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

[West is Best]

This looks pretty horrific for parts of Scotland. The Hebrides would cop it twice if this verifies

[NorthernRab]

Well it was nice knowing you all.

[SMU]

2 hours ago, Interitus said:

Wow, sub -92°C or 181K at 10mb would be record cold, previous lowest is 182.38K.

Vortex not quite collapsing in that image.

Hi mate

ref earlier post - I was looking at the trop heights when the zonal windspeeds started the massive drop & the fact that there was already HLB 5 days prior even @ peak - so the latter part of week 1 Jan could be interesting if the anomalies start to look similar to the days before historic SSWs

S

[Day 10]

An improvement... A step in the right direction for cold fans...

[Seasonality]

Cold is further west on this run. Ridging sharper and further north.

[Ali1977]

9 minutes ago, Seasonality said:

Cold is further west on this run. Ridging sharper and further north.

Yes, much better NH - this PV isn't as strong as we thought.

[Cheshire Freeze]

Frustrating....we'd be good to go here were it not for those horrid Euro heights. You can see the amplification upstream

[Summer Sun]

An unsettled Christmas day with gales possible in the north then settling down on boxing day

[Seasonality]

4 minutes ago, CreweCold said:

Frustrating....we'd be good to go here were it not for those horrid Euro heights. You can see the amplification upstream

Bolded the key word! Amplification is back, details can change but now in with a fighting chance compared to some recent output that was flat as a pancake....

[West is Best]

2 minutes ago, Summer Sun said:

An unsettled Christmas day with gales possible in the north 

 

Gloriously understated

To all my comrades peering out for cold weather ahoy, please do spare a model analysis or two for poor old Scotland. If the current run verifies these two storms are very serious at an awful time for those who may be affected. We're looking here at potentially damaging gusts.

[Cheshire Freeze]

7 minutes ago, Seasonality said:

Bolded the key word! Amplification is back, details can change but now in with a fighting chance compared to some recent output that was flat as a pancake....

Means zilch if we can't get LP into the continent...

The best bet I feel, would be low heights round the back door i.e down through W Russia and through E Europe

[Summer Sun]

Looking at the wind speeds closer the storm moves in early morning with the peak around lunchtime to mid afternoon where gusts could get close to 100mph large areas of northern Scotland see gusts exceeding 80mph

Boxing day is much calmer as pressure builds from the south

[Fozfoster]

9 minutes ago, West is Best said:

Gloriously understated

To all my comrades peering out for cold weather ahoy, please do spare a model analysis or two for poor old Scotland. If the current run verifies these two storms are very serious at an awful time for those who may be affected. We're looking here at potentially damaging gusts.

sure is WiB

[Seasonality]

Just now, CreweCold said:

Means zilch if we can't get LP into the continent...

The best bet I feel, would be low heights round the back door i.e down through W Russia and through E Europe

A few ensembles in the past couple of runs have shown the option of heights round the back door (Ohh Matron!). As I said, output has gone from flat to this so reasons to be positive.

[chris55]

Thats one perfect toppler scenario in GFS FI, looked like we were getting somewhere at around day 10 then boom, GFS flattens it like a pancake. Though the glimmers at days 8/9/10 need to be watched in forthcoming runs.

 

Edited December 20, 2016 by chris55

[Iceberg]

Gfs p has again followed the breakdown of the pv with heights rising dramatically. It has the wave activity again. All when we enter Jan 

got a feeling the 12z ops is following the same track. Quite a significant trend

[Singularity]

Well I never... the observed MJO signal just jumped toward the Pacific 6/7 in a way that none of the models came even close to predicting!

Could take until tomorrow evening to fully assimilate this change... to paraphrase on what GP said about a fortnight ago after a similarly large jump.

Such developments will help with trying to get a split vortex setup sooner than many might be expecting. Note that I say help, not guarantee 

If we can manage such a thing, the cross-polar ridge may help to drive some wave propagation into the stratosphere. At 30 hPa GFS seems keen on trying to repeat the mid-late Nov sequence with wave-1 and warming moving into Canada (in the 16-24 day range, extrapolated) but had it not flattened the blocking to our NE in early lower-res (FI) then more of a wave-2 signal may  have emerged.

 

I know this seems overly upbeat and perhaps it is, but I've not been convinced by the long range models drifting toward the idea of the vortex having its own way.

Though I am wary of the propensity for the Arctic, as it transitions from a cold desert to a stormy ocean, to encourage net rising motion there instead of net sinking motion, potentially changing the configuration of the major cells (Hadley, Ferrel and Polar Cells) from a three-cell to a two-cell configuration. In short, this would encourage storms to travel either within or close to the Arctic circle rather than close to Scotland for example. If such a change was to come to pass, mid-lat blocking would become our most common weather type. It's only a proposed mechanism that's awaiting critical analysis, so for now it's not difficult to play the idea down, but my resolve with respect to this has been taking a fair few knocks lately.

