Model Output Discussion - Into 2024

[MJB]

11 minutes ago, Bricriu said:

I can remember several occasions where we went mild but it stayed cold in the UK with heavy snow there while we had rain.  Although I see what you are saying in a robust zonal  set up the UK would eventually  go mild too.

We have a Belfast office and I remember countless times we have had decent snow and they are left with rain, so you make a valid point 

[Kasim Awan]

Just now, Cheshire Freeze said:

I think he meant it was 50/50 as to whether the cold made it on the op

My 5050 was in reference to my own assessment of probabilities as opposed to what was shown on the GEFS12Z. The GEFS is more 70/30 for proper cold / faux cold.

That is an equal chance of a potent ne cold spell and faux cold with the coldest air being shunted east. I think this is fair given the output.

[lorenzo]

Read the room EC for goodness sake...

 

Am not buying this run re: the 150hPa and 475K profile, I think it may be retaining too much energy in the Canadian daughter vortice. Still, it goes without saying, you really need the EC to align to have any sense of confidence in direction of travel.. doubt any of us would bet against it. Let's hope it's having it's own wobble 24 hrs after the US counterpart did.

 

[parhelion]

2 minutes ago, Kasim Awan said:

My 5050 was in reference to my own assessment of probabilities as opposed to what was shown on the GEFS12Z. The GEFS is more 70/30 for proper cold / faux cold.

That is an equal chance of a potent ne cold spell and faux cold with the coldest air being shunted east. I think this is fair given the output.

Ah, so something none of us can verify then? 

[Daniel*]

EPS again heading in wrong direction losing -NAO as it did in 00z, I think it’s more than small concern GEFS do not offer superior guidance. It was EPS which first advertised a potential change towards end of week 1 of Jan, let’s hope it doesn’t indicate an end as well.

[Polar Maritime]

Let's keep discussion friendly please.

[Met4Cast]

2 minutes ago, Daniel* said:

EPS again heading in wrong direction losing -NAO as it did in 00z, I think it’s more than small concern GEFS do not offer superior guidance. It was EPS which first advertised a potential change towards end of week 1 of Jan, let’s hope it doesn’t indicate an end as well.

That.. looks pretty good to me? -NAO out to the end of the run with residual heights left to the north of the UK? 

I’m not sure anyone is expecting a sustained strong -NAO without some sort of waxing & waning. 

[Malarky]

1 minute ago, Met4Cast said:

That.. looks pretty good to me? -NAO out to the end of the run with residual heights left to the north of the UK? 

I’m not sure anyone is expecting a sustained strong -NAO without some sort of waxing & waning. 

It’ll be reverting to seasonal default a bit more as signal fades right?

[sheikhy]

1 minute ago, Met4Cast said:

That.. looks pretty good to me? -NAO out to the end of the run with residual heights left to the north of the UK? 

I’m not sure anyone is expecting a sustained strong -NAO without some sort of waxing & waning. 

Was gona say that looks bloody fantastic!!!!

[That ECM]

Not bad at all.

[Met4Cast]

EPS mean remains absolutely solid! Days 8, 9 & 10.

[Mcconnor8]

Just now, Met4Cast said:

EPS mean remains absolutely solid! Days 8, 9 & 10.

As suspected the OP went off on one with the shortwave!

[Man With Beard]

34 minutes ago, That ECM said:

How do we get any cold in without a nhp that is in favour of delivering it?

Once the cold is in, a different pattern can maintain the cold. The chart for December 25th 2010 doesn't look too cold yet delivered max temps of -5C across some central areas, because the synoptics held in place the cold delivered earlier in the week. This is particularly true in January when there is less daytime heating.

But as you rightly say, the current issue is getting the cold in to begin with!

Edited January 6 by Man With Beard

[That ECM]

Gfs and ecm T240 mean.

[Daniel*]

1 minute ago, Met4Cast said:

That.. looks pretty good to me? -NAO out to the end of the run with residual heights left to the north of the UK? 

I’m not sure anyone is expecting a sustained strong -NAO without some sort of waxing & waning. 

It a significant decline from recent days both forecast for Jan 17th the newest on left and right from 12z of 4th. The blocking signal to NW has weakened it’s not a good trend and see stormy area across pond which further tries to erode. We see this a lot with Greenland blocking sadly as we get closer… I’m not saying it’s over with, but these are not giving me encouragement at all.

 

[seabreeze86]

If the ECM op was showing consistency in how it breaks down the blocking I’d be more concerned but it’s all over the place 

As ever more runs needed 

[sheikhy]

Just now, That ECM said:

Not bad at all.

Seriously you aint gettin a better mean than that!!!

[Mcconnor8]

1 minute ago, That ECM said:

Gfs and ecm T240 mean.

Not much in it at all between them, combined with Mogreps almost unanimous support I really don't think we should be worrying about the ECM OP at this stage.

