UK meteorology

Warning from Malcolm that the ECM is showing possible explosive cyclogenesis (at least 24mB drop for a low pressure in 24 hours):

According to the ecm there could be some quite strong winds across Wales and central southern Britain in the early hours of Sunday as the low deepens and moves into the North Sea gusting 50-55kts and a fair whack of rain.

It is also going in for some 'bombing'. A small wave depression is WNW of N. Ireland at T96 that tracks NE and NW as it rapidly deepens to be over Iceland 960mb at T120. the associated cold front with rain impacts Scotland, west Wales and Cornwall 0600 Tuesday having cleared N. Ireland with more strong winds, possible gale force

 
Today's post from Malcolm:
Today is pretty much of a mixed bag but essentially the main front and moderate rain is currently affecting south eastern regions but will clear during the morning to clearer colder conditions. But there is another band of patchy rain, sleet and possibly snow on the higher ground following on behind that will affect the SW, Wales, the Midlands and the north. Behind all of this squally wintry showers in N. Ireland, NW England and Scotland will be more widespread for a while and quite windy in places but later the showers will die out leaving a quiet night. Quite a cold day with a widespread frost overnight.





But as can be seen on the last fax the next set of fronts with cloud and rain are just about infringing on western Ireland by 00 and by 06 this has reached N. Ireland, NW England and Scotland where there may well be snow on the higher ground. But as can be seen a wave is forming on the front west of Ireland.



The fronts track south east across the country during saturday bringing rain to most parts accompanied by strong winds, possibly gale force in western areas whilst the wave deepens and tracks north east to be over N. Ireland 986mb by 1800.and then into the North Sea by 00 Sunday. If this turns out to be the precise track then perhaps blizzard conditions for a while in N. Scotland.



By 1200 Sunday the low is over south west Norway, having brought with it some very nasty conditions in the northern North Sea on it's travels, leaving the UK in a cold north westerly airstream with frequent wintry showers of just about everything in western and northern areas, This continues over the next 24 hours to 1200 Monday although the wind will gradually back westerly



As can be seen on the last chart there is a deep low 975mb south of Iceland with associated fronts trailing south west. The low deepens rapidly to be 955mb east of Iceland by 00 Tuesday with the front already impacting Scotland (where the precipitation could fall as snow) and N. Ireland and again bringing strong winds, possible gale force. But it's quite a complicated scenario with the colder air sweeping east behind the front which actually trails a long way south west along the interface between the colder air ( upper trough) and the high pressure to the south. And along this intyerface, as can be seen, lows are forming.



What happens next as the front tracks south east across the UK is not without interest but there we must leave it.


And the ecm charts for T24,48 7 72

Certainly not looking great tomorrow,

 
This evening's view:
After a quiet and cold night we arrive at this analysis at 06 tomorrow. A deep low Iceland with associated fronts already impacting western Scotland and Ireland with rain and a wave forming on further fronts west of southern Ireland.



During the next 12 hours the fronts and rain, heavy at times, track south east across the UK accompanied by strong winds in the west, perhaps reaching gale force whilst the wave becomes more organized and nips NE to be over N. Ireland 992mb at 1800.



This will bring more heavy rain, and strong winds, as it tracks across in to the North Sea still deepening, and perhaps snow in the north, Leaving behind in it's wake frequent wintry showers as the cold Pm air, that can be readily seen on the earlier chart, encroaches.

 
Today's post:
The band of rain (perhaps some snow on high ground in the north) associated with the frontal system expected today is currently lying south west Scotland, N. Ireland, NW England, Wales and the south west whilst there is a widespread frost to the east. And the wave expected later is currently getting organized away the south west. During the day the band of patchy rain will move SE with clearer weather behind but by 1600 the wave has arrived over N. Ireland bringing more heavy rain in the north and snow on the higher ground in Scotland and the north of England



The wave continues to deepen as it tracks into the North sea whilst the front tracks SE bringing more patchy rain in England and Wales. The rain more persistent in the north and much of it could be of snow over the higher ground in Scotland and the north of England and accompanied by high winds, perhaps gale force, across N. Wales and the central belt of England. Once the low has moved further east the UK will be in cold north westerly airstream with frequent wintry showers of just about everything concentrated in Scotland and western coastal areas.



The showery and cold north westerly continues overnight but by 1200 Monday the wind has backed westerly as a front associated with another deep low is approaching from the west Over the next 12 hours the low deepens to 960mb and tracks north over Iceland at Tuesday 00 whilst the front brings rain, snow in the north, and strong winds to the UK



The front clears by 1200 on Tuesday but during it's travels it develops a wave which impacts the north and could well bring a fair amount of snow to Scotland and the north of England, particularly on the high ground.



