Model Output Discussion 1st January 2014-06z onwards.

[Summer Sun]

Precipitation chart till Jan 20th based on GFS shows an improving picture with rainfall easing significantly

 

[Mucka]

I guess that is when a little experience comes in handy as well. I would say that when the ensemble trends in the same direction that the MJO, GWO and strat data point to then one will have a far better chance of picking out that needle in a haystack. Also you will have a far better chance of picking a trend looking at all of the ensembles over all the output over a number of runs, rather than just looking at the deterministic runs. I guess that you are trying to say that the ensembles can occasionally lead you up a garden path, but more often than not they will spot a trend especially if one looks at the cumulative anomalies set over a number of days.

 

Yup, where there is divergence between the Op and ensembles and deciding which to put more faith in - it's all about trends . Has the Op trended away from the ensembles or are the ensembles trending away from the Op? Ideally the ensembles will pretty much back the Op but when they don't the trend is your friend.

Edited January 4, 2014 by Mucka

[Summer Sun]

12z GFS ensembles show rainfall easing significantly after a very wet spell over the past 4 weeks or so

 

 

The 850's don't look too far away from average

Edited January 4, 2014 by Summer Sun

[Ukwoody]

no its not an old wives tail .if we are in a cold pattern say high pressure somewhere to our north and its mainly dry what happens is low pressure exiting the states moves across the atlantic and can bring snow if it moves close to the uk ,but it does not happen very often ,you need the right weather patterns especially the jet aligned right .Im feeling a bit more upbeat tonight lets hope something is a lurking out there perhaps at day 10/11 .cheers .just would add that i meant weather system rather than any wintry element making it across the atlantic ,cheers .

Ahh, ok many thanks!

[LomondSnowstorm]

I guess that is when a little experience comes in handy as well. I would say that when the ensemble trends in the same direction that the MJO, GWO and strat data point to then one will have a far better chance of picking out that needle in a haystack. Also you will have a far better chance of picking a trend looking at all of the ensembles over all the output over a number of runs, rather than just looking at the deterministic runs. I guess that you are trying to say that the ensembles can occasionally lead you up a garden path, but more often than not they will spot a trend especially if one looks at the cumulative anomalies set over a number of days.

 

I think as with anything in science it's always helpful to understand why something's happening - if you can find a plausible driver for the synoptics modelled (or in this case multiple drivers) alongside good model agreement then confidence in that outcome occuring is obviously much greater than just with the latter alone. It still looks like possibly quite a long haul to deep cold (if indeed we ever get there) most likely 10-15+ days out, but I'd like to think that those of us who are pointing to the increased number of colder and more blocked runs in the ensembles are doing so out of a bit more than just optimism (although there's always going to be at least a bit of that when it comes to snow and netweather).

[BlueHedgehog074]

Even though the block on the 12Z ECMWF run may not be in the most favourable place for wintry weather for the cold and snow fans (although I agree with Nick that the High Pressure outlook near the end of that run will be good news for those fed up of all the rainy weather), one aspect I have noticed about the ECMWF run is that the pattern at around 240 hours doesn't look very flat at all with a great deal of amplification to the flow - looks very zig-zagged with that amplified High to our West along with that High to our East. As such, would probably mean seeing a quick return to a flat, Westerly flow seems unlikely (though with the models trying to get a hang of the possible pattern change, then it wouldn't be too surprising to see many more changes, plus that outlook on the ECMWF run is in Fantasy Island anyway. I agree with some of the other posts, however, that more Lows/troughing could do with being thrown South-East without that Polar Vortex trying to become too much of a monster to the North-West to help increase the chances of Low Pressure systems, or shortwaves, undercutting any High Pressure over us and/or to our East. Otherwise, I think someone did suggest that possibility of relying on amplification to our West to perhaps help deliver a potent North-Westerly or Northerly wind, should a possible block to our East not deliver. But even then, the snow fans may just have to wait for that 'second bite of the cherry' to see some snowy weather.

