Model output discussion - 20th Feb onwards

[shotski]

34 minutes ago, fergieweather said:

Winter forecasting in the longer medium range/seasonal sense benefits from some areas of greater predictability, e.g. MJO forcing, which becomes indistinct and ultimately of no forecasting value as we move on into the summer, plus various global teleconnections known to have more distinct influence on winter outcome (as we saw very evident this past winter). Clearly however, in terms of forecasting shorter-range SFC conditions, both seasons have a raft of very differing challenges for the UK.

Hi Ian

Hopefully not going off topic but do you see the current SSW as a record breaker as many have commented and do you think the operationals have picked up on it yet ? I assume if it is a big one it will have a major effect somewhere in the Northern hemisphere 

Thanks

shotski

 

 

Edited March 2, 2016 by shotski

[Nouska]

The statistics we are looking at are for the whole of the northern hemisphere - a look at Europe yields a slightly different result - the root mean square error figures are lower in summer than in winter for the years in the archive. 

The data goes back to 2009 here :-      http://apps.ecmwf.int/wmolcdnv/

Last year in more detail.

Jan    July 

 

 

[Johnp]

Could we possibly move all this stats stuff to a dedicated thread and leave this one for the model output?

 

[Man With Beard]

4 hours ago, Man With Beard said:

So model accuracy is actually better in the winter than summer? Or has the zonal nature of the past three winters made it easier for the models?

Thanks for all the very interesting replies, and Knocker I think "strong polar vortex" summed up my thoughts better than "zonal" - anyway, better theories have been mentioned since then!

Back to the here and now, after some minor snow skirmishes today, Friday is sort of coming together on the charts. Certainly areas between Birmingham, Manchester and Sheffield can keep their eyes glued to the output, as agreement is starting to emerge:

and a similar story on the EURO4

http://expert-images.weatheronline.co.uk/daten/proficharts/en/euro4/2016/03/02/basis06/ukuk/prty/16030406_0206.gif

The big unanswered is (1) whether the whole band will drift south during the day intact and (2) will it still be cold enough for snow later?

Later in the GFS 06Z, high pressure continues to sneak in from the SW, warmer in the NW but perhaps still average in the south

But VERY interestingly, a scandi-high later on from the mean chart. Honestly, has anyone ever seen such a strong signal for a Scandi High at T288???

Some of the ens members are true winter classics - even though it isn't winter anymore, some of them have just enough bite to be wintry

Really unusual to see the GEFS do this in latter stages, so can only think something very interesting is about to hit our screens...

 

 

 

 

[Jonan92]

SSW effects showing up in FI

Edited March 2, 2016 by Jonan92

[Summer Sun]

Gradually becoming less cold next week and with high pressure coming into play more for the UK further frosts look likely on this afternoon's GFS its not until the very end things are shown to turn colder as a northerly flow sets-up again

 

 

Edited March 2, 2016 by Summer Sun

[Hull snow]

What is cse effect please

[Jonan92]

Just now, Hull snow said:

What is cse effect please

My mistake sorry CSE = Calentamiento súbito estratosférico = SSW = Sudden Stratospheric Warming

[049balt]

8 minutes ago, Summer Sun said:

Gradually becoming less cold next week and with high pressure coming into play more for the UK further frosts look likely on this afternoon's GFS its not until the very end things are shown to turn colder as a northerly flow sets-up again

 

 

Some nice charts there , lets hope they verify.

[fergieweather]

19 minutes ago, Jonan92 said:

SSW effects showing up in FI

It's possible. For sure, operational models will struggle in resolving that for a period now. The 12z GFS 500hPa pattern does lean towards where latest EC Monthly height anomalies (below) take us in the broadscale story late March. 

Edited March 2, 2016 by fergieweather

[Man With Beard]

Another decent Scandi High after D10 on the GEFS mean, that's two in a row...

[chris55]

This late SSW is certainly keeping the interest going regarding late winter (early spring) weather!

After all, statistically we are more likely to see a white Easter than a white Xmas.

Though in the mid term it looks like high pressure from the south could well be influential in keeping the southern half of the UK at least, relatively settled, and in any sunshine felling warm. 

[feb1991blizzard]

3 hours ago, Man With Beard said:

 

 

 

Really unusual to see the GEFS do this in latter stages, so can only think something very interesting is about to hit our screens...

 

 

 

 

Though not wholly unexpected given some recent strat charts have been showing a chunk of the PV as far south as France, I never subscribe to the view that you cant get severely cold uppers via an Easterly in mid March either, however it is reliant on the last bit of winter / early March setting the building blocks in motion, ie - really really severe frigid cold deep into continental Europe via a Northerly (not a slack one, a direct long fetch one straight from the Arctic), unfortunately this isn't likely so we are now limiting our chances as we need a direct hit to get severe cold, however though you don't need severely cold uppers even at this time to get a dumping, you need continuous heavy snow just the right side of Marginal, I give you Late April 81 as the shining example of all time.

 

Theres a few going between -5c and -10 but these are for N.England but the London ones are the same.

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=234.0399932861328&y=34.86000061035156

[nick sussex]

Two more chances for some snow before theres a likely temporary milder interlude.

Theres Friday with the low pressure and then Sunday into Monday as a shortwave is likely to head south/se from near Iceland.

