Model Output Discussions 18z 31/01/2016

[johnholmes]

2 minutes ago, johnholmes said:

 

well I tried to say, I wanted to delete the pictures and just leave the words from IDO, hey ho, no doubt its me.

One version of what the 6-10 day and further out may hold but not the only one.

In the 6-15 day time frame colder rather than cool is the word I would use if they 500mb anomaly charts I use are correct. I would trust them more than most other outputs in that time frame.

Edited February 8, 2016 by johnholmes

[marksiwnc]

15 minutes ago, Harsh Climate said:

Does increase the risk for north midlands/south yorkshire though

And Wales by the looks of that.  In actual fact it looks to be heavier in Wales on that view. All subject to change 

[chris55]

1 hour ago, nick sussex said:

The track of any shortwave low running into the UK is likely to change between outputs. So as for any snow on the northern flank its unlikely the detail will be sorted out for a few days.

At least the GFS so far hasn't backed the ECM which is a relief.

Agree Nick, if we can get cross model agreement on the slider scenario, then the northern edge snow details, either down to Cornwall or up to Liverpool will be unsettled for a few runs yet!

[Singularity]

 

Those little adjustments west even in the short range are of some interest. 

Bit of an unfortunate placement/timing issue with the 12z GFS run IMBY which shows the importance of getting some luck on your side, and also why it's best to have a whole stack of chances rather than just one or two.

Anyway, I'm treating the upstream developments day 6 onward with high skepticism given how the models of not that many days ago were looking for this coming week; the trough disruption theme was picked up consistency what, three days ago?

I'll admit though that with such an impressive cold pool moving out across the N. Atlantic, a major trough powering through is likely to occur. The angle of the jet, though, is open to some question. Essentially we need enough amplification retained across the U.S. that the next trough - after the big one coming our way in about 8 days time - digs south and allows a ridge to develop between it and the big one. The 06z got pretty close but we've not seen a run do this properly since yesterday's 12z I think it was. 

 

I imagine the model is going to produce many wild outcomes in lower-res in the near future, as it's going a bit crazy with the MJO:

 

It's that huge amplitude in phase 7 that's leading to some day 16 charts that feature a lot of anomalously high heights across the Arctic. Not yet has a run shown that to be aligned in our favour within the 16 day range, but I should think one will get there before long unless of course the MJO projection is adjusted downward considerably.

Also posted is UKME which lends good support in the mid-range.

Yet ECMF has lost the scent again:

 

This model keeps coming and going with the idea of a more amplified outcome and generally looks rather confused at the moment. I'm not sure what's causing that. It does at least hint at a signal for an amplifying trend in phase 7, which JMA shows more clearly despite being near the COD in 5/6.

It does seem to be a trait of the models that GEFS is typically very keen on the MJO in phases 7/8 and ECMF very hesitant. Twice last year I saw GEFS land much closer to the mark with activity in that area, which is a reason to be hopeful.

 

Back to the weekend potential, and UKMO does look pretty sweet for Sunday as a feisty Channel Low engages with the cold air moved across the UK by the preceding slider on Friday.

It does seem likely that the rain/snow boundary will take a step south during Saturday, the far south having to deal with heavy rain Friday but perhaps as a worthy sacrifice for a decent event on Sunday, should a Channel Low develop as UKMO shows. I wish we got to see 850 hPa values for that model but I guess sub-514 dam with heavy precipitation is not to be sniffed at! 

Honestly, if ECM doesn't join the slider camp this evening, my faith in NWP model watching will be hanging by a thread!

[nick sussex]

If the ECM sticks to its morning output I will be shocked. We're now talking of the GFS and UKMO both being wrong at T60hrs for this mornings ECM to be right.

I think looking at the GFS and UKMO I prefer the latter at T144hrs, that could hold a colder ne flow for longer and has better heights towards Greenland.

I should add NCEP are very confident in an amplified eastern USA trough towards the end of the week and the weekend and this correlates well with the Azores high ridging north and low pressure near the UK heading into mainland Europe.

