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Model output discussion - here comes the beast!


Message added by Paul

Please only post model discussion in this thread 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

We also have a special post SSW cold spell discussion open here:
https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

Thank you!

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Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and majo

Come on those looking for the breadown before the major cold and snow has begun You will be very lucky if that is the correct word to see this in ANY winter in the rest of your lives I would sugg

Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of nex

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GFS does go off on one from time to time, it is most likely wrong but the annoying thing is it does sometimes get it right. BUT it is well in the future in weather teams so enjoy the fun and games meanwhile. For what it is worth I am with Catacol on this one.

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Taken a while to catch up with all the posts this morning!  Incredible period of model watching, best since I joined Netweather.

My thoughts are that the GFS has been poor since the 18z - not poor for cold, poor for snow, or poor for any location - just poor in the sense that it hasn't got a sodding clue what to do with that low.  I'm inclined to (try to!) ignore it for the next few runs and see if the UKMO and ECM can converge on some kind of consistency.

But the low at the end of the week is only part of the story, it would be criminal if we were all in here berating the GFS, and not enjoying the incredible weather during the early part of next week!

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Interestingly the Gfs 6z op remained very cold across the far n / ne throughout with heavy snow and the cold block started fighting back towards the end with other central, northern and eastern areas seeing snow returning..anyway..the siberian beast will unleash its brutal cold in a few days time..can't wait for monday..and I hate mondays!!:D:yahoo::):cold-emoji:

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20 minutes ago, karlos1983 said:

 

snowyMcSouth face perhaps?

then there is plenty of opportunity for features to pop up and make it all the way across the south in the flow. Funnily enough there are now weather warnings out for said areas!

IF the south miss out, oh well never mind, still unbelievable output at the moment and I’m not complaining! 

Resume! 

EDIT; ecm ens again cracking!!!

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Three ice days in London on the trot at this time of year unprecedented! Phenomenally cold. And I agree southern coastal counties I can see doing best, can’t see misery of 2013 for some.

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A lot of anxiety about the forecasts for late next week I see. For objectivity I decided to create a graph showing how the GFS ensembles have varied since yesterday with regards to the Friday low. These scenarios are with respect to the south:

Continental air displaced - Low pressure makes such progress that precipitation is likely to turn to rain, not what I'd like to see because it would be very miserable here. Areas further north would get a good snow event but it would herald the breakdown of the cold spell.

Cold air wins out - Here the low still comes towards the UK, however cold air puts up a fight, leading to some big snowfalls. This is high risk high reward although some of these scenarios would see snow/rain/snow transitions down here. The best scenario IMO is if we get a channel low which then trundles towards the north sea

Low remains well south - Or doesn't really get going. Here the low goes through Spain instead and heads towards the Denmark area leaving the UK in cold pool still. Atmosphere would still be very unstable and there would be many heavy snow showers under cold uppers.

Finally I think a few people are forgetting that we can have uppers close to 0C and still get falling snow, provided we are under continental air.

So what does the graph show? Well there has been a marked shift towards riskier scenarios for the south since the 12z yesterday. A consequence of the easterly being too clean perhaps? Ideally we would want to see a more influential Greenland high to our NW to help the low pass through Iberia and central Europe instead.

There is so much uncertainty about that milder scenario however. Shortwaves are likely to form due to the intensity of the cold air, these can interact favourably for us and change the course of the Azores low. Finally is the GFS still falling for the old trend of deepening lows too much? The 12z's will provide some useful clues.

image.thumb.png.63adefebb4600d64b77ec0eef0fb9910.png

Edited by Quicksilver1989
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5 minutes ago, richardc1983 said:

Why are southern counties gonna do best what about the rest of the uk? Do you mind explaining?

Because it’s likely to slow down and in fact stall as it heads into very cold dense air. ECM and UKMO has SW of England in particular getting buried it just sits offshore for MANY hours.

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I don't understand all the wailing and gnashing of teeth based on 1 run (plus possibly the UKMO). 

If this showed a snowstorm dropping 6 foot of snow people whilst excited would be saying its 6 days out, it's 1 run etc but somehow because it now represents sods law it's like it's carved in stone by some of the hand wringing going on. 

Models are still showing nearly a week of bitter cold & snow for most can we just wait for it to start before panicking about the end. 

We know cold dense air is difficult to shift so once we've had a few days of cold it well be that low doesn't make it as far north and its pushed back in fact given the depth of cold I'd be surprised if GFS suddenly has it right and this has happened before overblowing low pressure systems North etc. 

Let's just give it a few more runs, see if its a trend rather than a spurious spike. 

Edited by Richard Waugh
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54 minutes ago, Weathizard said:

I'm sorry but for people in the south west and parts of central southern England they are relying on the lows from the south/west to bring snow, its a cold week but for many of them if the GFS were to pan out as is they would have nothing of note, hence why people in these areas are concentrating on this event.

