Model output discussion - late November

[Tim Bland]

8 minutes ago, BLAST FROM THE PAST said:

Nope, displaced PV and timing of peak energy bringing disruptive storm (gales and rain or gales and snow) on target.....

 BFTP

Definitely just plain rain on this run. When you said the other day about disruptive weather for Dec was it gales and rain then

Edited December 1, 2019 by Tim Bland

[Jordan S]

52 minutes ago, BLAST FROM THE PAST said:

So 21 days ahead are nailed on? What model goes that far?

RE Zonal, pM air with wedges chucked in bring some nice surprises.  The word zonal ‘normally’ makes many think of Bartlett and continued long fetch SW’lies.....we aren’t stuck with them.

 

BFTP

The GFS ensembles will early next year as JH has posted on the definition I'll just post a zonal vs meridional jetstream pattern for anyone that is unsure. 

Zonal a fairly straightforward west to east flow.. 

Cool/cold zonal pattern..

A Milder version of zonal.. the Classic assumption if you ask me..

Jet stream for the next few days.. 

A more meridional pattern.. 

Becoming more akin to zonal by next weekend..

A bit further ahead to the 10th Note the very strong jet streak from newfoundland and to the south of Greenland this may potentially aid in rapid cyclogenesis (rapidly developing/deepening low pressure systems).

Edited December 1, 2019 by jordan smith

[SMU]

The updated GEM at 186 note the shape of the jet diving south & NE in the atlantic

Thats X2 models that leave residual heights east of Iceland

@bluearmy

Edited December 1, 2019 by Steve Murr

[weathercold]

Struggling to see any positives with today’s NWP output.

A clear lack of blocking, Artic high looks like having v little positive impact (for cold weather for the UK).

Compared to where we were just a couple of weeks back we seem to be be venturing back into a much more familiar hemispheric pattern...

[Mike Poole]

GEFS control at T276, UK obliterated by polar vortex amid increasingly colder uppers:

And remember the day before this is Election Day.

And GEM T22:

Yes big depressions, but look at the position of the Azores high, would bode well for later...and it's nice to get a rare sight of  Rudolph the blue nosed reindeer...

Edited December 1, 2019 by Mike Poole

[weathercold]

3 minutes ago, Mike Poole said:

GEFS control at T276, UK obliterated by polar vortex amid increasingly colder uppers:

And remember the day before this is Election Day.

 

The 850’s look poor for most of the south ...0 looking at that chart 

[Mike Poole]

12 minutes ago, weathercold said:

The 850’s look poor for most of the south ...0 looking at that chart 

Precipitation in that would be strong, evaporative cooling could be in play, 50p flakes likely for many...

Edited December 1, 2019 by Mike Poole

[West is Best]

Bloody hell ... Election Day is looking lively 

 

[feb1991blizzard]

3 minutes ago, Mike Poole said:

Precipitation in that would be strong, evaporative cooling would be in play, 50p flakes likely for some...

Not sure about evaporative cooling,

 

Edited December 1, 2019 by feb1991blizzard

[Mike Poole]

19 minutes ago, feb1991blizzard said:

Not sure about evaporative cooling,

 

Maybe too windy?  Probably correct, but on what scale,  just pointing out marginal factors.  

Just to explain, evaporative cooling is air cooled by the latent heat required to evaporate the incoming rain, it can lead to snow locally when there isn't much wind, and the cooled air remains with the precipitation.  But if the rainfall is very widespread, the wind may play less of a role.

Edited December 1, 2019 by Mike Poole

[BLAST FROM THE PAST]

27 minutes ago, Tim Bland said:

Definitely just plain rain on this run. When you said the other day about disruptive weather for Dec was it gales and rain then

Yes, gales and rain or gales and snow is the forecast, not cold and dry and calm, or mild calm and dry......depends which side of the plunge....disruptive weather ‘anticipated’.  Let’s see.....still FI

 

BFTP 

[Methuselah]

A nice example of 'meridional flow', methinks...?

   

A meandering PFJ does not (necessarily) guarantee Snowmageddon!

Edited December 1, 2019 by Ed Stone

[BLAST FROM THE PAST]

9 minutes ago, Ed Stone said:

A nice example of 'meridional flow', methinks...?

   

A meandering PFJ does not (necessarily) guarantee Snowmageddon!

Correct, or mild!  Extremes is the example.....Azores freezing cold?! 
 

