Model Output Discussion 18z 30/09/15

[knocker]

I see potential in the evening ECM; far from a horror show, the lack of zonality this Autumn is perplexing. Who really cares if we do not have cold air in the short to medium term for any real cold synoptic of value we must look further out.

T168

image.jpg

 

I agree.....end of Feb. would be nice.

[legritter]

Well model output as just got very interesting ,and i,m sure its going to get a whole lot more interesting .

I think the 8/10 day period could go any way but it looks like an area of high pressure will be very critical as to what weather we get at the surface but my glass is certainly half full with current charts ,news worthy weather i think somewhere in europe as if as i expect our low next week could slip south  east but no guarantee .

[Man With Beard]

That T240 ECM has potential (hasn't it always...) - keep the Scandi HP in place for 7 days and we'll be in the freezer

[Newberryone]

Hello Everyone! Its quite clear from the Ecm And Gfs  that the theme is for an Atlantic Domination....! At T+240 take the captions below with a tanker load of salt! The Atlantic and jet stream is winding up now , so it looks like a turbulent and angry   end to the month, but  the   will be in the Detail!

Yes indeed, and while admittedly the block is proving quite a resilient feature, judging by these two charts it would appear, as is often the case with these setups, that Ireland will feel the wind of change more than anyone else.Still, the GEFS calling for a relaxation of the trough post day 11, as highlighted by knocker, may suggest a return to something less palatable for those seeking action weather..long term!!

PS  Amazed Frosty didn't come out of hibernation owing to ECM's false dawn yesterday.  WISE MAN!!   

[solarcycle]

I agree.....end of Feb. would be nice.

 

Completely possible in your neck of the woods. 

[knocker]

The ext ecm tonight is looking at the usual tale of trough to the NW and block to the NE with perhaps everything slipping slightly east by the end of the period. Still there is much potential flowering between now and then.

[Mucka]

This in not directly a response to John because he didn't quote me in his post but I feel he was talking about me so for the record I do not have a negative opinion of anomaly charts and have never intimated such. I have only ever said they are not so useful when used in isolation as a forecasting tool because just like the 500mb charts they change with every run, it is just that those changes are not so dramatic because we are seeing a mean average - that is both their strength and weakness.

 

I have not read anyone talk down anomaly charts in the way John describes so feel a response is required for balance.

 

The idea that the anomaly charts got the upper air pattern correct for the upcoming 5-9 day day period is of course unproven, we will have to wait and see.

 

Let's take the example of what was being discussed on 16 Oct re GFS anomaly charts.

 

Back on Oct 16 GFS anomaly charts were showing this (on the left) for period 25Oct 30Oct very weak negative anomaly over Greenland no positive height anomaly through Scandinavia. The image on the right is what they show this evening much deeper trough further South and positive height anomalies through Scandinavia. They can't both be right can they? Only if you are speaking in such general terms it is meaningless as a forecast.

 

 

Back then (16 Oct) I posted the following in relation to those anomaly charts; (on the left)

 

Yes we are starting to see how the potential breakdown will develop more clearly now in the last week of October.

The strongest signal is for a trough to drop into the Atlantic and heights build through the continent into Russia with possible Russian/Scandinavian high forming a block.

How far West that block can get (Or how far east the trough develops) will determine whether we get a lot of rain or very little, it seems an either is possible at the moment.

We could find ourselves in a long fetch S/SW draw for a while which would be very mild but we could also see ourselves under a cooler, drier continental influence.

 

I expect the anomaly charts will begin to reflect this pattern and we will get a better idea how far West any block will be.

 

Naturally there are other variations and anything is still possible so far out but this seems to be the theme that is emerging for the 10-14 day range.

 

In a second post I clarified that I expected the trough to be further South and deeper and there to be strong positive height anomalies through Scandinavia/Russia.

 

I think that was a reasonable assessment of where we were and how the anomalies may change.

The trough may be further West than I imagined and the trough not as far South but the anomaly charts have headed toward that from where they were and while GFS has come up with some flatter patterns which would be more in line with the original anomaly chart for the period other models show a deeper trough and better ridgng through Scandinavia.

Of course I could of called it wrong as well and still may be wrong if the pattern turns out flatter with a shallower trough and no positive heights anomalies through Scandinavia/Russia but that is the point, we need use all the tools at our disposal and not be afraid of calling something that isn't necessarily shown.

