a trailing cold front associated with an area of low pressure situated just south of Ireland moves in from the west, it is due to stall against the blocking high to our north-east (as shown in the Met Office FAX chart below), which could cause problems with prolonged rainfall:

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