Model Output Discussion 29th December - Into mid-Winter.

[booferking]

5 minutes ago, Ali1977 said:

Was thinking the same thing, some say 2 weeks some say 4 or more!! Does this depend on SSW strength or positioning or something different . What I do like is that this SSW; if it happens isn't too late on, so if we can Benefit from it it should be when we still have low sun etc...

Yea iv heard people mention 2-3 weeks but i see steve saying 7-10 days or if we are lucky immediate impact on the troposheric which would be nice.

[bobbydog]

18 minutes ago, booferking said:

Hey steve whats the Ave lag time follow a SSW to see the effects on models? Sorry edit that just seen you said 7-10 days after the ssw but maybe the possibilty to see it end of Jan. Cheers

I think (I could be mistaken though) when the vortex is in a weakened state (as it is now) the effects are seen faster. 

It's not looking too healthy right now,

and the forecast is quite toasty up there-

The effects on mean zonal winds are quite dramatic-

February 1991 revisited?.....

 

 

Erm.... can't seem to delete pic of captain Bobby...

Edited January 14, 2017 by bobbydog

[Ali1977]

8 minutes ago, bobbydog said:

I think (I could be mistaken though) when the vortex is in a weakened state (as it is now) the effects are seen faster. 

It's not looking too healthy right now,

and the forecast is quite toasty up there-

The effects on mean zonal winds are quite dramatic-

February 1991 revisited?.....

It would be nice to hear the METO mention it, effects by late Jan and expect some GFS FI eye candy at some point - maybe.

[Barry Reynolds]

HI all, is it unusual to have 100% ensemble agreement for an upcoming SSW?

[Gael_Force]

30 minutes ago, bobbydog said:

February 1991 revisited?.....

You never know... strat temp chart for late Jan '91 looks like a similar placement of the first warming.

[bluearmy]

1 hour ago, johnholmes said:

Browsing the web and came across this

http://www.ecmwf.int/en/forecasts/charts/medium/mean-sea-level-pressure-wind-speed-850-hpa-and-geopotential-500-hpa?time=2017011400,168,2017012100¶meter=Wind 850 and mslp&area=Europe

never seen it before, does anyone use it?

I Use the ens charts re spread john

nick F referenced these a week or so ago

also easy to look back at previous runs 

[Luke Attwood]

1 hour ago, booferking said:

Hey steve whats the Ave lag time follow a SSW to see the effects on models? Sorry edit that just seen you said 7-10 days after the ssw but maybe the possibilty to see it end of Jan. Cheers

Would you mind explaining what this means, is it a good sign for cold?

[Dancerwithwings]

3 minutes ago, Luke Attwood said:

Would you mind explaining what this means, is it a good sign for cold?

https://blog.metoffice.gov.uk/2013/01/08/what-is-a-sudden-stratospheric-warming-ssw/

[Luke Attwood]

3 minutes ago, Dancerwithwings said:

https://blog.metoffice.gov.uk/2013/01/08/what-is-a-sudden-stratospheric-warming-ssw/

OK thanks for that so the outlook is for cold..cold and more cold?

[fat chad]

Hello Luke. My (very) limited knowledge on sudden stratospheric warmings (ssw), is that it turns our mean westerly wind direction to a (negative) easterly wind direction. It makes cold weather more likely, but in no way is it a guarantee for cold over the British Isle's. Let alone a signal for snow. My understanding is that most of our notable wintery spells in the past have happened a couple of weeks after the warming commences. Something to maybe watch, but not to get excited about..... Yet.

Edited January 14, 2017 by fat chad

[Polar Maritime]

3 minutes ago, Luke Attwood said:

OK thanks for that so the outlook is for cold..cold and more cold?

Not always.

Quote

When an SSW brings easterly winds this tends to alter our weather patterns slightly, weakening areas of low pressure and moving our jet stream further south. This leads to high pressure over the North Atlantic, ‘blocking’ that flow of mild Atlantic air and dragging in cold air from the continent to the east. Exactly how cold it might be depends on the details of where the air comes from.

SSWs don’t always result in this outcome – but a cold snap follows more often than not, so the SSW greatly increases the risk of wintry weather.

 

[Buzz]

23 minutes ago, Luke Attwood said:

OK thanks for that so the outlook is for cold..cold and more cold?

As per the text on the linked page:

"SSWs don’t always result in this outcome – but a cold snap follows more often than not, so the SSW greatly increases the risk of wintry weather."

