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Paul

The hunt for cold - Model discussion (late November)

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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graphe3_1000_244_28___.gif

 

Well that's a pretty nondescript set of ensemble Pretty much all the snow chances have gone and any interest for the next 15 days might be the occasional frost

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I don’t know how true this is but I had heard that pressure rises in the mid latitudes may be the first response to a Stratospheric warming so would it be plausible to expect some milder weather or at least mild upper air temps before hopefully something colder.

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2 minutes ago, Interitus said:

Conditions seem right but it could go either way, or if there is one it could be marginal so as not to have much of an impact. Then depending on how it affects the waveguides it could be well into February before there is another shot.

Thanks for the reply, I have been thinking that the GFS maybe a bit too progressive in slowing and eventually reversing the zonal winds, as other models have yet to show such consistency with such a strong reversal. So still reasons to be optimistic but caution required for now I guess. In the meantime, trop lead for the next few weeks at least, hopefully the MJO cycle goes back into the colder phases in the New Year in a coherent amplitude potentially, which will help us out before any possible strat-trop coupling should the SPV displace/weaken in the New Year.

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is it possible the models are so confused by an incoming snowmageddon that they've gone quiet? We can dream can't we?

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2 minutes ago, booferking said:

DufP0BtX4AMsAde.jpeg

Although the above is from Saturday it does suggest there is low variance within models as the GFS 0z mean is very similar. Mesoscale the pattern looks to have a high degree of confidence for the remaining days of December. There are micro details that have yet to be resolved, from timing and wavelength longitude differences, Certainly for cold lovers little hope with the medium term from trop patterns, though the experts indicate Tropical waves due later this month, but that may just be the wave 1 activity of the Euro ridge? No wave 2 signs (that are more important). 

Nothing mild likely either so seasonal for many especially northern areas.

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2 minutes ago, Interitus said:

Conditions seem right but it could go either way, or if there is one it could be marginal so as not to have much of an impact. Then depending on how it affects the waveguides it could be well into February before there is another shot.

If there's one person on board i would want when it comes to strat events its you (chiono as well), your knowledge wrt SSW's and vortex strength analogues in terms of how things will pan out is second to none, so i am a bit disappointed, very wary now although i'm not changing my forecast (yet), as i have analogued around 10th to 15th Jan for a potent E/NE flow since mid Nov, with an SSW possible and a lot of knowledgeable people on board i would be mad to, but i am concerned now.

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10 minutes ago, mountain shadow said:

Meanwhile, back in the troposphere, we see a continued and growing signal for the return of the trop PV to exactly where we don't want it....

image.thumb.png.143eae8cad1073138ee673c520f5b3cc.png

Yup, never a good trend. It looks increasingly likely to me that if we are to get any cold air, it will now be from the east rather than from the north. The current window for GL height increases is diminishing and my fear is that the forecast SSW results in a displacement to N. America.

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I know it’s at T384 hrs but a stonking northerly would be following a few frames later 🙂

825EBC4D-D50E-411C-B5F4-00DC91AF23CB.png

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25 minutes ago, Interitus said:

Conditions seem right but it could go either way, or if there is one it could be marginal so as not to have much of an impact. Then depending on how it affects the waveguides it could be well into February before there is another shot.

This is a real reality check - this guy knows his stuff and is always level headed . Clearly the SSW that people have been saying is a done deal and we are beyond questioning whether it will happen or not is still not resolved !

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Can mention the SSW all you want but while I’m seeing charts like this at t300 I’m struggling to be overly positive to be honest, SSW isn’t  a guarantor of cold and whilst I’m seeing hideous charts like this I’m not getting my hopes up!

4EF87221-ED62-42DA-B4E9-EBB99D77BA25.png

Edited by Weathizard

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Just now, Badgers01 said:

This is a real reality check - this guy knows his stuff and is always level headed . Clearly the SSW that people have been saying is a done deal and we are beyond questioning whether it will happen or not is still not resolved !

06z GFS marginal again, minimum +0.1 m/s!

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Just now, Weathizard said:

Can mention the SSW all you want but while I’m seeing charts like this even in th darkest depths of FI I’m struggling to be overly positive to be honest, SSW is a guarantor of cold and whilst I’m seeing hideous charts like this I’m not getting my hopes up!

4EF87221-ED62-42DA-B4E9-EBB99D77BA25.png

 SSW are certainly not a guarantor of cold ...

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I seem to remember that last year the NWP struggled with the wave 2 event.  I seem to recall it was significantly after the event that the models picked up the implication for the troposphere but when they did the impact was marked.  Before the event and immediately afterward they did not cope at all well if my memory serves me well.

I'm not sure how well they cope with a wave 1 event.  Do they find a displacement easier to model than a total split?  Anyway, I'd say patience is a virtue right now.

