Model output discussion 02/02/20

[phil nw. 17,783]

A good time for a new thread now we are into the last month of what has so far been a very Atlantic dominated Winter.

A new thread but the same old pattern going forwards-at least for the next 10 days.

First a glance at mid-week where the GFS 06z run shows a brief spell of high pressure building in 

but as we know this doesn't last as upstream the Atlantic jet is firing up and ready to flatten the high so by the end of the coming week we see the jet right across us.

This then establishes a vigorous westerly set up again and by day 10 modeling shows this well established.

gefs jet and ecm mean 500 hPa charts for day 10

so another unsettled spell expected to take us to at least the middle of the month.No doubt with a fair amount of polar air in the mix favoured locations up north,especially over high ground,could well see snowfall.

Not great news though for the majority who would like at least one decent snow event before the season is done.

The vortex has been a brute this Winter but at some point the vortex will weaken enough to create gaps for heights to extend north because of seasonal warming.

The question is but whether it will come soon enough to allow a decent cold shot before it's too late.

[legritter 5,504]

Certainly looks like a stormy spell setting in next weekend, i expect models to start firming up on this soon. Lets just hope that lows dive to our south ,we all need something wintry   ,the hunt for cold continues  ,cheers all .

[General Cluster 60,047]

IMO, the pattern-change hinted at by the GFS 06Z operational looks rather like 'random' noise to me:

    

    

So, as suggested in the post I prepared earlier, I'll just wait and see what happens!

[Singularity 13,924]

GFS 06z probably ‘circumstantial’, but it does show how occasionally, a strongly Atlantic-dominated period suddenly gives way to an easterly flow across the UK.

Basically, one of the very large, deep troughs drives a huge surge of warm air advection right into the high Arctic, which breaks anticyclonically and builds high pressure N or NE of the UK.

The rarity is down to a tendency for complications - disturbances in the flow which prevent the clean surge of WAA from reaching beyond the mid-latitudes.

[carinthian 13,341]

I am not sure what is the mechanism for the last few runs of the GFS op to keep showing the presence of a Siberian High in the longer term, but its there. I can only assume that the model is incurring some sort of correction in the transport of air masses into (WAA) or southward out of the Arctic (CAA) as obviously the cold cannot remain bottled up for ever. Whether the present run of westerlies give way to easterlies cannot yet be determined and if its does so, complications always seem to occur down the line.  Lets hope the trend in shown in consequent runs. We need a break from this rotten winter to deliver something at least , remotely cold.

C

[knocker 57,545]

50 minutes ago, Singularity said:

GFS 06z probably ‘circumstantial’, but it does show how occasionally, a strongly Atlantic-dominated period suddenly gives way to an easterly flow across the UK.

Basically, one of the very large, deep troughs drives a huge surge of warm air advection right into the high Arctic, which breaks anticyclonically and builds high pressure N or NE of the UK.

 

Sorry nut which part of the 0600 run are you discussing here?

[Cuban Zebra 161]

Yes I know it’s a long way away but a few more frames of the 06z and this would look loverly!!?

[knocker 57,545]

But apart from the fact it's a struggle to get model agreement at day five at the moment, let alone out in the wilderness,, if this is the trough disruption being discussed I'm still struggling to locate the easterly flow across the UK

 

Edited February 2, 2020 by knocker

[IDO 8,077]

2 minutes ago, knocker said:

But apart from the fact it's a struggle to get model agreement at day five at the moment, let alone out in the wilderness,, if this is the trough disruption being discussed I'm still struggling to locate the easterly flow across the UK

 

No easterly flow over the UK on the 06z. The Siberian High brings it to Europe late in la la land, but really just jackanory at this range:

As you say, lots of non-agreement cross and inter-model ATM so no point looking beyond D10 for clarity, maybe just for interest, until the models get a grip. PNA going negative which GFS nailed a while back:

PNA>GEFS 2m temps>   

That may be interesting once the tPV loses some of its oomph, if it lasts that long, ditto the sPV displacement. Otherwise those looking for cold down south, tell me when you find it^^^

[Rocheydub 2,480]

New model thread was supposed to get rid of this dangerous looking storm in 10 days, not re-enforce it!!! Disappointed in the moderators and admins allowing this to continue! ?

