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Paul

Hunt For Cold: Model Discussion - Heading Into Christmas

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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8 minutes ago, Neilsouth said:

Why do they always have to have a mild sector thrown up from France! Arrgh

I like what i see coming in behind that mild sector.. some serious cold air there.

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1 hour ago, FiftyShadesofSnow said:

 

See also 

Regarding the FV3, the 06z minimum was +1.9 m/s for 3/1 0z but was +7 m/s by the end as the split vortices retreated northwards slightly.

It was like a stronger split version of the 00z where the min was 7.1 m/s and 18.9 m/s at the end as the vortex reformed and slightly displaced from the pole and back to square one.

 

 

 

Edited by Interitus

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The positives for the “Hunt” continue 

DF7CE256-EDD5-4D81-B90F-192E8560FEB5.thumb.gif.805ebb76154f0210d5520afbce570c92.gifC05666CA-4CFA-48F8-8635-DB0FA8642722.thumb.gif.f5d75a4b3eb33e33d893dcde8fc50abf.gif

AO way more negative than yesterday’s 👍

Edited by karlos1983

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Admittedly this is at 30mb, but a proper view of the FV3 stratosphere:

npst30.png

A complete split evident there with a minor geopotential wave coming in through the Atlantic sector to aid the Wave 1 displacement from the Pacific

Whilst you could argue that one of the daughter vortices being that close to Greenland is not ideal (were that pattern to impress itself on the troposphere too), assuming any ridging followed suit, then you're getting into high risk high reward scenarios with some blocking likely around the GIN corridor somewhere and a likely southerly-displaced but still potentially active jet stream roaring just underneath it if everything falls into place....a la 2013

Still, this is only a single run from an experimental output which has had lower anomaly correlation out at day 10 than the model it is supposed to replace....I would recommend for now sticking with the EPS guidance as I suspect this will (eventually....not yet while everything is still chaotic) give us the first glimpse of what effect the impending stratospheric shenanigans will have on the troposphere through the second 2/3rds of January

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30 minutes ago, karyo said:

We can 'thank' the Alps for that.

How so? Is it related to Foehn effect?

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18 minutes ago, Selliso said:

How so? Is it related to Foehn effect?

Yeap

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2 hours ago, weirpig said:

Wonderful Strat profile on the Para    Total Split   one side over above Canada which should stop anything becoming west based   and a additional warming at the end of the run.    Middle of January could well be fun 

would bring some serious cold my way...talking -30c to -40c right at the coldest time of the year.

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icon-0-180.png?21-12

 

 

ICON

Synoptically analogues of what we see at the moment progged for the forseeable are probably the winters of 97 - 00. That's the closest I can think of certainly for the next 2 weeks as things stand.

 

 

 

 

 

 

 

 

Edited by The Eagle

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Not a great deal of excitement to be had for the next ten days given recent op runs .

Just perhaps a small chance of something colder around day 7 and 8 ,  at the moment the upstream pattern over the USA is flat however some amplification is likely to work east as a Pacific shortwave develops as it runs towards the Great Lakes.

Ahead of this a Canadian high will develop , this will slow down the Atlantic . Depending on how much dig south we see in the troughing in the west Atlantic this may allow some cut back in the jet to the east .

The MJO forecast has improved today esp in the GFS which has a more coherent signal and eventually this moves in towards phase 6 .

Theres still a lot of scatter in the ECM ensembles but the NCEP monthly update does suggest the MJO should continue to move towards the more favourable phases over the next few weeks .

Edited by nick sussex

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Afternoon all 🙂

As usual, those wanting snow, ice and -20 uppers are complaining because there's nothing showing in the next 7-10 days. 

True and it looks a remarkably benign Christmas and New Year period for most which is no bad thing for those having to travel and visit their families and/or loved ones.

The signals for something of more interest in the early to middle part of January remain there - the 06Z Parallel was a thing of beauty in far FI and interesting to see both Control and OP toying with slowing the Atlantic to a crawl and rising pressure over to the NE of the British Isles. GEM 00Z looks more like an inflated ridge from the UK and that's ten days out.

The first HP for Christmas won't be strong enough to ridge NE combined with too much residual energy in the jet so it slides ESE but a second burst of HP at New Year looks more promising but nothing is settled. The 06Z GEFS does indicate more members taking the core of the HP to the north which may be good for cold fans but there's no snow in many of the members at this time. 

