Model Output Discussion - 23rd Jan - 12z onwards

[West is Best]

I continue to be rather cautious with regards to this oncoming cold spell and shall await the Wed/Thurs/Fri snowfall potential to come into range on the Euro4. Synoptically speaking the model output doesn't exactly excite me very much  The relatively tame N,ly appears to be toppled in the medium range around +240 as high pressure will become either centred over the UK or to our SW.

 

What is disappointing is the ECM ensemble mean suggests the PV will regroup over Greenland.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015012512/EDH1-240.GIF?25-0

 

Just to put things into perspective but the chart below is what I would call a screaming N,ly. I wasn't born but according to my mother this produced an amazing snowfall in Peterborough via a polar low.

 

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00119690208.gif

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00219690208.gif

Really useful archive charts, Dave because they remind us of how potent it can be with a block in place as you had there. This northerly might still produce the goods, but I'd love to see a proper block develop out west otherwise it's like scoring at one end but leaking goals at the others. Specifically, the 18z continues to show a very strong and relatively flat jet. We've got to worry that this will pick up Atlantic low pressure systems and in the absence of blocking or amplification … well you know the rest. Fingers crossed though.

[pages]

haven't a clue why people are looking at uppers on charts after 144hr they won't verify. its all about trends and that is looking very good. look at the charts 7am on the 2nd feb, each subsequent run as slighty increased the heights over the southern tip of Greenland and weakened the vortex. With the strat warming its not unrealistic in expecting the trop vortex to continue to weaken. would like to know Ian's thoughts and what GLOSEA5 & mogreps show for week 2.

6z

 

12z

18z

[inghams85]

I don't think this was ever forecast as a true Northerly. What's happened is an extremely cold unstable trough has dropped into North West Europe just to the East of us. It's a highly unusual set up that is potentially very snowy for many areas for 5-7 days

Really useful archive charts, Dave because they remind us of how potent it can be with a block in place as you had there. This northerly might still produce the goods, but I'd love to see a proper block develop out west otherwise it's like scoring at one end but leaking goals at the others. Specifically, the 18z continues to show a very strong and relatively flat jet. We've got to worry that this will pick up Atlantic low pressure systems and in the absence of blocking or amplification … well you know the rest. Fingers crossed though.

[chionomaniac]

I continue to be rather cautious with regards to this oncoming cold spell and shall await the Wed/Thurs/Fri snowfall potential to come into range on the Euro4. Synoptically speaking the model output doesn't exactly excite me very much  The relatively tame N,ly appears to be toppled in the medium range around +240 as high pressure will become either centred over the UK or to our SW.

 

What is disappointing is the ECM ensemble mean suggests the PV will regroup over Greenland.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015012512/EDH1-240.GIF?25-0

 

Just to put things into perspective but the chart below is what I would call a screaming N,ly. I wasn't born but according to my mother this produced an amazing snowfall in Peterborough via a polar low.

 

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00119690208.gif

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00219690208.gif

Funny enough Dave, when looking at that 1969 500hPa chart it isn't too dissimilar to what is showing in the 500hPa forecasts. It is just that when you look at the 850's all the similarities end abruptly.

 

[Hotspur62]

haven't a clue why people are looking at uppers on charts after 144hr they won't verify. its all about trends and that is looking very good. look at the charts 7am on the 2nd feb, each subsequent run as slighty increased the heights over the southern tip of Greenland and weakened the vortex. With the strat warming its not unrealistic in expecting the trop vortex to continue to weaken. would like to know Ian's thoughts and what GLOSEA5 & mogreps show for week 2.

6z

 

12z

18z

And the nice trend to see is the PV splitting. Look at 18z compared to 6z!!.Think the trend today has been a positive one today and the very absence of IF on here is a sign maybe that the Met O have rather a lot on their plate this week lol.Lets hope the foundations are in place and maybe this time next week the UK would have received some widespread snowfall with no margainility.Still a long way to go but all models broadly speaking singing from the same hymn sheet(a cold outlook)

[Jason M]

This looks rather like the chart I was criticised for posting earlier, which oddly, looked itself like a chart from the 06z suite.

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=174&code=10&mode=0&carte=0

Not saying it will happen, but looking at the 18z suite and even the opp, it wouldn't take a great leap really.

Edit: it has some decent support as well.

Edited January 25, 2015 by Jason M

[Vorticity0123]

With the models having been discussed extensively, the general theme for next week (the large-scale synoptic pattern) seems to be modelled pretty consistent, with a 500 hPa trough over western Europe dominating our weather from Wednesday onward. To give a slightly different perspective on next week's forecast, I'll use the MJO (Madden Julian Oscillation) as an indication for the global weather patterns to expect next week.

 

What is the MJO?

