UK meteorology

Boab said:

Chris, where can I have a look at long range forecasts?

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A quick overview.

After the dismal (for many areas) period of low pressure influence a major pattern change is now under way. Over the limited period of this thread this essentially involves a blocking high to the east and trough dominated Atlantic boosted by a vortex fragment/lobe dropping south east from Canada to become a major feature in mid Atlantic and then the whole caboodle sustaining some amplification. As ever with this sort of scenarion the precise orientation of the major features are critical when it comes to detail.



Anyway enough waffle. Today at the start of the transition the UK finds itself in a weak ridge so a mainly fine day with sunny intervals and light winds and temps much warmer than of late. By late this evening a front and some rain will be approaching Cornwall.





By 1200 Sunday the depression associated with the above mentioned front is 983mb west of Ireland and the front and patchy rain is moving east across the UK. with temps in the freshening south westerly wind above average, particularly in the east and Scotland. At the same time the major upper low/lobe has made an entrance in the western Atlantic.



But by 1200 Monday the aforementioned amplification is under way with intensification of the Bermuda and European ridges which flank the now nearly stationary intense upper low in mid Atlantic. Similarly the large surface feature and so the front and patchy rain tend to fizzle out over the UK leaving north west Scotland in the firing line of the fresh south westerly and any rain, Temps still a little above average.



Tuesday sees the battle between the two forces west/east reach a peak as the European high intensifies further, the trough is forcibly restructured and the UK becomes the filling in the sandwich between the two as the south westerly wind freshens further. and again any frontal activity and rain is confined to the north west Temps still a little above average in the east.



Last evening's fax chart for 12 Tuesday but look away now if you are of a nervous disposition.



By 1200 wednesdat the high cell has become established over northern Germany, and with the trough to the west now neutrally orientated, is the major influence vis the UK weather so a dry and warm day (temps well above average) for all areas.

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chrisbell said:

Malcolm's post for 14th:

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The front and patchy rain associated with the depression south west of Ireland are currently over the south west of England and Wales. These will track north west during the day leaving brighter and showery conditions behind the front and quite windy in the west. Pleasantly warm in areas that escape the cloud and rain such as north east Scotland.







Some more organizes showery activity will track north overnight but by 1200 tomorrow it will have cleared as the low to the west has been absorbed by the large and deep low in mid Atlantic, all courtesy of the intense upper low that been discussed previously. All this leaves the UK with a mainly dry south westerly airstream with temps shading above average.



But fronts and rain associated with the low are tracking slowly north east and by 00 Tuesday are already impacting N. Ireland and Scotland and during the day the rain will slowly progress south east but tending to fizzle out as it hits the block of the Azores high pressure that has become more amplified and is ridging north east between the restructuring Atlantic trough and the low in the Mediterranean. All of which massively redirects the very strong jet. So essentially this boils down to some wet and windy weather in the northwest, drier and sunnier in the south east and this is reflected in the temps.

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So by midday Wednesday the burgeoning Azores has phased with the European ridge and established a high cell over Germany and realigned the upper trough in the west to neutral and in the resulting SSW flow initiated some quite intense WAA. Thus a warm day for the UK with plenty of sunshine





By 1200 Thursday it's all getting a bit messy with the block to the east intensifying, the trough to the west deconstructing with a very strong jet running around it and little lateral movement. Resulting in the UK once again being in a col, but on the plus side another sunny and very warm day.




The ecm not dissimilar to the GFS in this time frame with the middle and end of the week being very warm but the analysis is really quite fragile and with still, it would appear. a fair amount of energy upstream, the further evolution is a long way from being definitive

The EPS 6-10 mean anomaly may clarify my slightly vague comment,

Quite an intense vortex lobe N. Canada with associated trough orientated SE through Greenland and a ridge NE North America Thus two energy flows, one tracking south east passed southern Greenland and the other exiting the eastern seaboard resulting in a strong westerly upper flow across the Atlantic and over the UK with the block weakening to the east and which also tends to suppress any ridging from the Azores,

The detailed surface analysis by the det will sort the likely interaction between the trough and the high pressure to the south and systems tracking east

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Patchy rain in Scotland and the north of England will dissipate quickly this morning from the north west leaving the UK with a dry day with sunny periods and light winds Note at midnight the major Atlantic depression is down to 943mb.



But by 1800 the low and associated fronts have slowly moved east and rain and strengthening winds are into N. Ireland and western Scotland. During the night this rain, heavy at times, and strong winds will track south east to include northern England and Wales but during the morning it will tend to fizzle out at it reaches the Midlands. Thus the south and east will remain dry and relatively clear.







So by 1800 on Tuesday the Atlantic is dominated by a large and complex low pressure area coming up against a strengthening block to the E/SE as the Azores and European ridges amplify leaving the UK in a strong south westerly with temps above average.



Overnight Tuesday the high pressure to the east continues to intensify and become more influential over the UK as it forms a high cell over Germany and spreads west whilst at the same time putting the upper trough to the west under pressure and this becomes more neutrally tilted.Thus a warm, dry day with plenty of sunshine and temps way above average.