It's a three phase process I think - the HP moves up from the south, transfers north or north east and later retrogresses. Ideally, we'd need a nice cool down before we get the easterly and then the northerly and then back to an ESE as the Atlantic tries to come back in from the SW. That's a 7-14 day severe cold spell for mid January (or maybe later).

The split PV continues to be modelled on the Parallel if not the OP with the split coming on January 2nd and indeed the 06Z Parallel initiates another burst of warming on the shattered PV which would pretty much finish it off. Even the OP weakens the PV significantly from what we would expect in January but it is a displacement not a full split. That said, even a displaced vortex offers opportunities for cold.

 

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4 minutes ago, mountain shadow said:

UKMO flat as a pancake but only goes out to Day 6 so not really concerned.

image.thumb.png.9f084ba820801d61898d4a84fca612b2.png

First, it isn't flat but yes, the first build of HP is declining SE and the second, more substantial build is coming NE from the Azores and Iberia. There's also a good sign the Atlantic is slowing and weakening on the UKMO as well which we also need to see.

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Im watching the GFS 12z strat-wise and i have a feeling (only out to 210) that this run will be the one that breaks the mould!!

Just watch it build a raging PV at the end lol..

 

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So far, the 12Z is about as exciting as the three-thousandth remake of Pride and Prejudice!

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diagram_40days_forecast_GEFS_member.gif

Well this is actually hilarious. From crawling along at low amp in P5 to roaring through to P6 in the space of 24 hours.

ECMF_phase_51m_small.gif

ECM's also adjusted faster and more amplified but in a much less frantic manner. It often comes around more slowly but steadily at times like this.

 

This should have the effect of promoting more NW extension of ridges from the UK past +7 days range, provided the operational models follow their ensembles with this trend.

Regardless of what they get up to this evening and tomorrow for that matter, this development is in line with anticipations and suggests we truly are on the golden path to a tropical-stratosphere co-operation with respect to bringing 'proper winter' to our shores next month.

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5 minutes ago, northwestsnow said:

Im watching the GFS 12z strat-wise and i have a feeling (only out to 210) that this run will be the one that breaks the mould!!

Just watch it build a raging PV at the end lol..

 

Split start a week on Sunday, will we see a trop response by the end of the run?

image.thumb.png.9850e889b6e00164aa8516caac89cce3.png

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Check out @judah47’s Tweet:

Total novice here but this looks good from Dr Cohen. Am I right in thinking this backs up what a lot of you guys have been saying about GFS being a dud strat model?

 

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A tweet from Mr Hugo
 
A simple observation. The UKMO model has been as much use as a chocolate fireguard of late. Hell it's having a rough week. Absolute pile'o dung... ICON consistent regarding the colder, sunnier Christmas. GFS, like usual all over the place like it's had too much sherry too.

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14 minutes ago, northwestsnow said:

Im watching the GFS 12z strat-wise and i have a feeling (only out to 210) that this run will be the one that breaks the mould!!

Just watch it build a raging PV at the end lol..

 

Out to 300 hours is a small improvement to the 6z but still not the perfect split.

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3 minutes ago, karyo said:

Out to 300 hours is a small improvement to the 6z but still not the perfect split.

Agreed, its better, and does show a split of sorts..but your right, its not great..

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3 minutes ago, Glacier Point said:

NH_HGT_50mb_360.thumb.gif.79b14e59546a5ac83c05a99e3bfff931.gif

Take a look further down. 12z op likely to be a significant outlier synoptically in our quadrant based on this.

Yes, will watch the Para to see if there is a difference-FWIW Stewart does this recently released tweet match your thoughts perhaps?

W COUNTRY: By Christmas Day & into early Jan, high pressure is set to dominate UK weather (ECMWF shown for 30/12, high cell position not to be taken literally!). However, this is likely to shift to Scandinavia further into Jan, with increasing risk of cold by mid-Jan on into Feb

Fergie this afternoon..

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11 minutes ago, Glacier Point said:

NH_HGT_50mb_360.thumb.gif.79b14e59546a5ac83c05a99e3bfff931.gif

Take a look further down. 12z op likely to be a significant outlier synoptically in our quadrant based on this. Placement of the vortex west of Greenland the vital thing here. GFS likely to have it too far east and north here.

Gfs has missed the sway..and imo the modeled vortex placements 'alone'..are of-mysterious miss modeling!!!

 

Edited by tight isobar

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If the 12Z is anything to go by, the Para can only be an improvement?😭 Is there such a thing as an Extra Slow Tropospheric Response (ESTR)?

Netweather GFS Image

 

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