Regardless, if we slavishly follow anomaly charts or operational runs and pretend they don't change their output from day to day for the same period (and even take in all the information) we will be wrong sometimes, that's the nature of the beast - or is that the beast of nature?

 

My sentiment is that anomaly charts just like our pressure charts change with time. They are useful for gauging reliability of Op runs and determining probability of outcome but they are not so good at telling us the trend because they are snapshot in time of a mean average.

Just as with a still photo of a ball in mid air, we can not know its trajectory, whether it is rising or falling, and where it may land. We have to see how that predicted pressure anomaly has come about to get the movie rather than the still shot of a single frame.

We can discern what maybe noise and muting the signal in the mean anomalies and thus get a clearer picture - it just may be the wrong picture if we filter the wrong information out.   

 

I'm not saying there is a right way and a wrong way to make forecasts at 10+ days, just that we shouldn't pretend any particular way is accurate.

As I say anomaly charts are great for probability forecasting and testing how operational runs stack up but they are just a more pure but filtered way of looking at the same data we can see in the ensembles.

 

Here is a freeze frame of tonight's GFS 18z op anomaly within that time period pretty much matching what I said a few days ago but of course the actual mean anomaly charts for the whole period will not look like that tonight yet if GFS 18z is near they will look a lot more like this than the forecast anomaly charts of 16 Oct and that is the point - the anomaly for the period hasn't verified so why are we talking as if it were an open and shut case? 

 

 

 

 

 

I actually don't disagree with most of what John is saying but felt there was abit of a false reality creeping in and the need to reiterate where I stand.

 

When I make suggestions of how the pressure patterns may differ from the anomaly charts at that time, which is actually not very often, they are just that, suggestions.

I'm not saying anything about the accuracy of anomaly charts or my suggestion and let's face it, I covered all the houses in that post anyway and I'm still non the wiser 4 days later! 

Edited October 21, 2015 by Mucka

[winterof79]

GFS at 144z takes some energy north of the UK which inhibits high pressure development there.

Ukmo does not.So if GFS has it wrong then analising the rest of the run is fruitless.

Edit.

ECM going with UKMO regarding not splitting the energy which is my preferred outcome going forward

Edited October 22, 2015 by winterof79

[IDO]

Looks like we have some parity with respect to the early next week storm from the models with the LP system stalling around the west of the UK and taking 3-4 days to fill in situ. The three main models:

 

  

 

So the further west the higher rain totals as it is currently being modelled: 

 

We have the cold front clearing east Friday into Saturday bringing some rain, before the rain associated with the LP system comes in on Monday.

 

The latest means from the top three at D10 are consistent with the long wave pattern (subtle variations that can be attributed to known bias):

 

   

 

These tie in with last weekend GEFS means for that time period, so little change in the medium term. Looking further ahead into the realm of true FI and at D16 there is still no pronounced signal for a classic Atlantic onslaught. The latest CFS weeklies for the first half of November tie in with the continuation of the Azores High staying rigid and feeding positive heights into our E/NE:

 

 

Not a bad outlook compared to some recent years.

 

 

 

 

[mountain shadow]

A good summary IDO. The large Scandinavian anti cyclone catches the eye in the extended period this morning.

If it stays in situ for a while, and I see no reason why it shouldn't, it may bring some early below average temperatures into the near continent.

Should it hang around for another three weeks or so, then Nov 2009 looms in my mind.

[knocker]

The GEFS 6-10 anomaly continues with the trough to the NW, HP away down in the SW giving a zonal westerly flow with any dodgy weather more prone to the northern half of the UK. The 11-15 also continues the retreat of the trough to the Greenland/Iceland area so the zonal flow is more influenced by the HP pushing up from the south. With the ridging being maintained Scandinavia there are no apparent signs of anything nefarious lurking in the woodshed.

http://www.tropicaltidbits.com/

 

[Singularity]

The last two GFS runs are parodies of Nov 2009, though with blocking to the NE becoming more influential in the 12-16 day period than was seen that month.

 

In the shorter term, there's emerging evidence in the N. Atlantic of what happens when you take cold Arctic air across some anomalously cold waters and bring it up against subtropical air that's been basking over anomalously warm waters... phenomenal baroclinic instability and Atlantic storms going kaboom.

