Focussed Model Discussion

[knocker]

Cloud depths about right I would think and we had some hefty showers here starting to die out by midday.

 

 

Edited February 10, 2019 by knocker

[phil nw.]

The expected High shows as building in the next few days but the gfs jetstream modeling shows plenty of energy heading across to the north which ultimately flattens the pattern at the end of the coming week.

UKMO model showing a similar evolution day 3 and 6 with the 500 hPa charts

As expected for this week really with fairly mild and quiet weather in a south westerly flow with signs of the Atlantic affecting the north later.

 

Edited February 10, 2019 by phil nw.

[knocker]

The Alaskan ridge facilitating the cold arctic plunge down North America which intensifies the thermal gradient across the south with a lot energy exiting  the south eastern seaboard presumably aiding and abetting the amplification in the Atlantic. Well that's the theory

[knocker]

And Sidney paying homage to winter exiting in grand style

 

[knocker]

Outlook - A period when high pressure becomes much more influential over much of Europe thus little precipitation but the odd ingress of frontal rain/snow in north west regions, courtesy of still impressive energy flows to the west, well illustrated by the precipitation chart

The NH jet profile and midnight analysis

Any residual rain from the occlusion/wave feature will peter out leaving a dry and sunny day for most with temps around average. But cloud and patchy rain will arrive over N. Ireland and western Scotland by 1800 and other western regions through the evening and night courtesy of a warm front associated with a complex area of low pressure to the west. Apart from the west quite chilly in other areas with a touch of frost by tomorrow morning

Tuesday will be a mild day in the south westerly wind which will be quite fresh in northern/western regions where there will also be a lot of cloud with spells of rain as an array of fronts sweep north east across the country, Elsewhere dry with sunny intervals. Clearer with showers after the passage of the cold front

As can be seen the atlantic is dominated by an upper trough and overnight Tuesday through Wednesday surface features are tracking NE by N along the eastern flank of this which takes the weakening, stalled, cold front back north east as a weak warm front with another cold front in close proximity to the north west. Ergo another mild day generally with sunny intervals in the south with more cloud and some patchy light rain further north

This theme is continued through Thursday, minus the fronts, with a tad more amplification thus another mild day with sunny intervals but perhaps cloudier and a bit breezier in the north west

By Friday the upper trough to the west is under a lot of pressure from the aforementioned amplification of the Atlantic subtropical high and deconstructs with a waving cold front starting to traverse the country bringing cloud and rain, snow on the mountains, to western parts by midday. Whilst further south yet another cut off low has formed over Morocco

Edited February 11, 2019 by knocker

[knocker]

According to the gfs this morning, from the point where we left it above the rest of the run in a reasonable time frame is essentially a battle between the impressive energy exiting the eastern seaboard and the subtropical high pressure attempting th amplify, The UK more or less sits at the coal face as the energy distribution swings around it;

A spot check

Anyway the upshot of all this is the next trough has arrived just to the west Sunday/Monday with the front stalled over the western regions of the country. This trough meets the same fate as previous ones but the weak front does stagger across the country before more fronts bring more rain and quite strong winds to the north by Wednesday

Edited February 11, 2019 by knocker

[knocker]

The overall  theme of the ecm is similar to the gfs and by 1200 Sunday has the trough to the west and the surface low centred over Iceland and wet and windy over the UK as fronts cross the country The trough disrupts over the next couple of days leaving the UK generally unsettled with sunshine and showers with temps a tad below average

[knocker]

Cloud creeping into the west from the warm front and some recent rain down here from that stray occlusion, clearing now

[Singularity]

 

Hmm so of all the models and runs it's the GFS 06z that's the first in some time to show an adjustment that bears at least some resemblance to what similarly dramatic tropical developments in the central-eastern Pacific have been known to force in times past.

 

That being the trough not being able to just shove the Sceuro High aside and instead being forced into submission with the UK in a continental rather than maritime flow. Much more pleasant if you like double digit maximums accompanied by dry weather in mid-Feb; this being what's on the table unless the high manages to position itself further north next weekend.

The better retention of high heights across the UK does however have an important knock-on effect; it encourages the -ve NAO development to occur more east than west. The ECM 00z showed us how a west-based initial development would pan out for us... not a pretty sight. So here's hoping the 06z GFS is onto something. Yes, the 06z GFS I can't say it fills me with confidence .

[knocker]

A quick glance at the clusters  T240 A pretty fair agreement with the trough to the west of the UK, albeit with a different orientation and thus the position of the high cell, T 300 is still all about sorting the positions of the trough and high cell with the UK at the coal face and, not surprisingly inconclusive, and I suspect will continue to be so for a while

[Man With Beard]

54 minutes ago, knocker said:

A quick glance at the clusters  T240 A pretty fair agreement with the trough to the west of the UK, albeit with a different orientation and thus the position of the high cell, T 300 is still all about sorting the positions of the trough and high cell with the UK at the coal face and, not surprisingly inconclusive, and I suspect will continue to be so for a while

For the mild/cold balance, those positive Euro height anomalies would pretty much shut the door on anything substantially cold until the very end of the month at least.

[knocker]

there was a veil of cs and a faor bit of high Ac down here at midday which is noted on the sounding and sat image but we what I'm nor sure. The warm front looks the possibly contender bu it doesn't rally look right and now,still a fair bit of Cs but plenty o sunshine

[knocker]

A generally cloud free day for many to end the day and this will remain the cast through this evening and overnight with perhaps some frost around in east and southern areas of England with the odd spot of fog. the exception will be the NW and later some western regions further south where cloud will spread in during the afternoon and some light rain will effect.Ireland and western Scotland by 1800.

