Model Output Discussion - 05/01/2016 18z onwards

[tight isobar]

When the cold gets in place

(Which looks highly likely) its then worth noting pop up features/disturbance's in the flow when looking for precipitation. 

-4 850hpa will most likely exact snow precip in current modelling. 

And also there "could"be some impressive surface' cold...as things unfold...but again lets see what continues to unfold!

[Geordiesnow]

Far too early to be taking about the details just yet but one thing I do like about the ECM run is that it has trended towards the UKMO of moving the trigger low eastwards quicker therefore the start of any cold actually comes sooner than it forecast previously. 

Still the bug bear of a developing shortwave mind which does affect the output but this particular ECM run does make the most of it. 

The GFS has no issues with the shortwave but its still sticking to its guns of making that trigger low dragging it heels but we do see the potential results of what an actual ridge to Greenland does. 

I'm still skeptical on whether we will see a successful ridge into Greenland but I am getting more confident on something colder on the way for potentially at the end of the weekend(if you believe the UKMO/ECM outputs) and into next week. 

[MR EXTREMES]

Certainly showing signs of 09/10 but I'm still not convinced although the surge and rapid strength in the mjo does show what can happen but I still think the end of Jan Feb perhaps March could be interesting.

it all depends on the strength and position of northern blocking and unfortunately this is always the last part of the jigsaw.

when I see confidence in the more experienced posters of this coming of then I go join knocker in the woodshed with the daffs.

but that's not to say the models are not throwing out some eye candy but all very fickle.

my birthday 15th this month what a birthday it would be to throw snowballs with my kids.

and they to have fondest memories of winter 09/10

and Feb 08 but I've not said anything as I'm unconvinced.

although the ukmo which I prefer over the gfs is showing small signs of a change nw flow northerly but will this topple maybe but extra bites at that cherry they call the vortex might be needed certainly signs it's on the ropes a lot better than the last couple of years.

but I feel end of Jan Feb will be more likely when winter bites back.

 

[bluearmy]

the next 48 hours may tell us a lot about GLOSEA-5's ability to change tack in the face of a marked pattern change. we have previously seen MOGREPS-15 being slow to the party.

of course, the extended eps may be clustering towards a weakening of the cold signal and that could be giving Exeter the confidence to state it wont be long lasting.

[garbagebags]

Sorry if this isn't the right place but I am curious. Does any of the potential forthcoming setup have any Northwesterly elements to it? or is it just North to East flows? Im just asking because a Cold NWerly is best for me (Glasgow) for snow. Usually get nothing from an easterly. And a straight northerly tends to have dried out by the time it gets down this far. although not always. 

[Methuselah]

Okay peeps (I know how easy it is to wander Off/T) but perhaps it's time to wander On/T? 

[nick sussex]

1 minute ago, bluearmy said:

the next 48 hours may tell us a lot about GLOSEA-5's ability to change tack in the face of a marked pattern change. we have previously seen MOGREPS-15 being slow to the party.

of course, the extended eps may be clustering towards a weakening of the cold signal and that could be giving Exeter the confidence to state it wont be long lasting.

I don't remember either picking up the Russian block. Indeed if my memory serves me right they were still going on about no pattern change as NCEP were busy ripping up their January outlook. I'm beginning to wonder whether GLOSEA and MOGREPS even realize the MJO is happening. I find it somewhat bizarre that NCEP have suggested that the NH pattern would be tipped into a neg AO with more HLB due in large part to the MJO but that those UK models seemed reluctant to go with that.

[Trom]

1 hour ago, captaincroc said:

Just a question for the experts.... I know the weather can technically go 'tits up' at any time but at what time scale can we safely say that 'something' is going to happen?  To my untrained eyes I take it that if the Greenland block appears then some sort of cold weather will come (with more specifics nearer the time).

Was just wondering when we can be sure of this pattern change? 

 

Cheers

One way of looking for certainty or at least high probability is to look at how tightly the ensemble members are clustered and at what point they start to diverge significantly.  So look at for example the GFS ensemble charts 850 Temps.  If you do that right now you can observe they are tightly clustered to the 13th of Jan and then start to diverge.  This gives you an idea that the ensembles strongly support the control up to this date.  This therefore tells you that the GFS is fairly confident in the pattern out until the 13th of Jan.  Also you want to look at clustering i.e. what proportion of the ensemble members are tracking down and which appear to be outliers.  Comparing the individual ensemble members to the mean is useful for this.

The next thing to look for is how similar the various models i.e. GFS, ECM etc appear to be.  

When the models diverge and ensembles diverge you will hear people talk on entropy which just means a lot of volatility in the output so hence more uncertainty.  How far into the future you have to go until you see significant divergence varies depending on how the various models and ensembles are handling the current set up.  More consistency basically means more certainty.

[Methuselah]

13 minutes ago, nick sussex said:

I do wish the BBC would stop this anti-cold agenda! Given that colder would equal less moisture and therefore less rain to those areas already flooded.