 

So yes, there's a good chance of some cold but it's not set in stone. The "severity" or otherwise of any cold also depends on where it's sourced from.

Edited January 14, 2017 by Buzz

[nick sussex]

Well the GFS 06hrs run continues with previous GFS runs  building a high pressure to the nw. Still not quite enough amplitude upstream to help pull the troughing over Scandi further west but it certainly shows the P word, I won't say it as we've seen this before.

Looking at the GEFS they do overall want to build some high pressure over Canada and a more western based negative NAO, yuk! However its looking like a battle of two high pressures, the weaker lobe to the nw and the main one much further west over Canada. Much depends on any troughing ahead of that and how that sets up.

Very hard to say at this point what solution we'll end up with because of the drop in zonal winds and whether that SSW does land and whether we might see a quick trop response.

I do think we have to start factoring in the MJO, even though there are disagreements there between which forecast you look at. Todays Macritchie one which tries to reduce interference has the signal moving into phase 7 in a couple of days time. The normal ones have a quick move into phase 1. Either ones are acceptable to coldies. The issue of course is how much modification other factors might be having on the MJO but at this point I'd be very dubious of any suggestions of a quick return of the Atlantic and theres still enough  in the ops to keep the thread interested.

Just been looking at the UKMO T168hrs output that looks to support the GFS more than the ECM, it actually is a nice looking chart with some decent amplitude over the ne USA.

I think if the UKMO went further we'd see high pressure pull nw with something similar to the GFS.

 

 

 

 

 

Edited January 14, 2017 by nick sussex

[fat chad]

8 minutes ago, nick sussex said:

Well the GFS 06hrs run continues with previous GFS runs  building a high pressure to the nw. Still not quite enough amplitude upstream to help pull the troughing over Scandi further west but it certainly shows the P word, I won't say it as we've seen this before.

Looking at the GEFS they do overall want to build some high pressure over Canada and a more western based negative NAO, yuk! However its looking like a battle of two high pressures, the weaker lobe to the nw and the main one much further west over Canada. Much depends on any troughing ahead of that and how that sets up.

Very hard to say at this point what solution we'll end up with because of the drop in zonal winds and whether that SSW does land and whether we might see a quick trop response.

I do think we have to start factoring in the MJO, even though there are disagreements there between which forecast you look at. Todays Macritchie one which tries to reduce interference has the signal moving into phase 7 in a couple of days time: The normal ones have a quick move into phase 1. Either ones are acceptable to coldies. The issue of course is how much modification other factors might be having on the MJO but at this point I'd be very dubious of any suggestions of a quick return of the Atlantic and theres still enough  in the ops to keep the thread interested.

 

 

 

Hello Nick, would the timing of the MJO moving into phase 7 effect the end result of the forecast stratospheric warming event that Steve highlighted. For example, entering phase 7 a day before or a day or two after the ssw?

Cheers in advance.

[nick sussex]

9 minutes ago, fat chad said:

Hello Nick, would the timing of the MJO moving into phase 7 effect the end result of the forecast stratospheric warming event that Steve highlighted. For example, entering phase 7 a day before or a day or two after the ssw?

Cheers in advance.

Well if the SSW does happen we're not sure how quick the response might be , SM mentioned a displacement likely rather than a split so the main PV probably moving east towards Siberia and high pressure towards Greenland. Its certainly shouldn't be a hindrance to have the MJO on board and theres some interesting research into the co-relationship between MJO phases as being pre-cursors or lets say possible signposts for that SSW. Interestingly the MacRitchie MJO forecast has the strongest correlation with a SSW, the key pre SSW phases being 6, 7 and 8 which you can see here:

 

Observed connection between stratospheric sudden warmings and the Madden-Julian Oscillation Chaim I. Garfinkel,1 Steven B. Feldstein,2 Darryn W. Waugh,1 Changhyun Yoo,3 and Sukyoung Lee2.

Its an interesting study , the summary conclusion:

] A strong connection has been shown to exist between the Madden-Julian Oscillation (MJO) and the Northern Hemisphere wintertime stratospheric polar vortex. SSWs in the reanalysis record tend to follow certain MJO phases, likely because the MJO influences the region in the North Pacific most strongly associated with tropospheric planetary wave driving. Similarly, the strength of the polar vortex is significantly modulated by particular MJO phases at speci- fied lags, and the magnitude of the influence of the MJO on the polar vortex (4 K) is comparable to that associated with the Quasi-Biennial Oscillation and El Niño.

