Model Output Discussion: 12Z (22/11/12) And On...

[Isolated Frost]

The differences between the GFS and ECM @168 hrs

-gfs has the trough in c europe, very organised and w-e aligned from germany to poland, ecm has the trough aligned n-s from sweden to spain, leading to a more n flow o/ the uk

-gfs has H5 +ve anomaly towards iceland, with the jet slipping below, ecm has a strong mid-atlantic high, with little passing through

-the arctic high on the gfs is near svalbard- and has a strong east flow across scandi, and a very strong connected ridge, ecm has the arctic high placed around the north pole- surge of cold air breaking the ridge around scandi

so far, the H5 anomalies support the GFS, but the ECM offers a plausible and progressive solution- will be a battle for sure

mind you, the end results are both cold- whilst the gfs looks like it could be more prolonged with heights rising to the nw- and a progressive arctic high, and the ecm delivers a weaker ridge and therefore less of a cold source flow

[Severe Siberian icy blast]

Uppers crap on 168 chart (thurs 29th) got the NW wind as well, but uppers of -4C wont be snow, too early in season yet

To be honest you couldn't be more wrong, we had snow 2 wks ago from -1 -2 uppers , the uppers of -4 is fine if due points are low and other variables play our way, which with the wind from the east, the due points are normally lower.

[Cheshire Freeze]

The ECM & JMA are very similar at T168 over Europe.

But very different around Greenland/Iceland

[January Snowstorm]

Yep at 192hrs it's getting there.

I'm off now cause it's getting exhausting

[snowmadchrisuk]

UKMO and ECM have the same Short Wave at +144 , the difference is on the ECM we can see what happens next , and it just kills the low from a 985mb to a 1005mb week feature,Will UKMO do the same ?? We will have to wait for the 00z's

[PubliusEnigma]

ECM 12z at 168 Hrs, is similar to the UK @ 144 Hrs . The mid atlantic High is more circular in shape which is more conducive

to atlantic lows traversing the northern flanks. In this set up we need to hope the lows riding around the top of the low move SE

to our west thus maintaining us in the northerly flow around our local low pressure system

Edited November 22, 2012 by PubliusEnigma

[Snowmadsam]

Seriously..why does everyone want a PROPER cold spell this early...I know you guys like and want a cold winter but you cant expect it to happen like that *clicks*

Please, please can we lower the expectations first and then raise them as the time gets nearer......there is a ramping thread on here as well....

also about the uppers.. I will keep saying it...you don't need -5 uppers to get snow.....

[bluearmy]

Cant see ecm being right at T192 so not much point disecting the remainder of the run. the trough to our ne is not supported at all by naefs at day 8. still detail unknown beyond day 5 to 6. charts remain superb for the time of year.

[bradymk]

Once again, another superb run from the BOM, shame it isn't one of the most reliable models. ECM ok but different at 192 but there is disagreement at and before +144 so who knows what is right, can't really see any of these runs being correct right now.

Matthew

Edited November 22, 2012 by bradythemole

[Isolated Frost]

192 and you see the arctic high slipping down russia way, leading to mild southerlies o/ scandi and a trough to the e of the uk- end result, a north flow-

time for retrogression, will be interesting to see 216 and 240 now.. see what comes of the next 2 frames- could become a new pattern

[Geordiesnow]

The ECM & JMA are very similar at T168 over Europe.

That JMA run looks awful for wanting to keep the blocking by the looks of it!

The charts do demonstrate why I prefer Northerlies at this time of year, much more reliable in terms of getting cold uppers heading southwards and the best easterlies do tend to occur deep into the winter months rather than late Autumn.

[Matty M]

ECM and the short-wave massacre!

[Cheshire Freeze]

192 and you see the arctic high slipping down russia way, leading to mild southerlies o/ scandi and a trough to the e of the uk- end result, a north flow-

time for retrogression, will be interesting to see 216 and 240 now.. see what comes of the next 2 frames- could become a new pattern

216hr chart isn't a good one? That trough splits, sends a shortwave north which completely isolated North Atlantic ridge from Arctic high with the rest of the trough sinking. I can't see a proper feed of cold air for quite a while (i.e within 72 hours) after that period?

Edited November 22, 2012 by CreweCold

[Liam J]

also about the uppers.. I will keep saying it...you don't need -5 uppers to get snow.....

This depends entirely on the synoptic set up. Don't expect snow from an easterly with uppers at or above -5c, not on lower ground on the windward side anyway.

[Geordiesnow]

To be honest you couldn't be more wrong, we had snow 2 wks ago from -1 -2 uppers , the uppers of -4 is fine if due points are low and other variables play our way, which with the wind from the east, the due points are normally lower.

