Model output discussion - 5th December 2016 - Into Winter we go

[Seasonality]

The polar vortex is travelling on his Christmas long weekend to Scandi. Looks like the weather will be getting more interesting at least. Colder uppers, precipitation and the Euro slug has been salted for now in the medium term.

 

[knocker]

First thing to say this morning is that the GFS is making no concessions to the position adopted by the ecm last evening so this morning's ecm run is not without interest. The problem area as far as the UK is concerned remains the complex vortex Canada/Greenland which is generating upper troughs via the Canadian vortex swinging south east across North America and tracking east on the jet or breaking off from Greenland and even phasing the two. 

The upshot of all this is according to the GFS we are still looking at two nasty looking depressions at the end of the week and over the weekend and it doesn't get any better after that. The second depression is looking particularly nasty with possible gusts up to 90kts over Scotland.

And the GEFS anomaly is also making no concessions to the ecm and basically supports the det run which it should do at this range

 

Edited December 19, 2016 by knocker

[northwestsnow]

Yes, GFS is classic +NAO stuff really.Ens are zonal sine wave , think we are going to need a SSW to shift this pattern now.

[Iceberg]

Just seen the ecm t96 and got a feeling it's looking dangerous more 12z gfs than 12z ecm

[Iceberg]

Ecm at t120 with a potent blast of cold pm behind it. 

[Long haul to mild]

ECM showing windy weather for Xmas Day but still not buying into the storm.

 

 

 

 

[Iceberg]

No the ecm doesn't quite buy in. It brings a potent early Christmas Eve storm but builds up the ridge behind the storm a bit more. 

A step toward the stormy weather

but still a hats off to the ridge idea. 

[snowbunting]

Hmmm. Think the ECM will show where the christmas low will be placed. Thank goodness we have had a dry autumn. Otherwise flooding nightmare with low after low present.

[Seasonality]

28 minutes ago, snowbunting said:

Hmmm. Think the ECM will show where the christmas low will be placed. Thank goodness we have had a dry autumn. Otherwise flooding nightmare with low after low present.

Could do. But still a while to go and storm tracks can throw out surprises even at a day or two out. Still more twists and turns on the output this week I bet.

[knocker]

It's difficult to know where the ecm is going with this. The evolution of the upper air is not hugely different to last evening's run until towards the end where it still goes for some rapid amplification but with the ridge over Scandinavia but still a very active and complex vortex Canada/ Greenland so looking quite transient.

Forgetting for the moment the nifty channel low early Thursday morning it has the two depressions traveling NE over Friday and the weekend but the winds perhaps less intense than the GFS but we are still looking at destructive gusts for N. Ireland, Northern England and Scotland.

Edited December 19, 2016 by knocker

[IDO]

Looking at the London ensembles and no frosts forecast apart from the op at the end of the run (which has little support). Overall above average as a whole the 2m temps for the mean but I suspect the "feels like" temp will be average to cooler. The further north you travel the temps get closer to seasonal averages and feeling colder.

So a period upcoming till about D8-9 where the lower heights pass to our north, of unsettled wet and windy weather, maybe wintriness to higher ground in the Highlands and the hills to the NW and Wales. The uppers are being moderated so not really cold, just brief spurts of below av. uppers before more average uppers move in. Just normal UK winter stuff in that respect. ECM and GEM similar in long wave pattern and as expected the outlier op of last nigh is not repeated by the ECM (cold high).

The deep low(s) around Christmas still has a high degree of uncertainty looking at the GEFS; from timing, to intensity, latitude and direction. Leave that for a few more runs.

Around D8-9 there is a brief hiatus in the PV lobe passing to the north and the models are firming up on how much the Azores can build in towards the UK from there: here 

By Jan 4 2017 the members have a small cluster attempting to build heights further north, so one to watch, though so far this Winter they have all  been false dawns.

Looking more Autumnal than Wintry for the south over the next week or so but cannot complain as it has been a mild settled month to date, much preferred to default Atlantic domination.

[carinthian]

2 minutes ago, Seasonality said:

Could do. But still a while to go and storm tracks can throw out surprises even at a day or two out. Still more twists and turns on the output this week I bet.

Morning all . not a lot of difference from the big 3 for Christmas morning. Looks like typical mild down south and more unsettled and a bit colder up north. I think we will see more chopping and changing again for the coming days. ECM seems the most volatile at the present  with big swings from mild to cold and back to mild in last two runs. Back to home our fine mesh snow model produced the spot on results again last night, 2cm in village and 7 cm at 2200 cm just as forecast. Just amazing .

 C

[Man With Beard]

40 minutes ago, snowbunting said:

Hmmm. Think the ECM will show where the christmas low will be placed. Thank goodness we have had a dry autumn. Otherwise flooding nightmare with low after low present.

