Model output discussion 8th Feb - Cold for now, but then what?

[Singularity]

2 minutes ago, carinthian said:

Weird pattern flow around the British Isles on this run between 144t-200t. Sure think the models are struggling with-in this period. Handling the low out west of Biscay is the problem and whether pressure rise to the North of the British Isles is again going to take hold. Probably best ignore this run until so more data becomes available in the reliable time frame. Sorry could not be more helpful but our team of fairly confident that the UK will remain in the below average temp range in the mid period (144t -240t )

 C

From recent Met Office updates it seems they are generally thinking along the same or at least similar lines 

It's the trends that are the big deal here; as the subtropical ridge signal is corrected downward, the jet makes more progress into Europe to support HP to the N and NW of the UK (NE less likely due to polar vortex movements). Or so the theory goes 

[cheshire snow]

Just to compare the temperature profile at T240

00z temperatures 5-9c North to South

06z temperatures -4c - 3c North to south

 

C.S

[mb018538]

The 6z completely loses the plot at the end - dropping the vortex back to Greenland, and spinning up some big Atlantic lows. Best chuck that in the bin for now, completely different to everything else we've seen recently. With the second SSW due, I don't think the models are really going to know what's going on (much like this spell that appeared out of the ether of endless zonal weather a while back).

[MattTarrant]

1 minute ago, mb018538 said:

The 6z completely loses the plot at the end - dropping the vortex back to Greenland, and spinning up some big Atlantic lows. Best chuck that in the bin for now, completely different to everything else we've seen recently. With the second SSW due, I don't think the models are really going to know what's going on (much like this spell that appeared out of the ether of endless zonal weather a while back).

I would somewhat agree with you, the handling of the lows is poor from around 120h. For those of you who want a GFS commentary the Metcheck did one this morning.  

[Weathizard]

A frustrating 6z run, you can see how we've been dealt the worst possible deal from the chances on offer. If only the low over Portugal could budge over to the med we'd have been in serious business.

Even the attempted ridging into greenland is ruined by that bloody low phasing with the energy coming out of the eastern seaboard, in fact the evolution between 96-168 is so stagnant(& unusual) we are almost stuck, as if being mocked as the days of winter tick away while the jet is dead and high pressure flounders around and mostly over us.

Need to see some encouragement from the ensembles soon.

 

 

[Summer Sun]

Ens shows the high slightly further west compared the 00z

 

Edited February 9, 2017 by Summer Sun

[Summer Sun]

Looking like the 06z Op is going to be on the cold side of the mean for later next week

Ens

Op

EDIT

Short term 06z ens does indeed show the Op to be just on the colder side of the mean later next week

Edited February 9, 2017 by Summer Sun

[weirpig]

Well for those looking for a few snow showers here is the latest  euro 4  going to mainly snow showers on Saturday

[johnholmes]

Interesting how the upper air cross section has changed since yesterday for this area, see link for those with Extra. It does suggest cloud tops up to 10,000 ft or so for a time and with near zero C surface temperatures before the less cold air gets in. One would expect, if this is correct, that the Peak District, Yorkshire Moors and Lincolnshire Wolds would have a decent covering of snow. Less reliable for me at 30 feet AS.

https://www.netweather.tv/secure/cgi-bin/premium.pl?action=cskew;sess=7e3c64a6f6a6c1de54ef85aa713480ec

I will do a check tomorrow, who knows it might be similar again, or then, maybe not!

[Nouska]

22 minutes ago, johnholmes said:

Interesting how the upper air cross section has changed since yesterday for this area, see link for those with Extra. It does suggest cloud tops up to 10,000 ft or so for a time and with near zero C surface temperatures before the less cold air gets in. One would expect, if this is correct, that the Peak District, Yorkshire Moors and Lincolnshire Wolds would have a decent covering of snow. Less reliable for me at 30 feet AS.

https://www.netweather.tv/secure/cgi-bin/premium.pl?action=cskew;sess=7e3c64a6f6a6c1de54ef85aa713480ec

I will do a check tomorrow, who knows it might be similar again, or then, maybe not!