At the moment we don't have a strong amplitude MJO but the research doesn't specify how important that is only that those 3 phases occur consecutively and within a certain time period before the SSW.

Sorry I'm rambling, whats new! lol
 

[fat chad]

3 minutes ago, nick sussex said:

Sorry I'm rambling, whats new! lol

Thanks Nick.. Your ramblings on the most part are informative, so thank you.

I find it truly fascinating how the weather around the other side of the globe can effect out small part of it.

[Nick F]

If anyone thinks GFS is top dog of the models, perhaps think again:

Although the ECMWF may have been too keen on easterly for the UK, an easterly is still going to happen, just a lot further south. Remember GFS was slower than ECMWF to cotton on to the blocked pattern we are now entering, preferring the much flatter and more zonal pattern across Atlantic and UK, before backtracking.

Be interesting which model comes out top with a rather complex trop pattern evolving over the coming few weeks .. couple that with a warming stratosphere setting up for possible SSW late Jan/early Feb.

However, there is the chance that the warming may level off like it did in late Nov/early Dec - so we may need a second warming to break the PV.

However, in the mean time, the MJO is probably driving blocky pattern for the rest of January, it's just where the block sets up which is causing problems for forecasting the medium range for now, the models perhaps again not factoring in the correct MJO signal?

Realtime and CFS forecasts suggest the MJO will be motoring through 6/7/8/1

[Faronstream]

The cold winners for mid next week is clearly the central and eastern parts of europe, in scandinavia and western europé there are very lame temperatures and somewhat mild for the season . We have to wait at least 1 1/2 week before we can get any decent cold with snow, the only hope now that i can see is from the ECM in FI

[nick sussex]

6 minutes ago, Faronstream said:

The cold winners for mid next week is clearly the central and eastern parts of europe, in scandinavia and western europé there are very lame temperatures and somewhat mild for the season . We have to wait at least 1 1/2 week before we can get any decent cold with snow, the only hope now that i can see is from the ECM in FI

You're assuming the ECM will verify and given other factors theres a lot going on behind the scene which could effect that. And NCEP factored in less of the ECM and its ensembles upstream in their medium term discussion. Theres a lot of uncertainty past a week and I doubt any of the ops have the correct solution at this stage.

Edited January 14, 2017 by nick sussex

[snowangel32]

Hi I don't know much about the strat implications or a SSW but current models show the PV migrating to siberia and leaving Greenland wide open for High pressure to form. Wouldn't a SSW risk pushing the PV back to Greenland and stopping any potential future retrogression in that area. 

[Faronstream]

10 minutes ago, nick sussex said:

You're assuming the ECM will verify and given other factors theres a lot going on behind the scene which could effect that. And NCEP factored in less of the ECM and its ensembles upstream in their medium term discussion. Theres a lot of uncertainty past a week and I doubt any of the ops have the correct solution at this stage.

What? I said " the only hope i can see now" so i am very uncertain about the high pressure over north atlantic at 240hours, what i mean is that the situation feels more or less hopeless

[JeffC]

3 hours ago, bobbydog said:

I think (I could be mistaken though) when the vortex is in a weakened state (as it is now) the effects are seen faster. 

It's not looking too healthy right now,

 

https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=-0.92,87.32,327/loc=-7.795,42.191 shows a really good visualisation of it

[Nick F]

A frustrating 12z GFS op, SW-NE aligned upper trough moving out across NW Atlantic is just very slow moving - so ends up with areas of low pressure sliding NE on the forward side of the trough towards Iceland which prevent the bitter cold up over Norwegian Sea and Svalbard sinking south and draws in milder Atlantic air toward UK eventually.

Really need to see that upper trough digging a lot further south over the Atlantic with a negative tilt, like 00z EC, rather than positive tile laike 12z GFS.

[karyo]

The 12z gfs is rather frustrating. The pattern is similar to the 6z but with less amplification.

The high makes an attempt to ridge northwards but fails and the northerly doesn't happen.

[StretfordEnd1996]

 

Thankfully this iffy looking chart is well after the reliable timeframe and I am hoping this doesn't come off any time soon! 

 

But on face value it's not the most exciting GFS12z I have seen which fails to bring anything significant to our shores after the high pressure over us next week - at least we can maybe get some frosts out of this. 

 

What is nice to know is we are not even half way through the Winter yet and we have plenty of time to get things going again soon, I am thinking that hopefully give it a week or 10 days or so and some eye candy will be propping up again within the charts. 

 

As well as this we have to remember it's a hugely uncertain outlook after 7-8 days or so anyway.