Model Output Discussion

[Wales123098]

BBC just said the snow is likely to hit S.Wales at first on Tuesday so going with what the models are saying.

[Ian Fergusson]

I tend to now only concentrate on charts up to a maximum of 5 days (apart from snow forecasts which I only look up to 24 hours), anything after 5 days I use as a rough guide only.

(snip)

Remember past memorable cold spells tended to appear with very short notice.

Hooray for a very sensible post from the lovely open fields of Buntingford!

[Optimus Prime]

importance of a southerly track before doing this bear in mind it's not down to a bias but generally them wanting a colder pattern to last for the WHOLE UK!

It's not just the southerly tracking system that may cause problems for some proper snow if it goes too far north, there's very little very cold pooling over the NE unlike what we had in mid December. Eventually some serious cold does get pulled out of that region but by that stage the whole pattern becomes a lot slacker.

Although the event itself is marginal the pattern is very impressive be it whether there is actually much cold out there in the source.

[Thundery wintry showers]

Yes- I agree with you. In particular the lows tracking further south implies the jet being further south, which in turn implies more chances of the British Isles staying on the northern side of the polar front jet as blocking can develop and extend more generally to our north.

The lows being further south would also permit a scenario of frontal snowfalls in southern England and a high probability of snow showers and trough systems affecting areas from the Midlands northwards, driven on by a combination of northerly and/or easterly winds. In that scenario, areas that missed out would be in the minority, as opposed to having the frontal battleground over northern England (say) where anywhere from the Midlands south would just get a huge dolloping of rain.

So I can certainly see your point- while in the short term, the front being placed over N England instead of S England might just mean a redistribution of snowfall, for the longer term it is a downgrade (and more likely to cause serious problems with flooding towards the SW, for that matter). But that also doesn't take anything away from the point that too many members are getting too hung up on changes from one run to the next. The ECMWF setup in particular is only a smidgeon away from entering us into a very cold easterly flow at T+168- and that is partly scuppered out at T+192, way too far out to be able to realistically expect the models to pin down any details anyway.

I agree that there isn't much cold pooling progged out there to the north and east- but if we get those airmasses, even though they're modified, they should still be cold enough to support widespread snowfalls.

Edited December 26, 2009 by Thundery wintry showers

[East Herts Snow]

Hooray for a very sensible post from the lovely open fields of Buntingford!

For the last week very snowy open fields, but all melted now!

Incidently Bristol could be in the prime spot for decent heavy snow next Tuesday, I think you deserve it!

[nick sussex]

Yes- I agree with you. In particular the lows tracking further south implies the jet being further south, which in turn implies more chances of the British Isles staying on the northern side of the polar front jet as blocking can develop and extend more generally to our north.

The lows being further south would also permit a scenario of frontal snowfalls in southern England and a high probability of snow showers and trough systems affecting areas from the Midlands northwards, driven on by a combination of northerly and/or easterly winds. In that scenario, areas that missed out would be in the minority, as opposed to having the frontal battleground over northern England (say) where anywhere from the Midlands south would just get a huge dolloping of rain.

So I can certainly see your point- while in the short term, the front being placed over N England instead of S England might just mean a redistribution of snowfall, for the longer term it is a downgrade (and more likely to cause serious problems with flooding towards the SW, for that matter). But that also doesn't take anything away from the point that too many members are getting too hung up on changes from one run to the next. The ECMWF setup in particular is only a smidgeon away from entering us into a very cold easterly flow at T+168- and that is partly scuppered out at T+192, way too far out to be able to realistically expect the models to pin down any details anyway.

I agree that there isn't much cold pooling progged out there to the north and east- but if we get those airmasses, even though they're modified, they should still be cold enough to support widespread snowfalls.

Excellent post TWS and hopefully many of the members will take this on board. In terms of the ecm ensembles these IMO are some good news, still alot to play for.

[Wilxy]

BBC just said the snow is likely to hit S.Wales at first on Tuesday so going with what the models are saying.

Maybe a chance here then i do think that theres a chance of snow maybe not at first but likely to turn to snow but why is everyone so excited about it is it meant to stall or something.

[Geordiesnow]

In terms of the low a northerly track would indicate not enough blocking to the north with the curve of the jet taking the colder air into the Atlantic, the low tracking into France on a more west to east or preferably wnw/ese trajectory would suggest blocking further east to the north this down the line will help sustain the cold and with it more snow chances. For those slating some posters from the south for pointing the importance of a southerly track before doing this bear in mind it's not down to a bias but generally them wanting a colder pattern to last for the WHOLE UK!

I've made numerous posts saying much the same thing all day and am beginning to wonder whether some members understand English!

Yep and even though we saw one run from the GFS showing the low being further north is not a complete disaster, it's alot more risky imo and i would prefer if it was over Northern France than where the UKMO currently suggests.

Whilst a southerly low does not guaranteed a lengthy cold spell, it does more or less guarantee alot of convective activity from the North Sea and sometimes even the Irish Sea. So those areas who may miss out on the frontal snow could get the convective showers and with the colder upper air are more than likely to be of snow away from the coasts.

[Paul]

Just deleted another off topic / argumentative post from here - please have a read of this:

http://forum.netweather.tv/forum-1/announcement-145-anti-social-posting-in-the-winter-area/

We will be stopping people from posting until the new year without any further warning if they continue to post any further 'anti-social' type posts - please bear this in mind..

[keithlucky]

Maybe a chance here then i do think that theres a chance of snow maybe not at first but likely to turn to snow but why is everyone so excited about it is it meant to stall or something.

It does stall and wriggles form on the front this is a 3 day event and south midlands are in for a battering.

[bluearmy]

i am surprised by the way the greenland blocking appears to be so impotent wrt our mid term pattern. there were plenty of clues on yesterdays ens mean output that the atlantic would make a stronger push ne than the ops were showing as we entered the new year. maybe we were spoiled by the strength of the block just gone. after all, its not like we've had much practice over the years in watching greenland blocking.

many of the runs today have dispensed with what looked to be a very strong -AO upcoming. in this regard, i remain suspicious of many of the op runs from today. let see what tomorrow brings.

and one final thing - recalling my youth from the seventies, maybe its not true, but i recall most snow events to have been either devon, cornwall, and other parts of the south west as a front approached and was rebuffed over a period of days or a midlands and wales experience as a front came north on an w-e axis and stalled before fizzling out and going back south. frontal snow events in the south/southeast were a rarity. (i stand to be corrected of course)

Edited December 26, 2009 by bluearmy

[snowray]

Maybe the next run will shunt it 200 miles further south, a few strange charts in there lacking much detail...could it be the lack of data issues which also occured this time last year but were resolved by 27th dec, there are no excuses from tomorrow if the models still don't show what some are expecting.

Well this is always a worry of mine, that things end up so far South that we end up missing out.

In view of all these 70s comparisons though, I would expect North of Birmingham to do best since I always remember the best snow being North of London back then, happy days!

I'm still in Northern Italy at my mums, cant believe 40cm of snow then freezing rain on tuesdays left me with the odd patch of white by Christmas day after 24hrs of heavy rain, was -20c before I arrived at 400 meters asl, yesterday 7c! Last thing we want is end up on the wrong side of the low since theres some very mild air in the med, upto 25c in Sicily, people sunbathing and swimming down there, crazy even for Southern Italy.

Anyway, here comes 18z.

[Paul]

New thread online, locking this one..