Model Output Discussion - Colder but how cold and for how long?

[Coopsy]

Jan 2004 redux?  

[winterof79]

3 minutes ago, Kasim Awan said:

I don't think there was any such streamer in early 2009. 

Sorry 2009/10 memory going but i didn't dream it.Regulary through into Feb

[frosty ground]

8 minutes ago, Kasim Awan said:

Yes but with a slack flow the coverage of these features will be relatively poor, slack flow also means they will struggle to develop into larger features. December 2022 and November 2023 spring to mind. We need the low from Iceland & the one to our South to make better inroads for anything really significant otherwise a slack flow will just generate a lot of very dry cold weather with snow limited to a few coastal areas.

Not sure how many more time you can basically write it’s going to be dry.

i think we get it now.

we've gone from storm of the century to dry as a desert, i now forecast change with new data but maybe just maybe we dial it back a bit.

looking at a few operation 5 days and dismissing unexpected features about 6 times in one morning is a bit much.

[Weather-history]

5 minutes ago, winterof79 said:

Early 2009 many occasions occurred of slack dense cold over UK.Streamers set up dumping 9" snow regularly off the Irish Sea through Lancs into Yorks.

Chart not exactly to the day but you get my gist

That cold spell was a short easterly blast followed by a kind of cold zonality with low pressure interacting withe the cold air.  No streamers coming off the Irish sea during that spell.

[winterof79]

Just now, Weather-history said:

That cold spell was a short easterly blast followed by a kind of cold zonality with low pressure interacting withe the cold air.  No streamers coming off the Irish sea during that spell.

I have corrected myself 

[Lukesluckybunch]

Pretty good ecm mean I have to say!

[winterof79]

3 minutes ago, Weather-history said:

That cold spell was a short easterly blast followed by a kind of cold zonality with low pressure interacting withe the cold air.  No streamers coming off the Irish sea during that spell.

Jan 4-6 2010 you did an article on it for netwx 

[Astral Goat Juice]

Snow and cold hasn't even arrived and folk are complaining about a lack of snow

[Malarky]

1 hour ago, Ali1977 said:

Boom what a chart that is at 216 - the Atlantic is dying - stoping moving east

Nice to see lower heights pushed down towards Africa there.

[Weather-history]

5 minutes ago, winterof79 said:

I have corrected myself 

Funny enough, early Feb 2009 is not a bad choice to use anyway because although we haven't got that easterly blast  the Atlantic interacting with the cold air is what happened and could happen again this time

 

Edited January 11 by Weather-history

[Kasim Awan]

22 minutes ago, MJB said:

Yep and in slack winds they aren't going very far, remember I am talking about IMBY, no doubt some areas that are close to the moisture will do ok.......I think, but my money would be on a dry week for many down the spines of England and Wales 

That's bang on Kas ,I remember Dec 2022, everyone saying instability and features will be popping up , cold for sure, snow no

Yeah only Kent and North York Moors got anything significant out of December 2022. Looking at the charts one might think instability would be extensive with features popping up regularly:

When in reality the lack of thermal gradient in the slack flow only results in very localized (but intense) features that don't last particularly long either, often only covering one or two counties. 

For the type of trough development many on here are suggesting is possible, i.e. covering large portions of the UK, a far more unstable flow is required. For example, this flow from November 2005. Or progression of a larger trough / low such as the one from Iceland / to our South West could provide the extent of convection required for more widespread snowfall.

Now I'm not suggesting that there wont be any snow chances in the upcoming cold spell. Just that if we end up with a quiet area of low pressure under slack winds then likelihood in building widespread heavy troughs is quite low, as proven by the previous cold spell and December 2022. This is proven by the accumulation charts shown by the GFS/ECM/GEM etc. These are fair in giving an indication of potential and if the slack flow indicated was indicative of heavy trough development then these charts would reflect this and show more extensive snow accumulation. This could still change though. We may still source an active and larger area of low pressure which is certainly possible.

Edited January 11 by Kasim Awan

[IDO]

For London, the ensembles confirm the op was an outlier for 850 temps at D10 (shocker!):

 Manchester: 

The trend was a rise versus the op, a fall at D10.

Also, there is an outlier at 500hPa at D9. 

But overall not a bad mean, even if the OP is maybe a tad colder than likely on this run.

The negative is the synoptic mean at D10:

No mean undercut going on there, and in fact very similar to GEFS:

 

[NewEra21]

ECM looks very good this morning, not so keen on the GFS.

With those 850s and flow on the ECM, there would be features popping up all over the place. No worries about that run being dry closer to the time.

Edited January 11 by NewEra21

[DJ Fart]

I tell you what, if the charts usually get upgraded throughout the day, as is the feeling on here, then we could be seeing some great charts later. 

