Model Output Discussion 12z 07/11/2012

[MR EXTREMES]

Not as detailed as some but my two penneth,

If you look at the current synoptic pattern it is looking rather ominous with a Bartlett style High over Europe and Polar vortex starting to takes it annual trip into Greenland.

However moving into the Medium Term/FI there are signs that Pressures are building over Greenland coupled with that the Jet continuing to be a long way south, with Channel lows being forecast and at least there are opportunities. Hopefully these will move into the more realistic time frame, so currently the improvement over Greenland start around T+180 and T+200, hopefully this will make it to T+100, by the weekend.

So I am looking at the this more at the moment, than the eye candy at the end of the run. As an example yesterday, there was a Scandi High, today a massive low over Scandi.

as i suggested in the last week or two so just goes to show you dont need to be super expert to see where things are heading.

the gfs signals have been there all along but because focus is only on cold which i might add i wish for as much as the next coldie thats why gibby is good at what he does.

i expect the weak wave break was not enough.

im still optimistic about the second half of winter.

but solar flux has increased which has in my opion has swung towards a shifting teleconnection in a fairly rapid way.

but the models have suggested as low pressure sweeps through theres always a chance of northerly topplers and the north will always fare best.

i also believe a early winter forecast revision might be in order for some.

but lets not be critical because this was a farely quick turn around by models but the signs were there two weeks ago.

[offerman]

Northern Rab, Nice pic of the Northern Heimosphere chart.

[bradymk]

Another good run from GFS but the cold coming from the N rather than E this time. Posts about these charts not coming into the reliable frame i feel are invalid because the time period where the cold is potentially going to arrive is not until late FI anyway so there aren't going to be any cold charts showing in reliable timeframe yet. Trends are key and there have been a number of consecutive runs now showing colder weather in FI with northern blocking and a displaced vortex.

[offerman]

Brady, yes but if the charts showing the cold are always at the end of the run then they don`t creep in to the 1 week period as they keep shifting away. I.E first chart might of show cold 23rd November , but as the charts progress by day they keep showing cold but as the end and not following the days as they get nearer.So the elusive 1 week is a good target to really get excited about.

[MR EXTREMES]

i might add everyday the models have shown eye candy but only in fi none are realistic or any closer to becoming reality.

[Frosty.]

According to the Gfs 12z op run we won't have long to wait for some cold weather, a strong ridge developing early next week and covering most of the uk for a time, colder in the north but below average in the south, any mildness just bordering the english channel coast but colder inland, some sharp frosts for the north but slight frosts just about anywhere. The settled spell is not expected to last long and deep lows begin to push east bringing wet and windy weather across the uk with s'ly gales developing, so an unsettled phase with temps returning to average but a much colder end to the run with arctic air flooding south and potential for a prolonged wintry spell but all very FI, can't ignore it though because the 6z showed something similar, 12z is a peach by T+384.

[Gael_Force]

I am a bit puzzled at this almost obsession with 'undercutting'. I assume folk mean the surface low to somehow dive under the surface high east and NE of the UK?

Ignore the surface and look where the 500mb trough is, the major part of it, does it show any sign of moving beneath the upper high? If not then it is pointless looking at the surface charts as they stream out looking/hoping for that to happen.

Nothing in the NOAA, ECMWF and GFS has suggested that over the past 6-10 days, that is for it to be happening over the next 24-72 hours.

The NAEFS output for 12z does show the ridges (upper) east and west combining in the 24-60+time frame. But it then re establishes the main trough/low at 500mb and keeps it there from T+72 onwards.

I'm glad to know that I'm not the only senior to be confused by the new terminology used on here.

I'm guessing that the undercutting is what will produce an easterly - it is not shown on this run - however, there are strong signals for an Arctic dipole anomaly akin to that of two years ago; whether it will produce the goods of the period remains to be seen but people should take heart that such unusual synoptics are even appearing again.

Late in the run, look at that frigid airmass advance in our direction!!

As I see it, the NWP is seeing change and in change all roads lead to cold - just how it evolves is yet to be determined.

