Model Output Discussion

[johnholmes]

ps not much talk about the covering of snow likely overnight for most places?!

yes, I had to smile as I ploughed through the posts about Tuesday onwards when everyone knows, or those who have been on this forum any length of time should, that the detail of the position and depths of the lows-and the consequent knock on effect of precip-type etc, will not be known until 24 possibly 12 hours ahead.

Exciting prospects yes but tonight through tomorrow is equally so I would have thought. Both main models suggest 4-12mm of precip as the feature tracks east. the major things to look for are marginal for some low lying areas, certainly not for high ground, and the 06z has got a rather larger ? than the 00z had but interesting all the same.

So, I'll be spending more time looking at the next 24+ hours with just occasional checks on how the early/mid week events seem to be shaping up.

[J10]

Very interesting synoptics for the early to middle part of next week. Certainty there remains the very real potential of some heavy localised snowfalls. However from an IMBY perspective, as Darren says we really need the low pressure to remain separate to allow the colder air to push in to the NW parts of the low as they push east.

IF this does happen could be very good for parts of South Wales next week, if not and areas further north are favoured as per the GFS 06Hz run.

[Guest North Sea Snow Convection]

Fully agree with what you are saying, I said pretty much the same myself in a earlier post.

Because of these spawning slow moving shortwaves that are developing off of the low to the west of

Norway they are blocking what could be some bitter true Arctic air from reaching our shores where

we could well be looking at powder snow and maximum temperatures widely across the country

into the negative digits.

Several days ago when the shortwave developed around Iceland if that had moved south down the

north sea we would then have seen the start of a prolonged freeze but for some reason that I can

not fathom out (apart from perhaps sea surface temperatures ) it decided to anchor off of the coast

of Norway leaving the UK in this rather coldish type of weather.

It has been a very frustrating couple of weeks knowing the UK was so close to seeing a prolonged

freeze that could have rivaled the likes of February 1986 perhaps.

As far as the models go this morning I would not start thinking of a snow event for any particular area

until you are only at a maximum 12 hours from a possible event due to the uncertain tracking of these

lows pressure systems.

Yes, it looks the end product of this MMW remains as a west based -NAO and blocking too far west to get the drier arctic air south to this part of the NH.

The trend is to be taking less cold upper air further north, if anything in the coming week, rather than the belief before that this annoying troughing from Norway through the Uk and phasing with southerly lows would get squashed south. The cyclonic pattern with the heights towards NE canada are going to keep preventing any significant cold spell to end the winter. At least for this part of the NH.

Still good for snow from the midlands northwards after this weekend though, although a much more marginal and messy pattern than it could (should!) have been.

Edited February 20, 2010 by North Sea Snow Convection

[kold weather]

To back up what you say the Met Office have issued a early warning for Wednesday in the exact locations you name Kold Weather!

I think the GFS 6z yesterday was the least favourable run so will be interesting to see what happens later!

I think John does make a good point, looking at the ensembles they back up his points very well, very small differences (and they really are tiny!) make a big difference for the Midlands. For example one run gives snow to the Midlands because the LP center is about 1-2mbs stronger whilst another doesn't because its 1-2mbs weaker with the low, or the angle is just slightly wrong. These sorts of errors probably won't be ironed out till 24-36hrs before the event.

However clearly the further north you are, say from the north Midlands northwards, you've got more chance/risk of snowfall, thats the very basics of this set-up.

[full_frontal_occlusion]

On a different note the jetstream pic Mr D posted I noticed the below average SSTS running from the gulf of mexico across the Atlantic into the Med/UK.

http://weather.unisy...ce/sst_anom.gif

What also shows up very clearly are the SST's associated with the established El Nino pattern in the tropical central Pacific.

Later today I will update my observations from the GSDM and hence prognosis for the extended range in the technical discussion thread.

ffO.

[Mole]

Anyone South of the M4 is more likely to see sleet or rain in the coming week,unless you live on the highest ground,is how i read the current situation.

Edited February 20, 2010 by Mole

[kev238]

Yes- it will be a very interesting week.

I will be looking a lot at the NAE-- it appears to move the snow areas around when they are troughs and small disturbances but it did really well with the larger system on Thursday.

It does look likely that there will be a good snowfall tonight/ tomorrow morning-- infact it could give Nottingham and Derby its best cover of the winter if the warning came off!

[TEITS]

yes, I had to smile as I ploughed through the posts about Tuesday onwards when everyone knows, or those who have been on this forum any length of time should, that the detail of the position and depths of the lows-and the consequent knock on effect of precip-type etc, will not be known until 24 possibly 12 hours ahead.

