Alternate Model Discussion - into 2022

[weathermadbarnsleylad]

37 minutes ago, Georgina said:

This may be a stupid question but how can you tell if the op is an outlier and what does that exactly mean does it mean that it’s not worth looking at ? Thanks and sorry for the daft question xx

Hi the main model run is the black line(gfs main model) on the graphic. If you look towards the left you will see it divert upwards away from the other lines( The other lines are the main models I will say brothers or sister for easy (ensembles)that predict outcomes from the data it's got .Same has the main gfs main model run does(blackline) the outlier part means it has moved away on its own from what its brothers and sisters are saying. Its not to say its wrong but the other brothers and sisters don't go with it. Tried to explain lol. hope it helps..

[Georgina]

6 minutes ago, weathermadbarnsleylad said:

Hi the main model run is the black line(gfs main model) on the graphic. If you look towards the left you will see it divert upwards away from the other lines( The other lines are the main models I will say brothers or sister for easy (ensembles)that predict outcomes from the data it's got .Same has the main gfs main model run does(blackline) the outlier part means it has moved away on its own from what its brothers and sisters are saying. Its not to say its wrong but the other brothers and sisters don't go with it. Tried to explain lol. hope it helps..

Thankyou I understand now thanks  

[weathermadbarnsleylad]

4 minutes ago, Georgina said:

Thankyou I understand now thanks  

No worries 

[knocker]

The medium term mean anomalies this morning indicate little overall change regarding the NH pattern. The relevant area effecting the UK remains the Russian ridge connection to the Greenland block and the energy flows involving the tpv lobes in the NW Atlantic and northern Europe respectively. These control the influence, or not, of the contrasting airmasses. Given that the UK is tending to be in no mans land, the detail, at this range, remains elusive.

A glance at the clusters over the beginning of this period illustrates the delicate balance involved here

Edited December 20, 2021 by knocker

[johnholmes]

The 500 mb anomalies I use do show changes from the last few days with troughing looking to be more relevant than the ridging. It is hard to say just how the surface weather will play out over the next 5-7 days, let alone further out. See the latest anomalies below

ECMWF/GFS DAY 8-10 MEAN 500MB HEIGHT COMPARISON

WWW.METEO.PSU.EDU

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

 

[mb018538]

1 hour ago, knocker said:

The medium term mean anomalies this morning indicate little overall change regarding the NH pattern. The relevant area effecting the UK remains the Russian ridge connection to the Greenland block and the energy flows involving the tpv lobes in the NW Atlantic and northern Europe respectively. These control the influence, or not, of the contrasting airmasses. Given that the UK is tending to be in no mans land, the detail, at this range, remains elusive.

A glance at the clusters over the beginning of this period illustrates the delicate balance involved here

Certainly looks mainly unsettled in the Christmas to new year period.....though some hints that pressure may begin to rise again as we enter 2022:

[BrickFielder]

CPC Blocking forecasts suggests blocking high over the UK will migrate to Greenland while a blocking low develops over Scandinavia before it fills and lifts out northwards.

From this I would expect an artic feed of air starting Thursday making its way southwards which steadily makes its way towards the UK before we get a breakdown next week as Atlantic mild weather returns.

Leaving out the beast from the east snow scenarios then two synoptic situations are known to give significant snow to the UK. The first of these is the occluded warm front and the second the polar low.

https://www.rmets.org/metmatters/snowmakers-uk-part-1
https://www.rmets.org/metmatters/snowmakers-uk-part-2

Fax charts hint at possibilities for both of these. The first hint may come on christmas eve as a possible disturbance crosses the UK. Models suggest the cold air flow from the north will not really have reached the UK by then. Christmas day afternoon does currently look like a possibility of snow although moisture looks a bit meagre.

Fax charts followed by wind patterns suggest that small low pressure systems could develop in the eddies to the south of Norway and later from Iceland. Low pressure positioning over Scandinavia would suggest steerage winds for Norwegian polar lows would take them into the Netherlands and France.

Possible Icelandic polar lows look a little late and may get shut out by the returning Atlantic flow.

It is hard to predict at this range but it could just be a few light flurries on Christmas day with sleet turning to rain as Atlantic mild weather returns. On the other hand the ingredients are there for some snow and anybody travelling needs to keep a close eye on forecasts. My gut feeling is the high pressure ridging across the UK breaks down quicker than models suggest and the artic air flow reaches the UK a bit late favouring snow more in the North of the UK.

