Model Output Discussion - The Start Of Winter

[Cheshire Freeze]

On the other hand the high pressure belt COULD move ENE and the low COULD swing south (Scandinavian one) and the Atlantic low COULD amalgamate with it to give a very cold flow into the UK?

Yes this looks the most likely scenario in the progression, with a snow event somewhere across the UK around the interaction of the two airmasses. Edited December 16, 2014 by CreweCold

[blizzard81]

On the other hand the high pressure belt COULD move ENE and the low COULD swing south (Scandinavian one) and the Atlantic low COULD amalgamate with it to give a very cold flow into the UK?

All conjecture of course John but I think the ensembles will be very interesting/enlightening this evening. 

Edited December 16, 2014 by Nick L
Duplicates removed

[carinthian]

Evening all, how did this chart 52 years ago today produce the coldest winter of the last century with a almighty cold spell starting 10 days later ?

Funny enough just reading some French ski -resorts have the least snow cover since 1962. I wonder if that is a foresight , especially for Blighty, as to what lies in stall ?

C

Edited December 16, 2014 by carinthian

[virtualsphere]

I know what the NAO is, but I'm sure I'm not alone in having no clue as to what you mean by "west based" NAO and therefore even less of a clue as to how it is bad for cold!

Help in that regard greatly appreciated - thanks in advance!

 

Try http://www.nc-climate.ncsu.edu/climate/patterns/NAO.html

 

Scroll down to "positional effects" - there are some nice charts with examples of how the height anomalies are further east or west based for -NAO.  

[shaky]

Well its just typical in all my years of model watching quite a lot of the times when gfs shows somethings we want the ecm spoils the party and vice versa!! I dunno why thats is but its always been like that!! Maybe its just me that has noticed it!! Bet ecm will look different tomorrow morning though! !!
 

Edited December 16, 2014 by Polar Maritime
Duplicates deleted.

[East_England_Stormchaser91]

All I know is, is that these prospects seem like heaven on earth compared to this time last year. At least there is some opportunity on the table for this Christmas.

Any amplification over new foundland/Greenland is a great help for us seeing some decent cold shots.

[Trom]

Not at all, as the mean is across all ensemble members the standard deviation is lost, now a purely standard deviation of the operational and control would be different and represented as the anomaly charts are would be a good way of seeing an outlier. The mean falls down exactly because of outliers throwing the mean out.

 

I think you may have understood me (or me you).  I meant you could look at an individual member and compare it to the mean to see how many standard deviations is was from the mean to see if it was an outlier.  I appreciate that the mean is an average but surely the further an a particular member lies from the mean the less likely it is to occur or am I miss interpreting what I'm looking at?

[chionomaniac]

The last three days of the GEF anomaly starting at T264 on the 14th. Although there are obvious variations with the detail I would suggest they are variations of a theme. The key features today being the eastern US trough and the NE Canada HP but no indication of change in the overall pattern.

Charts courtesy weatherbell

Thanks for putting those charts up knocker - genuine question, but can you see a trend in those GEFS anomaly charts as the timeframe gets closer ( the trend is more significant than the statement that you make of no overall change in the overall pattern - the charts are for the same time after all so that is expected)? Spotting the trend is important when viewing the anomaly charts. There has been a lot of nonsense written today about using mean charts (and some sense) but the main thing is is that a good forecaster will use all the information at his disposal whether it be mean or anomaly ensemble mixes or looking at the deterministic or control runs. Only when doing this over a period of time will you know which to disclude and which to follow. So, looking at the above charts there is a trend.....

[johnholmes]

a very sensible comment chio-many should take note of what he says

 

There has been a lot of nonsense written today about using mean charts (and some sense) but the main thing is is that a good forecaster will use all the information at his disposal whether it be mean or anomaly ensemble mixes or looking at the deterministic or control runs. Only when doing this over a period of time will you know which to disclude and which to follow. So, looking at the above charts there is a trend.....

[shaky]

Well its just typical in all my years of model watching quite a lot of the times when gfs shows somethings we want the ecm spoils the party and vice versa!! I dunno why thats is but its always been like that!! Maybe its just me that has noticed it!! Bet ecm will look different tomorrow morning though! !!

[nick sussex]

Hi Nick

I know what the NAO is, but I'm sure I'm not alone in having no clue as to what you mean by "west based" NAO and therefore even less of a clue as to how it is bad for cold!

Help in that regard greatly appreciated - thanks in advance!

 A west based negative NAO is not always a disaster but its an accident waiting to happen. You'll see the angle of attack into the UK is close to the weak point of the block, what can often happen is low pressure tracks ne and pressure starts to rise over southern Europe.

 

The coldest air will head sw to the nw of the UK:

 

 

It really depends on how west based it becomes, too far west and you end up with a sw'erly flow.  You'll see if the block was further east that the attack point would be further east aswell. Then the coldest air flows into the UK.

 

I wouldn't get too worried just yet because the models keep chopping and changing, unfortunately if I even get a whiff of a west based negative NAO I tend to go off on one as it's really frustrating.

 

I doubt any model has got a proper handle on things yet so we need a few more days to really see what could be on offer over Christmas.

[Ali1977]

All 51 EC members show a mild Xmas day...great

[Captain Shortwave]

Slightly amused by the op vs ensemble comparisons, as usual the ECM op looks over done which strangely is probably a good thing for us.

Op

Ensemble mean

The US trough is more significant compared to the op so we end up with the Atlantic ridge still present and the possible deep northerly following a couple of days later. The op frankly is a bad run as the high moves too far away and allows the souther arm of the jet to push north east through Europe and bring mild and wet conditions. 

