Model Output Discussions 18z 31/01/2016

[Radiating Dendrite]

7 minutes ago, Man With Beard said:

For me, the ECM op is not really worth following after T144 at the moment - the last two ops have probably been outliers at the both ends of its ensemble suite. GFS, not such wild swings but also doesn't fill you with confidence in that sinking trough. The only trend is some sort of easterly after D8 - but could as easily be Mediterranean sourced as Scandinavian sourced.

In all fairness it's not worth following any op past +144.

[IDO]

34 minutes ago, Severe Siberian icy blast said:

The GFS is totally ridiculous in the way it blows up a shallow flat low south of the UK into a monstrous dart board low with severe gales.  It's absolutely ridiculous and not even worth looking at after t144 at the very latest . Even the way it delayes the cold air Sunday now until Monday evening getting south of the Midlands is suspect . It's been Sunday evening all week but now it's Monday afternoon.  

Il be very wary of this model . Not because it's not showing what I want but because it's over complicating matters in typical fashion it's really annoying ! Anyway rant over lol

Why is the GFS scenario (and now the ECM take) ridiculous? I have no idea how this will go but with a ridge/trough combo and a diving low, you have CAA diving with the low and it has to go somewhere. The GFS blew up the low and last night's ECM had the CAA disrupting in the Scandi trough. Both IMO possible, but from my experience the GFS version is the most likely especially when you have the ridge toppling into the trough.

It is a difficult period to model but from past experience we know in such scenarios ECM always models the most extreme cold solution and steadily backtracks. Unless we see a consistent signal for the Azores to ridge in the Atlantic and be sustained we will just have repeating topplers and ECM will continue to overblow the cold prospects. Of course we dont know how the background signals are going and there is always a chance that one of the Atlantic ridges will last, but no long range model is hinting at this yet.

In fact the more likely pattern change is the Azores being displaced east for a while, into a Euro high and the UK settling down under a positive heights anomaly. The GEFS at D16 hinting at this and CFS on board week 3 and 4:

 

[fergieweather]

25 minutes ago, IDO said:

In fact the more likely pattern change is the Azores being displaced east for a while, into a Euro high and the UK settling down under a positive heights anomaly. The GEFS at D16 hinting at this and CFS on board week 3 and 4:

 

...in total contrast to the output from both GloSea5 and EC Monthly, which agree on a cyclonic theme throughout March, generally well-amplified/potentially blocked and with flow between NW-N and occasionally NE'ly. 

[mountain shadow]

Whilst the ECM 12z giveth the 0z took it away, however a period of model uncertainty will ensue as they try to get to grips with the MJO cycle.

 

[Singularity]

You can't really use the CFS at the moment; it leans heavily on climatology and for this season is weighted toward a standard El Nino background which is not actually the case.

 

Crazy model runs this morning with that low dropping to the SW. These systems are nearly always overcooked but by how much is open to question. The system becomes so powerful that the mid-Atlantic ridge is able to gain enough strength to wall off what would be further sliding lows from the Atlantic for a couple of days. With a decent cold pool to our SE/E we'd be laughing but instead it works against us and we see our first continental plume of the season 

Elsewhere in the hemisphere ECM's not all that different to yesterday, with the Canadian vortex lobe disorganised and some height rises across the N. Pole.

Still that chance of snow on Tuesday, looks marginal down here though!

Edit: just seen what Fergie posted about the (lack of) southern snow on the 12z ECM of yesterday. I was mislead by bluearmy's post  (which is rare on his part I must stress!)

Edited February 20, 2016 by Singularity

[Severe Siberian icy blast]

45 minutes ago, IDO said:

Why is the GFS scenario (and now the ECM take) ridiculous? I have no idea how this will go but with a ridge/trough combo and a diving low, you have CAA diving with the low and it has to go somewhere. The GFS blew up the low and last night's ECM had the CAA disrupting in the Scandi trough. Both IMO possible, but from my experience the GFS version is the most likely especially when you have the ridge toppling into the trough.

It is a difficult period to model but from past experience we know in such scenarios ECM always models the most extreme cold solution and steadily backtracks. Unless we see a consistent signal for the Azores to ridge in the Atlantic and be sustained we will just have repeating topplers and ECM will continue to overblow the cold prospects. Of course we dont know how the background signals are going and there is always a chance that one of the Atlantic ridges will last, but no long range model is hinting at this yet.

In fact the more likely pattern change is the Azores being displaced east for a while, into a Euro high and the UK settling down under a positive heights anomaly. The GEFS at D16 hinting at this and CFS on board week 3 and 4:

 

As Ian has just said that completely goes against every other computer model out there , despite the fact we have a high amplitude mjo as well , an east based. -NAO has always looked odds on toward the tale end of the winter , yet again refusing to look at the nearer time and use d16 gefs as your main guide to forecasting the weather , yet the met for example don't even look at it past t144 , if you have a look at the verification statistics which has been posted time and time again so you must have saw them (?) you really are just waisting unnecessary energy , it really baffles me but it's up to you .

 

the models today do make a hell of a lot of the shallow low to our southwest and blowing it up big time , I feel they Will ease off this over the coming days , its all a journey ! 

[Nick F]

Quite an unusual evolution next weekend as agreed on by GFS and EC operational runs.

A fragment of the 500mb polar vortex over northern Canada breaks away SE over the N Atlantic, the upper vortex/500mb cold pool dropping SE sharpening a shortwave trough in the jet stream diving SE into Iberia and thus allowing a surface low to deepen to the SW of Ireland into an intense depression off NW Iberia by Sunday

The 00z EC and GFS ops then diverge over what to do with the upper/low vortex once its over Iberia. ECM fills it over Iberia while GFS drifts it NE across France, Low Countries and Germany and subtly merges it with the 500mb vortex over Svalbard and northern Scandinavia. 00z GFS op the much more ideal evolutuon this morning, as it keeps the flow from a colder NE, whilst the build of pressure between the Iberian vortex and vortex up over Svalbard on ECM would give us a not so cold easterly .. though it maybe chilly at the surface off the continent.