Indeed they've noted an increase in amplitude over the last few model runs, this would help hold back the main PV chunk and angle the jet nw/se in towards the UK.

As Singularity has just mentioned if the ECM doesn't slide low pressure in then it would be going against what would be expected and NCEPs forecast would be completely wrong!

Come on ECM ditch the Grinch attitude!

Edited February 8, 2016 by nick sussex

[chris55]

I will be surprised if ECM doesnt come in at least as a"halfway house" our little patch is just that "little" lol. But the broader picture surely is odds on for a slider of some degree.

[Singularity]

In the really short term...

 

I had been thinking it was crazy how well the rain associated with tomorrow's shortwave running through the Channel hugged the south coast without moving inland on the ARPEGE 06z and GFS 12z runs. The ARPEGE 12s develops more movement N of E and this leads to some snow for the SE corner. Due to this relying on precip. intensity, I'll be watching the radar tomorrow as the system comes along just in case it tracks further north, as there now looks to be enough development of the low to draw in some cold air on the NW flank.

 

It's a long shot but stranger things have happened. Also, could be some wintry showers to follow across much of the UK but I suspect at best a rain/wet snow mix if you catch a particularly heavy, prolonged shower.

The theta-W values due look marginal but you can see how they improve slightly on the NW flank of the low by the evening, as the airmass is modified:

 

Good for a bit of a practice run ahead of the Fri-Mon shenanigans.

 

Edit: ARPEGE goes on to have the Friday slider but further north than GFS. Through Saturday it doesn't really pull the cold air south either so it's a reminder that the latitude of the snow line remains very uncertain.

ICON looks more promising as of +78 hours, if only it went even one day further!

 

That's ICON first and ARPEGE second. All of the lows are notably deeper to the west in the ARPEGE run, but it's the one furthest west that levers the jet into a more W-E alignment than NW-SE. UKMO keeps it shallower and so we get the slider nicely south despite the low that disrupts being deeper at +72 even than ARPEGE has it.

The complexity of the situation is becoming all too apparent, with more than one potential spoiler. Stay strong, snow hunters.

Edited February 8, 2016 by Singularity
High-Res Bonanza

[Snowyowl9]

UKMO not the blizzard that GFS 0z was showing,by blizzard I mean strong to gale east winds and very cold air and snow of course.

[nick sussex]

2 minutes ago, Singularity said:

In the really short term...

 

I had been thinking it was crazy how well the rain associated with tomorrow's shortwave running through the Channel hugged the south coast without moving inland on the ARPEGE 06z and GFS 12z runs. The ARPEGE 12s develops more movement N of E and this leads to some snow for the SE corner. Due to this relying on precip. intensity, I'll be watching the radar tomorrow as the system comes along just in case it tracks further north, as there now looks to be enough development of the low to draw in some cold air on the NW flank.

It's a long shot but stranger things have happened. Also, could be some wintry showers to follow across much of the UK but I suspect at best a rain/wet snow mix if you catch a particularly heavy, prolonged shower.

The theta-W values due look marginal but you can see how they improve slightly on the NW flank of the low by the evening, as the airmass is modified:

 

Good for a bit of a practice run ahead of the Fri-Mon shenanigans.

All I can say is remember January 6th 1994! A shortwave tracked ene and developed a circulation tucking in some colder air from the nw. Yes its a longshot but that one was even more so, the UKMO were completely taken by surprise. That though had better timing. The shortwave ran in through the evening and overnight, there was some frosty weather to the nw and this colder air got pulled in. Anyway I shouldn't big this up too much as its very marginal.

[Nouska]

17 minutes ago, Singularity said:

In the really short term...

 

This will be a chance to test the mettle of the 1.3kms AROME.

Your 22 hour chart in even finer detail.

 

[Peter H]

Models have all reverted back to a mild theme next week, after keeping us going for several days.

Even though the end of this week looks good, it's not really translating into anything particularly cold temperature wise.

