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Hunt For Cold: Model Discussion - Heading Into Christmas


Paul
Message added by Paul

If you're hunting for cold potential in the model output, this thread is for you. But if you'd like to look more widely at the models, please head over to the general model discussion thread.

This is a model related thread, so a general, frequent theme of the model output is a given, but it will not be strictly enforced:

  • Some topic drift, humorous responses etc are fine
  • Posts likely to lead the thread off on an entirely off topic tangent are not ok. For example (but not solely limited to): Posts entirely or mainly about Met Office, BBC or media forecasts with little or no model context, and posts solely asking for a weather forecast in a specific location.
  • Posts which start with something like 'I know this is off topic but ...' are not ok.
  • Posts which break the forum guidelines are not ok (eg trolling, troll-hunting, weather guilt tripping, overly defensive/aggressive, abusive, disrespectful to others)

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Posted
  • Location: Redhill, Surrey
  • Weather Preferences: Southerly tracking LPs, heavy snow. Also 25c and calm
  • Location: Redhill, Surrey
9 hours ago, feb1991blizzard said:

@BLAST FROM THE PAST

Can't remember, i know you said Look North not East at some point, were you thinking the same period as i am now?, i have a suspicion we might see a Northerly gathering momentum in the next few days modelling for around Jan 1-5th

Correct, displaced PV to NE with very cold air dragged south from northerly as troughs pass through....hopefully we’ll see further firming up. Nice step forward by ECM

 

BFTP

Edited by BLAST FROM THE PAST
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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL

EC maintains a similar theme to last night, GFS clearly clueless.

Looks like we are in a holding pattern with EC but i'm still waiting for signs of a change in the Atlantic sector..

EC 10

ECH1-240.GIF?18-12

OK not bad, main chunk of PV over scandy but on the down side, still the Iberian heights persist, we need them pulled west, and to my eye, at least for now, there is still too much energy in the Atlantic sector..

edit not trying to put a downer on things, i'm still optimistic, but the Atlantic sector/iberian heights is really becoming a pain ..

Edited by northwestsnow
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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL
8 minutes ago, northwestsnow said:

EC maintains a similar theme to last night, GFS clearly clueless.

Looks like we are in a holding pattern with EC but i'm still waiting for signs of a change in the Atlantic sector..

EC 10

ECH1-240.GIF?18-12

OK not bad, main chunk of PV over scandy but on the down side, still the Iberian heights persist, we need them pulled west, and to my eye, at least for now, there is still too much energy in the Atlantic sector..

Patience NWS! It’s coming. 

The Atlantic looks far from active to my eye, on the Mean also! Those Iberian Heights May end up being our friend if they go on their travels! ⬆️ 

674BA125-4478-4D3E-A440-CB9772BAA6C5.thumb.png.1e25b8ee2227c2a9b604650aa9c0dc02.png

 

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent

I’m wondering if we’re starting to see a run of upgrades within the model suites now but the models just picking different timeframes for the pattern change. 

GFS gets a weak blocking high to the North fairly early on

93118ED4-C9DF-46C2-8F4A-1EDA8A5451B5.thumb.png.c19e0c9dfc1211adc5a226c324cdc8f7.png

ECM begins to build a high Northwards at the end of the run

0B1A547E-AEB9-4763-85BD-0D132DA70006.thumb.png.efa40d742131ecbb1fc20ebd546b35b9.png

Discount anything beyond day 6 but I think we’re on the verge of seeing steps towards a colder pattern now. Extended EPS has a surprisingly strong signal for heights across the UK (somewhat similar to the ECM chart above, actually)

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Posted
  • Location: Scouthead Oldham 295mASL
  • Location: Scouthead Oldham 295mASL
Just now, karlos1983 said:

Patience NWS! It’s coming. 

The Atlantic looks far from active to my eye, on the Mean also! Those Iberian Heights May end up being our friend if they go on their travels! ⬆️ 

674BA125-4478-4D3E-A440-CB9772BAA6C5.thumb.png.1e25b8ee2227c2a9b604650aa9c0dc02.png

 

Hope your right Karlos

We wait to see the clusters etc, hopefully Exeter stay on target !

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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL
5 minutes ago, northwestsnow said:

Hope your right Karlos

We wait to see the clusters etc, hopefully Exeter stay on target !

Don’t expect any answers today! Volatile is how I’d sum up what I’m expecting to see run to run over the next fair few days. Pinch of salt for any run regardless of what it shows until we get broad agreement of the theme.

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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL

I think that’s a fair assessment @johnholmes . I too think anything cold before, on or a couple of days after Christmas is a long shot. 

After that........ 

