Model Output Discussions 12z 01/09/2016

[Mucka]

Wide range of possibilities portrayed among GFS 12z ensembles from Day 7 very much reflecting why Fergie and the MetO are so circumspect beyond this time-frame.

If anything the scatter has increased between more mobile less blocked solutions and those looking to rebuild heights toward Greenland.

That said we are not talking zonal returning, just  a messy breakdown attempt before blocking generally reestablishes itself even on those solutions that favour a short period of increased mobility.

 

 

 

Edited October 28, 2016 by Mucka

[Frosty.]

The Gfs 12z op run made for very nice viewing for a coldie with the first taste of chilly polar air next tues / wed followed by a brief frosty ridge and then even colder days and nights with quite a number of frosts and even a chance of some sleet and snow for some of us, especially on higher ground. Our weather comes in from the nw / n for most of the run with reloading pm / am outbreaks. Hopefully there will be more potent cold runs on the way. Even the end of the run hints at more cold air to swing SE beyond mid Nov and something unusually wintry could pop up..more runs of this type please

Edited October 28, 2016 by Frosty.

[knocker]

The latest missive from the woodshed has the colder air moving east 

[Matthew.]

16 minutes ago, knocker said:

The latest missive from the woodshed has the colder air moving east 

I like the way there's a little orange remaining for the SW though something for everyone!

[Johnp]

18 minutes ago, knocker said:

The latest missive from the woodshed has the colder air moving east 

Do you mean West?

[Ali1977]

1 minute ago, Johnp said:

Do you mean West?

He does mean East I think, as in this run wasn't as cold as the last and the colder weather is further East.

[Frosty.]

The GEFS 12z mean shows the first chilly NNWly incursion next tues / wed which is followed by a ridge which becomes a weak high pressure cell so some slight frosts on the way through the second half of next week. Thereafter pressure falls across the uk and to the n / ne, the high drifts away southwestwards with the uk in a rather cold run of polar air..so, just like the 6z mean, longer term, the 12z mean indicates a transition to below average to relatively cold temps with showers at times which would turn more wintry, especially in the north and on hills where snow could occur and frosts become generally more widespread too. 

[Matthew.]

The ECM 12z agrees with cold air pushing south on Tuesday into Wednesday-a real chill in the air. However high pressure edges in Thursday and by Friday the Uk is trapped in a zonal flow between HP to the south and North. First westerly like this I've seen in a while, stays coolish but not as so because of higher pressure to the south.

[Frosty.]

The weather headline is already written for next week..becoming colder from the NW as the Ecm 12z shows with some frosty nights.

[Matthew.]

Yes Frosty upper air 850's drop nearly 10c from this week to mid next week.

[Frosty.]

A much better end to the Ecm 12z than the 00z with cold air rushing south

[Ravelin]

^^^

That will feel decidedly chill up here. 

[Zakos]

Does anyone know if the GFS still has a tendency to "default" to south westerly patterns in FI since the update?

 I am amazed at how long we have seen no sign at all of a return to a mobile pattern. 

This is the most westerly chart I have seen in over a week from the GFS 12z at +384

However, we retain a broadly north-west flow,  the AO is still negative and the Atlantic is still very blocked.

Obviously we cannot guarantee deep cold for the UK... however, going purely on the model output, I cannot see any chance of a return to a south westerly pattern in the coming weeks.

Surely, if there was a possibility of the Atlantic firing up, we would have seen at least a hint of this?

run after run from the ECM and GFS shows a continuation of these very blocked conditions.. only a matter of time before the UK receives cold air in this pattern, unless we are very unlucky

 

 

Edited October 28, 2016 by Zakos

[joggs]

Going on all the charts,latest runs.What does bonfire night have in store for Northern England?.

Appreciate a heads up.Thanks.

[feb1991blizzard]

3 minutes ago, joggs said:

Going on all the charts,latest runs.What does bonfire night have in store for Northern England?.

Appreciate a heads up.Thanks.

Its going to be slightly below average temperatures and very likely dry.