Edited January 6 by Mcconnor8

[Met4Cast]

Just now, Daniel* said:

It a significant decline from recent days both forecast for Jan 17th the newest on left and right from 12z of 4th. The blocking signal to NW has weakened it’s not a good trend and see stormy area across pond which further tries to erode. We see this a lot with Greenland blocking sadly as we get closer… I’m not saying it’s over with, but these are not giving me encouragement at all.

 

It’s weakened from a place of ridiculous blocking though, some of the runs we were seeing were up there with the best possible solution that could have been plucked from the deepest cold spells in history. 

I don’t think it’s too much of a surprise we’ve moved a little away from that & towards something more realistic, not to mention the increased spread will be smoothing the means out in the extended somewhat. 

Nothing really to be concerned with at this stage, just a chopping & changing of the pattern but expectations still remain the same. 

[Ali1977]

3 minutes ago, Met4Cast said:

EPS mean remains absolutely solid! Days 8, 9 & 10.

That looks like the best set yet, noting we aren’t chasing day 12 anymore

[damianslaw]

Ah one of those GFS vs ECM situations I see, GFS has played around with loss of heights to the NW, but today brings them back strong, its now ECM turn to have cold feet.

We are talking of a timeframe outside the reliable, and consequently I wouldn't at this range hang my hat on either having it spot on.

It does appear we have a more complex set up developing with a split flow, trough to our NE, heights to our NW, and low heights to the SW, 3rd week Jan, UK at the mercy of all three, I can see why the met office are going for battleground cold/mild lines with snowy attacks from the SW.. we could be about to see a very snowy 3rd week Jan for some...

Regardless the ops continue to align poorly with ensemble means - the GFS and ECM are resolute with strong Greenland heights and a NE flow, it is these we need to take note of. 

Edited January 6 by damianslaw

[That ECM]

Just now, Man With Beard said:

Once the cold is in, a different pattern can maintain the cold. The chart for December 25th 2010 doesn't look too cold yet delivered max temps of -5C across some central areas, because the synoptics held in place the cold delivered earlier in the week. This is particularly true in January when there is less daytime heating.

Completely agree. This was one of a few posts and my reply was to a post that had screenshots of output that didn’t have the cold in. Hopefully that makes sense.

[Duane S.]

I’m a little lost as to why so many people are so shocked at the variable deterministic output from the models.

This warming and u-wind slow down is not your usual NH standard winter stuff. The models will struggle accordingly, more than normal, and head off earlier down different paths at times.

For a brief time this coming weekend, for the south at least, there has been a strong signal pointing to more average 850s for the past few days. Milder blip before the main event starts from early the following week. That has not altered.

The detached Atlantic low is going to be a huge player in all this I feel. Watch this be friend then foe and back to friend and then back to foe from run to run to run over the coming days   

As for heights to the south, just a natural response to a combo of retrogression and that low pumping up the Hadley Cell. IMO it should be temporary, if at all, as that low ought to drift SSE and fill eventually.

[stodge]

Evening all

Worth re-iterating the rather tired comment - we aren't there yet.

A mixed bag from the 12Z output - GFS OP is a thing of beauty especially for snow fans in the south. The key to a successful retrogression is not just getting in the N'ly (or NE'ly) but that being robust enough to force the Atlantic LP systems from the south west to disrupt and elongate along the Channel giving the south a real opportunity for snow.

ECM doesn't looks as friendly (though I've seen worse) and ends on a knife edge at T+240.

The problem is of course the dreaded shortwaves which may or may not be well forecast. ICON showed what can happen if they aren't there but GFS has had them regularly for the past few runs albeit on the 12Z OP it's very much a case of getting there in the end.

JMA looks very good this evening as well and let's be fair - we are desperate to nail down T+168 but we know evolutions change and can change radically until we get to T+72 to T+96 which means Tuesday or Wednesday before we start seeing something we can start to rely on. That means an anxious 96 hours for model watchers and especially those watching every twist and turn.

There are always outliers and "poor" runs which challenge the concensus (or should it be hopesensus?) - it's encouraging to see so many of the other background signals remaining solid. It's easy to put a lot of faith in an OP - it wasn't that long ago some OP runs were even doubting a southern Scandinavian HP or putting it over the Faeroes - the models suddenly firmed up en masse (or en bloc if you prefer) at T+96 so the Wednesday and Thursday 12Zs (which are the only runs I look at each day) will be critical as to whether we a) get a notable retrogression, b) it's a glancing blow or c) we miss out completely.

[Severe Siberian icy blast]

1 minute ago, Daniel* said:

It a significant decline from recent days both forecast for Jan 17th the newest on left and right from 12z of 4th. The blocking signal to NW has weakened it’s not a good trend and see stormy area across pond which further tries to erode. We see this a lot with Greenland blocking sadly as we get closer… I’m not saying it’s over with, but these are not giving me encouragement at all.

 

In complete honesty if you're taking things literally at t300 then you're setting yourself up for a bumpy ride, the computer models pick up on a trend and tend to over react to a signal then level out somewhat and its a process of two or three times it goes back and forth but the signal is strong. Northerly blocking and cold air moving south.

Leave the detail out for now