Winter Model Discussion 18Z 19/2/13 onwards.

[Isabellesnanny]

Are we still in for the milder/less cold spell next week or is this no longer forecast?

[davehsug]

Not really Pete, I picked up on this a couple of days ago that BBC were predicting temps above what should be expected and it was taken as a constant dig at MetO. There's no shift IMO, we were always likely to be petty cold and getting bitterly cold. Mention tonight of potential more increased snow chances into weekend, I suspect the story isn't over yet.

BFTP

The BBC medium range always overstate temps in cold weather, just as they understate temps in warm spells in the summer. It's hardly news & if it wasn't needed to fit in with the now broken drum that's been banged for weeks, would not be worth a mention.

[Mair Snaw]

Nope...not gonna happen unfortunately. I believe after this week winter will be ended.

Here we go again winters over blah blah blah, any charts to back up this claim?? the models cant even agree on whats happening over the weekend and first part of next week, yet here come the spring is in the air posts......

[BLAST FROM THE PAST]

The BBC medium range always overstate temps in cold weather, just as they understate temps in warm spells in the summer. It's hardly news & if it wasn't needed to fit in with the now broken drum that's been banged for weeks, would not be worth a mention.

They tend to show city temps, but do often quote what temps in sticks may well be. Noticed that has been quite forthcoming again recently so quite informative and good to hear.

Anyway folks lets see if 0z continue the potential elongation and indeed reload. Good night

BFTP

Edited February 20, 2013 by BLAST FROM THE PAST

[chris55]

The northerly tease continues with the GFS 18hrs run but still doesn't quite deliver, its crucial here to get the pattern further east and south before the Atlantic attack otherwise you end up stuck with troughing over the UK.

Interestingly the longstanding limpet east Pacific ridge decides to finally relent, shame it didn't do this a month ago. Remember here bog standard 850's won't cut it because of the increase in solar energy so you need to chase the coldest source.

This will only get advected south with the pattern further se, its a small step however and a trend in the right direction for those wanting a spring reminder of winter but gets a stingy 6/10 from me.

Time for more changes and we have seen a move from some of the operational runs today, we'll see if that move gathers pace over the next few days.

Well Nick it all depends what you want delivered! GFS 18z would bring some heavy snow in places out in Fantasy Island, obviously we are not looking at weeks of bitter cold and freezing lakes etc, but some snowfall certainly. Also on the point of the 850 temps, I do agree that as we head into later March the -5 line becomes less relevant but in early March and with low thickness's the - 5 line is fine for snowfall when considering all the other factors of course.

But as you say, way to far out to take with any semblance of credibility in the details, but the broader pattern remains worth watching.

[swfc]

Here we go again winters over blah blah blah, any charts to back up this claim?? the models cant even agree on whats happening over the weekend and first part of next week, yet here come the spring is in the air posts......

he does not need charts as the output beyond 96 hrs is probably fi,maybe its just an opinion?

[Mair Snaw]

he does not need charts as the output beyond 96 hrs is probably fi,maybe its just an opinion?

Maybe but i thought this was the model discussion thread, not the one liner without a chart thread, if t96 is fi then how can anyone say winters ended next week and same as deep cold and snow, the model output is showing cold in reliable and then in fi a slight less cold with chance of more cold later. and by tomorrow it could well be showing the opposite so then a winters over post would be fine if a chart to back it up is posted along with the post.

Edited February 20, 2013 by bigsnow

[davehsug]

he does not need charts as the output beyond 96 hrs is probably fi,maybe its just an opinion?

No SWFC, you must be wrong. The GFS is now the greatest model ever, especially in FI. I know some people haven't been saying that recently, but I hear some big boys made them say it & it's all okay again now, until the next time it's not!

[snowking]

Yes that's also something Snowking alluded to with the race of the troughs, hard to say which one wins, maybe we can do something to derail the Atlantic one?!

Yes the straw cold seekers can cling on to is the continuous over-strengthening of the Atlantic jet through this winter so far. The hope would be that the operationals are leading the way, though even then we tread a fine line between cold and snowy or cold, wet and miserable.

Ensemble means continue for now to favour the Atlantic cyclogenisis becoming the biggest influence on the UK, but the GFS in particular edging the Scandi trough closer and closer.

