Model Output Discussion - Spring Has Sprung

[Eagle Eye]

  @Tamara

Another great post but would it be more accurate to use +VE MT rather than describing just the EAMT given the NAMT strength, rather than EAMT each time, I'm guilty of using EAMT to describe it each time and whilst that is the strongest and typically is, wouldn't it also be a synoptic scale change from the +VE NAMT as well to consider so more accurate language to be more general?

[Catacol]

1 hour ago, Tamara said:

That much can be said with reasonable confidence. And to be blunt, it is all that should matter at the moment based on the timescales involved. My guess is that these tropospheric drivers are vigorous enough to overcome the strength of the SPV and, as a minimum, result in a de-coupling, if not major SSW (quite conceivable). But again, that is subject to watching the evolution over the timescales involved

Agree - spot on. I've been keeping my head down as we live through this westerly, mild mush that darkens my day so much - not because I dislike getting up into a warmer house or dislike opening the windows when the sun pops out and it is 13 degrees outside....because I enjoy that very much in Spring!! But the seasons define the ebb and flow of the yearly calendar, and when winter is routinely so mild and damp and windy and dross-like it does not improve my personal mood. I grew up with snow in the 70s and 80s and would love those days to return. CC likely means not for a generation or 3 at least.

Back on topic - I agree with you - this is what it will be all about. Can these substantial tropospheric drivers seize control of a pattern that could yet be held tight by the SPV? Showing another representation of peaking momentum, here is the relative tendency from earlier this week

Here is the sharply rising total AAM budget

and here now is the fast rising GWO orbit, a representation of windflows that demonstrate how predisposed to a blocking pattern these windflows are

This is all good news - as good as the last rising phase at an earlier stage I would say, and likely therefore to exceed the totals we got that set up the mid January cold snap.

Meanwhile....the vortex stays strong

but according to GFS a growing signal that the lower layers are going to be firmly displaced over to the Siberian side as they were in December by early season warming from Canada

The door for a NW centred block is very definitely being opened here. Can we push it wide and let the wintry floodgates open? The latest CPC text on the MJO, a key feature of the overall wave driving operation, is rather tasty:

"Good agreement exists in the dynamical models looking ahead, which initially favor a high amplitude MJO signal over the Western Pacific that weakens and slows after the week-1 period."

- because, weakening or not, a high amplitude west pacific signal that stalls is exactly what we would want to sustain this wave driving, with the potential to render the strong SPV less relevant than it might be. MJO plots, as ever a bit unreliable, are illustrated here and are lining up favourably:

January has done a lot to knock the stuffing out of cold winter forecasts and forecasters, whether that be because of failed late month progression that indicated cold longevity or the comments of those quick to jump on the fail as evidence of the pointlessness of trying to forecast the unforecastable. We move on from all that. February starts next week, there is a distinct chance of a cold spell through mid month and beyond and that without a SSW or even a weakened vortex. The cold light of post season analysis is going to provide some very useful bits of guidance and information for seasons ahead, whether or not we land a proper cold snowy surge this winter or not. And there is still March to come, arguably the month that has delivered the most over the last 10 years or so.

So.... here we go again on another chase. Winter would be dull without them even if, like the a tiger, we fail more than we succeed in our hunt.

Edited January 26 by Catacol

[Battleground Snow]

  @feb1991blizzard not a bad fit by the control to that composite 

  @feb1991blizzard not a bad fit by the control to that composite 

[Catacol]

12 minutes ago, Eagle Eye said:

Another great post but would it be more accurate to use +VE MT rather than describing just the EAMT given the NAMT strength, rather than EAMT each time, I'm guilty of using EAMT to describe it each time and whilst that is the strongest and typically is, wouldn't it also be a synoptic scale change from the +VE NAMT as well to consider so more accurate language to be more general?

A good question as I butt in here....but EAMT establishes the strength and direction of the Pacific Jet, and the Pacific Jet is all important when looking at wave patterns across the NA continent, far more than any impact off the Rockies. I would say that NAMT is significant when looking at warming of the stratosphere from the Canadian side. We have seen a lot of this through the current winter, and it is no coincidence the Aleutian Low has dominated as a feature, driving this torque. But I dont see that as impacting as much on the jet and jet angle across the atlantic as the much more significant Pacific Jet which gathers so much energy when Tibetan torque is engaged.

EAMT therefore the most important....?

[Dennis]

here is my reason for not posting;

- (sorry) - i feel that some only think that i  and others write here on an emotion 

so see you next week on new charts for my thoughts i started early her

 

 

 

[Jacob]

1 hour ago, Mcconnor8 said:

@Dennis

Yes the Control has a blizzard in the South East lol, at least we are starting to see promising charts in FI so there is some hope now.