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Need to bear in mind that predicating your strat forecast solely on gfs is not a great starting point .....

exeter will have eps and glosea - lets see if their tone changes in an hour or so 

 

Edited by bluearmy

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6 minutes ago, ICE COLD said:

I know it’s at T384 hrs but a stonking northerly would be following a few frames later 🙂

825EBC4D-D50E-411C-B5F4-00DC91AF23CB.png

Yes it is 384 but unusually deep cold air is poised in just the right place to the north of Iceland and looks ready to sweep down across the UK. All change next run.

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27 minutes ago, mountain shadow said:

Meanwhile, back in the troposphere, we see a continued and growing signal for the return of the trop PV to exactly where we don't want it....

image.thumb.png.143eae8cad1073138ee673c520f5b3cc.png

Is it returning though?

gfsnh-0-222.thumb.png.b3dfadc0a2fac7053c0f166bd37dc454.png

From that point, it then begins a slow steady shift towards northern Europe, allowing heights to build towards Greenland-

20181217_110439.thumb.png.199b9d6996d12fed4c59e82d2e99ba4b.png

All hypothesis at that range but sooner or later we'll start to see big changes in the trop profile. How they affect us remains to be seen but for now we're still in the game...

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This ssw in my opinion people have been putting too much influence on it bringing cold to the U.K. and it does now appear that some of the output is toying with the idea of the displacement been over N America. Which would in turn fire up the jet stream coming out of the states. Which in turn would bring us unsettled Atlantic driven weather. As the old adage goes if it can go wrong for the U.K. it normally does. I’m certainly not convinced this ssw will bring the goods in January for our tiny island. 

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3 minutes ago, terrier said:

This ssw in my opinion people have been putting too much influence on it bringing cold to the U.K. and it does now appear that some of the output is toying with the idea of the displacement been over N America. Which would in turn fire up the jet stream coming out of the states. Which in turn would bring us unsettled Atlantic driven weather. As the old adage goes if it can go wrong for the U.K. it normally does. I’m certainly not convinced this ssw will bring the goods in January for our tiny island. 

We just got to wait Terrier , January still a long way away.. 🙂

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8 minutes ago, bluearmy said:

Need to bear in mind that predicating your strat forecast solely on gfs is not a great starting point .....

exeter will have eps and glosea - lets see if their time changes in an hour or so 

 

Or even worse if their forecast of cold reverses completely!

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16 minutes ago, ICE COLD said:

I know it’s at T384 hrs but a stonking northerly would be following a few frames later 🙂

825EBC4D-D50E-411C-B5F4-00DC91AF23CB.png

Would it though? Potential spoiler there...

image.thumb.png.4a3be6cb0e49ba9a9850ffad96ac8978.png

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27 minutes ago, feb1991blizzard said:

Or even worse if their forecast of cold reverses completely!

Well i will be gobsmackedif it does!!

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It can take 1 or 2 weeks following a SSW for it to take effect lower down, so we are talking about 1st or second week of January we should see some impact at our latitude (not necessarily the UK ), so let’s not get too worried about FI charts - they are rubbish at the best of times so trying to forecast the fallout of SSW is impossible at this range. What we can expect to see is a typical borefest of UK winter charts, then Around XMAS a possible flip to something special hopefully. As long as this SSW happens, the UK has a good chance of “big freeze”, the METO are forecasting and monitoring it so let’s stay with that. 

 

Also, I think GLOSEA was seeing a big warming (SSW) in Jan a few weeks back, is this still the case I wonder - and is this warming next week just a precursor- if so 2 back to back SSWs could have some serious potential.

Edited by Ali1977

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Nothing much to worry about IMO, nothing is expected before the opening few days of Jan at the earliest - if (and it's a big if) the SSW (and other Pacific and tropical factors) takes hold. 

This anomaly at the far reaches of FI is interesting. I'm more interest in anomaly trends across GEFS at this point rather than the detail of anything: 

 

anom.png

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2 minutes ago, Ali1977 said:

It can take 1 or 2 weeks following a SSW for it to take effect lower down, so we are talking about 1st or second week of January we should see some impact at our latitude (not necessarily the UK ), so let’s not get too worried about FI charts - they are rubbish at the best of times so trying to forecast the fallout of SSW is impossible at this range. What we can expect to see is a typical borefest of UK winter charts, then Around XMAS a possible flip to something special hopefully. As long as this SSW happens, the UK has a good chance of “big freeze”, the METO are forecasting and monitoring it so let’s stay with that. 

Spot on Ali . Everyone using the GFS/GEFS is not even in range yet . The same happened last feb/ March , the models throwing out 💩 charts until they got a handle on it . Of course it doesn’t guarantee cold weather here but we have a higher chance than normal and the meto are bullish about cold in the new year . Gonna be a great watch over the Christmas period. 

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