Model Output Discussions 18z 31/01/2016

[feb1991blizzard]

The 6z GFS is actually a fairly severe run in terms of longjevity of cold, it starts off below average, by the middle of next week the Max temps are struggling to get above freezing and they continue to do so right until FI with some severe frosts at night involved, also some moderate falls of snow possible next week.

Edited February 12, 2016 by feb1991blizzard

[Singularity]

I have this theory that ECM tends to get carried away with the jet stream intensity when there are huge thermal gradients expected. This is based on more in the way of observations involving heat plumes in summer, though, so I'm not sure if it will apply so well with an exceptionally cold airmass pushing into the Atlantic.

UKMO not exactly clear this morning but the trough is weakening as of +144 so it could be close to GFS for +168.

GFS looking decent, even for my back yard if a typical correction west is applied. Too many times in recent years, I have read reports of snow  across areas east of Southampton while it's been dry or raining here.

 

Late Feb, the anticyclonic signal from GFS/ECM this morning fits loosely with an MJO move into phase 7, these ridges then trending north with time (currently not being captured very well). Issues with how the train of storms from the Eastern Seaboard can be halted - possibly too much assumption by the models of a classical El Nino regime there, as the conditions in the tropical Pacific have continued to move away from that over the past week. The latter stages of the GFS 00z highlighted the issue; a strong Arctic High was about to link up with mid-Atlantic ridging, but then a storm from the ESB bombed out and ruined everything. Hopefully we can see a trough held up in the far-western N. Atlantic instead. It's the last real chance I can see to score something capable of bringing lying snow to the south that doesn't melt within a day.

Interesting to see hints from the GEFS that, prior to that next mid-Atlantic ridge/HLB potential, enough low heights could be retained across southern Eurasia to support one of those long east-west ridges with an easterly on the south side. They are strange affairs and have a habit of being particularly cold for the far south. Potentially a good starting point for a move of high pressure to the W/NW of the UK too but now I'm getting ahead of myself!

[snowangel32]

1 minute ago, feb1991blizzard said:

The 6z GFS is actually a fairly severe run in terms of longjevity of cold, it starts off below average, by the middle of next week, the Max temps are struggling to get above freezing and they continue to do so right until FI with some severe frosts at night involved, also some moderate falls of snow possible next week.

Yh in my eyes one of the best runs of the winter so far.

[mushymanrob]

2 hours ago, johnholmes said:

The ECMWF-GFS anomaly charts this morning perhaps indicate the first signs by them of the flow turning more westerly in the 3rd week of February

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

The NOAA 6-10 last evening still had the flow N of W but the 8-14 had the flow shown as about westerly. So it looks as if the change will be underway after about another week?

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

yep , thats how i read them too john (im learning! lol)
 

ok, theres some 'tastey' runs being produced, which those of you seeking cold must be hopeful about. but the 'best' charts for something cold (deep/lasting) are being produced by the suits that have got a lower verification rate. i note no ones championing the ecm, but statistically it performs the best.

as some of you know, im a convert to the noaa anomaly charts as i found that what john was saying about them - and their high accuracy rate was pretty much spot on.

the current charts dont really allow for much cold, other then a brief 48 hour or so shot (maybe a little longer) but the upper flow remains in the western quadrant, and backs more westerly as john mentions. so they IMHO dont support some of the more amplified cold outputs, theres no strong lasting scandi ridge on these charts (please feel free to correct me if im wrong) . so i wouldnt have thought the chances for anything other then a transitory cold few days are very great, and theres no widespread 'big freeze' (3 + ice days/ lying snow) that some runs appear to hint at.

the lower ecm chart is the sort of synoptic chart id expect the noaa's (esp the 8-14 day) to produce.

 

[feb1991blizzard]

Just now, snowangel32 said:

Yh in my eyes one of the best runs of the winter so far.

Yes, it just shows you how rubbish winter has been though because normally even in the mildest of winters, you usually get one of those ridiculous Easterlies in FI with a direct flow all the way from Russia / Siberia with the -10c isotherm covering the whole country.

[feb1991blizzard]

2 minutes ago, mushymanrob said:

yep , thats how i read them too john (im learning! lol)
 

ok, theres some 'tastey' runs being produced, which those of you seeking cold must be hopeful about. but the 'best' charts for something cold (deep/lasting) are being produced by the suits that have got a lower verification rate. i note no ones championing the ecm, but statistically it performs the best.

as some of you know, im a convert to the noaa anomaly charts as i found that what john was saying about them - and their high accuracy rate was pretty much spot on.

the current charts dont really allow for much cold, other then a brief 48 hour or so shot (maybe a little longer) but the upper flow remains in the western quadrant, and backs more westerly as john mentions. so they IMHO dont support some of the more amplified cold outputs, theres no strong lasting scandi ridge on these charts (please feel free to correct me if im wrong) . so i wouldnt have thought the chances for anything other then a transitory cold few days are very great, and theres no widespread 'big freeze' (3 + ice days/ lying snow) that some runs appear to hint at.

the lower ecm chart is the sort of synoptic chart id expect the noaa's (esp the 8-14 day) to produce.

