Model output discussion 25th Jan - The final third of winter beckons..

[Dennis]

 

[Scandinavian High.]

Models looking interesting still it's an involving picture so lots of changes with the run by run that deep cold to the north east needs be   Watched .

[johnholmes]

A second look yesterday at the anomaly charts showed something I had not really picked up before. That is the amount of +ve heights and contour ridging across the far north west to east. Not sure if this is going to impact on our weather as south of this it looks quite mobile for the next 6-14 days.

usual links

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

also there on the 8-14, again with a marked -ve tilt on the 500 mb troughing

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

For the time being I sit on the fence although the sharp spike in 30 mb temperatures did interest me; 10-20 days down the line?

[Summer Sun]

UKMO extended has another deep low developing in the Atlantic

[alexisj9]

2 hours ago, That ECM said:

The backend of the week is causing the meto a few headaches and if you look at the t144 from the big 3 it's not hard to see why. Gfs not really interested, ecm more so and ukmo full on. Interesting to watch this unfold.

I like the ECM version, looks prime for going under the scandy block, may be a bit high for us down south though, however it would help the block to position much more favourably afterwards.

[Singularity]

It all looks a bit 'shrug of the shoulders' this morning. Clearly the Atlantic wants to put up a fight and then some, but the operational runs are keen on some trough disruption being forced by the extensive W. Asian blocking and once lows start settling down S of the UK the balance can change.

Ironically, the blocking currently looks so expansive that there is little coherent westward impetus for the cold air. This means to get anywhere much within the 14 day range we need to either see a more westward extension of the blocking days 6-8 (feasible if the Atlantic lows are less organised, especially considering the 00z GFS, but we rarely follow the quicker route to cold, unfortunately) or more of a negative tilt (stretched out SE to NW) of the (ideally less) vigorous low day 8/9 with less of it lifting out N and more sliding SE days 9-10 with the secondary low following trough disruption (the more likely improvement IMO).

Of course, both adjustments would be the best of all as we'd have an easterly starting to feed in about a week from now and then the Scandi ridge moving further west - but that's just getting greedy 

[stodge]

Morning all

As expected, some eye candy starting to appear at the furthest ranges of FI now. Far from being anything approaching a done deal and we have a potentially stormy and disruptive spell to get through especially over the coming weekend.

The emergence of the Eurasian HP as a player reflects a weakened PV but still sitting in the Canada/Greenland area. Slowing or disrupting that train from the Atlantic is now the key. Some models are keen to disrupt south into Europe and that will be welcome if heights can build behind it but we're still at the ifs, buts and maybes stage.

I feel the models have gone perhaps half a step back in some regard this morning with a more powerful Atlantic and a less disrupted PV into mid month and it's perfectly possible we'll get nothing out of this and end up on the mild west side rather than the cold east side. UKMO will show nothing for a week and given what's happened this winter we need to see solid consistent output from the UKMO before we get too excited.

Experience tells us caution is the watch word here - this time next week may be the time to start getting interested.  

[northwestsnow]

Well maybe im in the minority here but im underwhelmed by the 00z runs.

Of course things are starting to look interesting up high in the strat but downstream no sign to my eyes of us losing the mind numbing azores high and its ability to ridge into Europe.

The clock is ticking now, by mid Feb onwards for a proper cold spell ( taking into account the longer days/ sun strength) we are going to be needing -10 uppers to negate the above..

[stodge]

3 minutes ago, northwestsnow said:

Well maybe im in the minority here but im underwhelmed by the 00z runs.

Of course things are starting to look interesting up high in the strat but downstream no sign to my eyes of us losing the mind numbing azores high and its ability to ridge into Europe.

The clock is ticking now, by mid Feb onwards for a proper cold spell ( taking into account the longer days/ sun strength) we are going to be needing -10 uppers to negate the above..

What did you expect ?

Only GFS goes beyond T+240 and it was obvious last week we were looking at a 10-14 day spell of Atlantic-influenced weather (this is day 2 or 3 as I measure it). The next pattern change is being sniffed it in FI and it will ebb and flow between runs until a clearer picture emerges and that may not be until this time next week.

Even then we may get nothing.

As to a "proper cold spell", I don't know what you mean. Perfectly possible to get lowland snow until the end of March - to altitude well into April. If you mean days of blizzards, that ship has probably sailed but if you mean 7-10 days of significantly below average temperatures and lowland snow plenty of time for that yet. I realise the recent HP spell didn't do much for you - for others it was quite noteworthy.

[northwestsnow]

4 minutes ago, stodge said:

What did you expect ?

Only GFS goes beyond T+240 and it was obvious last week we were looking at a 10-14 day spell of Atlantic-influenced weather (this is day 2 or 3 as I measure it). The next pattern change is being sniffed it in FI and it will ebb and flow between runs until a clearer picture emerges and that may not be until this time next week.

Even then we may get nothing.

As to a "proper cold spell", I don't know what you mean. Perfectly possible to get lowland snow until the end of March - to altitude well into April. If you mean days of blizzards, that ship has probably sailed but if you mean 7-10 days of significantly below average temperatures and lowland snow plenty of time for that yet. I realise the recent HP spell didn't do much for you - for others it was quite noteworthy.

