Model Output Discussion 01/09/17

[Captain Shortwave]

A few posts have been removed, can we stick to model discussion please. 

Thankyou

 

Moving on, a little better from the GFS, that next low should feed into the Euro trough, I guess a pattern similar to the end of November 2012 would be a good comparison with a NW/SE jet with plenty of polar marimite/arctic maritime blasts with occasional milder days.

I am going to be honest and say this is probably more realistic compared to the ECM with a very progressive take on the retrogression signal. That said when I say milder, it would probably be a rise to near normal temperatures at best here.

Edited November 26, 2017 by Captain Shortwave

[bobbydog]

Just now, knocker said:

Actually I wasn't trying to be funny and the date of the chart is totally irrelevant to the point I was attempting to make. A point that predictable has passed you and others by, presumably because as usual you all know it all.

i get what you are saying. an hp cell could be placed anywhere over a wide area, the anomaly 'black hole' is showing the intersection of the various possible placements. the high anomaly does show that its very likely to be centred near to the 'black hole'.

[Singularity]

So... the dual cut-off lows are maintained by GFS and ECM and with an eastward adjustment that makes for some nicely positioned blocking to the NW and in the case of ECM, right across to the N and NE too.

On the other hand, UKMO fails to cut-off the low that exits N. America on days 5-6 and this makes for a much less appealing route forward. GEM is also uninspiring but via a different route; it lifts out the low by the Azores after only a short stint as a cut-off feature. The one off N. America does keep south and cut-off, but this can only boost the spatial extent of the ridging that ends up spilling across the UK and surrounds. They're not hideous outcomes as plenty of dry weather is on offer, but given what GFS and ECM are playing around with, they seem mediocre by comparison.

These cut-off lows are so notoriously unpredictable that IMO, all bets are off regarding the details of the transitional period between our current cold spell and whatever takes place as a result of the stratospheric warming, although the vigour of the westerlies does overall look to remain notably less than usual. 

[Singularity]

5 minutes ago, Captain Shortwave said:

Moving on, a little better from the GFS, that next low should feed into the Euro trough, I guess a pattern similar to the end of November 2012 would be a good comparison with a NW/SE jet with plenty of polar marimite/arctic maritime blasts with occasional milder days.

I am going to be honest and say this is probably more realistic compared to the ECM with a very progressive take on the retrogression signal. That said when I say milder, it would probably be a rise to near normal temperatures at best here.

 

Seems like GFS is trying to hop into the ECM powerboat, destination Greenland ridging round 2, but without such idyllic behaviour of the lows off Canada.

[Dancerwithwings]

4 minutes ago, bobbydog said:

i get what you are saying. an hp cell could be placed anywhere over a wide area, the anomaly 'black hole' is showing the intersection of the various possible placements. the high anomaly does show that its very likely to be centred near to the 'black hole'.

Thank you for your time in explaining/highlighting this  

Edited November 26, 2017 by Dancerwithwings

[northwestsnow]

22 minutes ago, Steve Murr said:

GFS already backtracking now as the upper air cold pool expands over NW europe-

The SE corner doesnt lose the -6line

where as the 00z had it over debilt-

s

Great news steve..:)

[bobbydog]

Just now, Dancerwithwings said:

Thank you for your time in explaining/highlighting this  

just to be clear, i wasn't knocking knocker, because he does have his knockers...

[knocker]

16 minutes ago, bobbydog said:

i get what you are saying. an hp cell could be placed anywhere over a wide area, the anomaly 'black hole' is showing the intersection of the various possible placements. the high anomaly does show that its very likely to be centred near to the 'black hole'.

Really. Same chart with contour lines. The point I was attempting to make and was just ridiculed is that anomaly charts on their own should not be used for this and can be misleading. I won't bother in future

Edited November 26, 2017 by knocker

[Derecho]

Morning here is my interpretation of the 06z GFS and 00z ECM and UKMO

Only interpretations upto T240 are made

Upto T120 little change in the output, Thursday still the coldest day with the chance of snow showers on eastern coasts.

However at T144 we come to a very important point:

GFS                                                          UKMO                                                      ECM

To keep the potential for cold in the medium time range it is very important that the two highs in the North Atlantic join together and the Azores low is kept stationary. It also limits milder air coming in from the NW next weekend

The GFS and ECM both achieve this but the UKMO is worrying because at T144  (showing yesterdays chart for some reason) there is some energy between the northern part of the two high pressure cells.

This could disrupt the link and send the high just to the West of the UK south.