 

Despite this, we have signs of jet amplification capable of being the catalyst for a classic step-by-step retrogression of blocking to our NE closer to our shores. If that transpires, the shape of the block will be a major determining factor for how chilly it gets; a block that kind of 'sags' south at any point - as seen in the GFS 00z det. run +240 to +336 hours - will take cold continental air sourced from NE Russia down close to the eastern Med. before it turns west and heads our way. That modifies the air substantially both at the 850 hPa and surface levels so it wouldn't be any use for wintry weather over here.

 

Get more of a straight west-east under the high and the cold air can move west more rapidly and without travelling as far south. The 18z GFS det. yesterday was closer to this but still far from ideal:

 

 

With the ECM 00z det. the draw of cold air is impressive but the shape of the high is not. Too far ahead and too uncertain to be worried about at this stage of course - for all we know the dramatic airmass contrasts going on in the North Atlantic will blow the blocking away. As much as it seems strange to think that the models could 'miss' such a thing at the longer range, the models are notorious for 'carrot-dangling', which I gather is most likely a product of making too many assumptions about the atmosphere, with simplification causing some important small details to be lost.

 

 

I do wonder how long the UK is going to be spared from the Atlantic 'bombs' for. Again and again, a ridge of high pressure seems to come to our rescue!

[Summer Sun]

GEM has a very deep low near Greenland at the end of its run for most of the UK its settled and relatively mild

 

 

ECM though has a SE'ly flow

 

 

GFS meanwhile has the center of the low south of Iceland leaving the UK in a SW'ly flow and fairly windy for most parts with the strongest gusts for the far west of Scotland and Ireland

 

[Nouska]

Couple of ruminations on earlier posts....

 

Mucka ... good post. The tropical tidbits anomalies are a blend of a blend (ie mean of either 50 or 20 runs then mean of 5 days), the detail is very vague and what is it being set against anyway.... that's another blend of a blend of thirty years.

The NOAA ones are also a blend but I assume the human input tweaks as they go, much like the NHC do for hurricane cones, thus continuity (and reliability) seems more apparent than in raw anomalies.

 

An edit to show an example of the 384 hour ensembles - mean is third from right, bottom row. Personally, I always prefer to look at the panel page on Meteociel. 

 

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

 

 

Singularity.....shades of 2009 in the NWP not surprising with the MJO forecast, projection of path is very similar to that year. Shown below with November in  green.

 

PS, another source of MJO composites.   http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/mjo/composite.html

 

Edited October 22, 2015 by Nouska

[knocker]

To continue with a rather bland assessment of the forthcoming evolution  The ecm anomaly has trough just to the SW, ridging over Scandinavia and some ridging to the west. Fits in pretty well with the ops consensus of low pressure over or adjacent to the UK. This analysis rapidly changes to a trough Greenland orientated to the west of the UK which will have a tendency to track systems emanating over Canada east then NE over the northern half of the UK. In the ext period with the Scandinavian ridge nudging east the trough to the NW and HP edging up from the south creates a zonal westerly flow.

 

 

[Man With Beard]

GEM has a very deep low near Greenland at the end of its run for most of the UK its settled and relatively mild

ECM though has a SE'ly flow

GFS meanwhile has the center of the low south of Iceland leaving the UK in a SW'ly flow and fairly windy for most parts with the strongest gusts for the far west of Scotland and Ireland

What I read into this is the Atlantic firing up but still failing to make decent inroads into the UK. A tiny chance perhaps of a Scandi HP alligned in a way that brings a colder and colder easterly.

[MR EXTREMES]

I think the sw northeast track of low pressure systems is not the likely outcome but battle ground Britain.

But judging on recent heights and longevity of the heights is a key factor moving on.

I certainly would not bin the ukmo and would favor blends of all models excellent post this morning from nosuka mjo is ramping up through the gears and certainly with those routes projected by the mjo 09/10 could be plausible.

Squeeze of heights to me low pressure moving out of the north Atlantic on a more south east trying to undercut but stalling up against the block but far from a repeat of last year.

But more runs needed and nothing cold yet but I more interested on where next.

I'm quietly optimistic for now

[nick sussex]

After the disagreements of recent days broad agreement at least for the pattern in Europe however it starts to go pearshaped upstream in the eastern Pacific.

 

This brings a question mark later as to how far east and se any troughing gets. The degree of amplitude upstream will determine this as this will either help force high pressure further north like the ECM or the flatter GFS 00hrs solution.

