Model Output Discussion - 19th - 25th December

[A Winter's Tale]

lol am I the only one who is happy with the output?

we now are looking at a possible snow event for Scotland with a low tracking north. Perhaps further polar incursions to come.

Hmmm, maybe for the high ground in the northern half as I feel it would be quite marginal. But I would love it if most of Scotland (inluding low lying areas of the south) see quite a bit of snow. Still, there's plenty of time left for change. However, I do agree with more polar maritime incursions to come judging by the theme of the models.

[Robbie Garrett]

I've labeled the chart, surely that ridge is stopping the jet being flat? Which would give height rises to our north/northwest?

[Kentish Kiwi]

I've labeled the chart, surely that ridge is stopping the jet being flat? Which would give height rises to our north/northwest?

I think you're misunderstanding the direction of the flow Robbie?

The Jet wouldn't travel south and then south-west on the western side of the high, it would travel NE and then E across the Atlantic. The Jet at the very bottom of the chart is actually returning on the southern side of the high, traveling back west over the Atlantic... Or have I misunderstood the point of your post...?

Edited December 22, 2011 by Kentish Kiwi

[Zenarcher]

Interesting charts from the GFS 00z run its placed that shallow low on the West side now letting high pressure build up and connect with the Greenland high. It may change but some sort of sign of a change ahead I think.

[Iceberg]

I am by no means an expert on strato warming as it moves through the 1, 5, 10, 300 hpa layers, however I think people need to understand it.

- strato warming will still be in the models(i.e look at the 10hpa temps for GFS using the N.Hemi option on meteociel) but might take 2-3 weeks to effect the Jet Stream or only a few days, it all depends on the positioning of the major features that need to be replaced to represent the warming above i.e a 1050 HP cell won't suddenly appear beneath a warming 100hpa spot above, if the HP cell is moving in the direction of where it's naturally due to be placed then it might take a few days, if it has to fight an existing strong jet etc then it might take 2 weeks.

- Due to the above some models and come members will adjust at different speeds to the warming, even though they all show it.

- What you really need to look at are the N.Hemi charts and only look at the major movements of the major pieces at this stage.

I think the general trend is clear, HP to migrate over the pole into western Canada/Alaska, the PV to move eastwards maybe to the east of scandinavia. IT's then a little up in the air, but we would see a buckling a decreasing of the Jet with HP to move towards the mid atlantic and greenland allowing northerlies.

However for the surface synoptics to react accordinly we are almost certainly looking at 2012. So allowing for FI unreliability etc the models would be unlikely to show any consistence in this setup at the surface until dec 27-30th.

so in a sentence my advice is look at the N.Hemi 10hpa and 100hpa charts until christmas, H.Hemi 300hpa charts from the 25-28th and the 500hpa charts from the 28th-5th.

[mountain shadow]

Good post ice. I believe that once the models pick up on any warming into the troposphere it will be like a switch has been turned on and more and more colder runs will begin to appear.

However for the time being the waiting game continues.

[shedhead]

A decent rise of pressure indicated on the big two for the middle of next week, but perhaps not unsurprisingly the MO is having none of it, with a weak LP over the country at T+144hrs. Thereafter the pattern gets flattened once again, so IF correct we're pretty much back to square one by this time next week - let's hope not!. In the shorter term all models indicate a bit of a mixed bag, but the main feature will no doubt be the anomolous warmth, Benbecula being 14c at midnight last night and heading a pretty impressive list!!

United Kingdom - Current Temperature Thursday 22 Dec 2011 00:00 GMT

Stations:

Benbecula (6 m) 14C

Liverpool (AP) (26 m) 13C

Rhyl (76 m) 12.7C

Hawarden (9 m) 12.5C

Edited December 22, 2011 by shedhead

[nick sussex]

Both the ECM and GFS drop the shallow low near the UK, the UKMO still has this at 144hrs.

The ECM ensemble maps at 168hrs have a wide variety of solutions:

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2011122200!!/

The ECM later output shows the beginnings of a change as the high begins to displace further to the west with an improving upstream pattern.