Exciting prospects yes but tonight through tomorrow is equally so I would have thought. Both main models suggest 4-12mm of precip as the feature tracks east. the major things to look for are marginal for some low lying areas, certainly not for high ground, and the 06z has got a rather larger ? than the 00z had but interesting all the same.

So, I'll be spending more time looking at the next 24+ hours with just occasional checks on how the early/mid week events seem to be shaping up.

You must of missed my posts because I have been commenting on tomorrows snowfall.

Generally speaking we're looking at around 5-7mm of precip with only 3mm N of the Midlands. Due to the timing of this precip I feel W parts are favoured for greater snowfall totals compared to those in the E.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/20/basis06/ukuk/rsum/10022118_2006.gif

[Frosty.]

Once again the 6z gfs is a straightforward very cold and wintry run for northern britain with polar winds mainly between N'ly and NE'ly developing during next week with some more enhanced shower activity giving significant snow at times and widespread sharp or severe overnight frosts until next weekend. Further south it's more complex with the low pressure tracks still adjusting north and south by some margin which will give someone a blizzard and five miles south, heavy rain. The 6z then shows an end to the cold spell for everyone during the first week of march but even then there are hints of cold weather from the east which has been a regular feature of the gfs in deepest FI.

[johnholmes]

yes I tire rather easily these days so probably never went back far enough.

Picking up the point from KW-this applies to differences between the 00 and 06z runs for tomorrow-00z looked more favourable, being selfish, for this area, 06z less so, precip totals much the same 6-8mm. In fact GFS/Extra has been quite consistent, even with its variety of ideas on where this feature might track, in the forecast precip totals for this area since Tuesday. Mainly in the 5-10mm range on each run.

But, yes, minor differences in the track, the intensity of precip, along with the usual parameters we need to check for the difference between rain and snow at low level, and there can be large differences between runs. What the models can do is point us in the overall direction of the main pattern-that is cold and unsettled for the next few days at least. Interesting tracks of the lows with marginal snow situations for anywhere from about north of the M4 corridor (what a much maligned area!), up to about southern Scotland. As others have commented then one area maybe several, at low level, seem more than 50% likely to have a fairly heavy snowfall. IF all things support it at the time then it would be almost certain to cause major transport problems.

Interesting watching that is for sure.

Currently this area MIGHT be lucky tomorrow and get anything from a thin covering to maybe 4-5cm. Indeed its not a promising prospect for hiking in the Peak for me tomorrow!

Edited February 20, 2010 by johnholmes

[MR EXTREMES]

well things are very messy but good for most it seems were stuck in this setup of low pressures wobbling all over the country what is clear though all thease systems wont all take the same track so snow in the midlands in one system then the next system could be rain,but all the same very intresting week for most im a little dissapointed for us in the south but then i always knew that this kind of setup would never favour us.

as for fi im still a little skeptical of anymore colder weather but as you most likely noticed im so bullish on the full alantic breakdown i think its coming its clear to see its unsettled this week northern england even the midlands for awhile and most certainly scotland looking very good to hold on to the snow events and colder air.

but i think systems will over time start to carve a more north track of systems coming in over the coming week.

but thats not taking away the dumpings people are going to see.

Edited February 20, 2010 by badboy657

[Ian Fergusson]

Anyone South of the M4 is more likely to see sleet or rain in the coming week,unless you live on the highest ground,is how i read the current situation.

Yes, that reflects the current UKMO view and even those counties just north of the M4 (e.g., Glos, Oxon, parts of Berks, Bucks etc.) will probably be very marginal.... that's IF the current evolution proves trustworthy.

Latest modified NAE output for Monday carries a rain signal across all of southern England but with the change to wintry PPN starting by ca. 06z in a line essentially from East Wales / Hereford across to Lincs and the Wash.

The real midweek snow threat based on UKMO GM (and accepting - as the MO Ops Centre does - a continuing degree of disparity between models for the Wednesday event, albeit UKMO-GM and GFS are largely similar) manifests itself central Midlands northwards; e.g., GM suggestive of up to 25-29cm snowfall (!) into northern districts / northern Ireland whilst in southern England (SW quadrant especially) it's the hefty rainfall totals, plus some quite tight gradients, that catch the eye. So, lively weather for sure, even sans snow (and indeed many might say: have we not seen enough already!?).

