Model Output Discussion - cold spell to end Autumn

[Nick F]

39 minutes ago, Weather Boy said:

John, for the years on this forum I've been puzzled about the difference between 'surface' And, erm, 'real' high for want of a better word and I still don't know. 

 

Furthermore,  how do you tell the difference from a chart like that? 

 

Assistance gratefully received from a bit so newbie....!

A surface high is usually always present over Greenland, as much of the interior landmass is an ice sheet which creates cold dense air on the surface (resulting in high pressure) while above the surface in the mid-upper levels the airmass is often cold shown by the low heights/ upper low (blues on 500mb charts) - this cold air circulation aloft over Greenland, often part of the tropospheric Polar Vortex, usually drives a strong westerly jet further south over the Atlantic, even if there is a surface high present over Greenland.

However, when there is warm air advection aloft from the south over Greenland, it causes geopotential heights to rise in the mid-upper levels (greens and yellows on 500mb charts), which combined with a surface high, creates a vertically-stacked high or ridge that contains very stable air with descending air aloft so cause blocking, which diverts low pressure systems around it. These blocking highs of course can happen anywhere, so long as there is high pressure at the surface and warm air aloft, Azores high is a semi-permanent version of this.

Edited December 8, 2017 by Nick F

[feb1991blizzard]

3 minutes ago, blizzard81 said:

Never seen this model before. How reliable is it? 

I think it is actually the Euro4, that's  what they use, I thought it was the Uk4 or UKV but ive just looked, the UK4 has retired. strangely though if you look at the actual weather chart for the same time, that's even further North so they must use the UKV for that (Guessing)

[swfc]

7 minutes ago, feb1991blizzard said:

Updated UK4 further North than most models still.

https://www.metoffice.gov.uk/public/weather/forecast/map/gcpvj0v07#?zoom=7&lat=52.35&lon=-2.88&map=Rainfall&fcTime=1512842932

 

 

I cant make head nor tale of that feb!!!!

[Met4Cast]

7 minutes ago, feb1991blizzard said:

Updated UK4 further North than most models still.

https://www.metoffice.gov.uk/public/weather/forecast/map/gcpvj0v07#?zoom=7&lat=52.35&lon=-2.88&map=Rainfall&fcTime=1512842932

 

 

Similar to the Euro4, then..

EURO 4 holding steady.. I find it's usually pretty spot on, APERGE/NMM can be hit and miss so their track South isn't quite as compelling to me

[Cov87]

1 minute ago, Danny* said:

Similar to the Euro4, then..

EURO 4 holding steady.. I find it's usually pretty spot on, APERGE/NMM can be hit and miss so their track South isn't quite as compelling to me

If the EURO 4 is correct think only the nw parts of the midlands will do well so south of staffs could be a little snow mixed in with rain

[feb1991blizzard]

Just now, Danny* said:

Similar to the Euro4, then..

EURO 4 holding steady.. I find it's usually pretty spot on, APERGE/NMM can be hit and miss so their track South isn't quite as compelling to me

I would have to say usually that I would have it much further South than the Met Office models, only the Icon has it further North than the Euro4 and UKV (guessing its the UKV), so if the Met Office / BBC forecasts are right, you have to give them credit, although they stressed uncertainty, those map charts ive been monitoring all week and they haven't wavered much.

[swfc]

5 minutes ago, Danny* said:

Similar to the Euro4, then..

EURO 4 holding steady.. I find it's usually pretty spot on, APERGE/NMM can be hit and miss so their track South isn't quite as compelling to me

Looks pretty close to the met and there amber warning area also

[shaky]

5 minutes ago, Cov87 said:

If the EURO 4 is correct think only the nw parts of the midlands will do well so south of staffs could be a little snow mixed in with rain

Looks pretty good to me mate!!still gives 10-15cms widely across the midlands!!dare i say snowline ever slightly south!!still furthest north out of all outputs!!

[mother nature rocks]

Personally I believe it will move further south as fergie has said on social media.

[Yarmy]

18z Arpege 0.1 Hi-res at T39:

 

Midlands + East Anglia Bonanza.

One aspect of this slider that I've not seen mentioned much: the front pushes through at the coldest part of the day. 

[joggs]

53 minutes ago, Weather Boy said:

John, for the years on this forum I've been puzzled about the difference between 'surface' And, erm, 'real' high for want of a better word and I still don't know. 

 

Furthermore,  how do you tell the difference from a chart like that? 

 

Assistance gratefully received from a bit so newbie....!

Real high are the yellows Nd oranges.Fairly rare tbh up Greenland.

But when they do happen,great chance of cold for us.

[weathergeek]

2 hours ago, nick sussex said:

This slider low has turned into Play Your Cards Right!

Instead of couples you've got the southern v northern contingent. Each output is met with desperate pleas of higher or lower or in this case go north or go south!