[Snipper]

I am slightly confused. Why is  so much faith placed with the models when they are so un reliable for the most part? Wishful thinking.?

[Mucka]

GFS ensembles say it is a bit of a coin toss but with the op and control supporting the colder cluster you have to favour that.

Then there is also support from UKMO and MetO fax charts so that increases confidence again.

If we can get ECM on board tonight and tomorrow mornings output sticks with it we should be able to call it.

JMA also look a little better this evening out to 84h

[Man With Beard]

12 minutes ago, nick sussex said:

All I can say is remember January 6th 1994! A shortwave tracked ene and developed a circulation tucking in some colder air from the nw. Yes its a longshot but that one was even more so, the UKMO were completely taken by surprise. That though had better timing. The shortwave ran in through the evening and overnight, there was some frosty weather to the nw and this colder air got pulled in. Anyway I shouldn't big this up too much as its very marginal.

Nick that event gives me hope in every marginal - I remember it differently though, it all turned to snow just after dusk in NE Hampshire where I was, seriously unbelievable, at 4.15pm torrential rain, by 4.30 whiteout. I don't think it was the night cooling but rather the intensity. The link to the current situation is - look for the intensity of the rain. Argape is going for some mega rainfall rates for the SE tomorrow - if that hits land, the heavier the rain, the more chance of snow. So basically, if this comes off, it will be a major snowfall somewhere, not a dusting - 6 inches or nothing!

 

[nick sussex]

Millions of pounds of NWP computing power and the big 3 can't even agree within T72hrs!

The ECM at T72hrs still disagrees but has a better Icelandic ridge than this morning, but really this is getting silly with these early divergences between the outputs.

Edited February 8, 2016 by nick sussex

[chris55]

ECM vs GFS/UKMO!

Who knows where we will end up!

Gut feeling is more towards ECM unfortunately, because I haven't seen and hints of northern edge snow on the BBC forecasts, that implies the MORGREPS etc are not in favour.

But as ever time will tell.

 

[snowice]

More runs needed ECM uppers at 120 not cold like Gfs!

[snowray]

11 minutes ago, nick sussex said:

Millions of pounds of NWP computing power and the big 3 can't even agree within T72hrs!

The ECM at T72hrs still disagrees but has a better Icelandic ridge than this morning, but really this is getting silly with these early divergences between the outputs.

Yes unbelievable. T120 chart.

[nick sussex]

7 minutes ago, snowray said:

Yes unbelievable. T120 chart.

Only in winter 2015/16 could the ECM have the most amplified eastern USA troughing at T120hrs yet still find a way to find the worst solution for the UK.

The ECMs more amplified solution in the ne USA at least delivers a nice T144hrs output so it hasn't caused me to throw my laptop out of the window!

 

Edited February 8, 2016 by nick sussex

[chris55]

The way the ECM handles that shortwave looks odd, could well be right but i'm suspicious.

Edited February 8, 2016 by chris55

[snowice]

How many times this winter have we see ECM going against Gfs at 120!If I remember early January ECM was going for a cold setup and Gfs was having none of it!I know ecm is better on stats at this range but the gfs was right post xmass!what a mad model watching winter this has been!Gfs may be right again? 

Edited February 8, 2016 by snowice

[Ali1977]

Early next week shaping up to be cold, as per GFS

[Man With Beard]

Even if ECM is right, I suspect a snowy trough will pass through the country N to S at T168. T144 looks as if it is lining up for it.

And I suspect northern areas have a chance of snow on the ECM T144 chart

[wishingforsnow]

So another model standoff! Hope the GFS and UKMO stick to their guns

[chris55]

1 minute ago, snowice said:

How many time this winter have we see ECM going against Gfs at 120!If I remember early January ECM was going for a cold setup and Gfs was having none of it!I know ecm is better on stats at this range but the gfs was right post xmass!what a mad model watching winter this has been!Gfs may be right again? 

Its at t72 that we get the divergence and that has the knock on effect!

Here is ECM and GFS at T72