[Methuselah]

5 minutes ago, Iceberg said:

Gfs p has again followed the breakdown of the pv with heights rising dramatically. It has the wave activity again. All when we enter Jan 

got a feeling the 12z ops is following the same track. Quite a significant trend

I do hope so, Ice...But, before then, we have a potential barbie-day before the year is out!

[booferking]

9 minutes ago, Seasonality said:

A few ensembles in the past couple of runs have shown the option of heights round the back door (Ohh Matron!). As I said, output has gone from flat to this so reasons to be positive.

My opinion is look to the west it ain't happening to the east just yet this has happen so many times this year,  and yes i think we will get lucky this time with heights to the west which will deliver northerly then followed by Easterly or North Easterly after heights being lowered in the med from the initial northerly. Thats my two pennies worth.

[mountain shadow]

Im confused Singularity. Apart from the GEFS all the other models retain the MJO in the centre and therefore of little impact.

If any GEFS do show this then they could probably be ignored.

[bluearmy]

1 minute ago, Singularity said:

Well I never... the observed MJO signal just jumped toward the Pacific 6/7 in a way that none of the models came even close to predicting!

Could take until tomorrow evening to fully assimilate this change... to paraphrase on what GP said about a fortnight ago after a similarly large jump.

Such developments will help with trying to get a split vortex setup sooner than many might be expecting. Note that I say help, not guarantee 

If we can manage such a thing, the cross-polar ridge may help to drive some wave propagation into the stratosphere. At 30 hPa GFS seems keen on trying to repeat the mid-late Nov sequence with wave-1 and warming moving into Canada (in the 16-24 day range, extrapolated) but had it not flattened the blocking to our NE in early lower-res (FI) then more of a wave-2 signal may  have emerged.

 

I know this seems overly upbeat and perhaps it is, but I've not been convinced by the long range models drifting toward the idea of the vortex having its own way.

Though I am wary of the propensity for the Arctic, as it transitions from a cold desert to a stormy ocean, to encourage net rising motion there instead of net sinking motion, potentially changing the configuration of the major cells (Hadley, Ferrel and Polar Cells) from a three-cell to a two-cell configuration. In short, this would encourage storms to travel either within or close to the Arctic circle rather than close to Scotland for example. If such a change was to come to pass, mid-lat blocking would become our most common weather type. It's only a proposed mechanism that's awaiting critical analysis, so for now it's not difficult to play the idea down, but my resolve with respect to this has been taking a fair few knocks lately.

Singularity, whilst I accepted a week or two ago that bimodality in the modelling was restricting the signal to the COD, that has presumably passed now. 

unless that signal gets to an amplitude outside the COD, I'm not really thinking the analogues are too relevant and expect the modelling will not be overly reflective of them. 

[IDO]

A cracking run in FI from the GFS op. Faced with very little chance of any HLB'ing, the choice between zonal or the resurgence of the Azores to build a UK high, the latter is an easy choice. From D7 and still holding on at D16 HP domination:

This looks likely a very mild version of where the core heights will sit, with some high anomalous uppers. It moves around so some cooler days mixed with some very mild ones I would have thought, that is based on this run. The mean at D10 promises more settled weather the further south you are:

 

Looking at Christmas Day the warm uppers remain all day in the south and according to the mean the colder uppers are washed out by the time they get south Boxing Day PM:

As with regard to upstream amplification, it is just not showing up, so a change to this current pattern looks very unlikely. It would appear heights close to the UK will keep the PV movement to our north for the medium range (post D7). How far north is the question, but the south looks very hopeful for another extended dry period.

[Singularity]

11 minutes ago, bluearmy said:

Singularity, whilst I accepted a week or two ago that bimodality in the modelling was restricting the signal to the COD, that has presumably passed now. 

unless that signal gets to an amplitude outside the COD, I'm not really thinking the analogues are too relevant and expect the modelling will not be overly reflective of them. 

The MJO might get out of the COD tomorrow for all we know. Or it might not - hence the uncertainty clauses I stressed. It could even move outside of the COD but into phase 5, which promotes more of a zonal setup for our part of the hemisphere.

Not that the 'Cone of Death' is truly an absolute phenomenon. Even an MJO signal in phase 6 that's a little below the +1 SD line looks good for helping the ridges on the Pacific side extend poleward so there's some hope there.

I feel the most hopeful that I have in about 10 days, but it's not saying much to be honest - I've gone from 'argh!' to 'ugh' 

[Paul]

Matt's latest synoptic guidance blog is online, as we stare down the barrel of a very unsettled spell of weather

http://www.netweather.tv/index.cgi?action=news;storyid=7850;sess=

[phil nw.]

The UKMO and GFS  models showing that the duration of  the upcoming more mobile pattern is going to be fairly limited but the prospect of at least 2 deep lows is very much still alive around the Christmas weekend.

The +ve anomalies building north over the UK quite soon after the holiday period.

 

A mid-altitude high somewhere around the UK/NW Europe again showing up and it follows recent gefs outputs,so some consistency starting to build on that evolution post Christmas.A short but what could be a quite notable visit from the Atlantic, especially further north, before it settles down again.