Model output discussion - 16th Nov onwards

[Geordiesnow]

A little bit more convinced of some sort of influence of the Euro high now, there is agreement on this but how long it influence affects the UK is less certain and the threat of a deep low pressure affecting the UK is there. 

 

Also the outlook is favouring more in the way of a mild weather than cold weather, especially with models agreeing on some sort of influence of the Euro high. 

[lorenzo]

A couple of GWO composites go along similar lines to the discussion Damian, once through the Mountain Torque phase we are into phases 5 and 6. These charts are built from the raw data for GWO and placed on same scale as the standard MJO ones that are on occasion dropped into threads.

 

Certainly some support for blockier evolution..

 

 

[tight isobar]

Gfs.

later suite"18z....

northern hemispherical drags" vortex lobe,

On a westwards retreat.

Allowing pressure infer to a position of

"At least partial" block.

An evolution that cannot be discounted via'its

undeniable mobile bias.(gfs)

On viewing its own evolution looks "atm" improbable".

The euro ECM runs in suite against its evolve....

but is prone' to an70/30%

Catch up.

and is mysteriously prone to jumping an' evolutionary

step in pattern change with the model mentioned.

VERY interesting times evolving.

#winteriscoming

[Mucka]

...compare/contrast where the larger (just) majority of the two clusters from EC 12z takes us by the same timeframe out into the distant yonder...

 

https://f1.nwstatic.co.uk/forum/uploads/monthly_11_2015/post-15852-0-46536900-1448839736_thumb.png

 

Hmmmm and here is GFS 00z this morning for the same time frame?

 

 

Cold weather fans may not have anything on the near horizon but plenty of positive signals that later in December could give us our first cold spell proper.

 

Edited November 30, 2015 by Mucka

[knocker]

There is really very little of consequence to add to the previous couple of morning's overview of the det. gfs. Still a very mobile pattern with the interplay of the Pm and Tm air with periods of the former bringing some wintry interludes particularly in the north. On the other hand there are also periods where the European HP has more influence. It does end with a Greenland high, Thought I'd better mention this as it may be worth keeping an eye on. Or it may not of course

 

I say that because last night's 18z GEFS(P) anomaly does in general tie in with this morning's run and is tending to some height rises in the western Atlantic.

 

Having said all that the percentage play is much of the same perhaps becoming more settled later in the run with temps still above average.

Charts courtesy weatherbell

Edited November 30, 2015 by knocker

[Duane S.]

00z carries on from where the 18z left off...

GEFS Ens not really buying into it yet (no real surprise) but no doubt in my mind that there is a window of opportunity around mid month for our next cold spell to commence.

Something stirring higher up in the Strat as well?

[knocker]

The ecm is cooking up some pretty wet weather next weekend starting 00z Saturday with a deep low Iceland and associated fronts Ireland. This is rapidly followed by another system winging in from the SW bringing some very wet weather  to the south. And a couple of days later yet another system arrives bringing wet and windy weather to all.

 

[northwestsnow]

The ecm is cooking up some pretty wet weather next weekend starting 00z Saturday with a deep low Iceland and associated fronts Ireland. This is rapidly followed by another system winging in from the SW bringing some very wet weather  to the south. And a couple of days later yet another system arrives bringing wet and windy weather to all.

Yes the reliable timeframe offers more wind and rain across the models this morning with some vigorous systems sweeping across the Atlantic destination UK.

Again GFS wants to shut down the conveyor in FI, i'm seeing a trend to something more seasonal as we get to mid December with the jet taking a more southerly track, certainly GFS has been hinting at this over the last day or two.

[Liam J]

...compare/contrast where the larger (just) majority of the two clusters from EC 12z takes us by the same timeframe out into the distant yonder...

Cheers Ian, Don't forget the vast majority of us aren't able to view such charts that far out on the ECM! Interesting nonetheless, but plenty more to get through in the meantime with potential for further disruptive weather over the next week or so. 

[MPG]

Yes the reliable timeframe offers more wind and rain across the models this morning with some vigorous systems sweeping across the Atlantic destination UK.

Again GFS wants to shut down the conveyor in FI, i'm seeing a trend to something more seasonal as we get to mid December with the jet taking a more southerly track, certainly GFS has been hinting at this over the last day or two.

Yes, but the GFS was hinting at a scandi block then binned it after a few days.

[BLAST FROM THE PAST]

That's a first from ECM but I mentioned yesterday that the 'normal' ECM was not without interest.  I'm a tad baffled at some posts saying GFS finally bringing some cold in FI.  It has for several days been showing a similar synoptic pattern as we approach mid month.  Maybe I've been looking at a different GFS??? Edit -MPG -  it was showing it during the period of the Scandi too and is keeping the idea.

I've been looking at this period particularly since its come into range.  let's hope it continues and firms up...I have confidence in it 

 

BFTP

Edited November 30, 2015 by BLAST FROM THE PAST

[johnholmes]

it might help Fred if you for once actually posted charts to illustrate your views.

[Summer Sun]

Further heavy rain and gales over the weekend if UKMO is correct flooding will be an on going concern this week

 

[knocker]

This morning's anomalies signal no change and generally support the recent det. outputs. Periods of unsettled weather, particularly in the north and temps varying around the average. The ext period signals no significant variation to this theme.

 

[fergieweather]

This morning's anomalies signal no change and generally support the recent det. outputs. Periods of unsettled weather, particularly in the north and temps varying around the average. The ext period signals no significant variation to this theme.