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A not dissimilar picture on Thursday but the High pressure to the east has become positively tilted and the trough to west has started to deconstruct under pressure from the twin upstream energy flows, in particular the strong jet leaving the south east seaboard. Thus the surface ridge over the UK comes under some pressure and resulting a freshening south westerly wind over north west Scotland But still dry and very warm day, even hot in the south east, with the temps way above average.





By 1200 Friday the energy continues to exert pressure and the trough duly deconstructs with a cut off low popping south east towards Marrakesh with the ridge over the UK now tenuously supported by the Azores ridging north east from a long way to the south west. This results in the UK remaining dry and sunny with light winds and with temps still way above average, hot in places,with the exception still being north west Scotland that remains in a fresh southwesterly and patchy rain.





Later on Friday perhaps a risk of some thundery activity drifting north from the continent. All of this is according to the GFS

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A quick look at last night's anomalies to try to see where we are going with this as a pattern change is in the offing after next weekend.

There are differences in detail, (see the GEFS and EPS vis the Greenland trough/European high pressure) .but they are in the same ball park. The key features being twin vortex lobes northern Canada, with associated trough Greenland/Iceland and N. Russia with the east European trough. There is a pretty flat westerly flow across North America, which is reasonably strong across the Atlantic and into the UK, which portends a much more changeable scenario as systems track east, but depending somewhat on the strength and position of the weakening European high how much of a N/S split materializes. Something the det. runs will need to sort.. Temps returning to near average perhaps a little above.



Today the frontal system associated with the deep low to the west of Ireland is already bringing strong winds and rain into western parts. The frontal band of rain will slowly track south east during the day but will gradually fizzle out during the afternoon as it struggles against the block to the south east. Heavy showers may develop behind the front in the north west and remaining windy but in the south east temps quite respectable in the sunshine









But all the time the block to the south east is intensifying with the help of the Azores and European ridges and a high cell has formed of Germany and is spreading it's influence west over the UK whilst the trough to the west re-orientates to a neutral tilt. Thus light winds and a fine and sunny day for the UK with temps significantly above average except for N. Ireland and the north west which will still be on the fringes of the trough with some patchy rain.



By Thursday a not dissimilar picture but the High cell to the south east is taking a positive tilt and the trough to the west starting to deconstruct under pressure from the energy exciting North America. This introduces a south westerly drift into north western areas which results in a tight NW/SE temp gradient to the very warm south east.

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By Friday the trough has deconstructed and the high cell taken on a much more positive tilt resulting in a surface cell settling over the UK. Thus another calm very warm day but the orientation of the cell does lead to quite a sharp temp delineation along a line roughly North Wales to Newcastle with temps NW of the line a fair bit lower, particularly near the coast.



The only difference on Saturday being a slight adjustment to the orientation of the high cell leading to a more uniform temp distribution with the temps not so high in the south but still a dry and warm day for all



Just to add the temps are obviously just according to the GFS and should certainly not be taken as definitive.

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Count of Undolpho said:

So usual British Spring then?

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Just a quick heads up on the GEFS 3-8 anomaly to start as it gives an idea on the direction of travel of the short term evolution.



Today patchy rain/drizzle will track north along western coasts as a wave to the west moves north but will quite quickly clear all areas apart from north west Scotland where it will linger all day. Quite breezy particularly in the north west. Elsewhere dry and sunny resulting in a very warm day. The rain may linger a while in NW Scotland during the night before clearing but generally a fine clear night with perhaps the odd fog patch by morning.

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The next three days essentially develop into a skirmish between east bound troughs/energy in the Atlantic, with low pressure over Iberia also playing a key role, and retreating high pressure to the east and the Azores ridging north east, with the UK sitting in the middle which is fine, albeit it leads to some quite marked regional variations of temp, but gets a tad complicated over the weekend.

So keeping this in mind Thursday sees the UK in a very slack pressure gradient as the two high pressure areas rather tenuously try to connect as the trough disrupts to the west. Thus a dry and sunny day in most areas and warm, very warm in the south east, with temps significantly above average,



Friday a not dissimilar scenario but the lows to the west and south west are taking closer order and another sunny and very warm day, the exception being the far north west of Scotland where there may be some showery rain. Temps again significantly above average particularly in the south east.



Saturday portends another very warm day but the analysis is getting tad messy with the upper low to west moving closer with some cooler air (relatively speaking) and towards late afternoon the weather could become more unsettled in Wales and the west with thundery showers entering the mix,





On Sunday the unsettled weather gathers pace as the upper low moves north west of Ireland and front associated with the surface feature tracks east and the thundery showers become more widespread. Temps still above average in the east but nearer average in the west.





This is of course the gospel according to the GFS

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The ecm not dissimilar to the GFS

The analysis at T96 & 120



Similar mini breakdown over the weekend with thundery showers.



https://weathermodels.com/index.php?r=site%2Fmodels&mode=animator&set=9-km ECMWF Europe Surface&area=United Kingdom&param=6-h Precipitation&offset=0

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