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Posted
  • Location: st albans
  • Location: st albans
Just now, smith25 said:

Anyone know where Mr murr is? I enjoy reading his take on things and he's been very quiet recently.

He is preparing for jan/feb as he is nearly 500 feet asl.....

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57 minutes ago, BLAST FROM THE PAST said:

Correct, displaced PV to NE with very cold air dragged south from northerly as troughs pass through....hopefully we’ll see further firming up. Nice step forward by ECM

 

BFTP

I’m guessing there will be some interesting polar low developments with that deep cold flow. Well done Blast, keep sticking to your guns. 

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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL
11 minutes ago, bluearmy said:

He is preparing for jan/feb as he is nearly 500 feet asl.....

I’ve not actually seen it, that’s how it came across though ?‍♂️. Anyone got any links to view it or is it behind a paywall these days?

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Posted
  • Location: st albans
  • Location: st albans
24 minutes ago, karlos1983 said:

I’ve not actually seen it, that’s how it came across though ?‍♂️. Anyone got any links to view it or is it behind a paywall these days?

Latter part not available for free afaik 

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

A wee look at the GEFS ensembles:

GEFS Ensembles Chart GEFS Ensembles Chart

T850s clearly suggestive of a sudden cool down, come early January...Could be hints of the potentially very cold northerly seen on previous runs?

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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

The xmas period runs from xmas to-new yrs day!!

There 'understanably' seems a lot of focus regards xmas day.

The 7 day period ( xmas)..

Is and has been the likely starting point....and i continue with that notion.....

 

Edited by tight isobar
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Posted
  • Location: Telford, c.150m asl
  • Weather Preferences: Snow, ice, cold
  • Location: Telford, c.150m asl
10 hours ago, feb1991blizzard said:

@BLAST FROM THE PAST

Can't remember, i know you said Look North not East at some point, were you thinking the same period as i am now?, i have a suspicion we might see a Northerly gathering momentum in the next few days modelling for around Jan 1-5th

That would be my preferred option... I turn 50 on the 5th January so if the Clerk of the Weather could arrange a white birthday, that would be lovely!

It is really exciting seeing the possibilities - I love the will-it-won't-it drama!

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Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL

There's talk a of a big East coast American storm around or just after New Year, with hints of Greenland heights East of the storm. I think our sights should be on for a possible Northerly around New Year too.

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10 hours ago, Bring Back1962-63 said:

Note that the previous strong spike was the one that should have created that powerful uplift from the Tibetan Plateau and Mongolian Mountains with those very strong vertical rossby waves which should impact on the stratosphere around Dec 22nd-24th. The further spike may well produce a similar response in very early January  (more below on that).

Remember from the paper that I referred to - the lower part of the jet is obstructed by the very high Himalayan peaks and is partly channeled and funneled across the Tibetan Plateau and rushes northwards until it is uplifted by the Mongolian Mountains.  It is that range (the Altai in particular) that is believed to generate the greatest uplift of all and it was probably no coincidence that the strongest EAMT (the red blob on the MT chart centred around 40N to 45N) was right over that range last week.  The lower charts suggests a repeat in about 7 to 8 days time and if this is roughly correct, that should coincide with the next spike in EAMT in that area (more below).

 

 

According to several specialists, this may well follow the pattern set up during the 2009/10 SSW when we saw many weeks of cold and snow in both Europe, the UK and the eastern CONUS. Too early to be certain of that yet.    

 

 

A couple of observations - 'uplift' from mountains doesn't produce 'vertical Rossby waves'. These would be orographic gravity waves - oscillations in the vertical which are restored to equilibrium through the density of the air parcels acting under gravity. They can increase in amplitude with height and reach a point where they break depositing their energy (possibly in the strat). But they are not planetary waves (wave 1, 2 etc) or Rossby waves. Rossby waves act in the horizontal plane perpendicular to the flow with the restorative force being the gradient of potential vorticity (typically north-south). This applies to the stationary waves from mountain torques also, where the height of the topography increases the amplitude of the wave, speed of the flow determines wavelength.

For winter 2009/10, the UK did experience cold weather after the SSW with a deeply negative AO - however the lowest AO and coldest UK weather occurred before the SSW on Feb 9th, as shown in the graph below (windspeed left axis, AO and CET right axis), with a healthy mid and upper strat vortex at the time -

2009-10.thumb.png.7e68f8e9abee6532907062a022df956d.png

 

 

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Posted
  • Location: sheffield
  • Weather Preferences: cold ,snow
  • Location: sheffield
5 minutes ago, northwestsnow said:

GFS still chalk and cheese to EC at 168..

Yes agree.Id suspect anything beyond the 5- 7 day mark is out in fi imo

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