It does, at least, still look like that the weather could become a bit more chilled out, probably most especially over Southern areas, with High Pressure trying to become a bit more influential to the South and help to dry things out a little.

[weather eater]

I guess that is when a little experience comes in handy as well. I would say that when the ensemble trends in the same direction that the MJO, GWO and strat data point to then one will have a far better chance of picking out that needle in a haystack. Also you will have a far better chance of picking a trend looking at all of the ensembles over all the output over a number of runs, rather than just looking at the deterministic runs. I guess that you are trying to say that the ensembles can occasionally lead you up a garden path, but more often than not they will spot a trend especially if one looks at the cumulative anomalies set over a number of days.

Thanks for the reply C, however, my experience on NW is that not many if any, have that experience, it is relatively easy to spot a trend but unfortunately the trends tend to come and go for the reasons I gave and on NW rather a lot of people call a trend when it is no such thing, frequently or more likely usually there may’ be more than one, how often do we see a few cold perturbations in an ensemble set called a trend while ignoring the bulk that are not, no wonder people get confused.

In simple terms, if the deterministic runs start to trend so will the ensembles for pretty obvious mathematical reasons, good run to run continuity in the starting data, of course they may well produce different synoptics and its often at this point that people start to pick up on a perceived trend in the ensembles, you get situations where the deterministic runs are trending zonal for example and the ensembles may show a clear trend for blocked, frequently there is a trend for both in the ensembles, although on NW the zonal will be ignored in favour of the blocked (if it’s a cold one) every time,

However, If the deterministic runs start to fluctuate then so will the ensembles, they must do because they are tweaks based on the same initial data, we often see this, when the threshold of FI is short and the deterministic runs start to produce big variations at short range the ensembles follow suit and you start to get a large scatter very early, it happens all the time. Now that’s not happening at the moment we actually have fairly good continuity out to 144hrs or there about, although it hasn’t stopped it being suggested that the models are fluctuating a lot at the moment, that often happens in winter when signs of a cold spell are not really appearing.

Edited January 4, 2014 by weather eater

[lassie23]

GFS still not interested in any worth while blocking. ECMWF, now that is starting to look promising.

[Ali1977]

What time to the ECM Ens come out anyone?

[Methuselah]

Hi all, forgive my total lack of knowledge here, but just wondering about the Ice storm hitting NY and Canada. What is the possibility of that weather coming our way - even as more rain? Doesn't it often follow that what they get we get a week later - or is that an old wives tale??

 

Many thanks, Woody

Afraid so, Woody...With very few exceptions, the UK's cold, snowy weather comes from anywhere between NW through NE and sometimes SE...But timings can sometimes lead to confusion...

[Frosty.]

Best news today is the MOGREPS increasingly cold signal and there continues to be plenty of cold and wintry solutions sprinkled throughout the GEFS 12z perturbations, some real corkers here and the 12z mean is still trending colder, especially later in the run. The way I currently see it, we are heading towards either a cold and unsettled outlook with lows sliding down from the north west with trough disruption occuring and the jet digging well south or we will see height rises to the east / north east with a scandi high and increasingly cold continental flow which would bring lots of sharp frosts and a growing chance of snow..I think there is growing evidence supporting a colder outlook with snow potential.

Edited January 4, 2014 by Frosty.

[Summer Sun]

The ECM ensemble isn't keen on building high pressure over the UK as per the Op run

 

[legritter]

Best news today is the MOGREPS increasingly cold signal and there continues to be plenty of cold and wintry solutions sprinkled throughout the GEFS 12z perturbations, some real corkers here and the 12z mean is still trending colder, especially later in the run. The way I currently see it, we are heading towards either a cold and unsettled outlook with lows sliding down from the north west with trough disruption occuring and the jet digging well south or we will see height rises to the east / north east with a scandi high and increasingly cold continental flow which would bring lots of sharp frosts and a growing chance of snow..I think there is growing evidence supporting a colder outlook with snow potential.

