Model Output Discussion - 15th March onwards

[damianslaw]

Quite an amplfied yet slow moving weather scene at present, with the atlantic long wave trough digging deep through the atlantic and becoming very slow moving inching it's way eastwards but taking an age. Hence we've experienced a period of wet weather and mild conditions thanks to a SW flow, despite the origins of the air being from further north, taking a long route south and back to us on the SW wind. 

However, by the weekend, finally the trough moves eastwards, and we pull in a long fetch northerly flow, cold uppers moving in and return of snow to modest levels in the north and widespread frost as we move into the new week - with a weak ridge toppling in behind.

Yesterday UKMO suggested this feature may become more robust and built north holding off the next low pressure, but the ECM and GFS quickly push it aside and its a repeat of the current conditions, the slow moving atlantic trough is back bringing more wet and milder conditions. As we end March and enter April, signs though of a change of sorts, with perhaps heights building more to the north west as well as the south - a pincer effect, with the low pressure filling somwhat as it edges eastwards, becoming more cyclonic in nature and possibly moving away to the SE, April could arrive a colder NE flow, conversely the ridge to the south could build northwards. Bit of a stalemate situation, with the UK sat in the middle, we could end up with a very slow moving trough overhead meaning cool wet weather with another low pressure ready to join it quickly with neither the heights to the NW or south having a strong enough influence to win out. I do like Spring for interesting weather synoptics, April and May typically bring our least 'westerly' period of the year, cyclonic conditions, northerlies and easterlies can often hold sway bringing unusual synoptics - the type snow and cold lovers would love to see in the depths of winter, but perhaps not April and May!

[Rain All Night]

I didn't bother posting Monday's, but as it is perhaps marginally more interesting, here is some of the extended output from this morning's 0z ECM ensemble...

For comparison with the above Z500 anomalies, here are the current CFS anomalies covering roughly the same period as the first two (not three, note the dates) ECM weekly charts above. Both models want to make us wait until the very edges of believability for a sustained ridge...

Just for fun, the SPV in the northern and southern hemispheres, from just after the equinox, to about seven weeks after... amazing how quickly the onset of polar night makes it explode...

After the ECM update in June, we will get this extended output from the 0z ECM ensemble run every day, instead of just twice a week (as we already do with the 0z GFS ensemble, though the publishing delay on that is something ridiculous like 24 hours), and it will have twice the number of ensemble members. I wonder if that "test" ECM website that I linked earlier will start showing some output from these runs before then?

Edited March 23, 2023 by RainAllNight

[feb1991blizzard]

Hello - whats happening here then?

[feb1991blizzard]

Didn't slide enough but not bad far N England / S Scotland.

[Nick2373]

 

At last something more warmer starting to trend from the 03rd onwards, i like the cold and snow but this is just dragging on now.

[Cambrian]

Better days ahead in week 2, according to the models of the last couple of days. Yesterday’s ECM extended forecasts show low heights and pressures on the weekly mean anomalies for the UK and Ireland in week 1 replaced by a rise in both to positive anomalies in week 2. That’s quite a switch. The return of a northern blocking signal through to week 3 too.

  
  

And on the weather regime forecast, look at that blocking signal from around the 6th. It has appeared quite suddenly too, if we compare it with Monday’s forecast. 

 

The 0z GFS ensemble mean anomaly shows heights working their way north from Iberia at day 10, linking up with those over Greenland and the Barents Sea establishing a blocked pattern by day 15. 

 

A long way off, but from the output of the last couple of days, a firm signal, and after a continued changeable period for the next 10 days or so, things are definitely looking up for a more settled period heading into the second week of April.

I know that it’s been quiet but I have really enjoyed the models of late, slowly emerging from winter, first struggling to shrug off the cold Scandinavian trough, then slowly introducing a mobile pattern for two or three weeks, before signalling a renewed blocking pattern and a continually improving prognosis for the Easter break. Have a great day. 

Edited March 24, 2023 by Cambrian

[ANYWEATHER]

1 hour ago, Cambrian said:

Better days ahead in week 2, according to the models of the last couple of days. Yesterday’s ECM extended forecasts show low heights and pressures on the weekly mean anomalies for the UK and Ireland in week 1 replaced by a rise in both to positive anomalies in week 2. That’s quite a switch. The return of a northern blocking signal through to week 3 too.

  
  

And on the weather regime forecast, look at that blocking signal from around the 6th. It has appeared quite suddenly too, if we compare it with Monday’s forecast. 

 

The 0z GFS ensemble mean anomaly shows heights working their way north from Iberia at day 10, linking up with those over Greenland and the Barents Sea establishing a blocked pattern by day 15. 