The UKMO 6-15d briefings now consistently offer the prospect of milder conditions developing across the south and the SIG snow risk being progressively excluded up into northern Scotland by the end of the period. I just photographed the first butterfly I've seen in 2010..... a biomarker of seasonal change afoot? We shall see.

[kold weather]

The real midweek snow threat based on UKMO GM (and accepting - as the MO Ops Centre does - a continuing degree of disparity between models for the Wednesday event, albeit UKMO-GM and GFS are largely similar) manifests itself central Midlands northwards; e.g., GM suggestive of up to 25-29cm snowfall (!) into northern districts / northern Ireland whilst in southern England (SW quadrant especially) it's the hefty rainfall totals, plus some quite tight gradients, that catch the eye. So, lively weather for sure, even sans snow (and indeed many might say: have we not seen enough already!?).

I think that part of the post shows just what a real prospect this set-up is, I have few doubts somewhere will get a foot of snow total in the next 7 days. Whats interesting is it also looks to favour possibly the 2nd most populated part of the country, with say Stoke to Nottingham being my southern limit ATM (though Brum has a real shot as well IMO still) and northern limit could well go well into N.England right upto the borders possibly.

Rainfall totals for the south also look quite hefty, the GFS suggesting 35-50MM is possible in the next 6 days, so my area will be sodden bog again!

Still tomorrow has its own fun and game sto be had, esp with regards to the development of the low pressure over then Midlands and another possible wrap around for eastern counties, timing is vital though with regards to that wrap around feature.

[andymusic]

I think that part of the post shows just what a real prospect this set-up is, I have few doubts somewhere will get a foot of snow total in the next 7 days. Whats interesting is it also looks to favour possibly the 2nd most populated part of the country, with say Stoke to Nottingham being my southern limit ATM (though Brum has a real shot as well IMO still) and northern limit could well go well into N.England right upto the borders possibly.

Rainfall totals for the south also look quite hefty, the GFS suggesting 35-50MM is possible in the next 6 days, so my area will be sodden bog again!

Still tomorrow has its own fun and game sto be had, esp with regards to the development of the low pressure over then Midlands and another possible wrap around for eastern counties, timing is vital though with regards to that wrap around feature.

I don't think you can confidently say where it's gonna favour just yet - looking any further than about two to three days ahead is all you can do now with this set up with any confidence and even then it could change - so the favoured spot for those sorts of totals could also be further south or further north - last night's 18z run from the GFS piled up the snow in the whole of Wales next week - amazing run - it's changed a little on the latest GFS runs today but can so easily modify again on subsequent runs

Edited February 20, 2010 by andymusic

[cooling climate]

Key post IMO, it wouldn' take much to see that extra energy from the secondary SW, develop into a new low IMO. The centre of the main low isn't well defined anyway, you would then probably see what was the main low swing down back south again, keep the whole lot much further south. IT will be interesting to watch out on the 12Z

I was thinking the same thing to be honest. It is the first low that pulls the second northeast

now if the first low is modeled to weaken further or perhaps disappear then the second low

would undoubtedly follow a more easterly progression I would have thought.

[johnholmes]

I don't think you can confidently say where it's gonna favour just yet - looking any further than about two to three days ahead is all you can do now with this set up with any confidence and even then it could change - so the favoured spot for those sorts of totals could also be further south or further north - last night's 18z run from the GFS piled up the snow in the whole of Wales next week - amazing run - it's changed a little on the latest GFS runs today but can so easily modify again on subsequent runs

Andy- I suggest you keep an eye on the blog by Ian F-he has insight into how the UK Met see events unfolding, believe me, whatever some on here may think, they are much much better placed than anyone on here to give a reasonable idea of how things may pan out. When I had access into the senior man's comments I found it highly illuminating-okay of course its wrong at times but it was always a balanced unbiased and highly professional view-so as I suggest keep an eye on Ian's blog-well worth reading when he does it and expands beyond the more localised area he does forecasts for.

This is not a go at you Andy-just a suggestion for others as well.

Edited February 20, 2010 by johnholmes

[bluearmy]

I've just noticed that Met O have removed the warnings over the threat of snow for Monday for the whole of the UK. I wonder if this is because of the change that has occurred in the outlook in the last day or so.

I still think the Northernmost parts of England and the whole of Scotland may get quite a few snow events in the next week. I can't really understand at the moment why people in the South-East/southern England are getting excited though - our only hope is that things change!

Matt.

i think reality will soon set in Matt

http://www.meteogroup.co.uk/uk/home/weather/services/ensemble_forecast.html

the latter part of the week certainly on the cool side but unlikely to be cold for anything notable.

