Model Output Discussion 29th December - Into mid-Winter.

[johnholmes]

The usual 3 anomaly charts shown below. All 3 have a flow into the UK from a strongish Atlantic flow showing just n of west, more so on the ECMWF-GFS variants. Remember they are mean charts so any particular day will show s of and more n of west than the mean. I would expect changeable at times as lows run across the Atlantic, with a tendency to be further south with time. So I still expect a deeper cold spell occurring in this period, say 1-3 days. The flow does not suggest anything longer. Equally there is likely to be a day or so at a time when milder returns into at least the southern half of the UK.

Just my ideas of course and not really borne out by our own Met Office, although there own thickness charts, see at the bottom of the Fax page link, does show that flow veering more to the north west late in the runs.

ECMWF-GFS

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

NOAA

http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html

 

UK Fax link

 

http://www.weathercharts.org/ukmomslp.htm

thank you to tightisobar for your text change last night

[bluearmy]

7 minutes ago, feb1991blizzard said:

And it drops further into Europe at d10, does this pattern persist d10-15 and any sign of -ve anoms backing west on current eps?

Yes if persists and no compelling evidence of the Russian ridge extending west across the top as yet.  The low anomoly transfers slowly from Denmark to Switzerland over the five days. We stay under low anomolies but whether cold wishbone settled or cold unsettled unknown.

Slight changes on the Canadian suite this morning - will watch the 12z for continuity

Edited January 4, 2017 by bluearmy

[northwestsnow]

5 minutes ago, bluearmy said:

Yes if persists and no compelling evidence of the Russian ridge extending west across the top as yet. 

Slight changes on the Canadian suite this morning - will watch the 12z for continuity

Thats the key Blue, getting some assistance from High pressure to the NE, otherwise any NW flow (if we do get one) will be transitory.

Maybe i set my bar to high last night but personally im a bit disappointed with the morning ops, granted the GEFS/ECM mean look decent...seen that before though.

Edited January 4, 2017 by northwestsnow

[Frosty.]

Judging by the latest models I would say we are on track for a couple of polar maritime outbreaks next week, cold enough at times for wintry showers to low levels and night frosts.

[Polar Maritime]

3 minutes ago, Frosty. said:

Judging by the latest models I would say we are on track for a couple of polar maritime outbreaks next week, cold enough at times for wintry showers to low levels and night frosts.

Certainly looks that way Karl judging the GFS & ECM.

[Seasonality]

17 minutes ago, johnholmes said:

The usual 3 anomaly charts shown below. All 3 have a flow into the UK from a strongish Atlantic flow showing just n of west, more so on the ECMWF-GFS variants. Remember they are mean charts so any particular day will show s of and more n of west than the mean.

Hello John,

I'm not sure what you mean by the bolded section. Sorry if I'm being obtuse but I do like the way you use anomaly charts and it is something I'm trying to get better at.

[radiohead]

11 minutes ago, Frosty. said:

Judging by the latest models I would say we are on track for a couple of polar maritime outbreaks next week, cold enough at times for wintry showers to low levels and night frosts.

I would agree with that. The models do show the potential for brief spells of cold northwesterly winds bringing wintry showers at times, rather than any prolonged type of cold setup. It could be wet and windy at times proceeding those spells too, especially in the north.

Let's see what the 06Z GFS offers. There has been no P run since yesterday morning.

[Frosty.]

20 minutes ago, Polar Maritime said:

Certainly looks that way Karl judging the GFS & ECM.

Yes PM let's hope so

P.S...Happy New Year all

[johnholmes]

24 minutes ago, Seasonality said:

Hello John,

I'm not sure what you mean by the bolded section. Sorry if I'm being obtuse but I do like the way you use anomaly charts and it is something I'm trying to get better at.

thank you S, re the bold=to reply now I have actually read what you asked!