 

In short, the MJO is a cyclical pattern of enhanced and suppressed rainfall anomalies over certain regions of the tropics. Usually, this pattern expresses itself as an area of suppressed rainfall trailing behind an area of enhanced rainfall. On average, this pattern circumnavigates the  globe in an eastward direction. However, of course this pattern is also influenced by other atmospheric influence (ENSO, stratosphere to name but a few).

 

Further reading about the MJO can be found in the following links:

 

https://forum.netweather.tv/topic/46153-mjo-rossby-and-kelvin-waves/ (Clear, though slightly technical explanation originating from the Netweather guides)

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/MJO_1page_factsheet.pdf (Easy to understand explanation about the MJO and impacts from NOAA)

 

The MJO can be divided into 8 phases, each having its own general position of precipitation anomalies (while maintaining a same general pattern). Each phase has its influence, via complicated connections, to the weather experienced near the UK. Without going into too much detail, these phases can be reflected in 500 hPa height anomalies over the globe, where certain patterns do exist.

 

Current state of MJO

 

Currently, the MJO resides in phase 7/8, with marginal amplitude (just above 1, see GFS and ECMWF phase forecasts later in this post). This phase is reflected in the tropics as follows:

 

OLR (Outgoing Longwave Radiation) anomalies as analysed as of 24-01-2015

 

For the time being, only consider the top image (the current state of the MJO).

 

To keep it simple, OLR (Outgoing Longwave Radiation) anomalies are a measure of the amount of cloudiness present at a certain region. Negative OLR anomalies coincide with higher than average precipitation amounts, while positive OLR anomalies indicate drier than average conditions.

 

What can be seen is that there is a negative OLR anomaly just to the northeast of Australia (thus higher than average precipitation), while positive OLR anomalies reside to the west of Indonesia (drier conditions than usual).
 

To correlate this to the weather in the UK, I'll use 500 hPa anomaly charts, assuming El Nino conditions, and neglecting possible lack of coupling between the atmosphere and ocean.

 

The current anomaly maps are as follows:

 

Phase 7

 

Phase 8

 

Green colours indicate higher than average heights (usually coincident with ridges) and blue colours indicate lower than average heights (often associated with 500 hPa troughs).

 

As can be seen from the anomalies, phase 7 matches fairly well with the current (weak) western European trough. However, the ridging over the Greenland area is less well visible. Phase 8 seems to be matching the current pattern to no extent at all. This does give some indication that there are other players influencing the current weather as well (think of stratospheric effects mentioned before).

 

MJO forecast

 

The MJO is forecast to weaken in amplitude, up to where its effects are no longer apparent on the weather in the tropics and extratropics. However, in a week time, the MJO seems to be restrengthening back into phase 6 or even 7. This can be seen on the MJO forecast as given by the GFS ensembles:

 

GFS ensemble forecast of the MJO phase for 2 weeks out (yellow lines). The average of the forecasts is given in green.

 

Note how the MJO seems to be restrengthening back toward phase 6 and 7.

The ECMWF ensembles, on the other hand, seem to be less bullish on bringing the MJO back toward phase 6 or 7. Its forecast can be found below":

 

 

ECMWF ensemble forecast of the MJO phase for 2 weeks out (yellow lines). The average of the forecasts is given in green.

 

Considerable uncertainty therefore remains, which has to be taken into account when using the MJO.

 

If the MJO would return to phase 6 or 7, the following 500 hPa anomalies (on average) can be observed:

 

http://www.americanwx.com/raleighwx/MJO/MJO/JanENMJOphase6gt1500mb.gif (Phase 6)

http://www.americanwx.com/raleighwx/MJO/MJO/JanENMJOphase7gt1500mb.gif (Phase 7)

 

The cycle from phase 6 to 7 could best be explained by anomalous Greenland troughing, associated with a stronger than average Azores high (signature of a positive NAO). Thereafter, the low heights near Greenland seem to be moving toward Europe, while the Azores high ridges into the wake of this trough. This is of course a very rough description, but does quite nicely resemble the patterns the models are showing (also of a Greenland trough diving into Europe). Therefore, the general synoptic pattern forecasted does seem to match fairly well with current model output.

 

Conclusion

 

It seems that a reasonable coupling between the MJO and the general pressure anomalies observed at the NH exists. However, this coupling is far from perfect, giving rise to think that other indices may influence the current weather pattern as well. Further ahead, an impressive seems to exist between the MJO and the forecast of the models for a week out. It gives credence to believe that there will be quite a strong coupling between the tropics and the extratropics in a week's time, but uncertainty remains.