Probably right. Since its upgrade, the ECM op has handled heights in the Atlantic quite well inside T192 so if it wants a temporary ridge for Xmas day, it will probably happen. The GFS, of course, can get a little overexcited with these Atlantic storms although we've seen it get them right at times too.

[radiohead]

Looking at the GEFS memebers, almost every member handles the Christmas lows considerably differently. So still a very high degree of uncertainty with these for the moment. Though there is a trend for the Christmas Day low to be further north now.

[snowbunting]

3 minutes ago, Man With Beard said:

Probably right. Since its upgrade, the ECM op has handled heights in the Atlantic quite well inside T192 so if it wants a temporary ridge for Xmas day, it will probably happen. The GFS, of course, can get a little overexcited with these Atlantic storms although we've seen it get them right at times too.

Very true. The GFS has tended to play lows up, this time around it was the ECM that brought in the monster low scenrio in the long range. Looking at the differences in air masses on the other side of the pond, I suspect the GFS has it spot on.. eeekkk

[Iceberg]

Ecm varies from the gfs as soon as t72 not so much in the Atlantic or the intensification of the lp systems per se, but in the ridge development over the states at t72.  Gfs has the stronger ridge which then pull downs more jet. Ecm is flatter with the resulting greater ridge potential from the Azores high. 

[Nick F]

00z EC suggests the deep low modelled passing north of Scotland Friday night looks like it could pack more of a punch across the north and west than the Christmas Day low, as the latter is further north in track.

Long way off, but could be quite wintry across the north and northwest Xmas evening/night where we have the showers - as colder polar air filters in from the west. Frosty elsewhere. So looks like we could see a white Xmas in the north in terms of falling snow.

Edited December 19, 2016 by Nick F

[Summer Sun]

Difficult to know which way this will go with ECM again the mildest of the main lot this morning for the 25th

ECM again has a very windy Xmas eve but improving for Xmas day and beyond

GEM has similar ideas very windy Xmas eve but improving Xmas day

GFS still keeps gales for most of Xmas day

Finally, UKMO is less stormy than GFS but has the low further south than ECM and GEM

 

Edited December 19, 2016 by Summer Sun

[Dennis]

https://www.netweather.tv/forum/topic/86783-model-output-discussion-5th-december-2016-into-winter-we-go/?do=findComment&comment=3496119

 

There are two major types of wave activity- Wave 1 and Wave 2. In Wave 1 activity scenarios, the stratosphere undergoes distress as a major ridge attempts to displace the polar vortex from the Arctic, while keeping it fully intact. With Wave 2 activity, the polar vortex is experiencing ridging across the upper latitudes, making the vortex want to split into two vortices.

Ill figure it out how things will happen in the next few days - its not an easy stuff but its exiting to follow all these things 

I think for W Europe some is still brewing it could be cold (see yesterday's EC12z)

 

[ArHu3]

21 minutes ago, Dennis said:

https://www.netweather.tv/forum/topic/86783-model-output-discussion-5th-december-2016-into-winter-we-go/?do=findComment&comment=3496119

 

There are two major types of wave activity- Wave 1 and Wave 2. In Wave 1 activity scenarios, the stratosphere undergoes distress as a major ridge attempts to displace the polar vortex from the Arctic, while keeping it fully intact. With Wave 2 activity, the polar vortex is experiencing ridging across the upper latitudes, making the vortex want to split into two vortices.

Ill figure it out how things will happen in the next few days - its not an easy stuff but its exiting to follow all these things 

I think for W Europe some is still brewing it could be cold (see yesterday's EC12z)

 

which waves should we watch, geopotential, temperature, heat and/or momentum?

[Dennis]

1 minute ago, ArHu3 said:

which waves should we watch, geopotential, temperature, heat and/or momentum?

in my opinion Geopotential wave2 but again its difficult maybe others have that answer

[bluearmy]

eps = sceuro ridge. Nw uk probably finding itself close to systems  moving sw/ne from time to time whilst se U.K. depends on cloud cover re damp/murky/frosty/bright 

also signs of a standing 4 wave pattern developing which is quite a stable but also could help to generate some trop wave activity up into the strat

[radiohead]

The first low is developing faster on the 06Z. It could mean that it will track further north. At 81 hours its down to 985mb when the 0Z didn't even have a closed low.

Edited December 19, 2016 by radiohead

[carinthian]

Latest N Atlantic chart from UKMO has second low at 168t crossing at 55N. That track would produce some interesting weather. Not sure what to make of it all really. Looks like a weather forecasters nightmare this set up to get it right for Christmas Period. Best sit on the fence and cover all options !

 C

[Iceberg]

Gfs pretty much sticking to its guns here very similar upstream with better lp interaction. A touch further north but stronger.