They are mean charts over the 6-10 days or 8-14 for the second set of NOAA charts. Thus on any particular day they may vary from the average shown. Be that more N of W or more S of W. Obviously these variations are what the synoptic models will give more detail on as the time approaches. Anomaly charts are very good, usually, for giving an overall idea of the type of weather, and predicting a change of type. Thus a pattern from changeable to more settled or vice verca, a change of airmass etc.They are much less so for any detail even after many years of use and my background in meteorology.

Hope that helps, happy to chat via pm if you wish rather than clutter up the thread for others?

Edited January 4, 2017 by johnholmes

[Seasonality]

Just now, johnholmes said:

thank you S, re the bold= I am abut to remove it as I have no idea why it is bolded other than my finger trouble

Sorry John, I bolded it myself. Was wondering what you meant by that comment rather than it being bolded! 

[Tristrame]

30 minutes ago, Seasonality said:

Hello John,

I'm not sure what you mean by the bolded section. Sorry if I'm being obtuse but I do like the way you use anomaly charts and it is something I'm trying to get better at.

He is using the mean chart of all the members some of which are milder south of west others colder north of west

so he's saying if it's the trend or accurate going forward then the main full run,the op run that's published twice a day on the 00Z or the 12Z could be a raging South westerly or a polar northwesterly 

The more likely  scenario that verifies will be one closer to the mean or average of all the ensemble members but with chaos theory not necessarily especially with charts beyond 4 or 5 days

Edit Sorry Jh got his reply in

hope mine helps 

Edited January 4, 2017 by Tristrame

[Seasonality]

1 minute ago, Tristrame said:

He is using the mean chart of all the members some of which are milder south of west others colder north of west

so he's saying if it's the trend or accurate going forward then the main full run,the op run that's published twice a day on the 00Z or the 12Z could be a raging South westerly or a polar northwesterly 

The more scenario that verifies will be one closer to the mean or average of all the ensemble members but with chaos theory not necessarily especially with charts beyond 4 or 5 days

Thanks, makes sense now, was just struggling with the wording.

[johnholmes]

10 minutes ago, Tristrame said:

 

so he's saying if it's the trend or accurate going forward then the main full run,the op run that's published twice a day on the 00Z or the 12Z could be a raging South westerly or a polar northwesterly 

 

 

hope mine helps 

that is not really how I see them but you are obviously entitled to give your view. As they are mean charts at 500mb they are far less liable to the switches one sees in the synoptic models. Part of that, not all, is due to the lowest 500mb in the atmosphere where the greater part of any moisture is held. It is also something old meteorologists used to call the level of non divergence. Prior to computers the surface chart and the 500mb charts were the basis of forecasting for 24 hours ahead, with some kind of guidance out to 48 hours. By gridding one with the other one arrived at the 'thickness' chart. Empirical research had shown that weather systems, lows especially, moved with these lines of 'thickness'. Convergence and divergence at this height helped decide whether to deepen a surface low or fill it.

Sorry to ramble clogging up the thread mods so feel free to delete, just getting carried away-silly old duffa.

[alexisj9]

8 minutes ago, johnholmes said:

that is not really how I see them but you are obviously entitled to give your view. As they are mean charts at 500mb they are far less liable to the switches one sees in the synoptic models. Part of that, not all, is due to the lowest 500mb in the atmosphere where the greater part of any moisture is held. It is also something old meteorologists used to call the level of non divergence. Prior to computers the surface chart and the 500mb charts were the basis of forecasting for 24 hours ahead, with some kind of guidance out to 48 hours. By gridding one with the other one arrived at the 'thickness' chart. Empirical research had shown that weather systems, lows especially, moved with these lines of 'thickness'. Convergence and divergence at this height helped decide whether to deepen a surface low or fill it.

Sorry to ramble clogging up the thread mods so feel free to delete, just getting carried away-silly old duffa.

Nothing silly about your post, a very relevant look into the history of forecasting, and interesting to me, and I'm sure others as well. 

