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Model output discussion - here comes the beast!

Paul

Please only post model discussion in this thread 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

We also have a special post SSW cold spell discussion open here:
https://www.netweather.tv/forum/topic/89358-ssw-related-cold-spell-will-it-wont-it/

Thank you!

Message added by Paul

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10 minutes ago, Weathizard said:

The high is still too close for many. I can read the charts pretty well but can anybody explain why that Iberian low isn't undercutting? Block stopping it? It seems like it just does not want to go under 

This may help as there are no drivers and will fill in situ over n/w portugal

icon-5-120.png?21-18

Edited by winterof79

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3 minutes ago, Quicksilver1989 said:

Wow you are not wrong! I'd never used that site for the ECM ensembles.

Anyhow here are some stats, using my north,south,bullseye and fail measures as to whether the Scandi cold pool hits the UK if I take 20 GFS and 20 ECM runs I get the following percentages:

North: 9%
Bullseye: 68%
South: 18%
Fail: 4%

https://weather.us/model-charts/euro/europe/m6_temperature-850hpa/20180228-1200z.html

Check out P6 for the -19C run! 

Yes I thought I might have been underestimating the number of "bullseye" runs!

I think what's developing is a two part cold wave - the first cold plunge on Monday/Tuesday, then the second cold plunge rolls into us 24/48 hours afterwards - and the second plunge unbelievably is colder than the first.

There will be no large cluster with high pressure pushing the cold south at D8 - it will be small. There may also be a small cluster that allows a break-in from the south. But the big clusters will be the cold ones.

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1 minute ago, Man With Beard said:

Yes I thought I might have been underestimating the number of "bullseye" runs!

I think what's developing is a two part cold wave - the first cold plunge on Monday/Tuesday, then the second cold plunge rolls into us 24/48 hours afterwards - and the second plunge unbelievably is colder than the first.

There will be no large cluster with high pressure pushing the cold south at D8 - it will be small. There may also be a small cluster that allows a break-in from the south. But the big clusters will be the cold ones.

The ops and control runs for both GFS and ECM also go for a bullseye, if I gave them higher weighting then the bullseye option looks even more likely. Lets hope we don't get any more issues from now :D

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1 minute ago, wiltshire weather said:

Updated 120hr FAX chart seems to have the HP further north than the UKMO model was showing earlier.

Also, an incoming trough just making landfall on the east coast.

Met Office Fax Synoptic Chart

Seems to have the 510 dam line along raw ukmo chart rather than other guidance. Seem to be coming out earlier now they no longer have to wipe Tomasz’s backside during the evening !  

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Very elongated hp-well into the pole via 18z..

This 'could' aid deeper cold on a westward march...

Getting the uppers more cleanly into play....

gfsnh-0-72.png

Edited by tight isobar

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Center of the high is slightly further North at t84 compared to the 12z for what its worth.

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10 minutes ago, Singularity said:

Still some tight/straightness of flow issues to resolve before we know how soon the deep cold lands, but by far the biggest message the model output of today has given me is this:

We need the southerly jet to drive a trough at least as far east as the Balearic Isles by Wednesday and then ideally as far as Italy by next Thursday.

Reason being the strengthened signal for the main focus of high latitude blocking to shift rapidly to the NW and with more exploration of a west-based negative NAO outcome; we need the LP to the SE so that deep cold will continue being pushed in our direction even as the blocking moves away. Inevitably the flow will then spread out and destabilise, but with enough of a residual E flow this could well leave the UK beneath a large area of air still cold enough for all-snow events and with numerous disturbances drifting across from day to day.

Alternatively, the negative NAO may set up more east-based after all, in which case you can get that splendid transition from the Arctic continental to Arctic maritime cold airmasses with only a narrow band of less cold air between, if even that - much as we saw ECM exploring yesterday.

 

If troughs don't make it so far east, you most likely end up with a GFS 12z scenario although probably not quite so fast to shove the less cold air in (let alone the JMA 12z with its unusually deep lows!).

I notice the ECM 12z has the LP sliding E over southern Europe before filling out in it's latter stages. Is this the LP you're referring to?

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3 minutes ago, wiltshire weather said:

Updated 120hr FAX chart seems to have the HP further north than the UKMO model was showing earlier.

Also, an incoming trough just making landfall on the east coast.

Met Office Fax Synoptic Chart

Quite a slack flow though isn't it? looks cold, but not very snowy

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6 minutes ago, Fred Sykes said:

Quite a slack flow though isn't it? looks cold, but not very snowy

Fred

The snow will come via instability over the sea. Not to mention the trough on the eastern side.

Get the cold in, then track the showers. Literally zero point in talking about snow until then.

Edited by Astral Goat Juice

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Upper high isn't as great in terms of its location on the 18z run at 96hrs, slightly further south for sure. Core high further north than UKMO but got to watch what it evolves into.

Also note the angle of the lower thickness in Europe, not as good as the 12z op run. It will probably still be good though.

Edited by kold weather

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'Catacol' saying the macroscale detail wont change for the start of next week which is 120 hours away is a ridiculous statement as far as UK weather is concerned. A slight change run by run between now and then could result in huge differences from a dry high sat over scotland to a full blown easterly with -16/17 850s and heavy snowfall for many. These kind of changes happen all year round for this part of the world over 120 hour period so i cant fathom how it is apparently nailed.

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Not great so far. Cold uppers being squeezed south into France. Iceland shortwave not allowing pressure to push the cold this way.... Lets see how it progresses from here. Cold delayed by 12 hours or so. Another setback? 

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this for monday

gfs-2-168.png

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2 minutes ago, SizzlingHeat said:

Not great so far. Cold uppers being squeezed south into France. Iceland shortwave not allowing pressure to push the cold this way.... Lets see how it progresses from here. Cold delayed by 12 hours or so. Another setback? 

Should still evolve fine but the upper high does take a little longer to shift, cold air I'd say IS a little delayed this run, nothing too drastic though, we are probably talking 6-9hrs delayed compared to most runs thus far.

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2 minutes ago, tinybill said:

this for monday

gfs-2-168.png

Non Monsieur that’s Sunday 

Edited by karlos1983

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1 minute ago, karlos1983 said:

Non monsiuer that’s Sunday 

opps 

 

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6 minutes ago, SizzlingHeat said:

Not great so far. Cold uppers being squeezed south into France. Iceland shortwave not allowing pressure to push the cold this way.... Lets see how it progresses from here. Cold delayed by 12 hours or so. Another setback? 

It's fine, yes the little low puts up a little fight against the huge block but I doubt the high will lose :)

PS that shortwave over Norway could develop into a polar low and usher in the cold air behind it :)

Edited by Quicksilver1989

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Having it too far north could be worse tbh. You're more likely to pick up a SE'ly flow which mixes the cold uppers ala 12z GFS.

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2 minutes ago, kold weather said:

Should still evolve fine but the upper high does take a little longer to shift, cold air I'd say IS a little delayed this run, nothing too drastic though, we are probably talking 6-9hrs delayed compared to most runs thus far.

Yes you are right. Seems to be back on track now at T120. Lets hope for further improvements

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