Model output discussion - heading into 2018

[snowking]

21 minutes ago, Catacol said:

I cant get my 23rd Dec frictional torque update to stick on my post - whatever I do it defaults to 22nd Dec which for the life of me I cant understand. However take it from me - frictional torque on the 23rd has climbed a fair bit - close to +1 and climbing on the gradient.

 

Update from 23rd:

[Ali1977]

26 minutes ago, Catacol said:

I cant get my 23rd Dec frictional torque update to stick on my post - whatever I do it defaults to 22nd Dec which for the life of me I cant understand. However take it from me - frictional torque on the 23rd has climbed a fair bit - close to +1 and climbing on the gradient.

 

And is this a god thing? For coldies that is and going into Jan?

[Catacol]

2 minutes ago, Snowy Hibbo said:

I can see the 23rd Dec update.....extremely weird, if you see the 22nd Dec one.

I am guessing MT is still strongly negative? That completely puzzles me, I will have to do some digging and talk to some people.

Yes - MT strongly negative. But frictional torques ought to lead MT upwards. Crunch will come with just how might the next wave gets. MJO forecast now into phase 2 at reasonable amplitude... and next surge of flux assault on the vortex imminent. I dont know just how much faith to put in Cohen - but one this is for sure: he is right when he sees the next 1 - 2 weeks as key for the winter as a whole. If the vortex resists this surge, and our pacific signal at the same time cannot get AAM spiking then it is likely curtains for the rest of this winter in terms of getting any sustained blocking and impactive sustained cold. Transient features like tonight over the Midlands will be possible, but a "special" spell of cold weather will become unlikely. Fingers crossed the vortex takes a hit, and we can regain some pacific momentum. 

 

[Snowy Hibbo]

16 minutes ago, Catacol said:

some pacific momentum

You mean a Pacific jet extension(stronger jet)? Or are you referring to something different?

16 minutes ago, Catacol said:

Yes - MT strongly negative. But frictional torques ought to lead MT upwards

Agree with that, that is normally the way the GWO cycle works.

 

16 minutes ago, Catacol said:

I dont know just how much faith to put in Cohen

I do like to put faith on him, about the strat. We either see a proper disturbance to the strat PV or we don't. The GWO is probably going to progress around the cycle, should be expecting a +AAM January IMO. Of course the specifics are unknown.

[Catacol]

23 minutes ago, Ali1977 said:

And is this a god thing? For coldies that is and going into Jan?

It's a faint start. But nothing to get excited about as we wouldnt expect torques to remain low for long. All part of the great global weather cycle... :-) For sustained cold we need a number of jigsaw pieces to fall into place at the same time.

[Catacol]

5 minutes ago, Snowy Hibbo said:

You mean a Pacific jet extension(stronger jet)? Or are you referring to something different?

 

Sorry - I was unclear. I mean a rejuvenated convection signal along the equator towards MJO phases 7/8. As a result scrub support for mid latitude ridges, reduce extra tropical AAM and thereby open the door for a high lat block. One of the many jigsaw pieces.

[Snowy Hibbo]

3 minutes ago, Catacol said:

Sorry - I was unclear. I mean a rejuvenated convection signal along the equator towards MJO phases 7/8. As a result scrub support for mid latitude ridges, reduce extra tropical AAM and thereby open the door for a high lat block. One of the many jigsaw pieces.

Yeah, that's fine. Certainly agree with that.

POAMA40 and EC46 were looking like a return to MJO Phase 7/8 around about Early/Mid February(and that's really more of an estimate), but there is only so much the models can see. But I don't see anything like that anytime soon IMO.

[Catacol]

Snow lovers look away - strongly +NAO into early January as GLAAM collapses and Nina strengthens its grip. Little of cheer for this part of the NH while we await any vortex impact and renewed pacific wave activity. 

[Catacol]

2 minutes ago, Snowy Hibbo said:

Yeah, that's fine. Certainly agree with that.

POAMA40 and EC46 were looking like a return to MJO Phase 7/8 around about Early/Mid February(and that's really more of an estimate), but there is only so much the models can see. But I don't see anything like that anytime soon IMO.

Yes - that might fit. I'll be a bit more optimistic and refuse to believe that the Autumn signal is all gone.. so maybe approaching phase 7 prior to the end of January and with luck attached to a moderate amplitude. I had hoped to see the Nina profile in the eastern Pacific moderate as winter progressed, but no sign of that yet. Phase 8 into February would be good, though vortex conditions will be key. Broad composite has a pleasing look

[northwestsnow]

4 minutes ago, Catacol said:

Snow lovers look away - strongly +NAO into early January as GLAAM collapses and Nina strengthens its grip. Little of cheer for this part of the NH while we await any vortex impact and renewed pacific wave activity. 