 

A long way off, but from the output of the last couple of days, a firm signal, and after a continued changeable period for the next 10 days or so, things are definitely looking up for a more settled period heading into the second week of April.

I know that it’s been quiet but I have really enjoyed the models of late, slowly emerging from winter, first struggling to shrug off the cold Scandinavian trough, then slowly introducing a mobile pattern for two or three weeks, before signalling a renewed blocking pattern and a continually improving prognosis for the Easter break. Have a great day. 

There's a long way to go before we can say a Firm signal. Conflicting signals is what I can see, that's why long range weather forecasts are often useless.

[Cambrian]

Most are all too aware of the fallibilities of the modelling tools at longer range, but I guess the point is how to best to use the available tools to deduce emerging patterns. It’s difficult to quibble too much with the current ECM and GFS anomaly charts for that period, particularly in light of the contrast with the week before - it’s the trend that is most revealing. 

The 0z ECM and GFS ensemble means both show a steady rise in pressure from day 7, the end of the month, like they have for a few days now. The pressure remains at that higher mean through to the Easter weekend. 

 

Fair enough, there are still plenty of precipitation spikes, but with both model ensembles, these thin out considerably after the 2nd, with a drop in the precipitation mean along with the rise in pressure, the contrast between week 1 and 2 again clear. 

 

One caveat, a potential fly in the ointment worth mentioning, is the falling away in pressure and the associated precipitation spikes of both the ECM control and GFS op out at day 13 to 15. This would be a fair point to raise for later in week 2, and it will be interesting to see if this has traction on future runs.

Whether the models turn out to be close to the mark, or not, in the actual event will be something that we’ll gain more insight into as that time approaches, and the long range becomes medium, then short range. 

To productively discuss the trends emerging in week 2 and pick out broad patterns in changes of heights and pressures has proven to be well within the reasoned and proven capabilities of these technologies for many years now. The models for week 2 can flip, sometimes wholesale, but it is nevertheless still worthwhile to comment on what in general they are currently indicating. 

[Rain All Night]

16 hours ago, RainAllNight said:

Hey guys, it's a testament to how uninteresting the model watching is at the moment that I seem to be the first to have noticed this today: the Meteociel site has added the new parallel ("beta") version of the ECMWF! As others have posted here previously, the updates to the "deterministic" (op) run seem comparatively routine, but the upgrade to the ensemble is fairly monumental, with the resolution doubled to be the same as that of the deterministic run, and this new version is intended to replace the current operational version in June: https://www.ecmwf.int/en/about/media-centre/news/2023/upgrade-forecasts-centre-our-plans-2023-says-dg

Here are the links for the deterministic runs...

Fast deterministic: https://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=1&map=1&type=0&para=1
Full deterministic: https://www.meteociel.fr/modeles/ecmwf_hres.php?ech=168&mode=0&carte=1&runpara=1

I've also found links for the ensembles, but at the moment there are no charts on these pages - hopefully there will be soon...

Fast ensemble mean: https://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=1&map=1&type=1&para=1
Full ensemble: https://www.meteociel.fr/modeles/ecmwfens_cartes.php?code=51&ech=168&mode=0&carte=1&runpara=1

EDIT: At the moment I get the impression that only 0z runs are available.

As a bonus, I've also found a link on Google to the ECMWF "test" website, where they seem to be previewing some charts generated from the new ensemble version: https://charts-dev.ecmwf.int/products/opencharts_meteogram_esuite?base_time=202303230000&epsgram=classical_plume&lat=51.5084&lon=-0.125533&player_dimension=base_time&station_name=London

Have fun!! Unfortunately, the outlook is still crap on the new version 

Look how much less spread there is earlier on on this Z500 plume!!

Just for fun, this morning's ECM op and ECM para, side-by-side:

The difference in precipitation on day one on those meteograms is odd!

Minor point, the 12z para did eventually appear on Meteociel, though not on the ECMWF site (where the meteograms are from). The ensembles didn't appear on Meteociel unfortunately.

Edited March 24, 2023 by RainAllNight

[PiscesStar]

10 minutes ago, RainAllNight said:

Just for fun, this morning's ECM op and ECM para, side-by-side:

These meteograms are for the south coast:

Minor point, the 12z para did eventually appear on Meteociel, though not on the ECMWF site (where the meteograms are from).

What can we deduce from these charts please? 

[Rain All Night]

11 minutes ago, PiscesStar said:

What can we deduce from these charts please? 

Not a lot really - the new version doesn't seem to offer any more clarity on a pattern change! The wind roses on the new version maybe looking a little bit more supportive of winds coming round a ridge later?

Edited March 24, 2023 by RainAllNight

[PiscesStar]

7 minutes ago, RainAllNight said:

Not a lot really - the new version doesn't seem to offer any more clarity on a pattern change! The wind roses on the new version maybe looking a little bit more supportive of winds coming round a ridge later?

