Alternate Model Discussion - into 2022

[phil nw.]

A look at the next few days with charts from the UKMO.

The 3 fax's below for tomorrow,Thursday and Friday 12noon show the High  setting up shop now and settling over England and Wales.

 s. 

A south westerly breeze over the top of the high blowing across Scotland and N.Ireland with occasional weak fronts affecting the far north at times with some rain or drizzle.Generally daytime temperatures near normal but somewhat milder further north.

Night time frosts and some fog are likely under the high further south although this could be patchy depending on cloud cover-UKV expected temperatures for the next 3 mornings.

A bit further ahead-

UKMO raw outputs for T96/T120hrs

 
 

show the high continues to be the main feature with a continuation of mainly dry and quiet weather into the weekend.It is shown to start to ridge north west by day 5 allowing more of a breeze from the nw.This would reduce any frost risk further south at this stage.

 

Edited January 11, 2022 by phil nw.

[knocker]

There is some disagreement between the gfs/ecm at the beginning of next week involving the storms along the eastern seaboard and the energy distribution/jet profile across the Atlantic. Particularly involving the amplification of the high pressure and the knock on affect downstream of the plunge of cold air from the Russian tpv lobe down into Europe. This has some relevance as the UK is on the western periphery of this. This is reflected by the medium term anomalies. Obviously the detail still needs nailing down but the percentage play is dry with surface temps below average.

[RabbitEars]

Dear Knocker and Phil thank you for these useful clear appraisals of what you see in the models and their trends. 

[knocker]

Regarding developments that attracted some attention yesterday. Both the gfs and ecm hang on to high pressure through the beginning of next week, albeit still indicating differences regarding energy distribution and any cold plunge down into Europe, which is well illustrated by the jet profile at t156

[knocker]

The ext mean eps is little changed from previous comments and the clusters are  indicating nothing sinister lurking in the woodshed with a fairly mobile Atlantic but with the subtropical high retaining a significant interest

[phil nw.]

The 00z eps height and 850hPa  5 day anomalies for Europe incl.the UK for days 1-5 and days 6-10.

Indicates high pressure never far away with a suggestion of perhaps of a little move west in period 2 with a tad more ridging.

This shows Europe cooling down quite widely as troughing heads south through Scandinavia and W.Russia feeding the colder air south into much of the continent.This leaves the Uk in milder air for the first 5 days although later on that colder air does edge closer to our east as the pattern amplifies a little so our temperatures will lower towards more normal values.

Overall a fairly quiet settled period with a lot of dry conditions away from the far north.

  

Edited January 12, 2022 by phil nw.
missing word

[knocker]

Trough disruption at the beginning of the week creating another cut off upper low and giving the high pressure a wee boost

Edited January 12, 2022 by knocker

[knocker]

The differences between the gfs/ecm/NOAA this evening still revolve around the amplification and position of the Atlantic HP, and thus the position of the Euro trough. And although high pressure does remain influential over the UK during the period these differences are reflected in the structure and orientation of it. Likely remaining dry with any precipitation in the NW

[phil nw.]

Looking at day 5 with the 500hPa on the operationals NH view

Whilst GFS shows a little more ridging in the Atlantic essentially at that stage it means little difference to the UK.High pressure over the country,settled mainly dry with a risk of night frosts and fog where skies clear.

[phil nw.]

Looking at the gfs mean nh 500 view for the days 5/10/15

 

shows the longevity of this pattern going forward.I dare say there will be some minor changes day to day but it's notable that the main features seem to remain throughout.These being the Azores/uk ridge and east Canadian trough moving over the pole and draining down through Scandinavia.Bitter Winter weather looks to continue in those areas. 

Edited January 12, 2022 by phil nw.

[knocker]

Tropopause fold at Keflavik with 187kt jet?

[knocker]

The 06 ecm

Edited January 13, 2022 by knocker

[knocker]

And a quick preempt of this evening's gfs ext/ec weeklies outputs with a glance at this morning's extended. The salient ppoints: Aleutian low/Alaskan ridge > Siberia adjacent to the tpv lobe northern Canada > northern Russia; strong westerly upper flow exiting the eastern seaboard around the subtropical high, amplifying to some extent in mid Atlantic, to the east European trough. Likely pretty dry with temps around average

[phil nw.]

A couple of fax's

show the high relents a little over the weekend as a weak front moves down the country,although any rain further north will die out as it comes south.It may well move some cloud about but will mean little in the greater scheme of things maintaining the quiet settled weather as the high rebuilds across the country by early next week.

Continuing prospects of night frosts ,especially further south where clear skies are more likely.Hopefully compensated by some Winter sun.

[knocker]

No significant changes with the NH profile this evening. Some slight differences with the structure/alignment of the tpv which impacts to some extent on the position of the surface high cell in relation to the UK and thus some variation vis the detail, Likely very dry and temps around average but perhaps a tad above over the northern half of the country

[RabbitEars]

17 hours ago, knocker said:

Tropopause fold at Keflavik with 187kt jet?

Hi knocker sorry newbie question... can you please explain what you mean and what the supporting chart shows? Cheers. 