 

Sources:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

http://mikeventrice.weebly.com/mjo.html

http://www.wetterzentrale.de/topkarten/fsavneur.html

https://forum.netweather.tv/topic/46153-mjo-rossby-and-kelvin-waves/

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/MJO_1page_factsheet.pdf

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ghazards/

http://www.bom.gov.au/climate/mjo/#tabs=MJO-phase

http://www.americanwx.com/raleighwx/MJO/MJO.html
http://www.ncdc.noaa.gov/teleconnections/enso/indicators/sst.php

Edited January 25, 2015 by Vorticity0123

[Daniel*]

I will sleep happy tonight I may not be in the prime place for snow, there are numerous opportunities for the whole country to join in...trend over the past week was to "buff" the initial toppler 24-48hr to something more lengthy, which is encouraging also 850s have took a hike down. If you are disappointed then you need evaluate where you come from :-) I actually see it to be a rather snowy setup if parameters give the thumbs up. Repetition, oooh 'uppers' are too high well they're really not -4C? It ain't in the league of snowy north but it will do with such cold upper air profile, there's been snow events with -2C 850s in place. Past day 10 I do not think the models have a didgeridoo...tomorrow will be important in firming up regarding Wednesday/Thursday. Exciting times ahead, just enjoy the ride and see where it take us, I do feel some in here have underdone what is being shown but then again it could turn out to be true. I think we will sneak in some upgrades, before the penny drops.

Out to D10 the cold is holding on - big block to the NE 1060mb not where we want it but worth a watch.

Edited January 26, 2015 by Daniel*

[pages]

This looks rather like the chart I was criticised for posting earlier, which oddly, looked itself like a chart from the 06z suite.

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=174&code=10&mode=0&carte=0

Not saying it will happen, but looking at the 18z suite and even the opp, it wouldn't take a great leap really.

yeah definitely possible, the 18z ensembles showing the same trend of the op of slighty better heights towards southern greenland, wouldn't bet against one of tomorrows op runs showing us proper Greenland high around 198-204hr

[Jason M]

yeah definitely possible, the 18z ensembles showing the same trend of the op of slighty better heights towards southern greenland, wouldn't bet against one of tomorrows op runs showing us proper Greenland high around 198-204hr

It's still odds against, and the 18z suite mostly fails to get there, but quite a few of the ptrbs get damn close.

[TEITS]

This looks rather like the chart I was criticised for posting earlier, which oddly, looked itself like a chart from the 06z suite.

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=174&code=10&mode=0&carte=0

Not saying it will happen, but looking at the 18z suite and even the opp, it wouldn't take a great leap really.

Edit: it has some decent support as well.

Well that is encouraging. What I find especially interesting is the timeframe. If this was at +300 then I would dismiss as usual F.I but the period of interest is much earlier. I see at +168 blocking develops over Greenland and the Atlantic is forced underneath this block.

 

http://modeles.meteociel.fr/modeles/gens/runs/2015012518/gens-10-1-168.png

 

Maybe I should stop being so negative and more open minded because this has surprised me somewhat.

[Geordiesnow]

I continue to be rather cautious with regards to this oncoming cold spell and shall await the Wed/Thurs/Fri snowfall potential to come into range on the Euro4. Synoptically speaking the model output doesn't exactly excite me very much  The relatively tame N,ly appears to be toppled in the medium range around +240 as high pressure will become either centred over the UK or to our SW.

 

What is disappointing is the ECM ensemble mean suggests the PV will regroup over Greenland.

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015012512/EDH1-240.GIF?25-0

 

Just to put things into perspective but the chart below is what I would call a screaming N,ly. I wasn't born but according to my mother this produced an amazing snowfall in Peterborough via a polar low.

 

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00119690208.gif

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00219690208.gif

 

Tame Northerly? I know what you mean in terms of the temperatures but because of various factors, the Northerly showing is perhaps not going to be as cold as it probably should be on paper but in terms of the strength of the flow in terms of wind, it looks a strong Northerly too me. 

 

What is dissapointing me is the lack of cold upper air temps(when is the -10hpa going to enter mainland UK!?), we just not getting the trough in the right place so the coldest air is not quite being tapped into, this of course could still change as no doubt the details will keep on changing but obviously it could downgrade further.

 

Still don't like the GFS trend of bring the low to close to us but its not totally out of line with other runs, its got the general idea but the important detail is different. 

 

Hopefully the 00Z runs will give a clearer picture on what may happen after the initial potent blast from the WNW.

[Jason M]

Hi TEITS

The striking thing is that a lot of the others get scarily close to a tipping point IMHO. Just one little nudge and we will be looking at very different charts tommorow.

We can't be that lucky though, can we ;-)

I wonder if mogreps is hinting at this, hence some rather bullish comments today from forecasters.

[Mucka]

ECM London ensembles.

 

 

GFS 18z short ensembles Central England.

