Model output discussion - 1st December onwards

[Captain Shortwave]

4 minutes ago, chrisbell-nottheweatherman said:

Thanks for the update.  Most concerning given the vulnerability of large swathes of northern England at present.

Don't worry the south joins in on the 18z

A slow moving deep secondary low with many areas seeing a solid 24 hours of persistent rain, more so over the south east where the low crawls across the Dover Strait.

You might get a few scattered wintry showers afterwards though. So don't forget to attach skis to your canoe just in case.

 

At this point it is trying to squeeze anything out of this if possible and avoid any potential flooding issues. The developments around mid month regarding heights to the west/north west looks more fruitful, if only as the pattern switch would likely develop drier conditions even if the cold pattern doesn't really get going.

Edited December 29, 2015 by Captain Shortwave

[chionomaniac]

Following on from last nights thoughts - here are the 12Z GEFS 5 day (11-16) mean anomalies:

Still not as strong on the EPS - but trending more than last night regarding a possible northerly.....

[Man With Beard]

Latest GFS is VERY close to the snow. A front diving mild and cold is sitting off the east coast and isn't moving very fast. Of course, this is following the floods and storms of the previous day.

Edited December 29, 2015 by Man With Beard

[snowray]

3 hours ago, mountain shadow said:

 

Thanks Singularity and Tamara for your great posts this evening, well balanced and also accurate as far as the psychology of this game goes where the Winter months are concerned.

Big changes with this run, Atlantic looking much more active.

[northwestsnow]

18 hours ago, Mucka said:

I'm happy with the output so far.

GFS doesn't get there but it is another step toward the Euros and UKMO maintains the undercut albeit we could do with that low disrupting more and getting some cold uppers across us.

 

Its all gone downhill since mucka

ECM was bitterly disappointing and GFS18Z has continued the theme, one must hope UKMO is on the ball here.00Z runs will be the defining moment insofar asthe 96 to 144 timeframe is concerned.

18z shows some strong blocking to the north east and a very dense cold pool over scandy but we just cannot seem to rid greenland of that horrid horrid PV!!!!! 

Edited December 29, 2015 by northwestsnow

[nick sussex]

The GFS started better with a more favourable pattern to the ne and upstream . Then it went AWOL with a typical overblown low.

 

[knocker]

And this doesn't look too clever either

[Geordiesnow]

Detail wise, not a very good 18Z run, seems to be following the ECM trend of perhaps the Atlantic kicking into gear but again, got to be careful not too read too much into the detail side of things because they will vary from run to run. 

I think the disheartening thing about the model runs at the moment, for all the blocking and what looks like strong blocking, there does not appear to be much in the way of a strong signal to send much cold in from the East, its all rather frustrating in this respect. The other frustrating aspect is the development and trend of a shortwave which splits the high with the strongest part heading into Western Russia and in turn, makes the route to cold looking a lot more harder and complicated. 

Potential is there but I get tired of saying that when there is not such a strong signal of much in the way of cold weather heading our way. 

[Captain Shortwave]

To try and post a more positive comment on here, the GFS (P) delivers something in the extended range, I wouldn't post but it fits well with the given anomaly signals for mid-month.

This will be something to watch over the coming days as others have already suggested of course.

[chrisbell-nottheweatherman]

Just now, Captain Shortwave said:

To try and post a more positive comment on here, the GFS (P) delivers something in the extended range, I wouldn't post but it fits well with the given anomaly signals for mid-month.

This will be something to watch over the coming days as others have already suggested of course.

Is that an Omega block I see initiating?

[booferking]

The 120 fax chart is out do any of you experienced members agree that it is more like the ukmo cheers for any replys.

It seems to be even better than ukmo with the low further south.

