UK meteorology

Here's the FAX chart for 0600 (06z UTC) tomorrow - note the isobars switching to the north west behind the front, indicating winds backing (swinging anticlockwise; veering is a swing to the right, or clockwise), and the upper troughs (indicated by short, curved lines like eyelashes running perpendicular to the isobars) behind the main front. These aren't the same as the main longwaves troughs of the polar jet, just small upper-level features of colder air which leads to atospheric thicknesses being lower and the airmass being briefly more unstable, hence they are often associated with lines of squally showers.
 
Here's an interesting post from Malcolm:
Excellent illustration at T60 of the different airmasses involved in this current pattern.

The cold front running south from Iceland with the very cold air associated with the Canadian vortex piling up behind whilst the warmer air tracking NE from the western flank of the Azores high pressure precedes it. Further east the UK is in a col between two high pressure cells with stagnant cold air settling in the very slack gradient whilst the low pressure to the south just about brings an easterly component to the very south of England,



Wind it on 24 hours and the warm air has been absorbed, the UK become appreciable colder and the PM behind the front is being modified bt warmer air sweeping north around the high pressure. The front will carry on tracking east but the question is how much is left in the tank?

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Malcolm's thoughts:
Today the occlusion already affecting the western half of the UK will wander slowly east whilst dissipating thus patchy rain, and sleet, the latter mainly on the higher ground to the north, and similarly some snow in Scotland. A small wave that develops on it will be over N. France by evening. Showery brighter weather behind already in to N. Ireland. The cold front to the east which is nudging west will also tend to peter out as it nears the east coast Temps ranging from 7C in the south west to 3C further north.



Tomorrow a much brighter day albeit quite cold with temps 4-5C at best and there may be some brief flurries in the south and east in the fresh north easterly wind



The clear skies and light gradient continues overnight in most areas leading to a widespread frost Monday morning but by midday the next front is approaching from the north west introducing a warmer south westerly airstream to N. Ireland and Scotland.



Through the rest of Monday and through Tuesday the front will track south east across the UK but it is rapidly losing it's identity so a rather similar scenario to today with patchy rain sleet, snow on the higher ground but clearer colder weather behind also in the mix



From here we await a repeat performance but that's for another day



Nothing to add detail wise from the ecm so just the surface and 850mb temps anomaly and wind vector charts for T24, 48, 72



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He also gives his thoughts on the Ensemble Anomaly outputs (I've already explained what these are, so, of you're unsure, have a check back over recent posts here and you should find the explanation (I'm going to watch the rugby!) In response to Malcolm's post, Netweather's retired forecaster adds his thoughts:
Quite an interest scenario looking at the 2-7 GEFS and EPS anomalies this morning.

Strong Canadian vortex elongated SE to encompass Greenland/Iceland with Azores high pressure suppressed with a strong westerly jet running across the Atlantic, But as the flow reaches the eastern Atlantic close to the UK it diverges quite sharply with the northern are tracking NNE around the east European ridge and a rather peculiar slack upper low over N. Scandinavia. The southern arm turns sharply south courtesy of the positively aligned upper trough S/SE of the UK. Where precisely this divergence occurs is important and will dictate how far active systems will progress east. Temps remaining below average.

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Yes I commented in the other thread about ec-gfs and noaa both showing a pattern that diverges much as you suggest k. I am at a loss to know just how that divergence is going to affect the surface weather. An interesting pattern for sure over the next 2 weeks.

Close in, the 72h period and the Fax charts are going to be the best overall guidance I would suggest. Talk of snow etc will be uppermost in most folks minds but I cannot see any widespread heavy snow. Localised low level falls are possible but may not be apparent until a few hours before they occur!
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Today's thoughts:
Today after a frosty start in many places it will be bright and quite sunny, particularly in the west, albeit rather cold with max temps in the 4-5C range. It will though become increasingly windy in the south during the day with a brisk north east wind which will lead to some showery activity in the south east, some of which will be of snow. in the unstable air.



These will continue overnight which being clear with light winds will lead to a quite hard frost generally. This is the general picture for the rest of Monday with temps struggling to reach 4C but the showers in the south east will die out as the wind abates.



