Model Output Discussion 29th December - Into mid-Winter.

[Frank Trough]

1 minute ago, That ECM said:

Got to love a 2/3 day topler that's lasts for over a week

that thought keeps popping into my head! this GFS op run actually shows a proper freeze - it would be a genuine shock to people I think if it's anywhere near close.

haven't had too many days feeling like this in recent winters!

[Seasonality]

2 minutes ago, Ali1977 said:

Look towards Greenland too, things could get interesting there. Can't post pictures but that PV is weakening fast.

Here we go, clear weakening over Greenland and movement into Russian Arctic and Siberia.

 

[Nouska]

The train of little troughs on the UKMO fax sheet, in embryonic stage.

Nice little comma cloud system in the frigid flow off Greenland.

Thank you, @Bring Back1962-63 for pointing out some may have no idea of what a comma cloud is. It is signature of mesoscale convection, allowed by very cold air aloft passing over warm seas below. These lttle convective commas are the signature of polar low development. Tiny, short lived, arctic 'hurricanes' with localised strong winds and copious quantities of snow.

A nice blog article from two scientists whose speciality it is.

https://polarlows.wordpress.com/tag/severe-weather/

 

 

Edited January 11, 2017 by Nouska
more meat on the bones!

[Snowman.]

Lets be clear about the scandi high. 

Builds at 144 still there at 288 

Once you have a Scandi ridge in place, they become incredibly difficult to shift 

[Seasonality]

13 minutes ago, warrenb said:

You look at that, and think PV shifting, retrogression, then watch GFS blow it away.

And like clockwork, in far FI that is what happens. 

[frosty ground]

2 minutes ago, Nouska said:

The train of little troughs on the UKMO fax sheet, in embryonic stage.

Nice little comma cloud system in the frigid flow off Greenland.

Comma Cloud? More than just Punctual?

[Ali1977]

8 minutes ago, Seasonality said:

Here we go, clear weakening over Greenland and movement into Russian Arctic and Siberia.

 

Thankyou, it doesn't get mucg better but then beyond this is way in FI.  That Scandy high will be hard to shift and whilst we see a big frontal snow event later on as the Atlantic comes in, this could well slide under with a few tweaks - it could also do the opposite I know but all very very interesting.

[Seasonality]

Have just checked Arpège and Arome high res for tomorrow and both have the bulk of precipitation falling as rain and moving through from around 14:00 - 17:00. Going to be an interesting short term forecast period, keep an eye out amongst all the longer term speculation!

[Methuselah]

Given that far FI is about as much use as a chocolate fireguard, my only reason for a wee bit of disappointment is that it's looking increasingly likely that incoming milder air may well meet little opposition, come Sunday. If that happens, any remaining lying snow will be leading a charmed life...That said, there's plenty of potential; the building blocks are falling into place!

[chris55]

delete

 

 

 

Edited January 11, 2017 by chris55

[nick sussex]

What drama! only just caught up with the outputs.

Same old story with an easterly, it really is painful with the models chopping and changing with the position of the high and with it where the coldest air goes.

Whats different about the current easterly soap opera is that its not a case of either shortwave behaves itself or its the Atlantic moving in with sw'erlies.

The models want to take the PV and associated low heights more ne rather than east. And theres the MJO, much talked about but hasn't done much recently to deserve the attention its been getting. Regardless of the UKMO dismissing out of hand any influence for the next 25 days theres still the possibility that this will have an impact.

Overall then its somewhat of a messy picture but theres no sign of a long term return to Atlantic sw'erlies with still a chance for a decent easterly. I think surface cold is looking very likely at least for the UK and still time for that to develop towards the colder uppers being pulled further north.

 

[SMU]

I will do a longer post as we head towards the 12s however easterly options on the increase in the GFS suite ... The reason - the track ( as ever ) / depth / sharpness of the azores low...

easterly confidence 65%

[The Weather Dragon]

Ok let's remember - getting the cold is the first step - we have that nailed on from tomorrow - what comes next - model chaos as they grapple with the possible abnormal outcomes. The first step is the cold and we have it.

Edited January 11, 2017 by Jonathan Evans

[mb018538]

n/t

Edited January 11, 2017 by mb018538
error

[Johnp]

16 minutes ago, chris55 said:

6z ens are a marked shift away from the milder 00z set, still lots of scatter but a definite move.

 

Unfortunately they are yesterday's!

[chris55]

Dam!

 @Johnp thought they were a bit different lol. I should learn to check before posting. Oh well let's see what TODAYS 6z ens bring :0 

[Nick F]

1 hour ago, Tamara said:

1. So, to take the excessive drama out of things, the theme of retrogression into the extended period is growing with renewed cold collecting to our NE as a result, at the same time as heights are drawn westwards across the Mediterranean to set up a -NAO. And we still don't know for sure how much cold is going to accrue within the nearer term 5 to10 day period before this.

