Winter Model Discussion 12Z 22/1/13 onwards.

[Tim Bland]

Does anyone know yet why the meto have backed away from a colder outlook into feb? Are they looking at ECM FI and making assumptions there? The ECM 32 dayer isn't updated until tomorrow night so they haven't used that? As GP and Cc etc have stated the background signals are for heights to our NW and lows to our SE with a potential ridge so what are the met office seeing that others aren't?

[Methuselah]

I love weather watching (particularly snowy weather) and have been following this forum this winter. I have learnt a lot from everyone even though you can be a bit scary to newcomers. Anyway my question regarding charts is at what timescale can you pin the charts down to a definate forecast and has there been a time when the weather has well and truly defied what the charts have forecast.

Apologies that this is a basic question I very new.

Welcome to NW, Dibdabbers...

Please can you pop your location into your profile??

[shaky]

it will be more North & East...

As said - it will depend on how far south the shortwave drops & subsequently what milder air gets into the front...-

S

So the southern extent would be maybe the midlands then!!

[Summer Sun]

Does anyone know yet why the meto have backed away from a colder outlook into feb? Are they looking at ECM FI and making assumptions there? The ECM 32 dayer isn't updated until tomorrow night so they haven't used that? As GP and Cc etc have stated the background signals are for heights to our NW and lows to our SE with a potential ridge so what are the met office seeing that others aren't?

It could be that there own MOGREPS model is showing something different into February and they favour that more over other models like the EC 32 dayer

The EC 32 dayer is updated again overnight so any changes in the text forecast could happen tomorrow it all depends on highly the met office regard the EC 32 dayer

One things for certain they won't base there text forecast on just one model they'll compile data from a number of longer range models and see which outcome is most likely at this stage

Edited January 24, 2013 by Gavin.

[Summer Sun]

Looking at the jet stream there could be some nasty conditions early next week it could become very windy for a time

With the ground still very saturated there is likely to be some river flooding again next week with localised surface flooding

[Snowman.]

I have done and to be fair ensemble No 20 is just as likely, infact that pattern outnumbers those suggesting cold E/NE,lys.

http://modeles.meteo...20-1-384.png?12

Just adding some balance to this thread to prevent members being disappointed, again!

What do you mean again?

[Froze were the Days]

I love weather watching (particularly snowy weather) and have been following this forum this winter. I have learnt a lot from everyone even though you can be a bit scary to newcomers. Anyway my question regarding charts is at what timescale can you pin the charts down to a definate forecast and has there been a time when the weather has well and truly defied what the charts have forecast.

Apologies that this is a basic question I very new.

A definite forecast can approximately be obtained at 12 hours in cold/blocked synoptics and 144 hours when mild Atlantic bilge kicks in...hope this helps.

[Catacol]

You may be right. Phase one of next cold spell 3-7th Feb are the dates I've been working with so cold may manifest circa day 14?

Then perhaps all the coming and going is really a debate over nothing! By Feb 7th I certainly wouldnt be declaring anything for certain, though the MetO statements are disappointing.

GP still seems pretty sure of something though. I'm a little puzzled why spiking angular momentum is a variable that is "missed" by the models so that we can expect them to flip as they come to terms with it. Advice needed from Snow Ballz, our resident mathematician... if GP is correct is this simply a variable which the algorithms havent been set to take into account, or is it possible for computer code to have a blind spot like this?

[Tim Bland]

Could be that there own MOGREPS model is showing something different into February and they favour that more over other models like the EC 32 dayer

Good point Gavin, didn't realise MOGREPS went out that far! Ie further than 240hrs Perhaps Ian can confirm or deny?

[nick sussex]

If the output was taken at face value a few weeks back the cold would have ended last weekend.

If the ECM and GFS outputs of a few days ago remained the same then it was zip interest upstream.

But wait that deep low is moving east engaging the PV lobe in northern Canada, where did that come from?