Stepping back a little now to get a quick overview, there is a complex cold upper trough dominating the Atlantic with a strong thermal gradient and thus an ideal breeding ground for some very active cyclogenesis and this is what we get. At Wednesday 00 there is a very deep low in mid Atlantic with the warm front SW Ireland to Cornwall.



Twelve hours later the low has deepened to 947mb south of Iceland and the front has brought rain, snow in the north, and gales to the UK




Some spot charts from the ecm essentially in support of the above post



 
He has since posted this, discussing the rest of today using up-to-date output charts and the latest FAX:
An update on today. Quite heavy rain later with snow in Scotland and high ground in the north of England and strong winds across Wales and the southern half of England.



And need to keep a storm watch, and possible snow watch, next week as the Atlantic depressions gear up



The westerly influence is reflected in the precipitation distribution

 
With Malcolm, we get post on a Sunday:p:
Today and tonight

The low and fronts associated with yesterdays bad weather have scooted away east leaving the UK in a a strong, unstable, north westerly airstream. This will mean frequent wintry showers of rain, sleet and in particular snow in N. Ireland and western Scotland. The showers will initially be confined to these areas plus Wales and the western coasts of England but increasingly further inland as the day progresses and the snow showers may well slip further south as well. Some reasonable accumulations could occur. There is always the chance of more persistent precipitation with the odd trough embedded in the flow. The showery activity will continue overnight, but perhaps more confined to northern areas with the wind backing a tad, but with ice an added danger Monday morning with a widespread frost. Feeling very cold in the strong wind





Monday another day of sunshine and showers, these confined to the west, but not feeling as cold as the wind abates. But by 12 a deep low 971mb is south of Iceland with associated fronts lying N/S west of Ireland and by Tuesday 00 they have tracked east to be over Ireland backing the surface wind over the UK to a strong south westerly accompanied by a band of rain. This is probably going to be another marginal affair with snow on the higher ground to the north.



The band of rain/sleet/snow clears to the east by 1800 Tuesday leaving the UK in a transitional weak ridge with showers in the west but there is an occlusion out at 20W associated with a deep depression 954mb south east of Greenland that is poised to move track east, which it duly does, and by 1800 Wednesday has brought more rain and strong winds to the UK. At the moment it would appear unlikely to bring snow apart from perhaps on high ground in Scotland.



Once cleared the UK is back in and unstable westerly with frequent wintry showers in the NW once more. The Atlantic is dominated by the cold upper trough but changes are afoot with the Bermuda high pressure beginning to amplify and surge north in the western Atlantic but there we must leave it. This is of course according to the gfs.



Having had a quick glance at the ecm for the purposes of this thread no significant difference to the gfs. I say no more.
 
Well, last night's winds were worse than the so-called/named storms we've had so far this year.
Naming criteria are complex, it isn't purely based on windspeed but also on calcilated impact. That said, there has already been a deep low this season so far that "bombed" over the UK but which wasn't named as the forecasts all indicated that it wouldn't deepen that rapidly until it was over the North Sea. Forecasting is incredibly difficult and there will always be mistakes as the complexity of the interactions between various drivers and influences over even 24 hours mean that, though the overall set up is fairly predictable, trying to determine whether something will happen over the UK or in the North Sea can come down to 20 miles either way, which to the layman seems quite a generous margin for error, but, with current data and computing power is a very narrow margin.
 
Met Office warning overnight covering Wales, SW England and the Midlands:
Between 17:00 Sun 11th and 10:00 Mon 12th
Icy patches are expected to form on untreated roads, pavements and cycle paths on Sunday night and Monday morning. This is likely to lead to some injuries from slips and falls.
Also, for tomorrow affecting N. Wales, N. Ireland, NW England and N. and W. Scotland:
Between 00:05 Sun 11th and 23:55 Sun 11th
Frequent, heavy hail and snow showers are expected through Sunday and will lead to snow accumulating on many surfaces. Longer journey times by road, bus and train services are likely while some vehicles could become stranded. Ice is likely to form on untreated pavements, cycle paths and roads leading to some injuries from slips and falls. Power cuts may occur and other services, such as mobile phones, may be affected.
 
