Alternate Model Discussion - into 2022

[knocker]

Position of front 1200 Xmas/Boxing day

 

[BlueHedgehog074]

Just looking at a number of 00Z models for 144 hours ahead - GFS, ECMWF, UKMO and GEM, they seem to generally agree to a rise of pressure to the South of the UK and Low Pressure in some form spilling over the top:

 

Some of this Low Pressure extending quite far South-Westwards into the mid and Western Atlantic assisting with the build of heights over South and Western Europe. We see a mild South-Westerly flow taking over for the UK. Although things can clearly change at that time-frame (and especially how models have been handling events up to Christmas), it for now seems like a likely direction to be heading in. Worth pointing out that the 00Z GFS, top chart above, does maintain a small wedge of higher heights over Iceland between 2 areas of Low Pressure to the West and North-East of the UK - a cooler Northerly flow towards Northern Scotland. (Though the GFS 06Z run did take away most of that Iceland wedge of heights):

So would say a milder spell, especially the further South you are, is at least still looking the favourite option. 

The GEFS 06Z ensemble mean around 144 hours reflects this too:

Likewise, the GEFS ensemble graphs below regarding the 2 meter temperatures for both the West Midlands and Aberdeenshire, after a bit of a chillier spell around Christmas, especially Boxing Day, is generally showing things gradually becoming milder as we get closer to the New Year:

This perhaps being more noticeable for the West Midlands area where as, although the graph generally for Aberdeenshire shows a rise in temperatures, they look to stay below double figures. It may not be the Christmas present a lot of the cold weather enthusiasts would like, but is worth noting there is a fair amount of scatter for New Year’s Day and beyond. So always a chance for the weather to change for the better, or the worse, depending what ever you’re after. 

For the next few days, some Northern areas, especially over high ground, does have the chance of seeing something wintry and white
Examples from today up to Boxing Day from GFS below:

 

Also, as a bit of fun, I plucked out this ensemble member below - Perturbation 12 - to bring about some cold and wintry cheer for those currently feeling let down by the outlook. To add to that, would like to wish everyone on here and rest of Netweather a Merry Christmas and Happy New Year. In spite of some continued difficult times, I hope it is filled with some warmth and joy. Has been fun taking part with the adventure with you all. May the New Year and beyond also provide us all with the weather we desire ?

[knocker]

Wave breaking and WAA

[knocker]

And ecm 850mb temps

 

[knocker]

Need to try and get a grip on where we are going with all this. The medium term anomalies are broadly speaking on the same page but I feel the detail may be a tad elusive. They are highly amplified upstream with the north Pacific ridge/west N. America trough resulting in a strong jet exiting the eastern seaboard around the tpv lobe in the NW Atlantic, which during the period has promoted the Azores ridge. The detail of this is very uncertain regarding the amplification of this and perturbations breaking off from the main trough, albeit temps rising well above average

[matty40s]

I'm just getting out of meeting the in laws tommorow so I can go snowchasing in the Grampians....

 

 

[knocker]

Some snow on the leading edge of the front tonight down to relative low levels leading to some tricky conditions in the quite strong wind

And then turning unsettled with temps way above average through next week with a wet and windy day on Weds

Before some wave breaking at the end of the week. Note the ecm does introduce some cooler air to the north

Edited December 25, 2021 by knocker

[knocker]

The salient points of the ext anomalies this morning. Continuing very amplified upstream with the north Pacific ridge extending into the arctic; The tpv not centred in it's usual spot northern Canada; Strong westerly upper flow exiting the eastern seaboard across the Atlantic with little amplification indicated by the Azores HP; Likely changeable with a N/S bias and temps above average

[knocker]

The 06 ecm

[knocker]

The salient points of the ext mean anomalies this evening. The strong north Pacific ridge extending into the Arctic adjascent to a weak tpv lobe northern Canada, albeit with an extended trough in the NW Atlantic beneath a ridge into eastern Greenland. A strong westerly upper flow south of this across the Atlantic which meets little amplification of the Azores high pressure, unlike in previous runs. Likely a tad unsettled with a NW/SE bias and temps above average

Edited December 25, 2021 by knocker

[knocker]

The general theme this week is to develop a deep low in mid Atlantic resulting in strong SW jet to the SW/W of the UK resulting in WAA and frontal systems tracking rapidly across the UK. Some difference in detail by the end of the week as the gfs does advect colder air down the eastern flank of the Greenland HP

[knocker]

The main thrust of the clusters 192-240 is for a W/SW upper flow with a likely predominance of the TM air and to a lesser extent some incursion of colder air, courtesy of the trough to the N/NE

 

 

[knocker]

Some varied outputs from the gfs/ecm medium term anomalies this evening. More or less agreement upstream on the north Pacific ridge extending into the Arctic resulting in Arctic air plunging south over the western half .and perhaps on a broader scale, of North America. This pumps up the jet exiting the eastern seaboard across the Atlantic to some influence from the Azores HP. This is pretty much where any comparison ends as there is complete disagreement regarding the position of the tpv lobe/ext trough in the NW Atlantic and heights over Greenland so confidence in the detail low for the period albeit temps likely above average.