[bradymk]

Offerman i take your point however i feel that the cold charts showing in fi are part of a trend rather than one of these "one off fantasy charts". Other models and certain teleconnections i feel back this up. CFS weekly charts agree with GP and show that we should be looking west and not necissarily east. http://origin.cpc.ncep.noaa.gov/products/people/sweaver/cfs_fcst/images1/wk3.wk4_20121111.z500.gif

[Glacier Point]

GEFS mean height anomaly at day 10.

Note the omega signature there in the western Atlantic as the jet flow splits and sets up the ridge development into Greenland. Whilst this is the most agressive of the GFS runs today in developing this block, it is not new and has been there on the ensemble means for the last few days.

We are entering a window where a holy trinity are at play which will set the scene for some rarified synoptics...MJO wave entering phase 8...poleward +AAM tendency...seasonal wavelength changes to the pattern dictated by the ridge in the Pacific. All of this at a time when the troposheric vortex is going to take repeated hits from wave 2 activity.

The 12z GEFS ends like this:

That mean anomaly includes some peturbations which flatten out the Pacific ridge and can be readily discounted. That makes this an understatement of the height anomaly, which is extremely strong at that range.

However, to take this back to earth somewhat, it's just one GFS run so we need to the ECM and other global models picking up the lifting out of the vortex from Canada and split flow developing in the Atlantic t192 through t240.

Edited November 13, 2012 by Glacier Point

[MR EXTREMES]

GEFS mean height anomaly at day 10.

Note the omega signature there in the western Atlantic as the jet flow splits and sets up the ridge development into Greenland. Whilst this is the most agressive of the GFS runs today in developing this block, it is not new and has been there on the ensemble means for the last few days.

We are entering a window where a holy trinity are at play which will set the scene for some rarified synoptics...MJO wave entering phase 8...poleward +AAM tendency...seasonal wavelength changes to the pattern dictated by the ridge in the Pacific. All of this at a time when the troposheric vortex is going to take repeated hits from wave 2 activity.

but surely a wave 2 hit must be of a good strength to have a decent effect?

[Met4Cast]

i might add everyday the models have shown eye candy but only in fi none are realistic or any closer to becoming reality.

Why not? Teleconnective forecasts back up what the models have been showing out in FI and these charts have been expected to show for about a week now - The fact that they're in FI simply means the models are going to flip and flop quite a lot with large differences between each run, but this time around it's not a simple case of chasing charts in FI because background teleconnective signals point towards this type of setup becoming established.

That's not to say of course the UK will see cold weather from it, but there's definitely some decent potential and to write it off like that at this stage seems foolish to me.

[offerman]

Hi Brady, Agree with that sentiment, the longer the charts keep pointing to cold then that synopsise will have a greater chance of happening.

GaleForce, Agree with you about the similar pattern to 2010.

[bluearmy]

GEFS mean height anomaly at day 10.

Note the omega signature there in the western Atlantic as the jet flow splits and sets up the ridge development into Greenland. Whilst this is the most agressive of the GFS runs today in developing this block, it is not new and has been there on the ensemble means for the last few days.

We are entering a window where a holy trinity are at play which will set the scene for some rarified synoptics...MJO wave entering phase 8...poleward +AAM tendency...seasonal wavelength changes to the pattern dictated by the ridge in the Pacific. All of this at a time when the troposheric vortex is going to take repeated hits from wave 2 activity.

dont go all religious on us stewart !! it should be noted that the op and control gfs for each run keep following the same overall solution, that should give us confidence in the solution but if it varies in each run, what are we to think apart from things remain uncertain on the road to a cold solution.

[Glacier Point]

the modelling is dopping big hints that the wave 2 actvity will be strong in the next 10-14 days, and the lagged influences of the pattern this week are taking effect further up the atmosphere. Don't forget this will likely be enhanced by the other favourable factors.

[MR EXTREMES]

the modelling is dopping big hints that the wave 2 actvity will be strong in the next 10-14 days, and the lagged influences of the pattern this week are taking effect further up the atmosphere. Don't forget this will likely be enhanced by the other favourable factors.

ok sounds very intresting and lets hope the models will refect thease changes in a more realiable timeframe

[nick sussex]

Given how bullish GP is about the outlook expect Sledgerama to be inundated soon by netweather members!