Oh its in relation to a more amplified wave moving east, that wasnt supposed to happen because the outputs upto day ten a few days back were wide of the mark!

My point being that if the models were intent on a limpet PV to the north and zero interest upstream they would have stuck to it, we've seen enough zonal set ups to know that you can easily model those upto day ten.

Lets give it a few days and see where we are, the outputs maybe worse but you never know they might be alot more interesting!

[Dibdabbers]

Welcome to NW, Dibdabbers...

Please can you pop your location into your profile??

Thankyou and done

A definite forecast can approximately be obtained at 12 hours in cold/blocked synoptics and 144 hours when mild Atlantic bilge kicks in...hope this helps.

Thankyou

[Cecil Hogmanay Melchett]

Dont want to start banding about emotional phrases but it really is looking like a protracted spell of zonal muck

# after tomorrow.It is a mugs game forecasting weeks in advance but the profile in our part of the world looks as bad as it can be really with a raging PV to the North west(as has been the case typically since November) and a big fat belt of high pressure stretching from the azores across southern and central europe.

I really think we are looking at at least 10 days of Atlantic dross which will take us into the first week of Feb,and then the clock will be ticking rapidly for another year.

[mcweather]

We are always told that FI is only for trends so hows this for a trend on todays 12z

240hrs 2/20 runs show greenie high or block to east/northeast

312hrs 5/20 runs " " " " " "

384hrs 8/20 runs " " " " "

Worth keeping eye on

[Summer Sun]

Good point Gavin, didn't realise MOGREPS went out that far! Ie further than 240hrs Perhaps Ian can confirm or deny?

Yes I'm not sure how far it goes out but thats the only thing I can think of as what we've heard from Matt regarding the EC 32 dayer that was showing something different upto Tuesday's update the next update is overnight

[Catacol]

Angular momentum continuing to tank, and good evidence of poleward fluxing of that energy as the Global Wind Oscillation gains amplitude in phases 5-6-7. It could well go even higher in the coming days as mountain and frictional torques get to work (might check record GWO phase 5 value).

NWP beginning to wake up at t168 mark to amplification signal coming out of the Pacific.

I would advise anyone to look at archived GFS modelling dated 18th November 2012 as your reference point here, and then maybe 12z control GFS (you'll need to substitute Kamchtakan ridge for an Alaskan ridge, but the general gist for our locale about the same). Flat and zonal ?

OK - quickly done that for our sector. This is 18 Nov - pretty atlantic driven

... and by 26 Nov this - much more meridional and blocked. The change from 25 to 26 Nov was quite swift if you run the charts.

So I guess Stewart is suggesting a change in about a week. Hmmm - how fascinating. Perhaps model watching in the next few days might get interesting after all. None of us really want atlantic driven weather after all... do we?

[Bobby]

Looks like a typical Atlantic 'warm conveyer' setting up next week, these can bring very large rainfall totals to the N and W and combined with the snow melt there could be some flooding I think. Some nasty looking winds and storms too with the temperature gradient. So some interesting weather coming up I think, there's more to the British weather than snow and cold after all.

Little sign of any cold in the foreseeable future to me/

Looks like the Atlantic wants to take revenge on us!

[Catacol]

However.... this is the NH chart for 18 Nov. Note that the vortex is very disorganised and fragmented. No single strong centre anywhere.

Compare that to now:

Are we really comparing like for like polar charts? The current pattern is also split, but the centres are much more powerful than the 18th Nov chart and the mass of all current data has a reforming vortex that will set up shop over Canada. Surely height rises in our sector are going to be much more difficult this time around?

[Jock Bingham]

Ta, I do try

It's a very interesting question. In principle, chaos is ever present, and - by definition - it is very difficult to predict. But 'chaos theory' I think is perhaps too loose a term accredited to a phenomenon which - at present - we just don't understand enough about. Indeed, if the weather was truly and absolutely chaotic, ie: that it has no discernible pattern, then it's hard to see how you'd improve a verification score? So, it's chaotic to a degree; the degree being, perhaps, our understanding of the variables at play.