[Ali1977]

I think a negative AO is a given, and the signs that it may go even more negative late Nov is potentially great news. The charts are really good now but they just don't fall in a great position just yet to sustain a Northerly. There is still the odd low spinning off southern Greenland disrupting the potential of a "perfect" block , and by the sounds of it these complicated little features are what's stopping the chance of some real early cold in Britain and hindering forecasting accuracy past late next week - it's too early at the minute anyway, but in 3-4 weeks when a potential better AO situation occurs this will be a different story.

[knocker]

One can't say it's not interesting watching the models at the moment as the ecm breaks ranks this evening.

Everything as expected at T120 as the trough drops SE into the Baltic States bringing with it a brief cold northerly

But then we go off script. The next trough arriving from the west does run north of the UK and phase in with the trough to the east but this reconfigures so plunging SE is not an option. Meanwhile ridging mid Atlantic is not quite so vigorous as of late so the next trough from Canada tracks further south and runs straight into the UK

[Froze were the Days]

To my untrained eye the ECM is getting flatter and flatter - 4/5 days ago Halloween was getting colder and it was 50/50 chance of the 0c isotherm over the south of England, now as we approach that date mild air continues until 1st/2nd Nov with a brief 'watered' down Pm slot, even as we get closer to Guy fawkes that too is looking less likely to be a chilly one (as the ECM has been modelling over the last 2 days). Once again the most tempting synoptics at 10 days time...When will we actually get some cold air over the country?

Has a new moans and ramps thread been set up yet?

[feb1991blizzard]

1 minute ago, knocker said:

 

But then we go off script. The next trough arriving from the west does run north of the UK and phase in with the trough to the east but this reconfigures so plunging SE is not an option. Meanwhile ridging mid Atlantic is not quite so vigorous as of late so the next trough from Canada tracks further south and runs straight into the UK

 

And then some more WAA up western side of Greenland means the floodgates from the North open up.

[knocker]

15 minutes ago, joggs said:

Going on all the charts,latest runs.What does bonfire night have in store for Northern England?.

Appreciate a heads up.Thanks.

I can tell you what the ecm is showing but frankly it's not worth a great deal at this range. There is a frontal system about 300Km west of N. Ireland at 18z so at that a fairly light westerly but those systems race in in the next 12 hours even here timing is critical. I would give it at least a couple of days.

[Zakos]

Remains unclear when/ if the UK will see a cold spell. Ive been an avid model watcher since I joined netweather in November 2010. I just started model watching before the coldest December in 100 years, and have forever since been hooked.

I've learned over the years that you cannot pin your hopes on each run, and the best way IMO during a cold spell is to use at least 3 consecutive runs to back up a forecast. One run could be a complete outlier.  2 runs could be a fluke. but 3 runs in a row showing cold air entering the UK, and the models are usually on to something.

12z06z00z

At 114 hours, unanimous agreement for a cold shot into Europe, the cold airflow just missing the Uk, which remains under the influence of the Atlantic block.

12z06z00z

Again, at 210 hours, unanimous agreement for a second, more potent cold shot into Europe.

The big difference on the runs here is that each run drastically increases the potency of the cold shot, and shunts it further west

That is a very cold airmass heading directly for the UK on the 12z... one more upgrade like that and we would be in the freezer.

I think this thread may well descend into meltdown by the second week of November if the GFS is anything to go by.

Im not getting my hopes up just yet. If the next 3 runs maintain this trend then we may well be on to something!

 

 

Edited October 28, 2016 by Zakos

[Richard Taylor]

1 hour ago, Ravelin said:

^^^

That will feel decidedly chill up here. 

Hmmm, might need to dust off my snowboots up here Ravelin, just in case.

[Zakos]

 Steve Murr was the first to identify the second cold shot from the models.Apologies Steve I didn't read your post. I agree, we are potentially entering the first notable cold spell for quite some time.

[SMU]

No worries

nothings certain, the second cold attack is a tricky evolution relying on that second low over Iceland sliding as far SE as poss!

The sustainability of poss second snap all depends on how far the atlantic ridge pulses north..

All if buts & maybes ATM - however make the most of the next 3 days as 16/17c may not appear again till april !

S

[Eye to the sky]

Just watched East Midlands Today and they had snowflakes over the Peak District! for tonight!!..