I doubt this will verify but that would be the dream lol, near a foot with blizzard of snow in my location lol

[Dennis]

  @Jacob sure me doubt it too , as in this outcome on a snow situation, but i try to reasearch and mixing diff parameters on  how an new wintersituation can seen back on the charts

 

Have fun 

Edited January 26 by Dennis

[MJB]

  @Dennis You carry on Dennis, I like seeing your posts

[Nick2373]

06z as per post this morning of a pattern change, some sort of change on its way from the 05th onwards. Control goes off on one but what is interesting is some members are toying with going just under the 30 year mean. A Greenland high quite possibly and a big one at that 

Edited January 26 by Nick2373

[Eagle Eye]

I mean it's a trend I quite like. 

[northwestsnow]

  @MJB me too !!

Keep posting @Dennis your positivity counteracts my negativity I suppose the world would be boring if we were all the same  

 

Edited January 26 by northwestsnow

[Catacol]

On 24/01/2024 at 15:57, RainAllNight said:

It's whether the probability of something unexpected like these two things occurring can be estimated that interests me, as if we can't do that, then I don't see how we can put a confidence level on a forecast. It was a surprise to me when the (earlier) SSW didn't occur and then again when the flattening occurred so quickly and stuck, just because the forecasts to the contrary had sounded so confident.

Coming back on this one. The probability of the unexpected. A genuinely relevant and interesting question in itself. Some will groan and grind their teeth at the tendency for anything that can derail a cold pattern from coming to pass almost routinely. How many times do we read curses around "short waves" messing up the pattern, for example?! I dunno. Some of this is micro stuff, and when we get to the micro analysis of tiny shifts of 50 miles or low pressure waves popping up - I begin to glaze over. We don't have the computing power yet to be able to forecast these with any accuracy and I think they are beyond the wit of the human brain to be able to interpret from an analytical perspective. So the unexpected micro development will be a thorn in our side, and a thorn that arrives on the scene frequently, until resolution and computer modelling gets better.

In terms of large scale "unexpected" features I do sense that these are less frequent than might appear to be the case. Having watched with a mixture of hope and horror a long run of winter seasons since the internet came into existence, I think the macro driver interpretations are not often derailed by the unexpected. Sometimes the unexpected comes to our aid. The BFTE 2018 pattern was a split SSW impact that was not seen at all until late in the day, and it didnt really feature in the long term analysis as something that was likely. Hindsight analysis has since picked up on hemispheric patterns in mid January that set up what happened....all part of the learning. But these were not screamed about at the time. Our current fail, the impact of a reflective strat response to wave driving, is another unexpected event. But this one, and the 2018 one - how frequent are they? Each season seems to me to run fairly accurately to script for most of the time. So...take the current winter. We got early cold as forecast by drivers. We got the relaxation as expected. We then didnt get an MJO enhanced Xmas spell - but this was likely down to some over enthusiastic interpretation of that phase rather than the drivers themselves misaligning. We then got the mid month cold as expected. And if we get the mid Feb cold as expected then, across the season, we have around 5 phases of weather with a single unexpected feature that derails things.

In  probabilistic  terms, we cannot hit 100% accuracy. In general pattern terms I think we should be extremely happy if a season gets to roughly 75% accuracy. 50% for me would be minimum satisfaction rating. And in all this the "unexpected" factor is perhaps not that common.

 

Edited January 26 by Catacol

[That ECM]

At last, something to chase, I’m sure it’s been posted. 

[Tamara]

1 hour ago, Catacol said:

"Good agreement exists in the dynamical models looking ahead, which initially favor a high amplitude MJO signal over the Western Pacific that weakens and slows after the week-1 period."

- because, weakening or not, a high amplitude west pacific signal that stalls is exactly what we would want to sustain this wave driving, with the potential to render the strong SPV less relevant than it might be. MJO plots, as ever a bit unreliable, are illustrated here and are lining up favourably:

 

I posted the VP200 anomalies earlier These will have resolution to identify tropical convection convergence much better than the RMM plots which lose reliability more than 4 to 5 days ahead.  This winter has already proved this fallibility based on the previous undercooked RMM forecasts of wave orbit (set against a Nino standing wave to engage convergence in the Pacific at and beyond the dateline)

Based on the GSDM analysis - gravity wave amplitude> significant +EAMT> engagement of a robust upstream jet  - all are hand in hand with a Phase.6,7,8 progression. 

Those of you looking for the outcome you desire in UK/NW Europe would appreciate a slow but complete progression of the tropical wave through the whole of the Pacific - not withstanding the longevity of the poleward extra tropical momentum transport in respect of how it impacts the polar field.

I think a comparison analysis to follow with that of the events of Feb 2018 are valid. Not saying at all that the outcome and more especially the surface conditions will be precisely the same - but because there are a lot of tropospheric forcing similarities with that time. 

Following the ongoing marvellous weather down here in PT, the return of the STJ would be very much welcomed by folk here who are eager for rain ahead of the heat and dryness of summer to come.