Dear Frosty ,i will hold you to this ,yes some good looking charts at longer range ,lets hope tomorrow continues as today ends ,

[Gibby]

Good evening. Here is the report on the midday outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Saturday January 4th 2013 lifted from my website http://www.norton-radstockweather.co.uk/Model-Analysis(2859336).htm

 

All models show a brief respite from recent rains overnight as today's rain finally clears Eastern and Central parts this evening. Tomorrow then shows a freshening SW flow again ahead of troughs of Low pressure returning rain to all areas through the day, heavy at times. Winds will also become strong again with gales in exposure but less problematical than recently. Following the troughs the parent Low moves gently NE towards an area North of Scotland between Monday and Wednesday filling as it does. All areas can expect showers or further rain at times with decreasing winds and temperatures close to average.

 

GFS then shows the second half of next week with troughs continuing to move West to east across the UK in lighter winds than of late but with still sufficient energy to hinder any drying up of recent flood waters. Through the second week a more definitive period of dry weather develops as High pressure forms close to the NE of Britain, sinking South later. Dry and frosty weather would develop for most before a deterioration in conditions creeps down from the North through the final days of the run.

 

UKMO tonight shows High pressure over France with a WSW flow over the UK with troughs moving slowly East in the flow carrying some rain for all in average temperatures. the heaviest rain will be more confined towards the NW.

 

GEM tonight shows the unsettled embers of the recent wet period finally dying next weekend as High pressure develops over the UK with frost and fog becoming much more likely over the UK rather than wind and rain, at least for a time.

 

NAVGEM shows a continuation of at least some Atlantic influence into next weekend as slow moving fronts cross the UK giving rain for quite a time as they go.

 

ECM tonight continues this morning's theme of gradually drier and brighter conditions developing from next weekend as Low pressure gives way to High pressure shown tonight close to or over Southern Britain. No doubt frost and fog at night would be commonplace with fine and bright days to compensate in temperatures by day being close to average outside of any persistent fog patches.

 

The ECM 10 Day Mean Chart tonight shows Low pressure biased between the members to be most likely to be in the vicinity of Iceland and Southern Greenland and High or higher pressure equally biased towards the Azores to France and Central Europe. This would favour a clamer spell of quiet weather with light winds and these most likely from a SW direction more than anywhere else.

 

http://www.wetterzentrale.de/pics/Reem2401.gif

 

The GFS Ensembles tonight show a continuation of rather changeable conditions over the extended period with more than a hint of an Atlantic influence still though rainfall will be greatly suppressed on recent levels with less gales likely too. Temperatures continue to look very average for January due to High pressure located towards the South or SW of the UK.

 

The Jet Stream continues to blow West to East across the Atlantic towards Southern Britain and France for a while longer. From later next week it disrupts more with a trend to drift it further North over the Atlantic before turning SE down over or just to the East of the UK later in the run.

 

In Summary tonight the trend towards drier and fine weather continues as High pressure develops closer to the UK finally ending or reducing the effects of the recent monsoon like rainfall as any Low pressure troughs become much weaker or steered much further towards the North and NW of the UK. How long such an improvement lasts remains an open question but to my eyes with the Jet flow riding over the top of developing High pressure it would appear that the High pressure areas could well eventually sink away South.

[Nick F]

Anyway, back to this evening's models ...

 

Certainly the ECM op is keen on a big pattern change to more 'blocked' pattern near the UK by 8-10 days, though there doesn't appear to be overwhelming support from the ENS for colder conditions looking at the 12z EPS meteogram for Reading nor the De Bilt, with the op at colder end for 2m temp:

 

 

There is fairly good confidence from all NWP output of a ridge building north into Scandi area at the end of this coming week/next weekend ... but it remains to be seen whether the ridge will hold like the ECM op or gives way to more troughing pushing east from the Canadian vortex as per GFS.

Edited January 4, 2014 by Nick F

[SMU]

In an attempt to discuss the models

 

this is what will hold our high in situ for longer- The energy & subsequent small shortwave at 120 aiming into the high on the Euro heads directly into the block in a NE direction.

