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

[January Snowstorm]

There's clearly a wave moving in early Thursday crossing from Southern Ireland over very South coast of UK. If it occurs as modelled it could give me a serious dump of snow! It would be very ironic if cranky toppler JS got all the snow for himself lol

[Nick F]

With regards to Thursday's wave low running in from the Atlantic across southern areas, with cold arctic air on its northern flank, now 12z UKMO, EC and 18z GFS take it through the English Channel, UKMO makes more of a feature with a closed low, whereas EC and GFS has an open wave.

UKMO T+72 ppn, T850s and 2m temps - look marginal for snow for low elevations but imagine SW Moors would get a pasting from snowfall

12z EC, has wave running similar route to UKMO, but doesn't develop heavy ppn until over eastern E Channel, weatherbell 6hr charts (not shown) shows snowfall across Kent and Sussex from this system

18z GFS now out and has a similar wave, very marginal to get snow on northern edge - SEE WHERE THE 0C DEW POINT LINE IS - need 0C or below

Of course the wave track may change north or south, or may disappear altogether!

But goes to show you there lots to watch out for, not just the favoured N and W until end of week.

 

Edited January 9, 2017 by Nick F

[snowice]

Just now, January Snowstorm said:

There's clearly a wave moving in early Thursday crossing from Southern Ireland over very South coast of UK. If it occurs as modelled it could give me a serious dump of snow! It would be very ironic if cranky toppler JS got all the snow for himself lol

We don't mind your due a bit of luck

[Man With Beard]

4 minutes ago, radiohead said:

That wave is more pronounced on the 18Z GFS. Becomes a closed low crossing the channel. Hi res models should handle it better than the global GFS.

And stop the press! Interrupt your broadcasts! Phone your relatives! THE GFS HAS GOT THE UKMO WAVE! THE 528 LINE HAS CLEARED THE COUNTRY! AND THERE'S SNOW ALONG THE M4 CORRIDOR AT T66!!!!!!!!!

(Disclaimer: please read other forecasts above before acting on this post )

Edited January 9, 2017 by Man With Beard

[bluearmy]

I know the mods don't like references to to forecasts but interesting  that the 10 day forecast was fairly clear on a westerly flow for next week. Last evening the scandi ridge got a mention on a diminishing likelihood. The eps have firmed up on it's probably since then (still not favoured) but to not mention the possibility seemed odd. 

[Timmytour]

1 minute ago, bluearmy said:

I know the mods don't like references to to forecasts but interesting  that the 10 day forecast was fairly clear on a westerly flow for next week. Last evening the scandi ridge got a mention on a diminishing likelihood. The eps have firmed up on it's probably since then (still not favoured) but to not mention the possibility seemed odd. 

Maybe they got fed up of the models crying wolf?

[damianslaw]

ECM once again holding firm with its easterly evolution - very noteworthy, that's 5 runs now in a run, and well within the reliable timeframe, GFS backing away from its quick zonal onslaught, UKMO trending more towards ECM.

The models are showing the deep cold pool over SE Europe not going anywhere, a cut off low in this region would most likely help prop up any heights rises towards scandi. 

I suspect a half way house pattern will develop, i.e. heights will attempt to ridge in towards scandi, but not sufficiently north enough to produce the easterly, instead we will maintain surface low level cold off the near continent, with the far NW exposed to weak frontal attacks, a rinse and repeat pattern, with another attack from the NW, and perhaps a greater chance after that one for a sufficient building of heights NE.

 

[January Snowstorm]

@Nick F looks very good for Southern Ireland though with us being below zero dew points too?

[winterof79]

Longer Ensembles showing cold clusters

[frosty ground]

GFS falling has been greatly exaggerated 

[Guest]

4 minutes ago, bluearmy said:

I know the mods don't like references to to forecasts but interesting  that the 10 day forecast was fairly clear on a westerly flow for next week. Last evening the scandi ridge got a mention on a diminishing likelihood. The eps have firmed up on it's probably since then (still not favoured) but to not mention the possibility seemed odd. 