Indeed. The theme of a shift to colder conditions (higher chance of blocking via SSW; greater incidence N or E'ly flow) is still the preferred likelihood later into winter and you'll find this represented and explained in the latest 3-month outlook for contingency planners from UKMO (just published a moment ago).

[Ali1977]

FI Looking good....again

Edited November 30, 2015 by Ali1977

[Tim Bland]

Definite trend from GFS to shift the PV east mid month allowing some blocking. There is a consistent signal now for a cold spell mid month. Hopefully a festive lead up to Christmas this year!

[MPG]

Indeed. The theme of a shift to colder conditions (higher chance of blocking via SSW; greater incidence N or E'ly flow) is still the preferred likelihood later into winter and you'll find this represented and explained in the latest 3-month outlook for contingency planners from UKMO (just published a moment ago).

 

 

Definite trend from GFS to shift the PV east mid month allowing some blocking. There is a consistent signal now for a cold spell mid month. Hopefully a festive lead up to Christmas this year!

image.png

Conflicting.signals perhaps...

[BLAST FROM THE PAST]

it might help Fred if you for once actually posted charts to illustrate your views.

Just for you John

 

And not for the first time.   Looks too good doesn't it

 

BFTP

Edited November 30, 2015 by BLAST FROM THE PAST

[fergieweather]

Conflicting.signals perhaps...

Bear in mind UKMO team specifically advise how the December summary in the 3-month probabilistic outlook must always be superceded by the 30-day forecast. As logic would dictate. Anyway: we watch with interest.

[northwestsnow]

Another beautiful GFS run with a stonking northerly as pressure rises across the north Atlantic.

This is a trend not to be ignored now , the model is for sure seeing a pattern change.

[MP-R]

Yet another run with a progression towards more seasonal conditions around midmonth - in fact slightly before on the last two runs. Without letting my coldie preferences get the better of me, I don't think this can be ignored now and in the current pattern I think it's a lot more likely a cold spell is going to come from the north rather than the east.

[Polar Maritime]

The GFS has been hinting a Northerly type flow around the 12/13th for a few days now, This trend continues/strengthens today so some interesting and seasonal Model watching coming up as we head into the start of Winter.

[Singularity]

Indeed. The theme of a shift to colder conditions (higher chance of blocking via SSW; greater incidence N or E'ly flow) is still the preferred likelihood later into winter and you'll find this represented and explained in the latest 3-month outlook for contingency planners from UKMO (just published a moment ago).

 

Hi Fergie, I'm liking those words of yours, having been going on about a SSW in Jan with impacts around the middle of the month. While that may be some two weeks or so ahead of that suggested by the outlook for contingency planners, the general theme is there. In many ways I see it as typical El Nino feedbacks enhanced by favourable SAI/sea ice feedbacks (to name just a couple) which stand a good chance of overcoming the issues with a westerly QBO and low/med solar activity. From reading around on the web, it seems a great number of the more respected forecasting organisations are thinking along similar lines. We stand to learn a great deal from how this winter pans out!

 

 

Now, to focus attention back onto the nearer term - having pushed all the way north by Tuesday and stuck around through Wednesday, the model output has the polar front heading back south on Thursday, but not without a major complication that has caught my eye;

 

 

Having picked up on it a couple of days ago, GFS has been very consistent in developing an area of low pressure along the polar front to the west of Iberia, which then travels NE with slight deepening:

 

 

As can be seen from the above, the track brings the warm sector of the low across a the southern half of England, while at the same time entraining some polar maritime air from the SW flank of the low that's passing through Scotland in the first of the two charts. Whereas that first low has a fairly typical thermal gradient spanning the cold front, the low from west of Iberia manages to achieve a difference of more than 10*C at the 850 hPa level across the space of just a few hundred miles. The thermal gradient may be twice as steep as it is for the first low.

 

This is well reflected by the surface temperatures (also implying a well mixed vertical profile), with a huge contrast in peak temperatures Thursday afternoon (below-left). Not only that but the warm sector is exceptionally warm and carries unusually high moisture levels (some models have levels I can't recall seeing before in December). So we have a recipe for some very heavy rain to occur, particularly where frontal occlusion is starting to take place.

 

GFS hits the middle third of England hardest with that (below-right), after which a less intense cold front sweeps through Southern England. A dramatic drop in temperature takes place there, from the mid-teens by day to the low to mid single digits overnight.

 

 

 

I measure my overnight lows and daytime highs in the same way as the Met Office official data, which means the evening drop in temps won't affect my diurnal mean figure. As a result I could be looking at a minimum of around 12*c and a maximum near 14*C, which would mean a diurnal temp. anomaly of more than +7.5*C. Very impressive.

 

 

Beyond that event, milder air quickly surges in to be in place by Friday afternoon with double digit maximums for most places. Then it's a familiar tale of moisture piling in from the west, mostly affecting the north, while the winds may become very strong indeed for a time - for example from the 06z GFS det.:

 

 

 - which agrees well with recent ECM det. runs. That model's been hinting at a vigorous low bringing particularly strong winds further south for a time early next week, which also needs to be kept an eye on.

 

 

The one bit of good news is that emerging agreement between GFS and ECM for a substantial ridge to build across the UK from the southwest by the middle of next week. Too far ahead to place much faith in yet, but better than nothing. It may help to really mess with the polar vortex in the longer-term so I'm rooting for it!

[northwestsnow]

The GFS has been hinting a Northerly type flow around the 12/13th for a few days now, This trend continues/strengthens today so some interesting and seasonal Model watching coming up as we head into the start of Winter.

It has, will be interesting to see the ensembles