 

where as the JMA has it going directly North- this is what we want!

 

Look at that acute angle-

 

 

S

[Cakie]

Hi guys and girls. I'm as excited as any of you but can we keep this about the model descussions. Ramping thread is here

http://forum.netweather.tv/topic/78466-the-winter-201314-ramping-thread/page-4

Or there is always banter, where anything goes (within reason)

[bluearmy]

ecm extended ens show some continuity with the 00z run but are less blocked to the north (further ne). hence, although heights drop over europe again, (gefs has strong iberian low anomoly later on), the battleground between the atlantic and ridging to our northeast has pushed through the uk.  the jet off the eastern seaboard at day 15 looks very strong again and there is less inclination for it to split as it crosses the atlantic. this run says that once we get through week 2, there may well be a return of strong atlantic jet and associated depressions. if true, we would need to have blocking established thus the jet is deflected se (or splits). not showing on this run though. its important not to draw too many certainties from any particular run so its good to see the general trend from the 00z ecm ens continue with blocking to the ene and euro heights dropping. this, in tandem with the latter stages of the gefs is a positive for coldies to take into tomorrow.

Edited January 4, 2014 by bluearmy

[R.P. McMurphy]

Any model that shows cold and snow is good enough for me, be it the boom..bom, jam..jma

 

I remain positive for a cold further outlook with an end to this stormy autumnal weather arriving soon.

 

Yep.

 

Looking at the models I can see cold developing middle of January and this will last well into April i would think,... With snow for the majority of places. the CFS clearly shows this, as does the GFS with support from every other model. I would think many ice days to come with the Atlantic completely shut down.

 

Fun times ahead. 1987 looks a certaintly.

[draztik]

ecm extended ens show some continuity with the 00z run but are less blocked to the north (further ne). hence, although heights drop over europe again, (gefs has strong iberian low anomoly later on), the battleground between the atlantic and ridging to our northeast has pushed through the uk.  the jet off the eastern seaboard at day 15 looks very strong again and we less inclination for it to split as it crosses the atlantic. this run says that once we get through week 2, there may well be a return of strong atlantic jet and associated depressions. if true, we would need to have blocking established thus the jet is deflected se (or splits). not showing on this run though. its important not to draw too many certainties from any particular run so its good to see the general trend from the 00z ecm ens continue with blocking to the ene and euro heights dropping. this, in tandem with the latter stages of the gefs is a positive for coldies to take into tomorrow.

 

have a similar view as BA re ext ensembles tonight, thought id add the Mean Pressure Anomaly for consideration (day 15).

[Methuselah]

Yep.

 

Looking at the models I can see cold developing middle of January and this will last well into April i would think,... With snow for the majority of places. the CFS clearly shows this, as does the GFS with support from every other model. I would think many ice days to come with the Atlantic completely shut down.

 

Fun times ahead. 1987 looks a certaintly.

Of dear, Glenn...That's blown it!

[Mucka]

Another small adjustment South and West so far which is what we want as the trend of course

 

[The Eagle]

A big positive of the next 7 days is the flood of cold air in to Scandinavia and the Baltics at long last. All models agree on this.

 

Overall i'm happy with the trend. I'd just like to see a bit more energy in to the continent to lower those heights which is our one stumbling block. 

[Geordiesnow]

At least next week does look quite a bit drier, after Sunday's rain, we get into a showery SW'ly flow turning into a more westerly flow but thankfully no real rainbelts during next week. 

 

Hopefully we will see something more colder eventually but theres no real signs of any significant colder heading our way at this stage but there is potential in the output for sure 

[Nick F]

Looking at the 18z so far, GFS still hellbent on merging the NE Canadian and Barents H500 cold pools/vortices into one large H500 cold pool to our NW/N/NE. Not great to watch.

 

Still, looks chilly though.

Edited January 4, 2014 by Nick F