 

Edited January 25, 2015 by Mucka

[blizzard81]

haven't a clue why people are looking at uppers on charts after 144hr they won't verify. its all about trends and that is looking very good. look at the charts 7am on the 2nd feb, each subsequent run as slighty increased the heights over the southern tip of Greenland and weakened the vortex. With the strat warming its not unrealistic in expecting the trop vortex to continue to weaken. would like to know Ian's thoughts and what GLOSEA5 & mogreps show for week 2.

6z

12z

18z

What a great post. In addition to this, the GFS has proved far superior to the ECM with regards to the modelling of heights towards Greenland in the medium term. I don't know why but the ECM really struggles with the modelling in that locale and as a result, each op is so different - tonight's 12z being a good example. GFS the one to follow when looking for amplification towards southern Greenland . I cannot stress that enough. Edited January 25, 2015 by blizzard81

[Kentspur]

I know all the main talk is concerning powerful NWly/ Nly flows this coming week

However- correct me if I'm reading these FI charts wrong- and I know these are a way off yet but are these GFS charts suggesting any possibility of a hint of a easterly for the South east?

(From a desperate Kentish man that's been snow starved for 22 months)

#miss them Easterly beasts!#

[Jason M]

I know all the main talk is concerning powerful NWly/ Nly flows this coming week

However- correct me if I'm reading these FI charts wrong- and I know these are a way off yet but are these GFS charts suggesting any possibility of a hint of a easterly for the South east?

(From a desperate Kentish man that's been snow starved for 22 months)

#miss them Easterly beasts!#

Nah, this is an easterly :-)

http://www.meteociel.fr/modeles/gefs_cartes.php?code=10&ech=240&mode=0&carte=0

taken from the ensembles rolling out now.

Edit: still very much a minority solution so worth raising one eyebrow maybe, but nothing more at this stage.

Edited January 25, 2015 by Jason M

[PolarWarsaw]

Well that is encouraging. What I find especially interesting is the timeframe. If this was at +300 then I would dismiss as usual F.I but the period of interest is much earlier. I see at +168 blocking develops over Greenland and the Atlantic is forced underneath this block.

 

http://modeles.meteociel.fr/modeles/gens/runs/2015012518/gens-10-1-168.png

 

Maybe I should stop being so negative and more open minded because this has surprised me somewhat.

 

Nope, can we have you and Steve continuing to be negative please...seems things have gone a little smoother whilst you pair have that mindset. 

 

Cold and windy this week with a chance of snow in all areas, but a larger chance of heavy falls anywhere in Scotland and down western coasts. I wouldn't want to pinpoint too much, but I don't see much in the way of snow chances down to the south coast, so this won't be a nationwide event or one to remember for most IMO, but cold nonetheless. Be interesting to see whether we can try and force any blocking together at all, but I won't hold my breath.

[Catacol]

The NAO may go negative for a short time - however then trending positive again - a cold start to February soon to be replaced by milder conditions

 

You need to go and read Chio's reference to the longest lasting toppler ever. The setup at the end of the week is not sustained by a -NAO profile, but instead by the elongated trough on the siberian side being sustained by the position of the dislodged vortex. Therefore a +NAO is not necessarily the end of the spell in this context providing the vortex keeps the trough digging south over Europe.

 

It would - of course - be better if we did get some Greenland heights building. 

[Mucka]

 

   

 

 

 

GFS not bad either but not as cold as UKMO would be.

 

 

GEM is excellent for coldies and unlike GFS is keen to keep us in a cold pattern.

 

 

So close to a cut off high

 

 

And given how GEM significantly underestimates 850 temps this day 10 chart ain't bad

 

 

 

So other than GFS bringing a relatively early demise to the cold I think this is a very nice set of morning runs. Over to ECM.

Edited January 26, 2015 by Mucka

[offerman]

Let's just enjoy what we can to this shortened upcoming cold interlude. Looks like we could see some wet snow almost anywhere in 3/4 days from Wednesday onward before typical high toppler. I am amazed how good the initial charts look on Wednesday with -10s chasing hard on the heals of -5s but then almost by magic just disappear over the Atlantic. This is the problem for us here as sat in a huge warm bath!!

[Liam J]

GFS not as good this morning with regards to the longevity of the cold spell, I know it's FI but it has too much energy going over the high causing a toppler. Still a good northerly before this happens though! And also the pretty potent W/NW'ly Wed/Thur to look forward to

[winterof79]

ECM has another cold and snowy outcome

 

 

[Liam J]

Unfortunately the ECM is also looking flatter in FI as well with a lot of energy coming out of the eastern states, but not before some bitter weather and a few snow chances

 

 

 

Edited January 26, 2015 by *Sub*Zero*

[chris55]

Mid term trending the wrong way this morning, let's hope that reverses throughout the day! But in the next week plenty to get interested about. Should be a fun week on the regional threads