Given the timeframes its less likely you'll get any big corrections but still room for some changes.

Anyway the next instalment of the slider low saga or better named attention seeking  model celebrity will soon be  arriving!

 

The only difference is that I think you could actually CHOOSE to Freeze on Play Your Cards Right??!! Lol!!

[snowray]

Loving the look of the HIRLAM this evening, I used to think this was a half decent model too.

[feb1991blizzard]

24 minutes ago, swfc said:

I cant make head nor tale of that feb!!!!

Its a Precipitation chart, ive realised now though, it is the EURO4 but you can go on the menu by selecting show, then select weather, then zoom in and out and move around the UK to see very localised forecasts.

[ITSY]

6 minutes ago, snowray said:

Loving the look of the HIRLAM this evening, I used to think this was a half decent model too.

This would be the heaviest snowfall in virtually a generation for Cambridge. I’ll swim naked in the Cam if that happens. 

[feb1991blizzard]

^^

Yes, I just don't see that wide an area getting so much, that has me getting a good tonking but also parts of the SE, I just don't see that because the low would have to be less elongated and fatter to give that much PPN, and if it was, there would probably be a lot more marginality in it for the Southern half.

[East_England_Stormchaser91]

Best model output watching in absolute years. Watching every run with baited breath now! 

Every run you make, every step you take, every tease you make, every spell you break I'll be watching you.. (Me watching the GFS and Hi-res this evening on a Friday of all nights!!) 

[snowray]

57 minutes ago, ITSY said:

This would be the heaviest snowfall in virtually a generation for Cambridge. I’ll swim naked in the Cam if that happens. 

Well you never know, we will require pictures of your frozen forfeit you know, I have known the HIRLAM to be bang on the money in the past for PPN, regularly better than Arpege and Arome anyway out of the French lot. 

Latest 18z fax for tomorrow, is that another shift south, the high over Iceland certainly looks more pronounced there? Well just something to muse on as we go to bye byes....

Edited December 9, 2017 by snowray

[The Enforcer]

On 12/7/2017 at 23:28, The Enforcer said:

And for a comparison of FAX chart progress - look no further:

T+120:

T+96:

T+84:

T+72:

Analysis: Fronts making faster progress, more negatively tilted and further south on each output.

T+60:

T+48:

Analysis: Increased negative tilting and waving, a third Low centre and a move South, followed by a move North

[PsychedelicTony]

But look where the 528 dam line is on the +48 chart. The old school cut-off.

[essexweather]

Here is the latest from the high-res UKMO run...

Modified CF consensus maybe 25-50 miles further South than shown where snow accumulates. A very short period of sleet/wet snow likely from North London to Clacton as well, mostly rain throughout to all areas South.

Conference call ongoing, Monday discussions will be next

Edited December 9, 2017 by essexweather

[geordiekev]

6 hours ago, Ice Day said:

I think we've seen so many great charts over the last few weeks maybe we're getting a little worn down!  This at 144 is another cracker....just think of the doom last December!!!

And decent uppers compared to 12z at 150

Totally agree, since before bonfire night we've been spoilt with cold charts, and for a pleasant change they have came to fruition, despite a few members consistently looking for crumbs for mild charts in the next 384 hours, which I don't understand.

Most know in the winter most here are cold hunters. Similarly in Summer most are plume hunters, so I wish the stealth trolling would desist.

Personally I'm excited by the charts,  and despite reliability charts for the models,  which I think show GFS lagging, but being a USA and Canadian service believe they handle colder solutions better and have been spot on picking up cold shots way out both now and previous winters. Simarlarly the European ECM model probs better verification at predicting warmth for France, Spain et al. 

We are only a week into Winter and had cold charts since bonfire night and looking At the bigger Northern hemisphere picture I can't help thinking where in for a treat this Winter. 

Edited December 9, 2017 by geordiekev

[Cheshire Freeze]

Very very close to swinging back the pendulum to extended cold once again on the 0z GFS- look at that little arc of heights heading N of the UK...usually a precursor to an E'ly. Don't think we'll quite make it this run though as not enough heights going N and the Scandi trough looks in no hurry to sink S and detach.

In fact, you look at this chart at day 9 and think hmm....

You look at Scandi on that chart and wonder if in two or three days time we won't see a Scandi ridge progged to form there..

Edited December 9, 2017 by CreweCold

[geordiekev]

Woo-hoo, Christmas now into view 

White Christmas for the highlands of Scotland on Dec 25th,  put your bets on. Just good to see chance of cold air around our island, step 1, tick 

 

Edited December 9, 2017 by geordiekev

[snowice]

Well over night output hasn't changed gfs/UKmo going for a cold week with a risk of more wintery showers next weekend.00z has snow in much the same place for tomorrow and a lot of it ,temperature to go sub -8 over snow fields

Edited December 9, 2017 by snowice