[Hammer50]

sorry to be a pain have been an avid cold weather watcher for a few years I want to get in on the model talking but don't know how to post charts I have only an iPad no computer can it be done then I hope to add some more chat to the debate.thanks guys and gals .

[radiohead]

Some cold air reaching the north on the 06Z at T156, though it would be mainly dry at this point with the high pressure pushing in.

[Spah1]

Look how much further the trough drops into Europe on the 6 z compared to the 0 z at 156hrs

Edited January 4, 2017 by Spah1

[knocker]

25 minutes ago, johnholmes said:

that is not really how I see them but you are obviously entitled to give your view. As they are mean charts at 500mb they are far less liable to the switches one sees in the synoptic models. Part of that, not all, is due to the lowest 500mb in the atmosphere where the greater part of any moisture is held. It is also something old meteorologists used to call the level of non divergence. Prior to computers the surface chart and the 500mb charts were the basis of forecasting for 24 hours ahead, with some kind of guidance out to 48 hours. By gridding one with the other one arrived at the 'thickness' chart. Empirical research had shown that weather systems, lows especially, moved with these lines of 'thickness'. Convergence and divergence at this height helped decide whether to deepen a surface low or fill it.

Sorry to ramble clogging up the thread mods so feel free to delete, just getting carried away-silly old duffa.

Keep on rambling you silly old duffer

[Alekos]

1 minute ago, Spah1 said:

Look how much further the trough drops into Europe on the 6 z compared to the 0 z at 156hrs

Looking good again for Greece at this range ! 

[radiohead]

4 minutes ago, Alekos said:

Looking good again for Greece at this range ! 

Well it's nice to see somewhere being turned into a winter wonderland!

[Seasonality]

1 minute ago, knocker said:

Keep on rambling you silly old duffer

John and Knocker are two duffers I always pay attention to, I won't call either of you old or silly! 06z certainly looking like a good run, low pressure in the med and cold troughing into Europe with lots of chances for snow. Agreed that it is a belter for Greece, and seems to follow the ECM and UKMO trend of keeping the cold in place longer. 

[Man With Beard]

Morning all - so the next colder shot firming up for 12th-16th Jan - at D10, 850hpa anomalies on both GEFS and ECM at -4C below normal - very tight clustering around or just below the -5C line for London on GEFS and a range from -2C to -8C on the ECM ensembles across the country.

So I imagine the ECM ensembles will look pretty similar to GEFS at D10, with a range of options from WNWlies to NNWlies i.e. both "cooler" runs and "colder" runs.

Longer out, ECM ensembles generally keep Atlantic heights and Euro troughing and looks like more "cold zonal" with occasional amplification bringing down something even colder. 

In summary then, we're on the cusp of a pattern cold enough to bring snow to all, but probably not potent enough for widespread snow without a few further tweaks (possible), and not amplified enough to prevent further flattening if the PV once again pushes the pattern more than forecast.

At least we're seeing a bit more consistency now, though.

I can't see the Murr sinking low coming off now as the pattern is too far east even with the most extreme corrections - good spot though Steve!

Edited January 4, 2017 by Man With Beard

[radiohead]

Another shot of cold air at T204 on the GFS. ECM was showing something similar too.

[legritter]

5 minutes ago, Hammer50 said:

sorry to be a pain have been an avid cold weather watcher for a few years I want to get in on the model talking but don't know how to post charts I have only an iPad no computer can it be done then I hope to add some more chat to the debate.thanks guys and gals .

Yes it can be done ,if i can do it so can you ,took me a while ,so if you click on a chart probably with finger and down load like you would a photo and save it in your files ,then follow instructions IE where it says Drag files here to attach , sorry just basic but plenty more posters will put the answer better ,back to charts and lets see if our cold n westerly is still on course ,cheers .

[Rocheydub]

7 minutes ago, radiohead said:

Another shot of cold air at T204 on the GFS. ECM was showing something similar too.

Only transient though. Still better than nothing!