Its really just a question of time of when the upstream energy fractionally adjusts to allow the deeper upper cold to advect across that betwixt and between little section of the NH called the UK - the bit that seems to continually be teased and promised, but appears to somehow manage to elude

 

Agree, an interesting period coming up mid to late January and beyond. Whether we get an easterly or not early-mid next week depends on how the surface high orientates which is uncertain for now, big EPS spread this morning, from as early as this Sunday/Monday, compared to yesterday, increases the uncertainty.

However, there is still  decent chance next week of a slack cold continental feed, though any snow is a big ask from that direction for now. But more consistently at upper levels for the medium range a 500mb ridge is drawn NE across the UK into Scandi in the EPS means, and there are signs that mid-Atlantic troughing may go under toward day 10 to thee SW of the mean ridge.

Further ahead, we have the MJO wave heading into phase 1 (often = colder phase for UK) on GEFS, EPS, JMA and trending that way on UKMO too. So we could see impetus for amplification to pull the block further north later in January.

Couple with that, the GFS and EC keen on shifting the strat PV back toward Russia/Siberia by day 10 - which suggests that, if indeed connected with the tropospheric pattern, could pull deep cold pool south into NW Russia - which may eventual pull west if the block drifts further N or maybe NW.

Given the background of unprecedentedly long westerly QBO, and recent muted MJO, AAM and GWO signal, we are doing quite well atm with the pattern we are seeing. But now it looks like 10 hPa zonal winds are on the decrease, the sPV looking perturbed and perhaps drifting to Siberia and the MJO waking up, interesting times ahead.

[nick sussex]

I'd happily accept the JMA at T84hrs, its 06hrs run is more amplified than the GFS.

So of the 3 global models this morning with 06hrs outputs all have increased the upstream amplification. We have one good model the GFS, one not so good the JMA and one only to be viewed in desperate times the NAVGEM also increasing that amplitude, that's only upto T66hrs so far but  better than its 00hrs output.

It seems the models are still having a problem with that area around Iceland, until this is resolved we won't know our starting point for how vertical any ridging might be to the n/ne.

Edited January 11, 2017 by nick sussex

[Met4Cast]

Just flicked through the ensembles for the 6z and there does seem to be an improvement in them this morning. A fair few going for an Easterly similar to the op, some going for a more extreme Easterly as per ECM, the mean isn't too bad at 180 either.

 

Mean

[snowice]

IN relation to the uppers shown by ECM and GFS if the Easterly comes.

There is three days snow forecast for Warsaw in Poland and by Wednesday next week day time temps are -10.

My point is heavy snow forecast for the weekend that should enhance the uppers next week as the event hasn't happened yet,

and  i do not believe the models account  for this.

 

[Gavin Hannah]

GFS blowing through in FI....   Get ready for the long dark... because Winter is Coming!

[Rollo]

4 minutes ago, nick sussex said:

I'd happily accept the JMA at T84hrs, its 06hrs run is more amplified than the GFS.

So of the 3 global models this morning with 06hrs outputs all have increased the upstream amplification. We have one good model the GFS, one not so good the JMA and one only to be viewed in desperate times the NAVGEM also increasing that amplitude, that's only upto T66hrs so far but  better than its 00hrs output.

It seems the models are still having a problem with that area around Iceland, until this is resolved we won't know our starting point for how vertical any ridging might be to the n/ne.

Sometimes I wonder why we tear our hair out over these will they won't they easterlies Nick,is it worth it_ in my case a definite yes and by the way thank you for all your input over the years.

[nick sussex]

Given Nick F's post this really calls into question the UKMO view which completely dismissed any MJO influence. How on earth they can make that call is beyond me. They should at least wait to see if the signal continued its movement out of the COD.

[Glacier Point]

There is a view, one which I would endorse, that the RMM Indices are not capturing fully MJO activity. For example, right now, upper and mid tropospheric winds are flowing all the way across the West and Central Pacific all the way to the East African Coast. Likely significantly enhanced convergence and convective activity around West Indian Ocean (MJO Phase 1).

Edited January 11, 2017 by Glacier Point

[nick sussex]

3 minutes ago, Rollo said:

Sometimes I wonder why we tear our hair out over these will they won't they easterlies Nick,is it worth it_ in my case a definite yes and by the way thank you for all your input over the years.

Thanks that's very nice of you. In terms of easterlies , I sometimes wonder why we're so fixated on them, a lot of the times they're drab snow grain affairs but when they're good they are so much better than any northerly toppler or PM flow.

I think its because they have become part of weather folklore in here and they can deliver non slushy snow and often can be a pre-cursor to a more extended spell if theres a signal for retrogression towards Greenland.