@Dennis Comments do not apply to your proactive posts in any way

[Kirkcaldy Weather]

As mentioned in my post here 

 

"With the above we can see some of the important 500hpa setups developing into our current timeframe and into week 4 of January (and beyond)

Low pressures from Greenland and into the Arctic

High pressure forming across the Maritimes. A secondary high toward the Northwest of the US and Canada which links with PNA behaviour more on that shortly.

Formation of cut off low(s) in that southwestern America > Mexico regions which also will lead into PNA behaviour.'

'Following on from this as the preceeding MJO phases input begins to feed into the setups from week 4 of Jan onward the above remains true with further developments.

Looks like this initial cut off low will develop into a +PNA during the very end of Jan"

As the positive PNA feedback progresses eastward pairing with the MJO patterns I've covered in depth, a +PNA does have a tendency of being supportive for Atlantic ridging / blocking which moves in the direction of Greenland and in connection to a trough further east ie Scandinavia, Baltic regions which gives a doorway for something cooler > colder from the north.

 

 

Though I'm not putting a massive amount of emphasis into exact timeframes from my POV ATM it's looking favoured for this by approx February 4th / 5th and starting to see a possible redux around 1 week later ie 11th / 12th February.

 

[northwestsnow]

Exeter now talking mid month for a change to something more settled / colder..

I guess this means we need to be looking at beyond day 10 from a NWP perspective...

All eyes on EPS / EC46 later ..

[February1978]

1 hour ago, Catacol said:

Coming back on this one. The probability of the unexpected. A genuinely relevant and interesting question in itself. Some will groan and grind their teeth at the tendency for anything that can derail a cold pattern from coming to pass almost routinely. How many times do we read curses around "short waves" messing up the pattern, for example?! I dunno. Some of this is micro stuff, and when we get to the micro analysis of tiny shifts of 50 miles or low pressure waves popping up - I begin to glaze over. We don't have the computing power yet to be able to forecast these with any accuracy and I think they are beyond the wit of the human brain to be able to interpret from an analytical perspective. So the unexpected micro development will be a thorn in our side, and a thorn that arrives on the scene frequently, until resolution and computer modelling gets better.

Agreed, will it ever be possible to model these small scale features at more than a handful of days? There will always be an error in the initial state, whether it’s instrument error, lack of coverage in certain parts of the atmosphere, topology or the like and that’s before any physics assumptions are made. Due to the chaotic nature of meteorology, there is often not a ‘steady state solution’ & errors grow, irrespective of how fine the resolution or accurate the dynamical equations are. Rubbish in, rubbish out……..so I think NWP will always struggle beyond a few days.

On a slightly different tack - the (off-the-) scale of EAMT anomaly highlighted in Tamara’s post is really something - must surely have an impact in due course….?

[Battleground Snow]

Things looking up this afternoon,

Teleconnections wise and the models themselves.

Icon shoving the tpv east much earlier on this run 

[Cambrian]

The EPS has been performing very well of late but it has tended to underestimate Atlantic heights past day 5, as well as the northward extent of the build of both Atlantic and European heights, while at the same time overestimating the relative heights over Iberia. 

First, the day 5 chart from the 21st 0z compared with the 0h chart from today’s 0z. Not much surprise, pretty much bang on. Happy days. 

 

Next, the day 10 chart from the 21st, compared with the day 5 chart from today, for the last day of January. Heights stronger than expected over the Atlantic and Eastern Europe. It didn’t pick up on such a firm development of that low pressure to the southwest of Portugal. 

 

Comparing the day 15 chart from the 21st with the day 10 chart from today, for the 5th of February. Again, an enhancement of the build of heights to the northwest in the more recent chart, as well as the adjustment of the Scandinavian trough a bit further east but markedly deeper.

 

So looking at these charts, how they have been faring and adjusting, when we then look at today’s chart for day 15, taking on board the westward movement of the Scandinavian trough from day 10 and the possibility of a stronger northward build of heights through the Atlantic…

…it’s evident that though there is little strongly indicative in the short term for those of us looking out for a bit more cold weather to round off the winter, there’s plenty to indicate that the next week or so of model-watching, looking forward to the week 2 period, may quite quickly become very interesting indeed. 

[Dennis]

febr ideas on a GH and MJO 7 (event)

i did study alot on this from start Jan24  , hope we see all the winter as we like to have 

Edited January 26 by Dennis

[Stephen W]

Some really excellent posts on here this afternoon especially @Tamara& @Catacol. Thank you! Such interesting analysis and it will be interesting to see how events unfold during February. 
@Dennis, please keep posting. I too really enjoy reading these!

 

 

 

[Dennis]

febr part 2

big (North) easterlies forseen by a 7 event 

Edited January 26 by Dennis

[Lukesluckybunch]

Absolute dire..gfs run again,all cold remains to the north of the uk!

[northwestsnow]

UKMO 168  v GFS 168

Edited January 26 by northwestsnow

[Dennis]

GH forseen