The gfs looks cold but not desperately so the further south you go.. Inevitably rain perhaps sleet during early hours for South East regions (imby) then a renewed push of heights to our northwest reinvigorate the northerly alongside northern blocking is my take,?? 

Edited March 24, 2023 by PiscesStar

[alexisj9]

3 hours ago, PiscesStar said:

What can we deduce from these charts please? 

Most don't want the para to happen now lol.

[Rain All Night]

I've been posting FI ensemble mean charts for days, with the sustained pattern change not getting too much closer. I'm hoping it's a good sign that we've now got this negative precipitation anomaly coming up from the south, and the positive anomaly disappears completely from the UK. I would have thought that in early April, the "average" rainfall (i.e. no anomaly) would not be terribly much rain for many places, and would allow for some completely dry days when averaged over a week as on these charts.

I have been curious, based on other posts here, whether this would be an unusual time of year to have an Atlantic-driven weather pattern persisting for weeks longer than has already been the case. I won't attempt to directly answer this, but if anybody wants to try to draw their own conclusions, I have written a little summary for each of the last 10 years giving each pattern change I can see on the ECMWF reanalysis charts in (roughly) the last week of March and the first week of April.

Charts: https://www.meteociel.fr/modeles/archives/archives.php?day=17&month=3&hour=0&year=2013&map=0&region=nh&mode=2&type=era

2013* - continental flow c. March 19th, Atlantic flow c. April 10th
2014 - continental flow c. March 25th, Atlantic flow c. April 4th
2015 - Atlantic flow with NW-SE tilt c. March 23rd, anticyclone over UK c. April 4th
2016 - Atlantic flow with strong NW-SE tilt c. March 25th, continental flow c. April 10th
2017 - anticyclone over UK c. March 24th, Atlantic flow c. March 28th, anticyclone over UK c. April 5th
2018** - Atlantic flow c. March 23rd (following 2nd "Beast") with the track pushed far to the south from c. March 28th, continental flow c. April 10th
2019* - anticyclone over UK c. March 25th, continental flow c. April 5th
2020 - continental flow c. March 20th, NW-based anticyclone c. March 28th, southerly flow c. April 5th, ridge over UK c. April 9th
2021* - Atlantic flow c. March 22nd, ridge over UK c. March 29th, NW-based anticyclone c. April 1st, northerly flow c. April 5th
2022 - anticyclone over UK c. March 24th, northeasterly flow c. March 30th
2023** - Atlantic flow c. March 8th, still going as of March 24th, still showing on semi-reliable model output (including today's 12Zs) up to March 31st...

* SSW in January ** SSW in February

Edited March 24, 2023 by RainAllNight

[Metwatch]

Much more like it with the latest GFS. Low chance of it verifying of course, but the chance is never zero. 

Edited March 24, 2023 by Metwatch

[Atmogenic]

Just now, Metwatch said:

Much more like it with the latest GFS. Low chance of it verifying of course, but the chance is never zero.

my eyes sparkle just seeing that 

[ANYWEATHER]

And for fun, the Easter period according to the gfs is going to be bonkers weather. Heat cold, rain and wind. Entertaining if nothing else

[lassie23]

9 minutes ago, ANYWEATHER said:

And for fun, the Easter period according to the gfs is going to be bonkers weather. Heat cold, rain and wind. Entertaining if nothing else

A white hot Easter

[Sunsetglimmer]

Oh that GFS run is such a tease!!! If that could verify pleaseeeee

[Stuie]

Looking at Sunday... very damp it appears and not pleasant on the South coast. The Arpege IMO is normally quite reserved with precipitation (accurate more like) but it is going with this forecast.

Edited March 24, 2023 by Stuie

[Don]

2 hours ago, Metwatch said:

Much more like it with the latest GFS. Low chance of it verifying of course, but the chance is never zero. 

 

That setup has got heat spike potential written all over it!! 

[Guest]

Spot the outlier

[Don]

5 minutes ago, Tidal Wave said:

Spot the outlier

Seen outliers like that a fair few times in recent years and they have actually been correct!!

[ItNeverSnowsInWindsor]

1 hour ago, Don said:

Seen outliers like that a fair few times in recent years and they have actually been correct!!

Heatwave in April sounds better than one in the summer months that’s for sure. Not sure how likely the GFS op is to verify though being at odds with the rest!

[Snowboy111]

Anybody make anything of this little channel low for midnight tomorrow. Showed up on the 12z and now the pub run. Gales for the Channel Islands ?? Moves towards se England for mid morning  

Edited March 24, 2023 by Snowboy111