Looks bleak..icelandic low/ euro high.

 

[Snowy Hibbo]

7 minutes ago, Catacol said:

Yes - that might fit. I'll be a bit more optimistic and refuse to believe that the Autumn signal is all gone.. so maybe approaching phase 7 prior to the end of January and with luck attached to a moderate amplitude. I had hoped to see the Nina profile in the eastern Pacific moderate as winter progressed, but no sign of that yet. Phase 8 into February would be good, though vortex conditions will be key. Broad composite has a pleasing look

Nothing wrong with a bit of optimism 

I still like the Early-Mid Feb period though, perhaps Late Jan too... amplitude is a big gamble at this stage unfortunately.

Edited December 26, 2017 by Snowy Hibbo

[MP-R]

Is there somewhere one can find out the current extent of La Nina? I thought we were in a weak nina state, i.e. supporting more seasonal synoptics? Some of the models are painting charts as bad as those from a super El Nino!

[comet]

17 minutes ago, northwestsnow said:

Looks bleak..icelandic low/ euro high.

 

All courtesy of strat forcing, AAM, GWO etc, etc following suite.

[Catacol]

4 minutes ago, MP-R said:

Is there somewhere one can find out the current extent of La Nina? I thought we were in a weak nina state, i.e. supporting more seasonal synoptics? Some of the models are painting charts as bad as those from a super El Nino!

The MetOffice is as good as any I reckon:

https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/el-nino-la-nina

If you look at the November graphs they have helpfully added the December stats so that you can see the actual progression still sits in the middle of the ensemble forecast runs. Essentially still a weak Nina, though regions 3 and 3.4 get closer to moderate than we would like.

All forecasts still seeing the bottom of Nina arriving prior to the end of January. There is some hope, therefore, that the next tropical convection wave may find conditions a little easier to progress through to phase 8 by February.

[Catacol]

2 minutes ago, comet said:

All courtesy of strat forcing, AAM, GWO etc, etc following suite.

The drivers create that chart.

[Man With Beard]

1 hour ago, Catacol said:

Snow lovers look away - strongly +NAO into early January as GLAAM collapses and Nina strengthens its grip. Little of cheer for this part of the NH while we await any vortex impact and renewed pacific wave activity. 

A flat period T216-T264 it would seem after a colder T168-T192, but by T288 there could well be a chill in the westerlies on the 2 main clusters:

(all according to ECM rather than GFS)

Edited December 26, 2017 by Man With Beard

[Justin123]

Was just browsing the GFS and saw this for the 4th of jan, a long way off, and I am pretty rubbish and amateur at reading charts, but that low seems to move in from the north with cold air cutting behind it, a potential snow even for northern England and scotland.

[Weather-history]

1 hour ago, northwestsnow said:

Looks bleak..icelandic low/ euro high.

 

Note the "higher" pressures anomaly runs towards Newfoundland. That suggest to me, polar maritime airmasses maybe more frequent or easier to reach the UK. If that low pressure anomaly around Iceland extended towards Newfoundland then polar maritime airmasses would really struggle.

[nick sussex]

Looking at the ECM 00hrs ensemble maps for each member theres still quite a spread of solutions for a possible second snow event effecting more northern areas between T72 and T84hrs.

This mornings fax chart showed an occlusion working ene with still some cold air ahead of that which then slows over southern Scotland with a wave forming on it.

Still some uncertainty with how the energy spills east from the main low at that timeframe so something to look out for but equally it might just disappear on the next runs.

You can see the occlusion lying across southern Scotland at T84hrs, to the north of that away from windward coasts likely to be some snow:

 

Edited December 26, 2017 by nick sussex

[SMU]

Interesting little feature on UKMO 72

[nick sussex]

Quite a big change in the UKMO with the T72 hrs bringing another possible snow event running nw/se across the east and ne.

Unfortunately any snow won’t last long with milder air pushing east after that but there seems to be a lot of uncertainty with how this cold snap breaks down .

Edited December 26, 2017 by nick sussex

[Daniel*]

GFS 12z somewhat upgrades the snow event for London and SE gives widespread 1-2CM depths WOW. 

GFS delays the clearance too snow / precip leaves the London area at 1600, disruptive snow for the capital? 1mm and things go hairy - we’ll see. But maybe a surprise in store. 

[knocker]

As a follow up to my earlier post still looking at a low deepening quite rapidly T66-T90 without bombing dramatically as earlier but  still two bites of the cherry for snow over Scotland Friday and Saturday.

 

[Man With Beard]

And interesting UKMO T144 - a short northerly for the north

[nick sussex]

The GEM also has a more interesting T72hrs output, shortwave energy cutting se through the UK.