If the strat forecasts verify then we should see the jet beginning to slow down and there are now the first signs of a warming at the 30HPa level.

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/temps.gif

I'm sure everyone has been reading that thread and although there are no guarantees with this warming in terms of sledging weather down the line, it's better to have this as a background signal than the raging very cold PV thats been in evidence since November.

[Timmytour]

My kids are off to Bergen for the New Year so I do cast on eye on how the weather is looking over there. Although the outlook for the New Year remains wild wet and windy, I notice that beforehand they might get some colder weather with snow, which was not showing (GFS) a few days ago.

So things can change. But at the moment the outlook seems to point to wind rather than snow being the newsworthy potential.

I wonder if we'll see any reference in the papers in a couple of weeks time to "The Back To School" storms!

[BLAST FROM THE PAST]

A decent rise of pressure indicated on the big two for the middle of next week, but perhaps not unsurprisingly the MO is having none of it, with a weak LP over the country at T+144hrs. Thereafter the pattern gets flattened once again, so IF correct we're pretty much back to square one by this time next week - let's hope not!. In the shorter term all models indicate a bit of a mixed bag, but the main feature will no doubt be the anomolous warmth, Benbecula being 14c at midnight last night and heading a pretty impressive list!!

United Kingdom - Current Temperature Thursday 22 Dec 2011 00:00 GMT

Stations:

Benbecula (6 m) 14C

Liverpool (AP) (26 m) 13C

Rhyl (76 m) 12.7C

Hawarden (9 m) 12.5C

Can you post the temps tomorrow evening or Sat morning, for balance.

Well models are as expected pulling away from the Bartlett for weeks on end scenario. Going back to a much earlier post I said come Christmas week we will be looking at very interesting charts with and I think modelling of a big pattern change in FI. Its around New year the filtering down/through of this pattern change 'emerging', in its infancy shall we say.

Mild Christmas Day approaching but I've had milder/warmer but colder air filtering south from a ridge developing to our west and moving across us....not a Bartlett set up that. It was either 1985 or 86, it was lovely as the winters that followed are well known!

Lots of mention of the strat warming, I'm backing that it will have a large hemispheric affect.

BFTP

Edited December 22, 2011 by BLAST FROM THE PAST

[nick sussex]

The GFS 06hrs run brings back the shallow low and gives a chance of some snow for Scotland.

Its quite a complicated set up and we saw earlier both the GFS 00hrs and ECM dropping this low, for areas away from Scotland hoping to get something out of this low this would need the ridge further north and the ridge to topple more favourably taking the low se'wards rather than ese towards Denmark.

I think this may take a while to sort out given the model disagreements.

Edited December 22, 2011 by nick sussex

[ITSY]

Certainly no decent cold on the GFS treadmill yet, methinks it will start to show in a weeks time

[snowingman]

nothing of hope in the charts,, a shame as we the days are now getting longer again - in about 3 weeks the sunlight will be making a difference to temperatures and any snow that falls will be shortlived !

[Grimsby Snow Lover]

nothing of hope in the charts,, a shame as we the days are now getting longer again - in about 3 weeks the sunlight will be making a difference to temperatures and any snow that falls will be shortlived !

This seems a bit misleading. Yes the sun will be gaining strength but if the temperatures are cold enough as well as the dew point then snow can last even in March in most areas of the UK. I would say mid February onwards is when the sun has enough strength to melt lying snow, but in shaded areas this extends well into March. I am sure our members in northern England and Scotland would agree with me there.

Edited December 22, 2011 by Grimsby Snow Lover

[Bobby]

No trace of any blocking on the ensembles, polar vortex still rampant

ECM mean +240

Mid-Jan onwards is when things might start to get interesting I think

Edited December 22, 2011 by reef
Removed deleted quoted post

[Downburst]

This seems a bit misleading. Yes the sun will be gaining strength but if the temperatures are cold enough as well as the dew point then snow can last even in March in most areas of the UK. I would say mid February onwards is when the sun has enough strength to melt lying snow, but in shaded areas this extends well into March. I am sure our members in nothern England and Scotland would agree with me there.