 

 

This might surprise you but I do actually have grave doubts about the GFS 6z verifying and if I had to put money on it then I would choose the ECM, might be somewhere in between though.

[snowangel32]

1 minute ago, feb1991blizzard said:

Yes, it just shows you how rubbish winter has been though because normally even in the mildest of winters, you usually get one of those ridiculous Easterlies in FI with a direct flow all the way from Russia / Siberia with the -10c isotherm covering the whole country.

Yh very true the classic garden path run I remember them well, but what gives me encouragement is that these charts are no longer deep in the realms of FI they are in the semi reliable if there is such a thing. A few slight tweaks and we could have a very interesting time ahead of us. 

[mushymanrob]

Just now, feb1991blizzard said:

This might surprise you but I do actually have grave doubts about the GFS 6z verifying and if I had to put money on it then I would choose the ECM, might be somewhere in between though.

not really, i understand you would like the gfs to verify, i agree that something in between will be the most likely solution.

[Frosty.]

Next week becomes wintry according to the Gfs 6z with snow, yes snow and increasingly frosty nights, some very sharp frosts actually ..great to see wintry weather in winter for a change!

[damianslaw]

High pressure ridging in an elongated NE-SW position with a strong upper cold vortex with very cold air embedded to the rear of associated front trying to edge in from the NW and into the building heights..

If we see a strong ridge build through there is no easy path for the trough to break through - it makes sense it will disrupt, and therefore GFS makes sense, ECM not so, just my opinion.

[Nick F]

Again, we see the Scandi ridge being the major player on the 06z in squeezing out any milder air making it in from the west next week, as the upper trough dropping down from the NW is forced to disrupt S/SE across the UK keeping cold air in place right up to the end of the week. EC doesn't build the block over Scandi, so we see Atlantic systems drive through to the north rather than slowing and disrupting. 

12z ECMWF backtrack tonight? Well, the 00z deterministic was almost a mild outlier after the the 19th, but the 00z GFS op was right at the cold end too!

[Berty73]

22 minutes ago, mushymanrob said:

yep , thats how i read them too john (im learning! lol)
 

ok, theres some 'tastey' runs being produced, which those of you seeking cold must be hopeful about. but the 'best' charts for something cold (deep/lasting) are being produced by the suits that have got a lower verification rate. i note no ones championing the ecm, but statistically it performs the best.

as some of you know, im a convert to the noaa anomaly charts as i found that what john was saying about them - and their high accuracy rate was pretty much spot on.

the current charts dont really allow for much cold, other then a brief 48 hour or so shot (maybe a little longer) but the upper flow remains in the western quadrant, and backs more westerly as john mentions. so they IMHO dont support some of the more amplified cold outputs, theres no strong lasting scandi ridge on these charts (please feel free to correct me if im wrong) . so i wouldnt have thought the chances for anything other then a transitory cold few days are very great, and theres no widespread 'big freeze' (3 + ice days/ lying snow) that some runs appear to hint at.

the lower ecm chart is the sort of synoptic chart id expect the noaa's (esp the 8-14 day) to produce.

 

Bib, dont understand what your saying rob, every forecast ive seen shows the cold to last 6/7 days and reading JHs post above seems to suggest similar, so im curious where 48 hours comes from?  Genuine question,  Ive just checked all the available websites and not 1 of them shows a max of more 3deg c imby for the next 5 or 6 days, am i missing something?

[weirpig]

Well from what i can see  the period wednesdy and thursday next week on the ensembles is a bit of a mixed bag  some have the front skipping through as rain, some have the front not reaching  atall some having the front stall over wales and parts of the midlands,  and some like the gfs run.  Place your bets 

[Lukesluckybunch]

Wow with the gfs control trickling out it looks even better than the op,with a stronger scandi high!

[Steeve88]

What I expect for this weekend and for the rest of the next week. We should hope to some snow if we are a bit lucky (in warm front cases you need to be lucky if you live in large city at low levels)....

http://www.northmeteo.gr/international-forecasts/uk-weekend-forecast-and-a-look-ahead-to-the-next-week/

[mushymanrob]

1 minute ago, Berty73 said:

Bib, dont understand what your saying rob, every forecast ive seen shows the cold to last 6/7 days and reading JHs post above seems to suggest similar, so im curious where 48 hours comes from?  Genuine question,  Ive just checked all the available websites and not 1 of them shows a max of more 3deg c imby for the next 5 or 6 days, am i missing something?

i mean 'big freeze', yes itll be a cold week, but not a week of deep cold, ice days, much snow and i dont think the noaa charts suggest a spell like that is likely to evolve, despite some 'building blocks' (awful phrase) being almost in place.

[Polar Maritime]

The 6z take on Wednesday/Thursday snow risk. Some disruptive falls model'd over the spine of the country.

With the cold holding on into the run and continuing to show an Easterly feed for the South, With -5/-6/-7 850's. Before the Atlantic wins out from the N/W.