The next step at T192 is to keep the high pressure to the NW and avoid any sinking into Spain. The ECM strikes the sweet spot, GFS is getting there on the 06z but the WAA towards Greenland isn’t as strong. The low around NE Canada also needs to be stationary and not interfere.

GFS                                                          ECM

If that happens then we end up with a northerly reload aka ECM T240. GFS not too far away with a chilly-ish North-westerly and sustained heights to our west but lacking the ECM's immediate potential from this point.

GFS                                                         ECM


Overall ratings

UKMO 5/10 snowflakes – Potential spanner in the works at T144
GFS     6.5/10 snowflakes – More prolonged colder temperatures though messier thereafter
ECM  7.5-8/10 snowflakes – Best of the bunch and sustained northern blocking

Edited November 26, 2017 by Quicksilver1989

[bobbydog]

4 minutes ago, knocker said:

Really. Same chart with comtour lines

my apologies, i thought it was regarding pressure anomalies not geopotential heights.

- in which case, your point is very valid. it won't show the placement of the hp cell.

Edited November 26, 2017 by bobbydog

[Ice Day]

Pretty quiet run this from around day 4 other than a brief incursion from the north days 8-9, but looking cold throughout.  Mainly dry and should be some decent frosts around.

[shaky]

35 minutes ago, Steve Murr said:

GFS already backtracking now as the upper air cold pool expands over NW europe-

The SE corner doesnt lose the -6line

where as the 00z had it over debilt-

s

Was just about to say the same thing steve!!since yesterdays 12 run that cold pool doesnt seem to wana leave england and is getting pushed further west with each run!!also the shortwave to the north east over norway seems to be cutting south further and further west with each run!!

[Catacol]

10 minutes ago, knocker said:

Really. Same chart with contour lines. The point I was attempting to make and was just ridiculed is that anomaly charts on their own should not be used for this and can be misleading. I won't bother in future

Very valid point - please keep making it. It is really important people understand the nature of an anomaly and use it only as a guide. 

[Frosty.]

The Gfs 6z becomes wintry from the north during the week ahead with frosty / icy nights and showers turning more and more to snow across the north and then to western and eastern counties further south with even a risk of persistent snow across the southeast later in the week..lovely jubbly as del boy used to say!

Edited November 26, 2017 by Frosty.

[Methuselah]

4 minutes ago, shaky said:

Was just about to say the same thing steve!!since yesterdays 12 run that cold pool doesnt seem to wana leave england and is getting pushed further west with each run!!also the shortwave to the north east over norway seems to be cutting south further and further west with each run!!

Hopefully, that cold pool (always assuming the models have it right, of course) will provide some freezing fog...just like what I remember from early December 1962?

[gottolovethisweather]

On 24/11/2017 at 10:04, gottolovethisweather said:

Or better still the actual weather, they are all but predictions/forecasts after all. But like James Brown, "I feel good" about things, currently as a coldie. I'll await the UKMO 12z and ECM 12z with interest tonight. 

"I still feel good" like James Brown and now that my D6 and beyond range of charts from my post earlier in the week have come to forecastable timescales, the overall consensus is that it remains cold, in fact, borderline cold for snow even in my neck of the woods during the following working week. It's just the sort of scenario one could only dream of in late Autumn, three to four days of Northerly incursions and if not, longer than that. The fly in the ointment being the 850s aren't quite forecast to be deep enough to deliver snow for everyone, as still the usual suspects mentioned in here remain best favoured for snow, hilltops and moors. Nonetheless, the chill is descending and with my eyes on lower than normal heights across the continent, the general picture has to be one which eventually favours early snowfall for many. Watch thsi space! The next particular timeframe of intrique comes about next weekend, well there's a recurring trend. 

Edited November 26, 2017 by gottolovethisweather

[swfc]

Gfs 6z a bit of any anticlimax tbh.no real forceful push north with the block ete after this week's cold snap.drifts into a a standard early  winter nhp outlook . Obviously subject to change but unless ecm has again over done the blocking then nothing out of the norm

 

Edited November 26, 2017 by swfc

[gottolovethisweather]

27 minutes ago, Frosty. said:

The Gfs 6z becomes wintry from the north during the week ahead with frosty / icy nights and showers turning more and more to snow across the north and then to western and eastern counties further south with even a risk of persistent snow across the southeast later in the week..lovely jubbly as del boy used to say!

Best headline summary of the day of the current situation, thanks, @Frosty. My ramble above was basically attempting to hint at the same, this forthcoming week has good/great potential (oh yes, that word again) for coldies. Two points to watch in the reliable out to D6-D10 or so. The longer the colder Northerly flow can be sustained, the better and the longer the troughing can remain in-situ over the continent, the better. 