[Matt12]

i think reality will soon set in Matt

http://www.meteogrou...e_forecast.html

the latter part of the week certainly on the cool side but unlikely to be cold for anything notable.

Yeah, I agree. I just don't want anyone south of, say, Birmingham/the north Midlands thinking they will be buried in snow, or even see quite a bit of snow in the next week. I guess the hilliest parts of England/Wales might see something (as per usual) though.

[johnholmes]

I've just noticed that Met O have removed the warnings over the threat of snow for Monday for the whole of the UK. I wonder if this is because of the change that has occurred in the outlook in the last day or so.

I still think the Northernmost parts of England and the whole of Scotland may get quite a few snow events in the next week. I can't really understand at the moment why people in the South-East/southern England are getting excited though - our only hope is that things change!

Matt.

nothing odd about it-the latest model output shows only southernmost counties having mod-heavy precip-thus, as the upper temps and surface conditions, were never going to give anything in the far south-they delete the warning-professional forecasting it would seem to me.

They then look at the prospects for the next low-late Tue into Wednesday and decide that requires a PRELIM warning but DON'T expect that not to change-it will as I've tried to explain earlier.

[andymusic]

They have moved it to Sunday.

Yeah - but the monday threat still exists as well - GFS still has this showing - what's going on there then

In Wales it is anyway

Andy- I suggest you keep an eye on the blog by Ian F-he has insight into how the UK Met see events unfolding, believe me, whatever some on here may think, they are much much better placed than anyone on here to give a reasonable idea of how things may pan out. When I had access into the senior man's comments I found it highly illuminating-okay of course its wrong at times but it was always a balanced unbiased and highly professional view-so as I suggest keep an eye on Ian's blog-well worth reading when he does it and expands beyond the more localised area he does forecasts for.

This is not a go at you Andy-just a suggestion for others as well.

It's ok I don't take offence - I'm a bit shakey in the BBC's and METO's take on things right now as even DAN THE MAN CORBETT made a major error yesterday in forecasting snow showers - and quite a bit of snow - 2 inches in fact - for Wales today from last night's forecasts - and it's glorious sunshine now - all day - I do read Ian's blog occassionally - in fact I talk to him too - The current set up is twisting and changing rapidly - I don't think we have much of a chance right now of really getting anything nailed on much past 2 - 3 days

[WINTRY WALES]

Andy- I suggest you keep an eye on the blog by Ian F-he has insight into how the UK Met see events unfolding, believe me, whatever some on here may think, they are much much better placed than anyone on here to give a reasonable idea of how things may pan out. When I had access into the senior man's comments I found it highly illuminating-okay of course its wrong at times but it was always a balanced unbiased and highly professional view-so as I suggest keep an eye on Ian's blog-well worth reading when he does it and expands beyond the more localised area he does forecasts for.

This is not a go at you Andy-just a suggestion for others as well.

Hi John/anyone

Can you point out where to find Ian F's blog?

Ta

[Matt12]

nothing odd about it-the latest model output shows only southernmost counties having mod-heavy precip-thus, as the upper temps and surface conditions, were never going to give anything in the far south-they delete the warning-professional forecasting it would seem to me.

They then look at the prospects for the next low-late Tue into Wednesday and decide that requires a PRELIM warning but DON'T expect that not to change-it will as I've tried to explain earlier.

I see. Thanks. I saw the latest forecast on the tv and that seemed to suggest snow still falling in the South East tomorrow. I guess anything's possible still, especially if the models change to something more favourable. I hope I was wrong and we see loads of snow everywhere - just want to keep expectations low in case of massive disappointment.

Edited February 20, 2010 by Matt12

[andymusic]

Hi John/anyone

Can you point out where to find Ian F's blog?

Ta

http://www.bbc.co.uk/blogs/weather/ianfergusson/

[Hedgehog]

You must of missed my posts because I have been commenting on tomorrows snowfall.

Generally speaking we're looking at around 5-7mm of precip with only 3mm N of the Midlands. Due to the timing of this precip I feel W parts are favoured for greater snowfall totals compared to those in the E.

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/02/20/basis06/ukuk/rsum/10022118_2006.gif

Remember this is only one run, the next runs may pull the cold air south again

[andymusic]

Remember this is only one run, the next runs may pull the cold air south again

Totally agree with you - models all over the place with this set up - I think it's because it's a very rare set up - struggling with the complexities and marginalities!!!!!!!!!!!!!! temps