This is associated with a weakening warm front which quickly tracks NE to clear N, Scotland but a second warm front will arrive around 0100 and this will bring more extensive cloud and patchy rain to western regions.during the rest of the night And by 0900 tomorrow the arrival of the cold front in the NW is imminent.

 

[knocker]

The quite noticeable difference with this evening's gfs is the snuffing out of any ridging from the Atlantic subtropical high post Tt80 which at that range which at this stage has to put down to run > run variation. But it didn't mess about

[johnholmes]

2 hours ago, knocker said:

there was a veil of cs and a faor bit of high Ac down here at midday which is noted on the sounding and sat image but we what I'm nor sure. The warm front looks the possibly contender bu it doesn't rally look right and now,still a fair bit of Cs but plenty o sunshine

It could be the first cloud sheet was the first warm front now well north and the second warm front already showing up with height?

[knocker]

12 minutes ago, johnholmes said:

It could be the first cloud sheet was the first warm front now well north and the second warm front already showing up with height?

That was more or less my thinking John. it certainly looks like the first warm front as it is a cracking clear evening here now with some thin Ci and a smidgen of Ac

[knocker]

Further to a post above the GEFS mean anomaly is along the lines the EPS and NOAA been indicating

 

 

[knocker]

And the ecm continues to do what it has been indicating for a couple of runs now which is ejecting a lobe from the vortex/trough into the Atlantic where it intensifies rapidly. There appears to be growing support for this scenario but the important question is how will this develop downstream

 

Edited February 11, 2019 by knocker

[knocker]

And the EPS response is a quite strong amplification vis the European ridge and the North Russian vortex/trough

[damianslaw]

On 29/01/2019 at 20:12, knocker said:

 

 

The EPS response is a foundation route to a possible cold end to the winter, depending on where central core heights situate themselves, further north, and we could have an undercutting scenario, or a slider low situation.

Significant WAA through east atlantic is forecast next week and this would help to pump the euro ridge northwards. We might just end up with a chilly SE feed, before the ridge is forced to collapse south again, conversely we might end up with a much colder feed from the NE doing battle with the atlantic. 

 

[knocker]

Outlook - the beginning of the period is dominated by upper troughs in the Atlantic doing battle with high pressure centred to the south east of the country with the UK in no mans land. Thus systems track north by north east along the boundary with any rain and strong winds favoring the NW and W regions with the east and south east dry and mild.

The NH 500mb profile and surface analysis for midnight and the WV image for 0300

Today the frontal system associated with the low south of Iceland will track south east down the country. But the cloud and patchy rain only gets so far as the warm front weakens against the high pressure and the cold front stalls across the country as a wave forms on it to the west. A mild day on what is going to be a mild week

through this evening and overnight the wave tracks north and thus the cold front and patchy rain do like wise resulting in the south staying dry with clear spells and with some fog around.

By tomorrow the wave is part of a complex area of low pressure to the west with fronts quite adjacent to the west of the country thus some cloud and rain here, perhaps more concentrated over western Scotland. Elsewhere, with the cold front, now a warm front, in the North Sea, dry with sunny intervals in the mild south westerly

Over Wednesday night and through Thursday a very similar day, very mild, sunny, and perhaps the odd spot of rain in the far north west. But in the Atlantic nasty things are happening to the trough as the Bermuda high starts to amplify as the next upper trough exits America

Come Friday the aforementioned trough and has become quite an intense feature putting the ridge under pressure and thus nudging the frontal system a tad further east  bringing rain and strengthening winds to the north west.

By Saturday the new low has taken closer order the west of Ireland and a front has been forced south east down the country but as usual it weakens against the high pressure and the patchy rain fizzles out. There is very much a N/S split temp wise with it very mild in the south

[knocker]

Moving foreword with the gfs and there is a transition that has been discussed previously and Initially there is the surge of the subtropical  high pressure zones next Monday

But this is quickly followed by a chunk of the Vortex/trough (Discussed last night and before) being ejected into the western Atlantic and intensifying which impacts the downstream patter and, initially at least, advects a lot of warm air into Europe.

Edited February 12, 2019 by knocker

[knocker]

The ecm has max temps (not of course to be strictly adhered too) in the 12 > 14C range Wed > Monday and then at t174 it ejects the above mentioned chunk of the vortex east over Newfoundland. It then, to some extent phases with the trough to the north of it but does drift further south in mid atlantic which does effect the energy flows and impacts differently downstream to the gfs. Thus colder air is advected into central Europe from the north east rather than the general WAA

[knocker]

I shall refrain from posting the ext EPS this morning as there is some suspicion that I could be held responsible for the consequences.

[Man With Beard]

56 minutes ago, knocker said:

I shall refrain from posting the ext EPS this morning as there is some suspicion that I could be held responsible for the consequences.

And I can well understand if you are worried about the cold crowd throwing virtual tomatoes at you! Between D10 and D15, most ECM members prefer to maintain a strong high pressure cell not very far from Germany, and as Knocker says in his previous post, the UK remains in "no man's land" - not particularly under threat from the Atlantic, nor at risk from the east. 

The question will be whether the UK engages a pure southerly flow and spring-like conditions, or a slightly continental flow that maintains a chill - though by the last week of February, the cooling influence of the continent will be starting to wane and a continental flow without easterly reinforcements will more likely maintain daily temperatures without boosting or suppressing them - perhaps a slight drop but no cold pool development. 

Naturally there are members that drift away from this exact scenario by D15, so impossible to say the high won't drift sufficiently north for a cold NEly, or that it won't drift sufficiently south for a return to wet Atlantic weather - but the signs are relatively strong for the status quo.

Chances of lowland snow during the rest of February = less than 20% (IMO)