Edited February 12, 2016 by Polar Maritime

[weirpig]

35 minutes ago, mushymanrob said:

yep , thats how i read them too john (im learning! lol)
 

ok, theres some 'tastey' runs being produced, which those of you seeking cold must be hopeful about. but the 'best' charts for something cold (deep/lasting) are being produced by the suits that have got a lower verification rate. i note no ones championing the ecm, but statistically it performs the best.

as some of you know, im a convert to the noaa anomaly charts as i found that what john was saying about them - and their high accuracy rate was pretty much spot on.

the current charts dont really allow for much cold, other then a brief 48 hour or so shot (maybe a little longer) but the upper flow remains in the western quadrant, and backs more westerly as john mentions. so they IMHO dont support some of the more amplified cold outputs, theres no strong lasting scandi ridge on these charts (please feel free to correct me if im wrong) . so i wouldnt have thought the chances for anything other then a transitory cold few days are very great, and theres no widespread 'big freeze' (3 + ice days/ lying snow) that some runs appear to hint at.

the lower ecm chart is the sort of synoptic chart id expect the noaa's (esp the 8-14 day) to produce.

 

I have to  agree  i find this tool the most realible  of course it could change like all models  but certainly favours the ecm than the gfs at this stage.

[swilliam]

37 minutes ago, mushymanrob said:

yep , thats how i read them too john (im learning! lol)
 

ok, theres some 'tastey' runs being produced, which those of you seeking cold must be hopeful about. but the 'best' charts for something cold (deep/lasting) are being produced by the suits that have got a lower verification rate. i note no ones championing the ecm, but statistically it performs the best.

as some of you know, im a convert to the noaa anomaly charts as i found that what john was saying about them - and their high accuracy rate was pretty much spot on.

the current charts dont really allow for much cold, other then a brief 48 hour or so shot (maybe a little longer) but the upper flow remains in the western quadrant, and backs more westerly as john mentions. so they IMHO dont support some of the more amplified cold outputs, theres no strong lasting scandi ridge on these charts (please feel free to correct me if im wrong) . so i wouldnt have thought the chances for anything other then a transitory cold few days are very great, and theres no widespread 'big freeze' (3 + ice days/ lying snow) that some runs appear to hint at.

the lower ecm chart is the sort of synoptic chart id expect the noaa's (esp the 8-14 day) to produce.

The thing is that the first chart perfectly agrees with GFS 06 and the protracted cold spell. If you look at the chart for 19th which is in the middle of your anomaly chart you can the Atlantic high, LP to the N, HP to the NE and near normal pressure over us.

The anomaly charts are great for broad brush average deviations from normal (over a few days) but can conceal local effects which is what is occurring here.  So your statement that the anomaly chart does not allow anything other than a 48 hr cold spell is not correct obviously

 

Edited February 12, 2016 by swilliam

[The Weather Dragon]

Not being down beat....but I can't see anything to get excited about with the current model output - we all know what we need for a decent cold spell. The current output doesn't even come close - just trying to get some balance back into the debate ! 

[Frosty.]

1 minute ago, Jonathan Evans said:

Not being down beat....but I can't see anything to get excited about with the current model output - we all know what we need for a decent cold spell. The current output doesn't even come close - just trying to get some balance back into the debate ! 

I can see plenty to be excited about in England next week with a slow moving band of snow, the SE could be the sweet spot!

[Isabellesnanny]

Which models do the NW forecast use? The forecast on there changes erratically every time I view it has shown snow on and of for weeks in my region and days which I understand from peoples views in the forum are likely for snow now seem to have a lesser chance percentage wise.

Do they use just one models and is it even worth viewing the  NW forecast?

Sorry If a bit OT but just wondered.

 

 

 

[Ripeberry]

So it seems that the East will get all the 'fun' next week. Yes, I suppose we in the 'West' are downbeat. Wasn't it only a few days ago that there might have been a massive dumping in central/South England? Hope the snow takes us all by surprise. If it ever arrives at all... 

[mushymanrob]

8 minutes ago, swilliam said:

The thing is that the first chart perfectly agrees with GFS 06 and the protracted cold spell. If you look at the chart for 19th which is in the middle of your anomaly chart you can the Atlantic high, LP to the N, HP to the NE and near normal pressure over us.

 

The anomaly charts are great for broad brush average deviations from normal (over a few days) but can conceal local effects which is what is occurring here.  So your statement that the anomaly chart does not allow anything other than a 48 hr cold spell is not correct obviously

 

yep, but its only a 'normal' cold spell, if you get what i mean. the 48 (or so) hour was referring to cold enough for snow/v cold. sorry i should have worded it better.
 

yep, a 'broad brush' which is quite good at ruling out some of the ops more outlying runs, it saves getting too hopeful (or despondent) when some op runs 'go off on one'.

[weirpig]

1 minute ago, Ripeberry said:

So it seems that the East will get all the 'fun' next week. Yes, I suppose we in the 'West' are downbeat. Wasn't it only a few days ago that there might have been a massive dumping in central/South England? Hope the snow takes us all by surprise. If it ever arrives at all... 

To be honest depends what charts you look at  and it is 5 days away.  actuallt the gfs does show snow in the middle of the country pushing east into the south east  pleanty time for changes  good or bad