Difference this time Shaun the winds are coming from the seas, that event the SW had has winds just coming from the UK only and the flow was quite slack and from what I heard, daytime heating meant the snow levels risen quite quickly.

I'm not dissapointed with the ECM run but its a run if you take at face value it is not a snowy run at all apart from the slight risk of some wintryness in Northern Scotland with the initial Northerly flow. That said, this run would be much worse if it was predicting the blocking to sink and the Atlantic coming back in so still plenty of potential but at this range and looking at most model runs, there has not been an awful lot of runs which suggest a cold spell is on the way. However the trends have been for the outlook to turn cooler and that what will probably happen, will the sustained cold air come later? We have to wait and see on that one.

[January Snowstorm]

Worth looking at the uppers we have right now and comparing to later next week.

Certainly cold enough for sleet at times next week and possibly snow too.

[ITSY]

certainly the feed of cold air is not quite as spectacular as GFS or BOM or GEFS...but it certainly is different from UKMO and still produces cold conditions. Still hinting at blocking and we may well end up with proper cold further down the line on this run anyway...could be a patience grasshoper set-up. Not as incredible as yesterday, but still some very optimistic synoptics

[I remember Atlantic 252]

This depends entirely on the synoptic set up. Don't expect snow from an easterly with uppers at or above -5c, not on lower ground on the windward side anyway.

I thought it was other way round, uppers of -2 to -3 generally okay off an easlerly, but off a northerly I need -7 to -8, anything off Atlantic I need below -10

[January Snowstorm]

This depends entirely on the synoptic set up. Don't expect snow from an easterly with uppers at or above -5c, not on lower ground on the windward side anyway.

And of course the opposie applies also i.e. expect snow on hills away from coasts

[Liam J]

216hr chart isn't a good one? That trough splits, sends a shortwave north which completely isolated North Atlantic ridge from Arctic high with the rest of the trough sinking. I can't see a proper feed of cold air for quite a while (i.e within 72 hours) after that period?

I'd say the cold air would get cut off altogether fairly sharpish from T240 onwards, look at Greenland, low heights & PV?

[Mucka]

That JMA run looks awful for wanting to keep the blocking by the looks of it!

The charts do demonstrate why I prefer Northerlies at this time of year, much more reliable in terms of getting cold uppers heading southwards and the best easterlies do tend to occur deep into the winter months rather than late Autumn.

JMA is a fantastic chart if you want sustained cold.

[January Snowstorm]

I thought it was other way round, uppers of -2 to -3 generally okay off an easlerly, but off a northerly I need -7 to -8, anything off Atlantic I need below -10

You are right but mainly because dewpoints are much lower from the East.

Away from coasts I would expect -3 / -4 to deliver esp on hills

[Liam J]

I thought it was other way round, uppers of -2 to -3 generally okay off an easlerly, but off a northerly I need -7 to -8, anything off Atlantic I need below -10

No you'd need sub -7c or lower in an easterly to see some decent snowfall, closer to -10c if you want some juicy snow making convection with a strong air flow. An Atlantic front could bump into T850's of 0c or just below and produce mega falls a la February 1996, if other factors are favourable to support snow.

Anyway wandering off topic here with this subject.

Edited November 22, 2012 by Liam J

[chris55]

The models will always struggle with the positioning of the Arctic high and associated troughs/Lows/shortwaves. The upcoming pattern is by no means a two day toppler and although in the past 10 years the said scenario was the most likely, the current synoptic pattern couldn't be further from that.

Just sit back and wait to see how things unfold, the Ens means are great as is the general NH pattern, if we are very unlucky it may come to nothing but IMO i doubt that.

[TEITS]

one liner and why if you please?

cold air and a -10C 850 almost over the country at times. Yes its in a far time frame but it is in keeping with the 500mb anomaly charts.

sorry you may be one of the few that likes mild but some comment from you would help-please?

Sorry john but im going to have to pull you up on this.

You cannot really use the 500mb anomaly charts to predict the upper temps because on a tiny island like ours that kind of detail isn't possible on those charts. Furthermore very few runs have actually shown -10 850s.

For newcomers the choice of models to use is simple.

500MB anomaly charts are a very good guide with regards to the general pattern because these are less prone to sudden changes.

The GFS/UKMO/ECM are better for details i.e precip, temps etc but only out to +144.

The Fax charts are even better than the models especially from +0 to +72.

Even more detail can be gained from viewing the NAE which goes out to +48.

So for newcomers that is the order of the models to use.