Edited November 26, 2017 by gottolovethisweather

[johnholmes]

2 hours ago, Dancerwithwings said:

Hopefully the pattern carries onto December and talk of mega reloads that shows itself in the GFS anomaly charts.....Two black hole together in the same chart....Can't be bad

The two very high anomalies on the 500 mb chart shown are just that - anomalies to what the 500 mb pattern normally shows. Please be very careful when using anomaly charts and how you interpret them. They can and do give very useful guidance on the probable placement of upper ridges and troughs but they do need very careful assessments. I am not knocking anyone but just be careful. you will soon get used to a few who use them sensibly and if anyone has any questions then please pm me and I will do my best to answer you, or point you to someone who I feel could perhaps do it better than me. Rather than clutter up the model thread.

[gottolovethisweather]

And as if to illustrate the upcoming situation this next working week, from a European/Northern Hemisphere viewpoint. What a way to end November and start the Winter season? Actual Temperatures will likely struggle to reach 2-3c in our bigger cities even down South and a lot of us will likely see an ICE day, should this mean 850 chart come off as shown. Wowzer. 

 

I'm not looking post-Friday 1st December but I am hoping the cold pool lingers and the blocking High largely remains in-situ out in the Atlantic and perhaps it could be a case of looking towards the action out E/NE by then.

Edited November 26, 2017 by gottolovethisweather

[Derecho]

Just another quick post from me, the 06z ensembles are actually pretty good. At T168 a small minority have gone to sinking heights in Europe, but there are quite a lot like the ECM. The OP was one of the less interesting members this time round. Anyway here are my ratings from one to ten snowflakes upto T240:

Op - 6.5                P7 - 9                   P15 - 8
Ctrl - 7.5/8            P8 - 8                   P16 - 7.5
P1 - 7.5/8             P9 - 7.5                P17 - 8
P2 - 8.5                P10 - 7.5              P18 - 8
P3 - 6.5/7             P11 - 6.5/7           P19 - 8/8.5
P4 - 6.5                P12 - 7.5              P20 - 8
P5 - 5.5/6             P13 - 7.5/8
P6 - 7.5                P14 - 3 (UGH)

Maybe there is more potential for the high to hold then I saw on the UKMO but a really good set of ensembles! Quite a lot of easterly/anticyclonic cold options!

Edited November 26, 2017 by Quicksilver1989

[Snowy L]

1 hour ago, Catacol said:

Very valid point - please keep making it. It is really important people understand the nature of an anomaly and use it only as a guide. 

 

1 hour ago, knocker said:

Really. Same chart with contour lines. The point I was attempting to make and was just ridiculed is that anomaly charts on their own should not be used for this and can be misleading. I won't bother in future

This is why I can't stand anomaly charts. They build up hope with anomalies literally off the scale over Greenland yet in reality all that translates into is a little wobble in the jet.

[knocker]

10 minutes ago, Snowy L said:

 

This is why I can't stand anomaly charts. They build up hope with anomalies literally off the scale over Greenland yet in reality all that translates into is a little wobble in the jet.

Not necessarily little  Mentally take the contour lines away And hey a Rex Block as well

Edited November 26, 2017 by knocker

[feb1991blizzard]

19 minutes ago, Snowy L said:

 

This is why I can't stand anomaly charts. They build up hope with anomalies literally off the scale over Greenland yet in reality all that translates into is a little wobble in the jet.

And if ever you want to see an example of them 'lying', head to the CFS monthly page on meteociel, keep looking at the Mean, and the Anomalies in terms of height, Greenland (because the default iss very low heights) will provide you with a classic example,  you'll find one within a few days if you view every run.

Edited November 26, 2017 by feb1991blizzard

[Methuselah]

45 minutes ago, gottolovethisweather said:

And as if to illustrate the upcoming situation this next working week, from a European/Northern Hemisphere viewpoint. What a way to end November and start the Winter season? Actual Temperatures will likely struggle to reach 2-3c in our bigger cities even down South and a lot of us will likely see an ICE day, should this mean 850 chart come off as shown. Wowzer. 

 

I'm not looking post-Friday 1st December but I am hoping the cold pool lingers and the blocking High largely remains in-situ out in the Atlantic and perhaps it could be a case of looking towards the action out E/NE by then.

What a stonker!

Your post is worth a sticky note, GTLTW; but, alas, it'll be too cold for the adhesive!