Comments like " hopefully it won't last long" in relation to cold is always the same story. Hopefully for whom, since when did the BBC become the weather preference mouthpiece for the whole country.

Come the revolution all mild ramping BBC forecasters will be shown the door! I will clone Helen Willets and John Hammond to replace them.

Its winter its supposed to be cold,  also any ALIWBM comments from BBC forecasters will also be met with their P45's! lol

With all due respect, Nick, that's utter nonsense...Come to think it, it's not model-related, either???

[wanzelbin]

29 minutes ago, winterof79 said:

Ditto. -16 inside the Barracks corridor.Breath froze.

When I mentioned in reply to SMs post that we could dream of a link between our Atlantic ridge and the Arctic high, I was thinking further down the line in output not the 06z

Hi

I read lots of the posts on here, year after year, and regularly get caught up in the excitement, but despite having tried going through the nw guides (unfortunately a lot of broken links), wikipedia etc I still struggle to understand the detail of what's going on. 

The terminology is tricky and mostly learnt (probably not correctly) from context - e.g. I think a "ridge" is a line of high pressure while a "trough" is an area of low pressure - but what would be really, really fantastic is if someone could use something like the chart above and explain why it would be so great for there to be a "link between our Atlantic ridge and the Arctic high" as winterof79 says above. Also, why is one called a "ridge", and one termed as a "high"? If these high pressure areas linked, this would increase the potential for cold in the UK? Is this something to do with "blocking"? This seems to be where a high pressure system holds up or directs the movement of a low pressure system, or vice-versa perhaps?

As I understand it, a high pressure area will be pushing air down and out across the earth's surface - if this is in the polar regions, this is especially cold air, which is then sucked up by the moister slightly warmer and lower pressure area over the UK which might provide snow?

Also, the colours on the chart - am I right in thinking this is something to do with DAM - the height above sea level at which pressure is 500 mb? If so, what does the purple spot over the Baltic Sea mean? On the colour chart this would be approx 510. Does that mean the pressure is 500 mb at 510 metres(?) with a surface level pressure of 1005 mb (judging by the numbers on the isobars)? So pressure is reducing quickly as you go up where there is a low DAM value? And that means what?

I'm obviously building assumptions on assumptions, some of which are probably embarrassingly wrong. As I say, I've tried various resources to learn more, but it's very difficult without relevant examples. I hope this is considered acceptable for the modelling forum as it refers to current charts, but it would enormously help a very interested but struggling observer should anyone be able to provide a little insight.

Many thanks

 

[ALL ABOARD]

32 minutes ago, joggs said:

Maybe I fergieweather could she's some light on tge glosea)))) 

Unfortunetly to my understanding Fergie weather will not be posting on here anymore due to reasons of ummm well....

 

Back to the charts and I said when I was watching the 00zs gfs come out, the gfs is pushing more and more heights not only into Greenland but it is building them more into the arctic. This allows the heights to link better with the Greenland heights. This is something i'll be looking for when the 12z starts rolling out.

[karlos1983]

WSI certainly seem more confident about how long the cold stays.

I think I may have to watch the 12z  from behind the sofa.

[johnholmes]

35 minutes ago, nick sussex said:

I don't remember either picking up the Russian block. Indeed if my memory serves me right they were still going on about no pattern change as NCEP were busy ripping up their January outlook. I'm beginning to wonder whether GLOSEA and MOGREPS even realize the MJO is happening. I find it somewhat bizarre that NCEP have suggested that the NH pattern would be tipped into a neg AO with more HLB due in large part to the MJO but that those UK models seemed reluctant to go with that.

You seem to have a very blinkered view of UK Met from your position abroad Nick. I suggest you have a close look at what they use and how on their web page. Get the facts rather than what you think happens. Sorry if it sounds a bit OTT but I like facts not fiction. Of course any model USA, UK, European will get it wrong at times, or rather, perhaps the man part of it will not get their interpretation of the models correctly. It is easy to be critical.

 

[terrier]

If the gfs ukmo and ecm start singing from the same hym sheet in the days ahead I would expect a change from the met. But don't forget they have much more data than us mere mortals. So to expect them to suddenly jump to cold on a few gfs runs is slightly over the top I feel. Let's see if the same is showing by the weekend then maybe just maybe we might be onto something. 

[london and south east kent]

The 12z will be coming out soon I think I'm going to get behind the sofa for this one..

Edited January 6, 2016 by abbie123456

[cornish snow]

18 minutes ago, karlos1983 said:

WSI certainly seem more confident about how long the cold stays.

I think I may have to watch the 12z  from behind the sofa.

Can i ask,what is the WSI? never heard of it.

[El ninyaknow]

1 hour ago, nick sussex said:

I'm wondering whether we're seeing the different MJO forecasts played out here. The ECM is much more bullish about rushing the signal into phase 8, the GEFS is slower and has the signal meandering around just as it enters that phase.