[knocker]

Still some significant differences with the ext mean anomalies. Notable; the gfs/ecm both have different interpretations of the upstream amplification involving the north Pacific ridge, the plunge of Arctic air down NW North America and subtropical ridging in the south east. And although they both agree on the resulting strong westerly upper flow exiting the eastern seaboard there remain ongoing differences in the Greenland/NW Atlantic area. A work in progress

[knocker]

Still upstream differences from the medium term anomalies this evening involving the alignment of the north Pacific ridge/ tpv ext trough and the incursion of subtropical air into the S/SE of the US. Despite this they all agree on a strong westerly upper flow exiting the eastern seaboard south of the Greenland ridge/adjacent trough, but differ again on the influence, or not, of the Azores HP, Obviously much to be sorted regarding details but the percentage play is changeable with temps above average

[Sky Full]

The GFS 6Z 0.25HD shows an interesting evolution from 4:00pm Monday 3rd January to 1:00am Wednesday 5th January as warmer air meets colder air during a brief northerly airflow following a channel low:

 


Some strong gales briefly in the channel and the possibility of snow as the cold air moves south.  Still time for this to change even in this short time frame but it could be a disruptive spell of weather if it happens like this.

 

[phil nw.]

No sign yet of any prolonged cold weather as head into mid month ,more the chance of brief colder snaps in a fairly mobile setup. A couple of fax's shows a pretty typical Winter pattern for the UK.

A fairly active Atlantic flow with a mix of cold polar air interspersed with brief milder interludes as the next low heads in.

Wintry showers for some places in the colder air with some more noticeable snowfall over parts of Scotland.Night frosts more widespread before the change over later in the week.

A glance at the ens and clusters indicate a quieter spell within the 10 day range.

 
 

Pressure rising from the south pushing the westerlies further north.Surface conditions re.temperature and cloud levels really depending on the exact location of the high. Overall though an unremarkable  January period with temperatures varying near average.

[knocker]

Indications from the medium term anomalies. of a deep low tracking south of the Aleutians, promoting the ridge over western North America, which in turn shifts the tpv lobe/trough ext east. The downstream knock on effect of this is to promote the Atlantic jet and, to varying degrees, the Azores HP. Thus a trend to more settled conditions with temps a tad above average but perhaps a fair diurnal spread.

[knocker]

The cold front should just about clear the SE by 1400 with blizzard conditions develping over northern Scotland in the frequent heavy snow showers in the very strong NE/N wind. Wintry showers also developing over Wales and SW of England with snow over the high ground

But this cold snap is relatively short lived and one of the reasons for this is not without interest. Between 00 Weds and 00 Thursday a low in mid Atlantic undergoes rapid cyclogenesis near the left exit of the jet and deepens from 975mb to 929mb to be just east of the tip of Greenland. After a widspread early frost on Thursday fronts associated with this sweep east across the country accompanied by rain. hill snow, and strong winds

Edited January 4, 2022 by knocker

[knocker]

And the outlook cointinues to look hunky-dory in the ext period. The salient points; west North American ridge extending to Siberia adjacent to tpv lobes N. Canada/N. Russia; strong westerly upper flow exiting the eastern seaboard to the Azores high flexing it's muscles in the vicinity of the UK. Ergo likely quite settled with any precipitation concentrated in the NW with temps around average, perhaps a tad below. What's not to like!

[Singularity]

ECM 70 hPa charts show the gradual eastward drift of the polar vortex in the lower stratosphere that has been giving rise to some mid-Atlantic high pressure build scenarios in the troposphere modelling lately.

The ridge across the UK has a presence here too, which implies some strong staying power. Might make it harder for the high to gain much latitude though.

If there was one on the Pacific side to pinch the polar vortex, the situation would be a lot more interesting!

For UK snow seekers, the tropics are doing their part but the lower stratosphere has to open a door for the amplification to establish in the high latitudes.

Otherwise, it seems it will be at best cold and dry with some sunshine, at worst mild and cloudy with light rain at times, depending on just how far north high pressure manages to set up shop in 8-10 days time.

For mild seekers, there's a shot at another impressively mild spell if the high focuses over mainland western Europe. The ECM 00z is along those lines, though it appears the high would migrate north a bit after D10.

Edited January 4, 2022 by Singularity
...as all things should be ;)

[knocker]

And today that would appear to be down to losing the Aleutian ridge and evolving along the lines indicated In the ext Troposphere paatern

[davehsug]

Thanks for the updates all. I hope this science based thread will continue, and you'll continue to tell those of us who are interested, what the models actually show, and not what they might if x became y and black, white.

[knocker]

Some snow on the front Thursday, likely over the higher ground, and quite windy

[phil nw.]

Looking ahead to days 5/10 on the ECM mean 500 charts and 850s anomalies.Northern hemisphere view.

We can see the pattern changing as the Canadian trough, which has seen Canada and parts of the northern states in deep cold, move east into the Atlantic 

Downstream of this trough the Azores high ridges ne with milder air enveloping much of western and northern Europe by day 10.

 

Edited January 4, 2022 by phil nw.