 

Its to be noted that the GFS 06hrs run is more amplified than the earlier 00hrs and this helps to edge the pattern west with a stronger ridge nw, a bit more like the UKMO but still not as amplified as the ECM( we've been here before with the ECM!).

 

If you look at comments from NCEP this morning:

 

THE GENERAL THEME OF THE FCST REMAINS INTACT... WITH AN EVOLUTION
TOWARD GREATER AMPLITUDE OF FEATURES ALOFT.  BY TUE-THU EXPECT AN
ERN PAC TROUGH TO APPROACH/REACH THE WEST COAST BEHIND A WRN NOAM
RIDGE WHILE A TROUGH HEADS INTO THE EAST.

 

The UKMO does not amplify the pattern in the eastern Pacific at T144hrs, given the ECM and GFS both do then the former is for the timebeing an outlier solution for that region.

 

Moving forward the outlook is likely to be troughing near the UK and high pressure to the east or ne so the UK likely to be the battleground. The question really is how much energy gets disrupted off that trough and this will be effected by the pattern in the eastern USA.

 

If the pattern upstream is more amplified then a slow change to colder conditions as the continental flow gets cut off from a warmer Med input as low heights develop in that region. If its flatter then more average to milder, if energy spills over the block then much milder a bit like this mornings GFS 00hrs run.

[legritter]

very interesting weather patterns showing on todays charts in the longer outlook .

As nick sussex points out the UK could become a Battle zone , which will make for some interesting discussions on our forums and hopefully a few more posters will join in ,i,m realy looking forward to the coming Months ,who knows what mother nature will cook up this winter ,some interesting things happening now across the northern hemisphere lets hope it can be the same as we progress .

Well i,m going to Dust off my weather journals have a good read get out the pack of straws ,pram out from the garage check the prozack supply and rig up the winter halogen light for flake spotting ,IS frosty in hibernation i miss those colourfull charts .

[knocker]

A glance at the GEFS upgrade for 00z gives an idea how mobile the pattern is for while next week ( i realise of course the anomalies are pretty rough). The upper trough to the SW earlier in the week soon gives way to a more vigorous trough to the west which in itself is quite transitory. It the settles down as the Scandinavian block gets a second wind and the trough settles to the NW giving a zonal westerly flow.

Charts courtesy weatherbell

 

[Newberryone]

A battleground scenario becoming more and more pronounced in the medium term with the probability of a certain little isle in green copping some appreciable rainfall totals. Still signs however of a weakening of any further trough activity, even further west  beyond Day 10 due to a strengthening of the block further east.

[MR EXTREMES]

The thorn in the Goldie's side the Azores high but could be the precursor of things to come either aiding further on or losing to low pressure there for allowing lows to undercut scandi heights.

No real full on attack by the Atlantic just the western side effected but I can see this progressing towards a easterly in time which don't matter how long just need some real dig of cold air to our east.

[nick sussex]

Marked differences between the GFS and UKMO at T144hrs.

 

The UKMO is much more amplified upstream, the GFS much flatter. The UKMO does leave that low to the north at T144hrs which does complicate what could happen next but given the upstream pattern a pressure rise to the n/nw could happen as WAA ahead of that digging Atlantic trough seems likely to happen.

 

The UKMO is more amplified than this mornings ECM 00hrs so the interest will be on whether the ECM backs this later on.

[london and south east kent]

The met office going for colder weather the end of month...

Edited October 22, 2015 by abbie123456

[chris55]

The general feeling I'm getting from the Autumn so far is that the general pattern is in a much more favourable state if you like colder conditions. Generally, with regards to blocking and the jet stream positioning, it looks more conducive to less Atlantic influence than we have seen in recent years. This displaced and more favourable trend, if it was to continue into the winter months, would be good news for us cold lovers. A raging vortex over Greenland and the usual onset of Atlantic storms seems less intrinsic this year as it stands. A dry and settled October is often talked about as the precursor to a more seasonable winter.

 

A long way to go but I'm optimistic that this winter ahead may well deliver at least a few weeks of cold and snow.

 

Although not cold at this stage, the general feel and pattern looks decent, if we can keep this theme going into late Autumn and into winter.

 

http://www.wetterzentrale.de/pics/Rtavn1201.gif