Hi, John - a question.

I'm useless with all the criss cross lines on the skew T diagrams - prefer the cuts on Meteociel.

Today is just a flat strat picture but tomorrow shows plenty of lift to get convective cloud higher up and blown in. Is that just a matter of slightly colder temps aloft than today or some other ingredient?

 

Cut is from Lincolnshire out into N Sea.

http://www.meteociel.fr/modeles/coupes_arpege.php?region=uk&ech=3&mode=2

[winterof79]

3 hours ago, Devonshire said:

Umm - movement of what, from where, to where, with what possible effect?? (I realise yours isn't the only 1-liner in here this morning, but it is rather perplexing - this is the model discussion thread after all!)

Sorry for my ignorance!

Possibility of the warm front moving up from the South engaging colder air in situ.

[mb018538]

6z ensemble shows the operational as cold compared with the rest of the suite, and also quite wet compared to the mean. I guess everything will now hinge on whether we can get some heights built around Greenland, or if the PV will shift back there enough to scupper things.

[MattStoke]

Saturday's more widespread snow risk is now coming into range of the high resolution models.

Looking marginal, with those near to the North Sea coast more likely to see sleet or rain. Higher ground and areas further west having a greater chance of snow. It is in the form of showers though, so any accumulations will be patchy.

[Devonshire]

16 minutes ago, winterof79 said:

Sorry for my ignorance!

Possibility of the warm front moving up from the South engaging colder air in situ.

No intention to suggest ignorance! - probably the opposite; those more experienced and with the knowledge often throw out a one-liner without realising the analysis in their head doesn't automatically leap into the minds of those viewing. For instance on the chart you posted there appeared to be 4 different fronts in close proximity (from my schoolboy geography) and one static chart doesn't tell me what is going where, what with the East-West to-ing and fro-ing - there might be an interesting story in there but I wouldn't be able to guess!

It often feels as though there is a communal attempt at Haiku formulation going on once the one-liners really start flowing.

[Duane S.]

I'm surprised more is not being made of the GFS 06z. I think it looks very interesting and is on to something, indeed compared to a lot of the output of recent days!

There really has been a feel of the models not being able to process the information being fed in and, with the very weak Atlantic, coming up with strange and improbable looking flabby charts. As though waiting in situ to be told where to go next!

Key is the evolution once the AH has completed its pesky ridging and energy should once again drain out from our NW in an SE direction. The ECM toyed with it and the GFS 06z has moved it along, I think this has legs.

I don't think we are looking at any sort of full on retrogression just yet but What I can see occurring is the creation of a weak but influential small HP system centred somewhere around the west coast of Norway. May come to nothing but one to watch IMO as the cold come be back in an instance should something like that occur.

[Seasonality]

10 minutes ago, s4lancia said:

I'm surprised more is not being made of the GFS 06z. I think it looks very interesting and is on to something, indeed compared to a lot of the output of recent days!

There really has been a feel of the models not being able to process the information being fed in and, with the very weak Atlantic, coming up with strange and improbable looking flabby charts. As though waiting in situ to be told where to go next!

Key is the evolution once the AH has completed its pesky ridging and energy should once again drain out from our NW in an SE direction. The ECM toyed with it and the GFS 06z has moved it along, I think this has legs.

I don't think we are looking at any sort of full on retrogression just yet but What I can see occurring is the creation of a weak but influential small HP system centred somewhere around the west coast of Norway. May come to nothing but one to watch IMO as the cold come be back in an instance should something like that occur.

I agree, just check out the GEFS postage stamps further into next week and beyond. GFS definitely sniffing out the ECM option. I think folk may be a little 'model fatigued' to use the old cliche. As you say, with the Atlantic and the jet stream in a very weak state, the modelling has been a bit odd. I'm still interested, and think slow changes may add up to something interesting.

[johnholmes]

1 hour ago, Nouska said:

Hi, John - a question.