Of course, snowingmad is suggesting any snow from 15th January would be short lived, news to me. The average air temp in Jan and Feb is almost identical, plenty of time for snow. I must say I'm loving the weather this week, in a T Shirt here with the jumper near at hand. If it's not going to snow then I want it as warm and dry as possible. Far less arguments this Christmas as people can get out and walk etc. As for the last month or two on here the pure maddness looking into every run for snow? Where do we live? Lapland????

Models suggesting little change in overall pattern for 10 days.

[BLAST FROM THE PAST]

nothing of hope in the charts,, a shame as we the days are now getting longer again - in about 3 weeks the sunlight will be making a difference to temperatures and any snow that falls will be shortlived !

There's a saying, as the days lengthen so the cold will strengthen. Jan and Feb are colder months than Dec and that sentence does not hold up.

BFTP

[Thundery wintry showers]

The models are making more of the high pressure to the SE during the period 22nd-27th December, suggesting that it won't be a mild grey drizzly scenario everywhere. Many parts of eastern England are seeing some sunny intervals today, and after the polar maritime incursion on the 23rd/24th December, high pressure looks set to continue ridging into the SE on the 25th-27th. Thus, the 25th-27th will probably be dry with broken cloud and sunny intervals across much of central, southern and eastern England, and in any sunshine it will feel notably warm out of the wind. Other regions, though, probably will end up grey and drizzly.

The low pressure for the 28th/29th is prone to considerable uncertainty, and I won't be surprised if it largely disappears on future runs. There is, though, a consistent signal for a colder anticyclonic end to the month with brighter weather extending further north and west.

[KTtom]

No trace of any blocking on the ensembles, polar vortex still rampant

ECM mean +240

Mid-Jan onwards is when things might start to get interesting I think

It is comming up to Christmas.................must be some missing data! :smilz38:

Edited December 22, 2011 by KTtom

[Thundery wintry showers]

Looking at the ECMWF ensemble mean and the models' operational runs, the outlook strongly suggests a temporary colder interlude towards the end of December with a ridge of high pressure moving across the country, followed by the jet sinking south leaving us back in westerlies. The extent to which the jet sinks south will then determine whether we get mild, average or cold zonality into the New Year, but too far out to determine at this range.

[Frosty.]

The worst possible christmas day weather with a rather cloudy but mainly dry and mild day, cringeworthy weather for the big day but for scotland it looks like there will be heavy rain and strong winds on sunday. The models are not showing any signs of changing the general pattern in the next few weeks.

[danm]

The worst possible christmas day weather with a rather cloudy but mainly dry and mild day, cringeworthy weather for the big day but for scotland it looks like there will be heavy rain and strong winds on sunday. The models are not showing any signs of changing the general pattern in the next few weeks.

To be honest, if it's going to be mild i'd rather have dry and sunny than wet and windy,

[BLAST FROM THE PAST]

The worst possible christmas day weather with a rather cloudy but mainly dry and mild day, cringeworthy weather for the big day but for scotland it looks like there will be heavy rain and strong winds on sunday. The models are not showing any signs of changing the general pattern in the next few weeks.

I beg to differ Karl, FI is definitely looking like a change in New year is possible.

06Z has come up with interesting LP/Feature on 27th [can't post links]. Interesting because I felt that around Boxing Day we could see some gales with LP hitting us. Models had this showing last week in FI but generally ditched the idea with just a very breezy SW'ly set up. Is it something to watch? Some Colder air digging in behind it up north/Scotland.

BFTP

Edited December 22, 2011 by BLAST FROM THE PAST

[Uncle_Barty]

Still looks mainly average to mild (especially for the South) for the foreseeable.

I would not look beyond the start of next week on the models, however, as things may well be on the change beyone the reliable/semi reliable timeframe.

[stratty]

Still looks mainly average to mild (especially for the South) for the foreseeable.

I would not look beyond the start of next week on the models, however, as things may well be on the change beyone the reliable/semi reliable timeframe.

There are certainly some more interesting runs from the ensembles coming out, coldwise. Good to see these become more common over the next few days, with what some people are saying about the changes into January. Although a snow fan - it's actually a beautiful day out there today!