After that the Azores high is likely to edge ne but I think we'll find the models will start shortening any milder interlude and then we wait to see the full effects of the major SW. The zonal wind reversal looks like one of the strongest  in recent years.

PS Feb1991 makes a good point re easterlies in March. The key thing is where the PV is , if that drops south to the east this can inject some deep cold into any e/ne flow.  The difference being that compared to mid winter you can't rely on a cooling landmass to develop cold pooling to the east so if you're going to get that March easterly you have to have a proper injection of deeper cold.

 

Edited March 2, 2016 by nick sussex

[chris55]

10 minutes ago, nick sussex said:

Two more chances for some snow before theres a likely temporary milder interlude.

Theres Friday with the low pressure and then Sunday into Monday as a shortwave is likely to head south/se from near Iceland.

After that the Azores high is likely to edge ne but I think we'll find the models will start shortening any milder interlude and then we wait to see the full effects of the major SW. The zonal wind reversal looks like one of the strongest  in recent years.

PS Feb1991 makes a good point re easterlies in March. The key thing is where the PV is , if that drops south to the east this can inject some deep cold into any e/ne flow.  The difference being that compared to mid winter you can't rely on a cooling landmass to develop cold pooling to the east so if you're going to get that March easterly you have to have a proper injection of deeper cold.

 

Good summary Nick. Spot on. I concur.

[nick sussex]

9 minutes ago, chris55 said:

Good summary Nick. Spot on. I concur.

Thanks. Its always fun looking back at notable snow events and colder spells during March and how they developed. March is one of those months that can give you some notable extremes from a taste of early summer to mid winter. March 2013 was exceptional and the depth of cold very rare and of course there was that amazing blizzard for the Channel Islands and northern France. That's not on the cards but certainly there could be a lot more interest than for the whole winter.

Edited March 2, 2016 by nick sussex

[bryan629]

10 minutes ago, feb1991blizzard said:

Though not wholly unexpected given some recent strat charts have been showing a chunk of the PV as far south as France, I never subscribe to the view that you cant get severely cold uppers via an Easterly in mid March either, however it is reliant on the last bit of winter / early March setting the building blocks in motion, ie - really really severe frigid cold deep into continental Europe via a Northerly (not a slack one, a direct long fetch one straight from the Arctic), unfortunately this isn't likely so we are now limiting our chances as we need a direct hit to get severe cold, however though you don't need severely cold uppers even at this time to get a dumping, you need continuous heavy snow just the right side of Marginal, I give you Late April 81 as the shining example of all time.

 

Theres a few going between -5c and -10 but these are for N.England but the London ones are the same.

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=234.0399932861328&y=34.86000061035156

FEB... March 23rd 2013  brought minus 10 uppers off the continent , but fair do`s ...headed largely into Scotland.. but these were on the back of a south easterly 

Obviously the pattern probably wont be identical this time around.. and as Cohens blog suggest the `cold blob` over eastern Siberia is expected to advect westwards to Western Siberia ... thats as far as he mentions ... 

However , this chart that Fergie posted above suggests the surface flow coming from a north east quadrant should it verify.. 

Indicates a more than likely chance of tapping into the predicted cold pool piling into western Siberia.  ( it also looks like the extended anomaly chart that NIck F posted this morning ) 

IM not ruling in that this is what i expect to directly evolve... but im definately not ruling it out either... at the moment im sat in the plausible camp.. 

 

[chris55]

It will be interesting to see how far East this little feature running down to the West can get Sunday into Monday!

Fridays front looks like edging quite a bit further east than initially suggested, so if the above follows suite then some parts could well be in the firing line.

 

 

 

[nick sussex]

4 minutes ago, chris55 said:

It will be interesting to see how far East this little feature running down to the West can get Sunday into Monday!

Fridays front looks like edging quite a bit further east than initially suggested, so if the above follows suite then some parts could well be in the firing line.

 

 

 

Its a bit frustrating with the ECM as we don't get the 6 hour intervals so hard to see exactly where the shortwave goes but it looks like it might be heading sse as on the next frame it looks to be close to me here in sw France. Interestingly its associated with some colder uppers to the nw.

[knocker]

15 minutes ago, chris55 said:

It will be interesting to see how far East this little feature running down to the West can get Sunday into Monday!

 

 

0z Monday just south of Cornwall 10002MB  Six hours later western central France coastline 997mb.

[Alexis]

1 hour ago, chris55 said:

 

After all, statistically we are more likely to see a white Easter than a white Christmas.

 

That actually depends where you live! It's actually a complete myth in NW England at least. 

[kumquat]

10 minutes ago, knocker said:

0z Monday just south of Cornwall 10002MB  Six hours later western central France coastline 997mb.

The Azores High really does have it in for us, doesn't it

[chris55]

11 minutes ago, knocker said:

0z Monday just south of Cornwall 10002MB  Six hours later western central France coastline 997mb.

Yes knocker, at present it tracks to far west, but a little to far out to nail track exactly. One to watch, for the next few runs at least.

[chris55]

10 minutes ago, Alexis said:

That actually depends where you live! It's actually a complete myth in NW England at least. 

I guess that's because the NW is more  prone to colder interludes from a PM flow, so in a cold Zonal pattern then intermittent snowfalls are more likely, be that December or late winter/earl spring?.

[snowray]

I like the way the Arpege has it further East, virtually Nationwide snow there.