Just because yours or other locations are favoured by the initial spell, others aren't.

Wrong southern parts and eastern side country will be worse affected..

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I remember that channel low from the south 2010 i think. The red warning moved west and South 6.hours before the event. In these setups nothing is set in stone. I may be wrong on the year. But I remember it Well!

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30 minutes ago, karlos1983 said:

Without wishing to barrel this completely off topic, parts of the south west and central southern England could still do very well next week, before any (in my opinion) failed attempt of a low crossing England/Wales, I actually think it will mainly be a fish blizzard, maybe extreme south will pick some snow from it, but it’s a long way off in modelling terms when it comes to this sort of feature! Cough March 2013! 

Fax chart feature we usually see in northerly flows known as a Pembrokeshire Dangler, I’ve no idea what we call this

9538BD59-BB67-49F9-8E4D-C99F3488E317.thumb.png.b5e2d4207b6d14bef7dd80537f6eff82.png

snowyMcSouth face perhaps?

 

Fish blizzard and SnowyMcSouthFace! Biggest laugh I've had in a while, nice one Karlos! :rofl:

I wonder if this will be a good test of whether compact lows are encouraged to follow the Channel due to the greater moisture availability and vertical temperature gradient there.

GFS 06z does get closer to this than the 00z, shame the progressive bias still won out... oh wait, it's a virtual outcome at nearly a week's range that's not well supported by other models :D.

For what it's worth, the UKMO +168 looks like one of the most severe outcomes possible, as a compact LP tracks along the very far south. With such a small circulation, the wrapping in of deep cold air dominates, with minimal intrusion of less cold air aloft. To the east of the centre, the onshore flow may turn snow a bit wet at times right by the south coast, but as I witnessed first hand in Portsmouth back in Dec 2010, this may actually increase the snow accumulations for the event as a whole, albeit more in terms of mass than depth; the snow tends to compact and transition to a more ice-like state.

Just something to bear in mind in case my supposed Channel attraction does come into play.

 

In the meantime, seeing more and more showers in the higher-res models as we draw nearer to Mon-Wed next week, with greater overland travel too. Really neat to watch streamers come and go, occasionally interrupted on some models by a larger area of snow associated with a disturbance in the flow.

You know, despite having talked about such things for about a week now, I still can't seem to stop writing 'disturbance in the force' and having to correct it :crazy:.

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No sign of spring on the GEFS 6z mean, next week becomes extremely wintry nationwide and even beyond it stays cold / very cold, especially further north..lots of snow on the way and absolutely bitter cold..I'm not complaining!..I'm a very happy coldie!:D:cold-emoji:

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1 hour ago, Man With Beard said:

ECM clusters T156: The low to the south looks like getting close on all clusters. Many different routes, including the GFS/UKMO route but also routes to maintain the easterly flow and the low staying south.

ec-ens_nat_z500scenarios_2018022400_156.

the variation from quite early on shows that there is little point trying to second guess the back end of the week. Infact the gem corrected the Tuesday shortwave further east on the 00z run so even that still has a small question mark against its track.

 

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11 minutes ago, Summer Sun said:

London 06z ens has a rapid rise around the end of next week going from -15ish to around -3 in 24hrs - beyond the mean is consistent around -3 to -5

graphe_ens3_gny6.thumb.gif.f9e25de9eeb9d3cb64367a0aac898c9f.gif

 

Remarkable consistency in the 6z Ens says everything regarding the low, i think we can safely say with confidence that the low will be pushing further north, how far north is now the key. I suggest there will be a fair amount of rain in the south, flooding could be a major issue as we head into the weekend.

 

Edited by jayb1989
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3 minutes ago, john w said:

I remember that channel low from the south 2010 i think. The red warning moved west and South 6.hours before the event. In these setups nothing is set in stone. I may be wrong on the year. But I remember it Well!

That was an small Atlantic shortwave that ran around the sw of the cold sceuro trough and hit the s coast - a very different situation John 

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2 minutes ago, jayb1989 said:

Remarkable consistency regarding the low in the 6z Ens says everything regarding the low, i think we can safely say with confidence that the low will be pushing furher north, how far north is now the key. I suggest there will be a fair amount of rain in the south, flooding could be a major issue as we head into the weekend.

 

I'm gonna repost this at then end of the week for a laugh!

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8 minutes ago, bluearmy said:

We can jay ?  Further north than where ? 

The 06z is often considered the more progressive suite (be it less cold or more cold ) so I wouldn’t be making any judgements based on one issue of it.

Well certainly there was doubt that the low would even clear North of France on previous days output across all models. We now see pretty much all members of the 6z GFS suggesting milder air being pulled in across London. Based on that output it’s logical to assume a northward push of the low across the UK to some degree?

I note this is not shown in the ECM suite however, so we do need to see a few more runs.

Edited by jayb1989
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