I'm useless with all the criss cross lines on the skew T diagrams - prefer the cuts on Meteociel.

Today is just a flat strat picture but tomorrow shows plenty of lift to get convective cloud higher up and blown in. Is that just a matter of slightly colder temps aloft than today or some other ingredient?

 

Cut is from Lincolnshire out into N Sea.

http://www.meteociel.fr/modeles/coupes_arpege.php?region=uk&ech=3&mode=2

hi nouska

Just the opposite with me, your diagrams seem hard work to me, but each to our own, no worries.

Yes it is somewhat colder air moving in ahead the upper air warming later Saturday into Sunday.

[tight isobar]

Whilst we prepare for nowcast-situ' regarding pin-pointing accuracy via precipitation/dew points etc.

Its worth noting the euro 4 model seems to handle overheads and precipitation at nowcast scenario pretty well.

Also worthy of note is the potential for impactual banding of showers beginning to flag up!...

In any given locale- there could be notable accumulation. 

But as again its a suck it and see on a tight scale. 

[Frosty.]

The GEFS 6z mean shows a gradual return to average temps with a north / south or northwest / southeast split as time goes on with predominantly higher pressure for the s / se with  lower heights more influential across the n / nw where most of the Atlantic / unsettled weather would tend to be.

[Frosty.]

A real mixed bag from the GEFS 6z with some mild / average but also a few cold outcomes longer range.. my impression is the current cold spell will start to fade later in the weekend and through next week with temperatures slowly recovering, however, it will still feel cold as SEly winds strengthen and then further ahead we may settle on a nw / se split..nw most unsettled with the s / se having the best of the conditions and only occasionally unsettled.

[Ali1977]

With the latest GFS precip charts it looks like many may still see a dusting of snow over the weekend.  DP look marginal but I'd say the right side of marginal, so anyone with a  bit of altitude or showers falling overnight may have best chance of putting a covering down.  Definitely a now-cast situation and scope for an up-tick in snow activity, but I guess that goes both ways.

Not sure what the lastest BBC forecasts are showing, but this morning it showed rain and 4c for central England for Sat - I'd say that is wrong and will be a bit colder than that and at 2/3c.

[AWD]

6 minutes ago, Ali1977 said:

With the latest GFS precip charts it looks like many may still see a dusting of snow over the weekend.  DP look marginal but I'd say the right side of marginal, so anyone with a  bit of altitude or showers falling overnight may have best chance of putting a covering down.  Definitely a now-cast situation and scope for an up-tick in snow activity, but I guess that goes both ways.

Not sure what the lastest BBC forecasts are showing, but this morning it showed rain and 4c for central England for Sat - I'd say that is wrong and will be a bit colder than that and at 2/3c.

GFS 12z isn't a million miles away from that projection on Saturday afternoon;

Although, like you say, I wouldn't take such detail too literally as a tweak either way could be the difference between a flurry or some drizzle.

Either way, roll on the Spring convective season I say.  I'd take thunderstorms over snow any day.

P.S.  This is the reason the GFS 12z forecasts rain for the Midlands on Saturday afternoon;

Edited February 9, 2017 by AWD

[danthetan]

The GFS has continued to show slight adjustment West with both the high pressure to the north of the UK and the deep low to the NE Scandinavia if this continues in the next few days and that trough can drop south into europe surley this will aid retrogression towards Greenland.

[bluearmy]

the ecm op was pretty well a cold outlier for the south east of England

dont expect such a slack se flow on the 12z op

 

[MattTarrant]

Looking at the Dew points and surface temperatures I think most low lying areas will only see sleet, or wet snow in any 'heavier' bursts. Places above 150/200m metres may see 1-2 cm where above 250 I would say 3-4 cm. This is obviously only an opinion and it will come down to nowcasting and a bit of luck! Looking at current Precipitation charts I would say the Cotswold's would be a favoured place, though the current track will be open to change in the next 24 - 36 hours. (This is for Saturday)

Overall from the 3 days where precipitation will likely be wintry the North York Moors will get at least 1-2 cm.