Bit like the other week when they were touting winds from the North East only moments before or after the runs switched on them... they were wrong then so maybe they will be wrong again this time and them Westerlies will turn to Easterlies...

[Nick F]

1 minute ago, January Snowstorm said:

@Nick F looks very good for Southern Ireland though with us being below zero dew points too?

Yes, and the wetter3.de precip type charts show some flakes for south Wales and southern England on northern flank of wave ppn too, snow showers kicking in form the NW behind the wave

[edo]

2 hours ago, radiohead said:

What time frame is this chart please??

[tight isobar]

For point-in basis. .

Anything following north/north eadt of m4 corridor on 18zgfs would highly likely be of snow precipitation. 

With mixing out of warming sector of air south west-wards..

However at this juncture. .there will be defined alignment of sectors of wet bulb/and upper air mixing. Equalling ..AGAIN making for 'now cast promo. 

Anyway the exactement of cold prolonging is another story until resolution. ..+36/48 hrs

Edited January 9, 2017 by tight isobar

[Mucka]

GFS still bringing the Atlantic in on Saturday but the last 2 runs have made incremental improvements.

 

Gfs 18z V 12z

Edited January 9, 2017 by Mucka

[radiohead]

Good news. The hi res 18Z HIRLAM has -6 uppers reaching the North Sea at 48 hours. 18Z GFS has -6 uppers barely reaching the Irish Sea at the same time.

Colder air, further east, quicker. When it comes to the fine line between snow versus rain these are the kind of margins that can make a big difference in places.

[nick sussex]

The GFS is beginning to get on my nerves now! for heavens sake just stop all this attention seeking. Anyway its better upstream with the direction of the PV and if that digs south like the ECM we should still force some ridging ne'wards.

Its not just the ridge that's important but the direction of the elongated PV, that keeps digging south you'll see an attempt to ridge ne ahead of it.

Edited January 9, 2017 by nick sussex

[Ali1977]

1 minute ago, frosty ground said:

GFS falling has been greatly exaggerated 

Yes it just didn't happen, sitting firm. How can two powerful models get it completely different so close - half way between won't be that good so I hope the GFS op is way out early on from its ENS - I feel a depressing morning in here though with the ECM again backing down.

[radiohead]

3 minutes ago, edo said:

What time frame is this chart please??

T78-T102

[BARRY]

Just now, festivalking said:

A severe warning with a yellow warning....mmm paper talking it up.

hope so got to much to do in and around

[West is Best]

It's worth bearing in mind that the GFS ensembles are consistently heading colder. I'm very cool with the operational sticking out on a limb if it's getting less and less support from its buddies. Sooner or later the inevitable will happen and, knowing the GFS, will then produce an Armageddon op run.

 

[Memories of Feb '91]

1 minute ago, Ali1977 said:

Yes it just didn't happen, sitting firm. How can two powerful models get it completely different so close - half way between won't be that good so I hope the GFS op is way out early on from its ENS - I feel a depressing morning in here though with the ECM again backing down.

Depressing? All Models are showing the best chance of snow within the next 72 hours.. I think some people are too busy looking ahead that they miss the here and now!

[Mucka]

4 minutes ago, nick sussex said:

The GFS is beginning to get on my nerves now! for heavens sake just stop all this attention seeking. Anyway its better upstream with the direction of the PV and if that digs south like the ECM we should still force some ridging ne'wards.

That would annoy me though as it is a mild ridge with a quick thaw. If it gave a roaring Easterly later I guess I could forgive it

Edited January 9, 2017 by Mucka

[Man With Beard]

Might not be the best time to bring in the EC32 anomalies but if you're interested 

D14-D20

D21-D28 has no anomalies near us at all

 

[Snowy L]

1 minute ago, Ali1977 said:

Yes it just didn't happen, sitting firm. How can two powerful models get it completely different so close - half way between won't be that good so I hope the GFS op is way out early on from its ENS - I feel a depressing morning in here though with the ECM again backing down.

What I don't understand is surely 1 or 2 of the runs in the last few days would show a scandi, but no, every single one has shown westerlies by Friday night. It's the equivalent of flipping a coin and getting heads 20 times in a row.