Edited December 29, 2015 by booferking

[Hotspur62]

Just saw the BBC 10 day forecast on News 24. with Darren Bett and although fresher than the last 6 weeks nothing particulary cold with the man difference being the shift in the rain hitting the South as the jet moves South with the North having the best of the drier weather, something I am sure everyone on this forum will be glad of. I think we can pretty much discount the possibility of the UK tapping into the cold uppers from the East now but the NH is certainly looking good for a cold spell to develop hopefully in next 2 weeks       

[Essex snowman]

First post from me love this forum I'm a cold lover snow yes please but by looks of it not yet but I'm patient so here's hoping and frosty u always put a smile on my face when u post on here fella Stella's all round me thinks 

[East_England_Stormchaser91]

One thing that I have seen a few times in the past is for the models to suddenly throw these knife edge lows to the SE into France and overestimate their left turn northwards. The next 96 hours will be interesting. Nothing is nailed down until the last minute in these situations and can often go right down to the wire.

[karlos1983]

9 minutes ago, booferking said:

The 120 fax chart is out do any of you experienced members agree that it is more like the ukmo cheers for any replys.

It seems to be even better than ukmo with the low further south.

Follow the 528 dam line all the way up to the north of Scandinavia, like a finger pointing to where our future cold shall come from.  

 yes it certainly does resemble the UKMO 12z to my eye 

Edited December 29, 2015 by karlos1983

[Sperrin]

Rookie question; could someone briefly explain what a dam line is and how it relates to cold weather? Cheers.

[booferking]

2 minutes ago, Sperrin said:

Rookie question; could someone briefly explain what a dam line is and how it relates to cold weather? Cheers.

The 528 dam line is known as the snow line which you are usually guaranteed snow to fall.

[Ben Sainsbury]

3 minutes ago, Sperrin said:

Rookie question; could someone briefly explain what a dam line is and how it relates to cold weather? Cheers.

I'm by no means an expert, but certainly an old poster but I believe a dam line of 528dam or less can produce snow most commonly, aslong as other factors are right. This isn't always the case though.  Not quite sure what "dam line" means though.

[shuggee]

Here you are Sperrin:

https://forum.netweather.tv/topic/2237-guide-todam-lines/

[chris pawsey]

Long time lover of this thread (+8 years) and my appreciation goes out to all regular posters, you know who you are... your insight and knowledge is really appreciated, i have learnt alot!! My advice for what it's worth is that things can change very quickly, one run to another... don't get your hopes up on a dumping of the white stuff until 24hrs away, ppn charts indicating snow +48hrs away should be taken with a pinch of salt.

[nick sussex]

6 minutes ago, Sperrin said:

Rookie question; could someone briefly explain what a dam line is and how it relates to cold weather? Cheers.

This from the UKMO is a good description:

Thickness lines

Pressure decreases with altitude, and thickness measures the difference in height between two standard pressure levels in the atmosphere. It is proportional to the mean temperature of this layer of air, so is a useful way of describing the temperature of an airmass.

Weather charts commonly show contour lines of 1,000-500 hPa thickness, which represent the depth (in decametres, where 1 dam = 10 m) of the layer between the 1,000 hPa and 500 hPa pressure levels. Cold, polar air has low thickness, and values of 528 dam or less frequently bring snow to the UK. Conversely, warm, tropical air has high thickness, and values in excess of 564 dam across the UK often indicate a heatwave.

 

The 528 is a rough guide, you're not guaranteed snow with that it depends on many factors like how much sea modification etc. However you can get snow off an easterly in a frontal type situation with dam higher than 528, in mainland Europe snow can fall with dam as high as 540.

 

 

[Sperrin]

Cheers for the replies, very useful.

[Frosty.]

26 minutes ago, Essex snowman said:

and frosty u always put a smile on my face when u post on here fella Stella's all round me thinks 

Thanks, much appreciated and I hope you enjoy posting on here as much as I do. 

[Cloud 10]

Day 7 ensemble means from GEFS and ECM still with some key differences regarding how the cold pool to the East can affect the UK,with the ECM quite a bit colder.

 

More twists and turns still to come over the next few days.

 

GEFS..ECM..

[Tom Jarvis]

Nassa just posted this. https://twitter.com/nasa/status/681978507199688705