The ceiling is an interesting idea: is there one? Impossible to tell. Some mathematicians would say that there is, whereas other theoretical physicists would disagree and align themselves more towards a constant intellectual evolution; one which continually raises the ceiling, if you will.

In terms of extending the window (growing the 80% and 20%) I think we'll see more atmospherically encompassing forecasts, where long-drain phenomena (such as SSW) extend the range of sight. More powerful supercomputers, satellite ranging and observation density will drive this forward, as it always has. This crosses over into the realms of climatology, so a marriage of sorts is close on the horizon I believe.

My personal view, is that we'll come to see more accuracy/detail within the 5-7 day range; the sort of accuracy which we come to expect from, say, a 48hr forecast. This in itself would be quite an achievement. The narrowing of uncertainty regarding, for instance, mesoscale modelling of depth and path of features (precipitation intensity, pressure track, general behaviour of cyclogenesis)

Hope that helps?

SB

Very interesting post. Your profile pic does not shout "expert on mathmatics and weather", which makes it all the more intriguing..!

[Iceni]

Some thaw!

It was snowing slightly this lunchtime in Baker Street as we were on our way to a funeral in Brompton Oratory. Then on the way back on the M11 a sign said "Severe weather expected tomorrow". I'm not sure about the models, but my four senses tell me it's still bloody cold.

[chris55]

Yes I'm not sure how far it goes out but thats the only thing I can think of as what we've heard from Matt regarding the EC 32 dayer that was showing something different upto Tuesday's update the next update is overnight

I'm pretty sure MOGREPS is a 15 day ensemble forecast.

[Iceni]

Very interesting post. Your profile pic does not shout "expert on mathmatics and weather", which makes it all the more intriguing..!

Never judge a book by its cover. I'm in total awe of Snowbalz's brilliance and love reading her posts.

[Summer Sun]

Looks like a typical Atlantic 'warm conveyer' setting up next week, these can bring very large rainfall totals to the N and W and combined with the snow melt there could be some flooding I think. Some nasty looking winds and storms too with the temperature gradient. So some interesting weather coming up I think, there's more to the British weather than snow and cold after all.

Little sign of any cold in the foreseeable future to me/

Looks like the Atlantic wants to take revenge on us!

Yes after going quiet for 5 weeks the Atlantic is coming back with vengeance next week all we can hope this time is the rain is blown through quickly and doesn't stall like it did last year on a number of occasions

That still doesn't aviod the possible flooding but if it moves through quickly we may avoid the huge totals of last year when it stalled

[Methuselah]

Never judge a book by its cover. I'm in total awe of Snowbalz's brilliance and love reading her posts.

I agree Iceni. What is an expert mathematician supposed to look like: Clark Kent?

[Catacol]

Final logic progression on this before I go off and do something else. 26 Nov NH chart finishes like this:

Notice the reduced Canadian energy and the stronger pulse over Siberia. Here is the GFS projection for 8 days from now, same time span:

Just not the same - although of course this is a forecast and not an archive chart! Time to go wrong... but my point about modelling of energy setting up in the NW atlantic and over Canada is consistent. In this scenario I dont see how heights over the mid to north atlantic can be seen as likely.

At the very least we have an interesting case study: Vortex energy and westerlies to retain sway into week 2 vs energy flux and rising AM from the equatorial pacific region with an impressive MJO plot to support a swiftish return to cold in about a week. Which to win?

Bets please. What's the bet we get a return of some blocking at about day 10 - a compromise solution...

Edited January 24, 2013 by Catacol_Highlander

[Jock Bingham]

I agree Iceni. What is an expert mathematician supposed to look like: Clark Kent?

Stereotype would be male, old, socially awkward