Today's post from Malcolm on the Netweather forum:
Today will start with a reasonable severe frost in many places compounded by ice in many western and northern areas where snow showers have persisted overnight. These showers will continue during the morning in these areas, more particularly west Wales, N. Ireland, NW England and Scotland whilst most other areas will be quite sunny if a little cold. The showers will become less frequent later as the surface wind backs south westerly with arrival of the occlusion west of Ireland associated with a depression 972mb to the NW



By midnight the front is over Ireland with the triple point over Cork and the band of rain, sleet and snow will move steadily east overnight and through Tuesday. There could well be some significant snow falls in Scotland and perhaps the north, mainly on the higher ground but not exclusively, with some quite strong winds in the south. Clearer weather behind as the front clears to the east with some wintry showers mainly in the north west



But by 0600 on Wednesday there is a deep low 944mb SWS of Iceland with the associated fronts just to the west of the UK with the wind once again picking up from the south west. By midday the frontal systems are over the UK along with the associated precipitation.



The question is once again will the precipitation be of snow in places and the answer is probably some preceding the front in the north but in general the temps/dew points will be too high and rain will be the order of the day.



Once all of this has cleared to the east a strong westerly wind prevails with frequent wintry showers in western Scotland with cold Pm air dominating the Atlantic By Friday quieter weather will have arrived in the south as the westerly abates with the arrival of a little high cell

 
This morning's thoughts, including what would normallly have been yesterday evening's anomaly post (my notes in bold):
For one reason and another I couldn't do the usual medium term anomalies up date last evening so for the sake of conformity and because of the interesting times and recent major pattern changes just a quick run through this morning.

Everything is now more amplified and upstream still a Siberian vortex lobe (blue are top left in the Northern Hemisphere images below), strong Aleutian ridge into the Arctic (red/pink area between Alaska and eastern Russia, bottom left) and still an active Canadian vortex (blue lower section of the same two images) with a trough running SW through central canada to the SW United States and still with a strong westerly flow leaving NE North America. So far so good but not so downstream where there is disagreement as to the the orientation of the Atlantic trough/ridge duo (bottom right corner of the images, in mid-Atlantic) and consequently the trough to the east/south east as well. This will obviously impact on the det (deterministic) runs and the subsequent surface analysis so I'll just leave it here for the time as it will be updated today.



Back to the here and now.

The occlusion is currently over western parts (moderate rain here) and it and the developing wave will move east during the morning bringing with it strong winds, snow sleet and rain. Fairly significant snowfall in central and southern Scotland even at low levels and perhaps down to the north of England and higher ground further south but here it will essentially be rain. A case of radar watching. behind the front still windy in the north and wintry showers, particularly in the north west but everything will die down later with a quiet night ensuing with a widespread frost by morning.





so a quiet start to Wednesday but by 1200 the next frontal system has arrived over Ireland, SW Wales and Cornwall heralding very much a replay of today with strong winds and rain, sleet and snow tracking east The snow is again likely to be in the north and favouring the higher ground but as always this doesn't rule out some further south and again probably down to radar watching



The occlusion will have cleared the east coast by 00 Thursday leaving most of the UK in a fresh, west/south west airstream with frequent wintry showers, particularly in the north but the triple point is still over east Anglia so the rain will persist in the south east for a while



The westerly showery routine continues through Thursday and Friday but ridging in the Atlantic is becoming more influential



And by the weekend a more settled and drier regime is on the cards with temps around average albeit quite a diurnal variation.

 
Quick early evening update from Malcolm, with indications becoming more likely (though not yet certain) that the weekend will be dry and comparatively mild, at least away from the far north-west (though Johnny will no doubt be interested to hear that even his area should be dry on Saturday!:eek::cool::p:D)
Well get tomorrow out of the way and we might see a few days of drier, quieter and warmer weather (relatively speaking), excluding the north at first but then maybe everyone.

But first tomorrow. A fairly clear night tonight tonight for most places with frost in many areas but by 0600 cloud and rain associated with the next frontal system will already have reached N. Ireland, western Scotland, west Wales and Cornwall. The band of rain, heavy at times will track east during the day, perhaps some snow preceding it in the north leaving showers in it's wake predominately in the north west.



So by Thursday 1200 after the fronts are out of the way the UK is in a very breezy westerly and quite sunny but frequent wintry showers in the north west. But away to the south west the high pressure is shaking a tail and beginning to stretch north east and by 1200 Friday has become much more influential with drier and quieter weather in most places apart from remnants of a front affecting the NW of Scotland



Much the same on Saturday with max temps around 8C in many places (according to the gfs so pinch and salt applies) and Sunday in the southern half of the UK but windier with showers in the north courtesy of a weak front.

 
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