By 00 Tuesday the cold front that can be seen to the north west on the above fax has occluded and is lying western Scotland Ireland. During the day it will track south east and slowly lose it's identity but as the preceding air is much colder now the precipitation may well fall as patchy sleet and snow, particularly in the north At this stage, as can be seen, all of the warmer air has been squeezed out and the nearest WAA is on the western flank of the ridge

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By 12 Wednesday the fronts associated with this have tracked east, suppressing the ridge, driven by the energy leaving the eastern seaboard and are approaching western Ireland.



So now we are back to familiar scenario of the fronts occluding and becoming weaker as the reach the UK


Both the ecm and gfs have the UK pretty dry over the next ten days

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Here's his view this evening:
In the near time frame nothing much different to this morning's assessment.

A cold clear night tonight with the showers continuing in the SE and a widespread frost in the morning. Another clear sunny day tomorrow with the showers in the SE dieing away but with the next frontal system gearing up to th north west.



The front tracks south east overnight and through Tuesday, after another moderate frost, but by now it has occluded and lost much of it's oomph so patchy rain sleet and snow before it fades away.



Overnight and into Wednesday the ridge reasserts itself before the next front arrives from the north west for a repeat performance but the upper trough to our east has become more positively aligned which impacts on the orientation of the front as little waves form on it which slows down it's progress south east across the UK

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This morning's thoughts show little change from last night:
Today after a frosty start in many places it will be dry, sunny, and quite cold with temps in the 4-5C range, The exception being the SE and East Anglia where wintry showers, many of snow, may well continue. By evening cloud and rain on the occlusion will have reached N. Ireland and western Scotland.



The front will continue to track south east overnight and through Wednesday increasingly turning to snow in the north and Midlands and sleet and snow further west and the showers dieing out in the south east. Frequent wintry showers behind the front, initially in the north west but spreading further south to western areas as the front progresses.



some scattered rain and snow showers in some areas overnight and in the early hours of Wednesday but after after a clear night quite a moderate frost in many areas. But by early afternoon cloud and rain/snow has reached N. Ireland and western Scotland from the next front.



The front makes quite slow progress through Wednesday and Thursday as the upper trough becomes positively aligned south of the UK and yet again it will be marginal bringing patchy rain/sleet/snow in most areas but more especially the NW/W.



So in a nut shell continuing cold and dry apart from western Scotland and NW England

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Blademonkey said:
I take it back....flakes of snow in Cornwall ! Max temperature today is 4 or 5 and dropping to -2 tonight.
I know this is nothing when compared to part's of the country but chilly for here! P.
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We had snow grains earlier here in one of the showers coming down the North Sea that headed slighty further inland.
Anyway, having had Malcolm's permission to continue quoting him on TSR, here are his thoughts from earlier today:
Today and tonight

After a frosty start this morning (not too bad in many areas of England and Wales where it is cloudy, around 0-- -2C,) snow will move south east with the occlusion that is currently over southern Scotland, NW England and Wales. A reasonable coating in the north and central areas but lighter in the S/SW where the wind will pick up later as the ridge squeezes in. Behind the front some wintry showers, already into N. Ireland and Scotland which could give a fair covering of snow, Overnight clear skies and quite a severe frost for most but light snow lingering in the SE and perhaps more showers in th west on troughs in the general circulation



Tomorrow

As noted a frosty start but by 1200 fronts have arrived in the north west bringing rain and some snow, probably confined to the high ground, and these will attempt to track south east. But progress is negligible against the ridge and they will either stop or weaken considerably leaving most of the country dry but cold.



Thursday/early Friday

As can be seen the fronts have introduced a wedge of warmer air temporarily across the UK with the deep upper trough and the much colder air away to the north west. As the fronts finally clear the south east by 0600 Friday morning this colder air will also ingress the UK, albeit somewhat modified, bringing clearer colder condition for most with some wintry showers in the north west





Friday/Saturday

Cold and dry for most on Friday except the north west which could experience frequent wintry showers on the prevailing westerly wind before overnight the whole process starts again with fronts, rain and snow impacting the north west by 0600.



And looking at the GEFS anomalies this morning certainly signs of some rapid changes round day 11




I might have played this down a bit above but the ecm has it quite wet in the early hours of Friday as the front(s) tracks south east and then wet and windy over the weekend with gales.

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