[knocker]

6 hours ago, RabbitEars said:

Hi knocker sorry newbie question... can you please explain what you mean and what the supporting chart shows? Cheers. 

Sorry RabbitEars, I should have included this in the original post. Hope it helps

Tropopause fold is the extrusion of stratospheric air within an upper-tropospheric baroclinic zone which slopes downward from a normal tropopause level ( ~200--300 hPa) to the middle troposphere ( ~500--700 hPa). The tropopause fold is a mesoscale feature which forms in response to strong descent at the tropopause level. It constitutes an intense phase of upper tropospheric frontal development in which the tropopause undulation collapses. In regions of confluent flow the tropopause may be deformed such that it will form a fold (as shown in Fig. 1.9) which will decay after 1 or 2 days. During the build up phase of a fold the flow is generally conservative, whereas the decay phase is characterized through nonconservative flow, e.g., diabatic heating and turbulent mixing. It is these nonconservative processes which achieve the stratosphere-troposphere exchange.

The most vigorous tropopause folds occur during the winter and spring and are less frequent than cyclone development. They are usually observed downstream from a ridge, where there is large-scale descent in the entrance region of an upperlevel jet streak. Ozone-rich air originates in the lower stratosphere, west of the trough axis on the cyclonic side of the upper-level jet streak. This airstream then descends anticyclonically to the lower troposphere east of the surface high-pressure system or crosses the trough axis and ascends.

Two major types of tropopause folds are noted. One is associated with the polar front jet (PFJ), which may extend deep into the troposphere along the polar front. In some PFJ tropopause folds, significant intrusion of stratospheric air deep into the troposphere occurs. The other one is associated with the subtropical jet stream (STJ) and subtropical front, which is confined in the upper troposphere only and rarely extends downward below 500 hPa. The positions of the tropical tropopause and the polar tropopause along with the formation of subtropical jet stream over the rnidlatitude region are schematically shown in Fig. 1.10. Vertical intrusions of the dynamical tropopause into the troposphere, which are folded due to differential isentropic advection, are also known as tropopause folds.

Source: Stratosphere Troposphere Interactions K Mohanahumar

Edited January 14, 2022 by knocker

[knocker]

Some dense fog around over England and Wales at the moment but if and once this clears through the morning another sunny day beckons. But more cloud over Scotland, particularly the north where it might hang around all day with some patchy drizzle. Frost and fog developing again tonight and tomorrow likely cloudier day than today

 

 

[phil nw.]

Gefs day 5 NH jet stream flow and the days 5 and 10 500hPa height anomalies.

The Atlantic high acting like a large boulder in a stream splitting the jet and sending the northern arm over the top of the high and eventually south as an upper trough into Scandinavia and E.Europe.

The height anomalies continue to show a ridge over the Pacific side of NA and a pronounced trough over the east of the continent.This will bring notable cold to that area in the coming days.Meanwhile our Atlantic block remains steadfast as low pressure and the Arctic air runs over the top and down through N and E.Europe within the next 10 days.This colder air mainly diverted east of the UK.

[knocker]

A weakening cold front tracking south down the country on Sunday, eventually becoming just a c;loud feature, as high pressure beats a tempory retreat.

And as there ls not much to be said about the rest of the output that hasn't been said before, a quick glance at the second week of Feb. from the latest gfs ext/ec weeklies. But actually they indicate a not unfamiliar picture with the tpv lobe northern Canada; relatively strong westerly upper flow across the Atlantic to perhaps some influence from the Azores HP and temps around average. Now what's that quote I'm looking for. Ah yes "They think it's all over - it is now"

Edited January 14, 2022 by knocker

[damianslaw]

Watching the high is the same as a slow moving picture.. what trigger is needed to shift things along..

[knocker]

Much cloudier day today, particularly over England and Wales, where the early low cloud/fog could well persist resulting in quite a chilly day. But tonight the cold front, mentioned in previous posts, is starting to move south over Scotland and through the night and tomorrow will continue it's travels accompanied by cloud and some patchy rain/drizzle as it slowly weakens. But behind the front much fresher air and more sunshine, albeit the odd shower in the NW. Note some rain/showers from a trough in the SW/S in the early hours tomorrow

 

Edited January 15, 2022 by knocker

[knocker]

After the high pressure biefly reasserts itself on Monday it starts to slip south east Tues/Weds as another front tracks down the country

Edited January 15, 2022 by knocker

[knocker]

8 hours ago, RabbitEars said:

I've asked this in the volcano thread but I'll ask here too... what, if anything, might the effect be on our weather or even the northern hemisphere's pattern from the large eruption in the Pacific Ocean? And what is the likely time lag?

To quote Chris Jones from Met Office Hadley Centre

"the key thing - to affect climate - is that it gets ash/dust up into the stratosphere. Otherwise it's not long-lived enough in the atmosphere. As I understand it this one was underwater, so probably unlikely to do so".

Of course this is early days

[knocker]

The medium term anomalies are still about the structure and orientation of the high pressure and position of the Euro trough which dictates the variation of the detail vis the surface analysis. Likely generally remaining very dry with any unsettled weather running around the northern periphery if the ridge

Edited January 15, 2022 by knocker