No arguement with any of that stodge, i was commenting on the 00z runs which as you say dont go past mid Feb.Still hoping for a decent cold spell before feb is out ..:)

Ps im not interested in snow what melts by dinner time which is what will happen without the cold uppers and im certainly not interested in snow in April when ive seen about 9 hours worth in Dec and Jan !

Edited January 30, 2017 by northwestsnow

[stodge]

2 minutes ago, northwestsnow said:

No arguement with any of that stodge, i was commenting on the 00z runs which as you say dont go past mid Feb.Still hoping for a decent cold spell before feb is out ..:)

Ps im not interested in snow what melts by dinner time which is what will happen without the cold uppers and im certainly not interested in snow in April when ive seen about 9 hours worth in Dec and Jan !

Fair comment, my friend. The journey to the next pattern change will be fraught I fear. Getting snow to settle for any length of time in the heat island known as London is a real struggle even in mid winter.

It's perfectly possible we've had the coldest weather of the winter and we'll drift gently into an uninspiring spring with northern blocking aplenty.

I don't know - no one does.

The question for the coming weekend is as the first LP recurves NW away from Ireland whether any secondary features will deepen rapidly to the SW and sweep over England on Saturday and Sunday as both ECM and GEM modelled overnight.

[chionomaniac]

Classic omega block related to the strat displacement is demonstrated in the modeling especially 06Z GFS. Pity it's situated over Alaska.....

That's why it is better to be on the blocked side of the displacement.

[Ali1977]

I'm guessing we are still unsure on the full SSW, but this is good news. Still don't think we are seeing FI pick up on this, but the PV is definitely showing signs on weakening. Getting some warmer uppers into the NH earlier on like we're seeing now is a good building block for day 10 onwards. Just need that jet to dig and the starting pistol not too jam!!

[Interitus]

11 minutes ago, chionomaniac said:

Classic omega block related to the strat displacement is demonstrated in the modeling especially 06Z GFS. Pity it's situated over Alaska.....

That's why it is better to be on the blocked side of the displacement.

It's been modeled for some time - there has been a hint at some sort of brief coupling or downwelling shown in 60°N zonal wind charts, this from yesterday -

The reduced tropospheric wind a few days after the strat minimum happens with the cut-off Alaskan anticyclone and might be coincidental. But it is interesting how upper and lower anticyclones are drawn together -

It is best illustrated in Attard's animation -

http://www.atmos.albany.edu/student/hattard/realtime/dt_500/DT_500.php

 

 

 

[Alexis]

4 hours ago, That ECM said:

The backend of the week is causing the meto a few headaches and if you look at the t144 from the big 3 it's not hard to see why. Gfs not really interested, ecm more so and ukmo full on. Interesting to watch this unfold.

Unusual - the UKMO is usually first to spot a downgrade of low pressure strength and its the GFS that overdoes it. Could the UKMO be behind the pack on this one? It wouldn't surprise me to see the dartboards continue to swing up to the west on the next few model runs.

[Dennis]

30Hpa split

[feb1991blizzard]

2 minutes ago, Dennis said:

30Hpa split

Yes, in fact the split covers a huge area of the atmosphere vertically, from 18000ft to over 100000ft.

[stodge]

For a change, time to consider something more immediate and the likelihood of stormy conditions this coming weekend.

The GFS 06Z Ensembles at T+126 are a mixed bag - some develop nothing secondary but the majority do develop quite a vigorous little feature crossing southern counties on Saturday.

Timing, intensity and track are still to be determined but certainly one to watch.

Compared with the Op at the same time:

Plenty of rain and wind on offer for the SW in particular.

 

[Johnp]

Some lovely eye candy appearing in the ensembles now.

P20 is my personal favourite but there's plenty of others!

 

[feb1991blizzard]

5 minutes ago, Johnp said:

Some lovely eye candy appearing in the ensembles now.

P20 is my personal favourite but there's plenty of others!

 

Yes GEFS getting a good wiff off the weakening SSW / wave 2 upwelling  combo coffee now, watch these start to flatline over the next few runs, nothing really doing on the ECM ens but we cant see the individual prbs so might be joining the fun in a few days time - medium confidence for me now - not low.

[Day 10]

1 hour ago, Johnp said:

Some lovely eye candy appearing in the ensembles now.

P20 is my personal favourite but there's plenty of others!

 

Yes I count just over 50 - 60% in the second half of the run going for some form of easterly

[Ali1977]

I'm wondering why it's so quiet in here, can't post picture but what a great set of ENS with several Stella setups.  I understand it isn't full support but some of these bring some really cold air with great looking prolonged blocked setups.

P20 is pretty severe cold, especially in the south in the wind - day time wind chill would be below -10c with plenty of snow.  If only this became reality.

Edited January 30, 2017 by Ali1977

[Day 10]

1 hour ago, Johnp said:

Some lovely eye candy appearing in the ensembles now.

P20 is my personal favourite but there's plenty of others!

 

Here's the uppers to go with it

[Guest]

18 minutes ago, Day 10 said:

Here's the uppers to go with it

Marginal them uppers at that time of year.... Joking...

[ACCOUNT DELETED]

BBC weather for the month ahead says wet & windy weather for much of the upcoming month.

Well looking at the models, it looks like an unsettled 7 days or so to come but thereafter, there are hints of the jet stream easing off again somewhat. I'm not sure which chart they use and as I'm still learning about the weather patterns and how to read and understand various models etc then we'll just have to wait and see if they're correct or not.....