 

[Singularity 13,924]

1 hour ago, knocker said:

Sorry nut which part of the 0600 run are you discussing here?

Hi Knocker, I'm referring to the general evolution of the westward extension of the Siberian High.

Admittedly it doesn't quite reach the UK during the run, so I should have specified that to be clear - my bad!

[SMU 80,650]

12z GFS puts NW Scotland & NI in a prime location for snow ( at elevation >200-300M )

A very very unstable flow

[Mike Poole 26,544]

GFS 12z with another insane northwesterly draw, the extent of it is extraordinary, here T192:

I don't have confidence even with -6 uppers encroaching that many low level areas will see snow, but those with elevation in the north may well do.

[Griff 4,203]

Interesting to see what follows this. Lots of pressure on our purple 'friend'. 

[mb018538 9,959]

12z ditches the monster high (no shock there), but does show sings of the PV relaxing from the middle of the month.

Not a surprise - +5 sig AO events don't last for long. Sharp drop back towards zero as we head on towards and past mid Feb.

 <---Huge Aluetian high there!

[Mike Poole 26,544]

A thought...it is getting late in the day now for a SSW and the time for even a quick tropospheric response to happen, especially as there isn't a SSW progged in any model at the moment.

One last straw, could the trop vortex collapse without any help from a SSW? The idea occurs based on the outer reaches of the last two GFS runs (probably for the bin then!), here vortex sliced from the south T300 on the 6z, and here sliced from (well it's the south again just the other side!!) T270 on the 12z:

One to watch for on future runs, it is one way we could see eventually colder conditions reach our shore by end Feb rather than in mid-Spring.

[General Cluster 60,047]

Nae much sign of any easterlies, on the 12Z, peeps...That said, the last thing I want to see is a cold, dry and cheerless Smarch like 2013!?

    

[Mike Poole 26,544]

One final thought on the GFS 12z, here is precipitation and wind gusts at T186:

Now I've already said I'm not comfortable with this system having uppers cold enough for snow at low levels, and the GFS snow precipitation charts are an approximation to put it mildly, but for those who haven't seen a snowflake this winter, and I am one such, a week Monday early in the morning, might be worth a look, in a very windy rather cold weather pattern. 

This broad pattern does seem likely to verify in some sense, so it will be possible of course as it gets closer, to use the higher resolution models to get a better idea of impacts...

Edited February 2, 2020 by Mike Poole

[northwestsnow 24,415]

EC is hideous, the PV continues to dominate northerly latitudes.I honestly didn't think Feb could be any worse than the Dec and Jan coldies have endured but ....

[jules216 2,183]

just for fun,but models have been shifting ever so slightly westwards with that next week plunge which puts my location in eastern Slovakia in shout with pehaps the coldest snap of winter so far ?

[Mike Poole 26,544]

ECM T192 - T240:

WOW the size of the cyclonic circulation at T192, the wave in the flow at T216 with UK avoidance,  and it is full on again T240.  And the cold air is on the ship, but it is over warm waters...

Just another variant given the uncertainty at this range.  

[sebastiaan1973 1,667]

We have to be honest. Although I highly respect Stewart (Glacierpoint) his ideas of February don't realise. The first part of his forecast was excellent. 

[North-Easterly Blast 425]

2 hours ago, mb018538 said:

12z ditches the monster high (no shock there), but does show sings of the PV relaxing from the middle of the month.

Not a surprise - +5 sig AO events don't last for long. Sharp drop back towards zero as we head on towards and past mid Feb.

 <---Huge Aluetian high there!

The +5 AO index lasted for some time, it was virtually that positive for the whole of the first half of January.  After a full fortnight at that level, it became less positive in the second half of the month; that highly positive AO index resulted in the CET's third warmest January in the last 30 years, and the first "notably warm January" (CET 6*C+) since 2008.

[SLEETY 5,169]

Signs of the jet slowly sinking South in the weeks ahead,perhaps also worth keeping an eye on the Arctic High,which startied to look promising on gfs before low-res kicked in.

Can winter go out with a bang.

[Dennis 1,724]

winter wake up call by CFS