A key feature of the MJO phase 7 composite in positive ENSO is that Arctic high joining forces with the Atlantic ridge. Interestingly reading the NCEP state forecasts a few days back they mentioned the idea of some cross polar blocking.

So looking  you can see circled black the cross polar blocking, and the blue arrow denoting the joining forces of the Atlantic ridge and the Arctic high:

One would think that looking at the dynamical model forecasts that we're about to enter phase 8 which would be a different composite, the GEFS slower to get to that phase however the smoothed out version reducing ENSO interference and Kelvin wave has the MJO only getting into phase 7, bearing in mind the tropospheric timelag MJO response the MJO is only just in this phase and the strongest impact would start showing within the week.

Now this is where it gets a bit more interesting, bear with me!

We know that MJO trop influence is moderated by ENSO and also its impacts effect different parts of the NH to differing degrees, ie some have a greater/lesser impact dependent on what the El Nino is doing.

 

This quote from some excellent research into ENSO/MJO:

Although the global mean amplitudes of geopotential height anomalies associated with the MJO do not appear to vary dramatically with the MJO phase, the nonlinear component of the global flow associated with the MJO and ENSO might be more substantial in some geographical regions than others. Figures 10a–d show the absolute values of the composite geopotential height anomalies averaged over all the MJO phases during declining, cold, warming, and warm ENSO, respectively. During each ENSO phase, except Nin ˜o-3.4 rising, the largest anomalies associated with the MJO occur over the North Atlantic and regions to the immediate east and west. During Nin ˜o-3.4 increasing trends, the strongest composite anomalies occur over the Bering Sea.

You'll see from those maps the MJO still expected to have a strong impact to the west of the UK even with the positive ENSO, indeed over the last few weeks we have seen a small decline in region 3.4, I don't think enough to call it a declining but at least its moving in the right direction.

PS sorry those maps are so small, I've tried to enlarge, circled red is the area just to the west of the UK!

 

 

 

 

I did a little post of the ENSO discussion thread re the decline or lack of forcing over the next month 6 weeks which ties in well with your thoughts..I hope :-) 

[karlos1983]

2 minutes ago, terrier said:

If the gfs ukmo and ecm start singing from the same hym sheet in the days ahead I would expect a change from the met. But don't forget they have much more data than us mere mortals. So to expect them to suddenly jump to cold on a few gfs runs is slightly over the top I feel. Let's see if the same is showing by the weekend then maybe just maybe we might be onto something. 

Well their own model is none to shabby from the 00z output.

Which one would assume could easily go the same way as the GFS as the modelling at that time frame was  almost identical

[Pembroke Dangler]

I'd be very interested if this up coming cold can go as far as to produce a polar low given the fetch of the air from up north it looks like it could have enough instability to produce such features looking at the gfs 12z and 6z after t96

[Liam J]

4 minutes ago, mickpips said:

Well the Met Office are sticking to their guns in using the word 'brief' so they obviously don't see any sustained cold spell on the model output they are observing

Well It was looking quite brief up until the latest runs which have now moved towards a possibly longer period of colder weather, do you expect the Met Office to change public forecasts based on a few model runs in favour of a more extended colder outlook? Hardly solid evidence to base a forecast on IMO and it could all go boobs up, as others have mentioned we've seen things implode well inside reliable time frames before.... The Met obviously have a more grounded approach and will remain cautious with forecast wording until such time the probability of a much colder & possibly prolonged weather type becomes high enough.  If things keep moving in the right direction over the coming days with cross model/ensemble agreement then the wording will change to reflect this, and it will probably be subtle rather than a huge turnaround.  

12z's rolling soon - I don't think I can watch lol... 

[AWD]

I'm going to do something rather daring and post a couple of ens graphs in the model output thead;

A cold spell next week courtesy of mid Atlantic amplification is all but assured.

 

However, you can see why media forecasts are reluctant to call out the lonegativity of such a cold spell as the cluster splits at the end of next week, one maintaining cold, one less so.

 

I suspect though, that the less cold members go down the route of a west based -NAO rather than return to a positive NAO state so even those clusters have the potential of further cold outbreaks towards months end.

Hopefully I'll get away with this rather on topic post, apologies if not mods.

[bryan629]

BRrrrrrrr

Would love this to pan out  

and i swear i havent been using any of these .... lol .

Oh and could someone nip down the woodshed , rescue the fat lady and tell her she`s gonna be needed up front pretty soon . 

Edited January 6, 2016 by bryan629

[Methuselah]

Here you go, folks: Will it snow? Where will it snow? When will it snow?

 

 

[SMU]

Updated AO suite from the 00z 

EPIC a la 2009 & 2010

s

[Shuga ice]

The output observed today show a 3 day spell of mainly dry and bright weather, on the cold side with night frosts.

 Temperatures gradually rising to above average thereafter.