BFTP

[Mike Poole]

12 minutes ago, Ed Stone said:

A nice example of 'meridional flow', methinks...?

   

A meandering PFJ does not (necessarily) guarantee Snowmageddon!

I agree, and for newbies this is absolutely key to understanding winter for the UK.  A strong polar vortex, largely westerly zonal, or straight west to east flow, means weather off the Atlantic which will most likely be wet and mild.  A weak polar vortex, with a large meridional, or wiggly, flow gives the opportunity for cold for the UK, or alternatively much warmer weather, depends which sides of the wiggles we are on, but these patterns tend to move west to east in general, so we would experience both.  Finally, there's blocked patterns, when a meridional wiggly pattern is stopped from moving west to east by one or more big high latitude high pressure system(s). You get what you were getting when the music stopped, could be cold, could be mild, but could be for some considerable time....hence the search for these blocks by the cold contingent...

Edited December 1, 2019 by Mike Poole

[blizzard81]

48 minutes ago, Steve Murr said:

The updated GEM at 186 note the shape of the jet diving south & NE in the atlantic

Thats X2 models that leave residual heights east of Iceland

@bluearmy

Isn't gem considered cannon fodder on the whole? 

[Duane S.]

1 minute ago, FiftyShadesofSnow said:

The Arctic high never does...Anyone saying it does is getting the annuals out....1987 is a poor vision...It was a mis placed Azores which eventually drifted North East that gave me burst pipes in 1987....Not an arctic high 

 Spin it how you want, it WAS an Arctic High that was mainly responsible for that event. Without it we simply wouldn’t have got the extreme event that we did. No ifs no buts...

[Mike Poole]

10 minutes ago, blizzard81 said:

Isn't gem considered cannon fodder on the whole? 

No, GEM is a good model, and has recently been upgraded in resolution apparently, faring well against the other big models at day 5 (labelled as CMC on this chart:

Vying for second place behind ECM, but a little behind UKMO and GFS, although with the caveat that the stats are for NH, for UK weather, UKMO anecdotally is the strongest.

Edited December 1, 2019 by Mike Poole

[blizzard81]

3 minutes ago, Mike Poole said:

No, GEM is a good model, and has recently been upgraded in resolution apparently, faring well against the other big models at day 5 (labelled as CMC on this chart:

Vying for second place behind ECM, but a little behind UKMO and GFS, although with the caveat that the stats are for NH, for UK weather, UKMO anecdotally is the strongest.

Thanks for that 

[knocker]

The salient points on tonight's ext GEFS mean anomaly

Upstream Aleutian low/ridge/Canadian vortex complex

Thus good amplification resulting in a strong westerly upper flow (I've refrained from using zonal to avoid another emergency meeting of COBRA) exiting the eastern seaboard across the Atlantic to quite a marked negatively anomalous trough that has retrogressed a tad to be north of the UK

This would portend unsettled with temps around average but the usual caveats apply as systems track east in the strong flow

[Skullzrulerz]

Honestly in my point of view these charts never see to get to T0 let alone into a reliable timeframe it's just feels like we're chasing fl charts till oblivion...

Though thankfully we could be in a lot of a worse position at the moment but looking forward it's more of the same and a +Nao for a at least 2 weeks 

[syed2878]

2 hours ago, booferking said:

M ore blocky less zonally the 12z so far all in the right spots keep the trends going please.

 good to see the GFS coming back in line from what they were showing before I think they have the aircraft up for the Sunday is 12 hours run.

 

[Mike Poole]

ECM T168 compared with GFS at same time, ECM first:

Much better amplification, and bought some time to do it in from UK perspective by virtue of being sharper further west...

[Mike Poole]

ECM T192, again comparison with GFS:

Much bigger wedge and stronger Arctic high, for those who like those.

Zonal? that's a laugh!

Edited December 1, 2019 by Mike Poole

[Gael_Force]

25 minutes ago, FiftyShadesofSnow said:

I don't need to spin any thing, it was not the Arctic high that had ANY influence over the 1987 cold spell, for some reason I cannot post the archives I'm unsure why on here ....PM me if you want to discuss it but 1987 was not a result of a marauding Arctic high..far from it...

delete

Edited December 1, 2019 by Gael_Force

[ICE COLD]

1 minute ago, Mike Poole said:

ECM T192, again comparison with GFS:

Much bigger wedge and stronger Arctic high, for those who like those.

Yes nice ecm run so far a lot better than the gfs . Better split in the pv lobes in the artic .