Personally I'd like to see a ne first then northerly and thats something that this mornings ECM hinted at. We can get both so lets hope the ECM delivers a nice run when it comes out.

[Tom Montalbano]

the modelling is dopping big hints that the wave 2 actvity will be strong in the next 10-14 days, and the lagged influences of the pattern this week are taking effect further up the atmosphere. Don't forget this will likely be enhanced by the other favourable factors.

Stewart,

What I've found interesting in the last couple of weeks model watching is the continuation of such positive height anomalies, forecast in the Aleutian/Kamchatka region.

What is causing such an anomaly and will any resultant blocking in our part of the NH more likely involve a rise in pressure over Greenland or Scandinavia?

Regards,

Tom.

[Met4Cast]

More ensembles trending colder at the end of the run on todays 12z

[bluearmy]

Stewart,

What I've found interesting in the last couple of weeks model watching is the continuation of such positive height anomalies, forecast in the Aleutian/Kamchatka region.

What is causing such an anomaly and will any resultant blocking in our part of the NH more likely involve a rise in pressure over Greenland or Scandinavia?

Regards,

Tom.

Tom, GP posted the other day that this feature is enhanced by the swift accumulation of snowcover over eastern asia through october. the downstream teleconnect of an aleutian ridge is a ridge in the north atlantic/greenland. area.

[snowblues]

As other posters have said,its nice to see a diffrent pattern forming from the very beginnings on N/H charts.You can see the bottled vortex over Greenland and even by day 5 you can see it displacing in sections Not sure how accurate that will be.Still,a good trend.Hoping that it will still be bottled up around Siberia as showing in Fl

[Tom Montalbano]

Hi ba,

I thought I'd read something along those line somewhere from Stewart, couldn't remember where though.Thanks.

Is the persistance of this upper ridge also aiding the forecast fragmentation of the PV and displacement to N.Siberia?

Regards,

Tom.

[chionomaniac]

the modelling is dopping big hints that the wave 2 actvity will be strong in the next 10-14 days, and the lagged influences of the pattern this week are taking effect further up the atmosphere. Don't forget this will likely be enhanced by the other favourable factors.

I think that there are possibilities that the strat vortex could relocate to Scandi and if this is the case then the possibilities open up for not only further wave activity but I suspect a warming of the strat as well.

(Not a SSW for those who think that every warming means that - but one that would raise the temperatures of the mid strat through wave breaking)

Where do you think that the asia MT is heading, Stewart?

[bluearmy]

Hi ba,

I thought I'd read something along those line somewhere from Stewart, couldn't remember where though.Thanks.

Is the persistance of this upper ridge also aiding the forecast fragmentation of the PV and displacement to N.Siberia?

Regards,

Tom.

i would have thought that the coninued push of WAA into the arctic, each time the ridge is restored will be casuign damage to the vortex. it certainly prevents it from settling down over the pole. over many years of chart watching i dont recall too many occasions in winter when a mean ridge in this area hasnt been followed by something cold in nw europe. we are a bit early in the season but it looks as though it may happen again with a reversal in the AO on the cards

[Ian Brown]

Given how bullish GP is about the outlook expect Sledgerama to be inundated soon by netweather members!

Personally I'd like to see a ne first then northerly and thats something that this mornings ECM hinted at. We can get both so lets hope the ECM delivers a nice run when it comes out.

How do we get a NEerley from the present position ? Also, the North Sea is very mild in November - you would need a perfect synoptic set-up such as late November 2010 and that is a big leap and a jump of faith away, when what we actually have are low heights and deepening pressure to the West and North West.

[Gael_Force]

More ensembles trending colder at the end of the run on todays 12z

In view of thecurrent run, I had a look at Nuuk and Reykjavic.

http://www.wetterzentrale.de/pics/MT8_Nuuk_ens.png

http://www.wetterzentrale.de/pics/MT8_Reykjavik_ens.png