The biggest story is the developing strong positive PNA signature, and I just wonder whether this added amplification of the pattern may help to us to derail the Atlantic push somewhat. Unfortunately even with such help though, whilst we may catch a glancing blow from the Scandi trough, with that west based negative NAO, we are only likely to see the jet angle SW-NE on our side of the Atlantic. We therefore also have to hope for the Greenland height rises to be more centrally based (and in turn this relies upon the remaining Greenland energy draining away through into the Scandi trough quicker than presently modelled)

There's a lot of pieces of the puzzle that will have to come together to not only ensure our Scandi vs Atlantic trough race goes the way of the Scandinavians, but that the victory isn't in vain as the Atlantic sneaks in and modifies conditions.

SK

Edited February 20, 2013 by snowking

[fergieweather]

I'm not absolutely sure Ian will be around in the next 4 or 5 days as he posted last week about having leave time off from being on BBC

Points West from today until next Monday.

It's more Monday of interest. Prior to then, UKV establishes convergence zone(s) Fri through London area, picking-out some 2cm accumulations locally. Monday tricky, with that weakening occluded plume running across W, giving awkward forecast mix given the rise in WBFL (temporarily up to 400m) and longer sea track given more backed flow. Exeter modified the GM's more extensive light rain signal using 30% Boyden, but nonetheless the areal extent and potential impacts from resultant snow remain v unclear at this point. Cheers for now.

[damianslaw]

It remains a cold mostly dry outlook for the foreseeable future. The trend from the models continues to be one of showing the high moving west into mid atlantic thanks to a split jet with energy focused in the Southern arm, hence the move away from sinking heights southwards. Not Surprised to see Borg gfs and ecm suggesting a northerly for the start of march, v plausible with heights progged to build v strongly over w greenland provided we dont end up with the atlantic trough establishing itself over the country, if it stays to the South the odds of a northerly pattern developing would be high.

[nick sussex]

Well Nick it all depends what you want delivered! GFS 18z would bring some heavy snow in places out in Fantasy Island, obviously we are not looking at weeks of bitter cold and freezing lakes etc, but some snowfall certainly. Also on the point of the 850 temps, I do agree that as we head into later March the -5 line becomes less relevant but in early March and with low thickness's the - 5 line is fine for snowfall when considering all the other factors of course.

But as you say, way to far out to take with any semblance of credibility in the details, but the broader pattern remains worth watching.

You've got to be a bit wary of the GFS 850's that far out as its known bias is to overplay the southwards push of those, additionally shortwaves this far out that can delay the cold won't be picked up. Also in terms of its snowfall predictions at that range again a bit dodgy.

The problem with the GFS 18hrs run is that the cold air never really gets a chance before you have phasing of energies with troughing over the UK and a western negative NAO.

The crucial point in these types of set ups when you're trying to fight against that NEG western NAO is to get the pattern further se, the weak point then is further east so the Atlantic energy is more likely to move ne further east which gives the UK a better chance to stay in the cold on the western side of any troughing.

Of course I agree its very difficult to get ice days and long lasting snow away from higher ground as you head into March but seeing as theres a good cold pool to the north it would be a shame to waste all that cold on some fishing trawler in the west Atlantic!

So we'll see over the coming days whether we can get some se corrections in the output.

[Panayiotis]

Ensembles show the cold from the east lasting 5 days (21st to 26th), if you take the warmest member for my area from the 26th to the 2nd March,nothing warm there; average temperatures (and remember I live in the SW).

I viewed the ensemble's graph of the 12z and it showed the mean post March being at 0C therefore there was a split between warm and cold members. However the 18z shows the mean has dropped towards -1/-4C, so one can say that there are more members at least going for just below average temperatures-Positive sign.

Edited February 21, 2013 by reef
Quoted post removed

[LomondSnowstorm]

A below average March does not mean snow unfortunately.

Not necessarily, but nor does 'prolonged cold'. What is being shown is a prolonged spell of below average temperatures for the British Isles for the foreseeable. Most of this period is likely to be dry, all of it for the northwest, with snowfall mostly limited to the east and southeast, although perhaps getting further inland on Monday. After that, dry and anticyclonic with temperatures average to below average for most, before the heights transfer westwards and at that point the models diverge between average-mild or another shot of cold from north, at least for Scotland and northern England.

[Panayiotis]

A below average March does not mean snow unfortunately.

Well if its mild and sunny you want, you wont get anything soon looking at the ensembles.

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=348

[LomondSnowstorm]

Well if its mild and sunny you want, you wont get anything soon looking at the ensembles.

http://www.meteociel...&mode=1&ech=348

Interesting, a surprising number keep heights high over Scandi and attempt another undercutting setup, an incredibly stubborn pattern over the last three months. It would be nice to get the Scandi trough into play though with some really deep uppers in play, the one thing missing so far in this winter has been a decent Arctic sourced northerly or northeasterly.