So in my view, a snowy Christmas still looks unlikely, but maybe something wintry after this (though my feeling again is a transient feature of 2-3 days). 

Week 3 though if the second amplification occurs in the Pacific then we may see something more significant develop then.

Edited December 16, 2014 by Captain shortwave

[IDO]

All 51 EC members show a mild Xmas day...great

 

  MattHugo81

Incredibly all 51 EC ENS members between 24th - 26th Dec develop low pressure to the NW with a mild SW'ly and not a hint of cold weather!

16/12/2014 20:30

 

ECM is notorious for op led ensemble bias. It tends to do this when there is uncertainty in the system. I would wait for at least two more runs before I took it at face value (two as it usually backs down in instalments).

[johnholmes]

NoaaNoaa

6-10 and there are v slight changes over the chart, the +ve area in e pacific is not much different from the last 2 days but is from about 4 days ago, as is the +ve now forecast to be over ne coast Canada, before (3-4 days) it was the lakes area

The 8-14 shows similar slight changes with perhaps the trough into the gt lakes still there but with the +ve area now ene of it.

These are only slight changes BUT they may become more significant in 2-3 days time. I remain yet to be convinced of a marked shift in where the major ridges and troughs are likely to be in 6-10 or even 8-14 days time but it might happen, maybe 35-40%. IF it did then the UK would be on the forward side of a cold ridge but for how long 24-48 hours or longer. Utterly impossible to tell at this stage and far too many ifs at the moment even to get a 48h cold nw shot. For sure again IF it does happen it will NOT bring cold weather from the NE but from the NW !

The above is also supported to some extent by the ec-gfs charts over the past couple of runs. They both exhibit a greater degree of split flow, see below for comments

Tue 16dec

Ec-gfs

Both, not quite the same, but both suggest the +ve/ridge development over ne America this morning turning the flow into the trough over/e of the uk a bit n of west, more so on ec

Check later today for closer look

Both continue to show this ‘split’ flow into the trough/ridge set up over/e of the uk, there are differences w of this over n America but not large differences.

See what noaa show tonight?

 

The nearest you will ever get cold lovers to a jh ramp!

links below

ec-gfs

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

noaa

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

Edited December 16, 2014 by johnholmes

[Gavin Hannah]

  MattHugo81

Incredibly all 51 EC ENS members between 24th - 26th Dec develop low pressure to the NW with a mild SW'ly and not a hint of cold weather!

16/12/2014 20:30

 

ECM is notorious for op led ensemble bias. It tends to do this when there is uncertainty in the system. I would wait for at least two more runs before I took it at face value (two as it usually backs down in instalments).

 

 

 

Yup, even with the GFS, a few more runs are needed.  Though that could be why the METO updated the outlook to mild today.  Time to strap in for the pub run tonight and see what we get.

 

From the banter thread...

 

Rumour has it pub run is a belter and will cause many a sleepless nights upon members.

Edited December 16, 2014 by IBringTheHammer

[johnholmes]

Can anyone throw up latest AO and NAO forecasts please cannot seem to paste from NOAA site thanks in advance....

scroll down on the lhs for them and mjo outputs

http://www.cpc.ncep.noaa.gov/index.php

[IDO]

Can anyone throw up latest AO and NAO forecasts please cannot seem to paste from NOAA site thanks in advance....

 

 

 

[Man With Beard]

NOAA 8-14 getting closer to some sort of north Atlantic block, maybe even a Greenie High?

www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

Can't exclude a west based -nao on that, but certainly possible it could be further east

[ukpaul]

De Bilt shows op as being at the warmest end by days nine and ten. 

 

[terrier]

Well normally it seems to be the ECM that leads us all up the cold garden path. But is it the gfs that's taking us that root this evening. Guess we will find out over next few days. But with the met output changing its wording today with a milder outlook. I'm wondering if there glosea model and all there in house data are showing something along the lines of the ECM. Next few days should give us our answer.

[LomondSnowstorm]

I'm not sure I understand how it's possible that every ensemble member has a SWerly flow around Christmas when the mean flow from the Ensembles is northwesterly, with mean upper air temperatures ranging from -2C in the south and -4C to -5C Midlands northwards:

 

 

I doubt there's too many runs in the suite like either of the GFS op runs but that mean chart would definitely put at least a few of us in the hunt for a technical White Christmas.

[knocker]

Thanks for putting those charts up knocker - genuine question, but can you see a trend in those GEFS anomaly charts as the timeframe gets closer ( the trend is more significant than the statement that you make of no overall change in the overall pattern - the charts are for the same time after all so that is expected)? Spotting the trend is important when viewing the anomaly charts. There has been a lot of nonsense written today about using mean charts (and some sense) but the main thing is is that a good forecaster will use all the information at his disposal whether it be mean or anomaly ensemble mixes or looking at the deterministic or control runs. Only when doing this over a period of time will you know which to disclude and which to follow. So, looking at the above charts there is a trend.....

 

The increased ridging of the East European HP and a movement east with the Scandinavian trough?

[Harsh Climate]

When I saw the 12z ECM churn out I thought to myself : you've got no fans, you've got no ground, what a s**thole!!!!!

Sorry couldn't resist.

 

[ukpaul]

MattHugo via twitter also posted the following.

 

https://twitter.com/MattHugo81/status/544957954462863360

 

850s for Central England there are difficult to square with his earlier comment, seems to be a cluster from -4 to -7 by the 26th.