 

[knocker]

Small differences of  the energy distribution are still resulting in some uncertainty in the movement of Atlantic low, and associated fronts, and the possible phasing with the tpv lobe to the NE, at the end of the week and beginning of next, and thus the boundary of the cold/milder air

[knocker]

For a short while now the ext mean anomalies have been hinting at the retrogression and weakening of the  Greenland block allied to a corresponding weakening of tpv lobe northern Russia. This facilitates amplification of the Azores  ridge and a rise of temps to around average

[knocker]

The ecm this morning is not a million miles away from last night's fax

[mb018538]

50 minutes ago, knocker said:

The ecm this morning is not a million miles away from last night's fax

Have you turned American knocker? Dew points posted up in Fahrenheit? Whatever next! 

[knocker]

3 minutes ago, mb018538 said:

Have you turned American knocker? Dew points posted up in Fahrenheit? Whatever next! 

For some reason WB don't give them in Centigrade

[knocker]

Stark differences between the gfs/ecm medium term anomalies this morning essentially involving the energy flows around the north of the Greenland block. As last night the ecm is still establishing a high cell over the eastern Arctic, the gfs not interested, which pretty much negates one of the energy flows and thus makes a big difference to the temps over western Europe

[knocker]

Looking at the clusters 120-168. Perhaps the milder airmass shading it? But I'm glad most of this is above my pay grade

Edited December 21, 2021 by knocker

[phil nw.]

Latest faxs from the MO for noon Thurs 23rd and Friday 24th show frontal systems across the UK moving north and then slowing with the occlusion over Scotland starting to head south on Christmas eve.

The raw  850 hPa chart shows the cold air behind the occlusion to the north expected to come south over the following days.

[phil nw.]

Just for Christmas interest the charts below from the 06z GFS wrt 850 temps and snowfall.These are just snapshots at noon on both days.Not to be taken as a forecast.

 

They do show the cold air coming south and engaging with the milder air over much of England and Wales.The boundary area showing some snowfall but this is just the latest idea.A cold easterly wind to the north of the frontal zone as the Atlantic trough disrupts up the English channel.

[knocker]

Hold the front page. Mean ens surface temp forb the weekend from the 06 ecm

 

[jvenge]

3 minutes ago, knocker said:

Hold the front page. Mean ens surface temp forb the weekend from the 06 ecm

 

ECM Control and ENS favours cold rain for the majority for the period of interest. Although from the mean there is probably a cluster seeing something closer to the much loved GFS Op.

[knocker]

7 minutes ago, jvenge said:

ECM Control and ENS favours cold rain for the majority for the period of interest. Although from the mean there is probably a cluster seeing something closer to the much loved GFS Op.

Yes I would imagine that would be the case. I'm not sure what the excitement is all about as at best it likely be a  minor snow event in a limited area. In fact it could well be quite wet and windy in my neck of the woods.

[knocker]

Interesting that the gfs develops a wave near Coruna midnight Friday and rapidly develops it as it runs north to be  967mb at 2100 Saturday

[jvenge]

Although there is obviously a signal for what the GFS Op shows, the ensemble mean is distinctly not as enthusiastic and generous as the Op. 

[jvenge]

ECM 12Z Op is still not going along with the GFS Op regarding the snow prospects for the period 25th to 27th.

[knocker]

You can see where the gfs idea of the developing wave on the front in the SE quadrant of the main low comes from, even if the ecm does not go along with it. It will be interesting to see how this pans out. Either way I can't see me going out for an Xmas stroll

Edited December 21, 2021 by knocker

[phil nw.]

Yes the Christmas period looks either wet or wet in various locations Knocker.

Anyway 12z GFS latest upper air temps and snow/rain charts for noon Christmas and boxing day,

 

The snow risk area extended just a smidgen south compared to the 06z showing the N. Midlands and a large part of Wales under the risk on both days.That channel low retaining milder air into southern areas coming up on it's eastern side.

Edited December 21, 2021 by phil nw.
amended text

[knocker]

Some wave breaking in the 5-10 period that promotes the Azores ridge. Interesting that this has been indicated by the ext. anomalies over the last couple of days. Temps below average for this period