[IanR]

Not as tiring as people moaning about it constantly. Most people on the Winter Model Discussion are, shock horror, looking for cold scenarios, it's still February and March can still produce prolonged, deep cold and very snowy episodes. If reading all this 'ramping' is too much for you maybe pop back in a couple of months!?

Very snowy episodes with deep cold are rare in March , here anyway, In my 40 years I have never seen prolonged lying snow in March, Covective showers with sleet brief snow and hail yes , but tend to melt after an hour or two. Some models are showing milder spring like senarios after next week,its still all to play for , Continental air will get modified as we progress through March so deep cold is on its last legs after the next fortnight. Northerlies here in March dont really give much snow, Howver ther is always a possibility , the weather will do as it pleases

[Cheshire Freeze]

Trust me here, if we get that deep cold air associated with that vortex that looks to land to our NE there will be snow. I don't think some people realise the thicknesses tied into it......There would be convection/troughs galore with possible thundersnow. It wouldn't matter one jot that we were into March other than snow would thaw in sunny breaks away from high ground.

The hardest thing in March is getting thickness values low enough due to warming from the ground up and modification. Not a worry in this situation if some of the ops/ens are to go by.

I'll just add I've seen snow lying here (at a mere 55m asl) in March off a watered down Nwl'y and Cheshire gap streamer. A set up which has been hinted at by some of the ensembles would make that look like a warm stroll in the park.

This is just one example of many in the 18z ensemble suite....

Edited February 21, 2013 by CreweCold

[rory o gorman]

so the 18z op is not an outliner would sure be interesting to see if we can indeed tap into the P.V and some deep cold. Could see some strong convection as a result of sub 528 dam and diurnal heating.

[winterof79]

http://www.wetterzen...chester_ens.png not bad at all.Most output hinting at a northerly outbreak,a cold one at that.

Snow chances for a few this weekend too

http://www.meteociel...ax60s.gif?20-12

http://www.meteociel...x120s.gif?20-12

Edited February 21, 2013 by winterof79

[fergieweather]

UK4 indicative of circa 10cm snow parts of Kent by end of Friday but this is almost certainly overestimated: 3-6cm more likely. The backing flow into Friday means we will see 2 or 3 discrete shower bands: one through Lincs; another through Thames Estuary to S parts of London; and a third probable into E Kent. Meanwhile, the Channel shower stream focussed into Dartmoor/S Devon/SE Cornwall remains a very consistent feature through Friday.

1-2cm accumulations fairly commonplace under any such convergence areas through Friday, with scope for 3-6 as previously mentioned. However, given lateness in the season, there's likely to be a marked diurnal bias governing longevity of settling: i.e. generally only from late afternoon to mid-morning at low levels wherever amounts of snow are 3cm or less (the majority).

Edited February 21, 2013 by fergieweather

[shaky]

UK4 indicative of circa 10cm snow parts of Kent by end of Friday but this is almost certainly overestimated: 3-6cm more likely. The backing flow into Friday means we will see 2 or 3 discrete shower bands: one through Lincs; another through Thames Estuary to S parts of London; and a third probable into E Kent. Meanwhile, the Channel shower stream focussed into Dartmoor/S Devon/SE Cornwall remains a very consistent feature through Friday.

1-2cm accumulations fairly commonplace under any such convergence areas through Friday, with scope for 3-6 as previously mentioned. However, given lateness in the season, there's likely to be a marked diurnal bias governing longevity of settling: i.e. generally only from late afternoon to mid-morning at low levels wherever amounts of snow are 3cm or less (the majority).

Thanks ian!

[Ian Brown]

All the models are now picking up on an Azores Low at around day 7 which sees pressure rise in the mid-Atlantic, the question is whether or not the pressure will be in the right place to pull northerlies down across the UK. I think a return to mild is now less likely in the 10-14 day range.

[No Balls Like Snow Balls]

I wouldn't say we are odds on for a northerly just yet but the odds have certainly increased overnight. Its a long way to count down from T168 without no major dramas. Northerlys tend to be watered down to.

[Liam J]

Well not a very fitting chart for the third day of spring! Usual caveats apply looking at this range but a very diverse March looking more likely, more extreme than usual. Some cracking winter charts however you look at it. However such epic charts have yet to verify this winter!

You'd be looking at some heavy snowfall here given such low thickness values and sub -6c 850's, blizzards over parts of Ireland.

Edited February 21, 2013 by Liam J