I think some are being a bit unfair to Kasim this morning. He's merely reporting what he sees. Individual reports of "well it snowed in my back garden last time" are purely anecdotal. 

[stripeyfox]

2 minutes ago, Kasim Awan said:

 

Now I'm not suggesting that there wont be any snow chances in the upcoming cold spell. Just that if we end up with a quiet area of low pressure under slack winds then likelihood in building widespread heavy troughs is quite low, as proved by the previous cold spell and December 2022. This is proven by the accumulation charts shown by the GFS/ECM/GEM etc. These are fair in giving an indication of potential and if the slack flow indicated was indicative of heavy trough development then these charts would reflect this and show more extensive snow accumulation. This could still change though. We may still source an active and larger area of low pressure which is certainly possible.

Sure about that? You did say "Dry as a Sahara run for most of UK."

Edited January 11 by stripeyfox

[winterof79]

8 minutes ago, winterof79 said:

I have corrected myself 

Slack flows and breathe

[TillyS]

35 minutes ago, MJB said:

I'm a bit underwhelmed if I'm honest, seen these situations before, MBY will end up bone dry . Yes it's nice to see frosts which stays all day but ultimately its all about the snow. I await the lot of ppn to approach,

 

Yep not a great ECM run. All very slack. Likely just to see the cold air peter out from that without producing anything very much down south. Should be decent for Scotland though especially off those northerly snow flurries.

The models are all miles better than they looked 2 weeks ago. Just nowhere near as good as they looked 2 days ago. And with a week to go, that’s a worrying trend.

[frosty ground]

3 minutes ago, IDO said:

For London, the ensembles confirm the op was an outlier for 850 temps at D10 (shocker!):

 Manchester: 

The trend was a rise versus the op, a fall at D10.

Also, there is an outlier at 500hPa at D9. 

But overall not a bad mean, even if the OP is maybe a tad colder than likely on this run.

The negative is the synoptic mean at D10:

No mean undercut going on there, and in fact very similar to GEFS:

 

Those charts don’t show outliers with maybe the exception of day 10 .

those ensembles charts aren’t great at showing individual runs, like what met4cast showed yesterday.

[snowking]

21 minutes ago, Kasim Awan said:

For 8 days of very cold weather that is very poor snow coverage.

Kasim come on, I appreciate you’re commenting at face value on the exact precipitation output shown in this single deterministic run, but you’ve been here long enough to know how poor modelling of precipitation is at such range under such conditions.

———

This next part is not aimed at you because I appreciate you try to provide a face value overview direct from modelling. But I do think in general these forums in the morning might provide psychologists with the best possible data source they could have for the effects of sleep deprivation.

Nothing has changed from where we were yesterday. Deterministic runs are still just picking scenarios at random from the range offered in the ensemble suites over the last few days. Usually at the sort of ranges we’re talking you would start to err towards the view that deterministic runs, with their superior resolution, should be getting a handle on things. But this is such a difficult setup to compute, far from the usual west - east flow one would expect locally (never mind globally) that I don’t think the deterministic runs are any more use to us right now than the rest of their respective suites.

And whilst it’s a fun exercise in imagination, there is absolutely no use in looking at any form of precipitation chart beyond (if I’m being really generous) 90 hours other than for a brief fanciful glance if you really want to torture yourself.

[MJB]

Just shows what apps are like, I have refreshed and refreshed but where are Metcheck getting that from for MBY LOL

[Barking_Mad]

6 minutes ago, stripeyfox said:

Sure about that? You did say "Dry as a Sahara run for most of UK."

"Most"

[TillyS]

2 minutes ago, snowking said:

 

And whilst it’s a fun exercise in imagination, there is absolutely no use in looking at any form of precipitation chart beyond (if I’m being really generous) 90 hours other than for a brief fanciful glance if you really want to torture yourself.

This is very true.

It’s the synoptic trend which concerns me more at the moment.

There’s no escaping the fact that the past 48 hours the models, all of the big three anyway, have been backing away somewhat from 1. deeply intense potent northerly and 2. powerful under-cut low across southern Britain.

It may all pep up again but I’m not liking this trend. It usually only means one thing.

[Zero Visibility]

3 minutes ago, MJB said:

Just shows what apps are like, I have refreshed and refreshed but where are Metcheck getting that from for MBY LOL

GFS 8z run for today, not available to us

[Weather-history]

Just a small point but look at the ECM 12z  850hpa mean at Friday 19th Jan 12z and the -5°C dotted line

Now compare to ECM 0z for Saturday 20th Jan 0z

 

 

[rotherhamsnowman]

10 minutes ago, stripeyfox said:

Sure about that? You did say "Dry as a Sahara run for most of UK."

That was on the back of one chart someone had posted.. I don’t think he meant the whole thing….