In the shorter term, looking quite snowy for the northern half of Scotland this weekend, with frequent snow showers, some whiteout conditions for the Highlands. 00z ECM high res on wxbell still showing snow for Wales, south Midlands, M4 corridor and northern Home Counties Tuesday morning - on the northern flank of a shallow low moving through the English Channel. -5C T850 line digging into the northern edge of the precip:

Edited February 20, 2016 by Nick F

[Captain Shortwave]

8 minutes ago, Singularity said:

You can't really use the CFS at the moment; it leans heavily on climatology and for this season is weighted toward a standard El Nino background which is not actually the case.

 

Crazy model runs this morning with that low dropping to the SW. These systems are nearly always overcooked but by how much is open to question. The system becomes so powerful that the mid-Atlantic ridge is able to gain enough strength to wall off what would be further sliding lows from the Atlantic for a couple of days. With a decent cold pool to our SE/E we'd be laughing but instead it works against us and we see our first continental plume of the season 

Elsewhere in the hemisphere ECM's not all that different to yesterday, with the Canadian vortex lobe disorganised and some height rises across the N. Pole.

Still that chance of snow on Tuesday, looks marginal down here though!

Edit: just seen what Fergie posted about the (lack of) southern snow on the 12z ECM of yesterday. I was mislead by bluearmy's post  (which is rare on his part I must stress!)

I think one thing to hope for is that the models have perhaps over done the upstream ridge and as such correct the path of that low towards a more south easterly trajectory (like the 12z run) which of course would probably be good enough in the mid range for some snow events.

In terms of the end game I would be happy with the low being correct either west (A pleasant and sunny south to south easterly with rain restricted to the west of the UK if at all), or correct east to allow a cold north of east flow to develop in the wake of that system. Pretty much anything other than the ECM op which is a grey drizzle fest for the majority of the UK. But how often do we see those patterns develop at this time of year, it would be typical to get cross model support this morning for the set up to develop and then verify in the face of some dreadful verification in similar patterns during this winter.

[IDO]

32 minutes ago, fergieweather said:

...in total contrast to the output from both GloSea5 and EC Monthly, which agree on a cyclonic theme throughout March, generally well-amplified/potentially blocked and with flow between NW-N and occasionally NE'ly. 

Wishful thinking on my part then...

[Weather-history]

Low pressure diving and deepening from early November 2010

[Nick F]

1 hour ago, IDO said:

 

In fact the more likely pattern change is the Azores being displaced east for a while, into a Euro high and the UK settling down under a positive heights anomaly. The GEFS at D16 hinting at this and CFS on board week 3 and 4:

 

I would say that's the least likely scenario based on current and recent 500mb anomaly charts from GEFS,  EPS and NOAA CPC. All have Atlantic ridge building north at times but a persistent -ve height anomaly over Europe.

Edited February 20, 2016 by Nick F

[johnholmes]

Agreed there Nick. Just what to make of this morning from ECMWF-GFS I am not sure, the ridging is there to see along with both showing a cut off upper low beneath it. Something NOAA did not show last night. So I need my thinking cap on to see what this may mean I think!

links

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

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

[fergieweather]

Snow signal Tues (as alluded to by Nick and others) is now stronger in 00z EC through M4 corridor. I've yet to see UKMO-GM fields. 

[northwestsnow]

8 minutes ago, fergieweather said:

Snow signal Tues (as alluded to by Nick and others) is now stronger in 00z EC through M4 corridor. I've yet to see UKMO-GM fields. 

Sounds very interesting for the guys in that locale Ian- good luck to them i say

[northwestsnow]

32 minutes ago, IDO said:

Wishful thinking on my part then...

Im still not convinced about that! GFS has been pretty damn good this winter imho.

Although with the output again pretty volatile i suspect longer term guidance is fairly meaningless at this stage..

[mushymanrob]

8 hours ago, Man With Beard said:

NOAA tonight - baby steps towards an Omega block?

close, but these charts have been rather stuck like this for several days now. a strong azores high is about all thats certain? its looking rather messy to me, with great uncertainty, no easterly on this (other then brief).  unsettled and cold id have thought?

[Man With Beard]

42 minutes ago, IDO said:

Wishful thinking on my part then...

Not really IDO. You simply reported what the GFS shows, and you had every right to do so. Besides, recently the GFS has sometimes been right (e.g. early Jan failed easterly) and many others wrong, so why not this time? Northern blocks are so nasty to forecast that, although, some modelling is going for a heavy northerly influence at the moment, anything beyond D15 has to be treated as tenuous. 

Having said all that, though, high pressure does seem to want to take a regular journey towards Iceland at the moment. I imagine one of these resulrant wintry setups will deliver for many before too long.

[Nick F]

The extended 00z EPS at 500mb has a -ve height anomaly centred over Germany and +ve heights over Greenland + the north pole at day 15, so not much room for mild air to return as we head into early March. The far north Atlantic certainly looking more blocked and the upper flow remaining meridional.

Edited February 20, 2016 by Nick F

[Pembroke Dangler]

Why do temps show so high on Tuesday ahead of the advancing front? It's showing between 6-8 for most of the U.K. At the surface so how can this mean that the approaching system can be anything other than rain? Sleet if your up on pen y fan in the beacons? 

[karlos1983]

4 minutes ago, Pembroke Dangler said:

Why do temps show so high on Tuesday ahead of the advancing front? It's showing between 6-8 for most of the U.K. At the surface so how can this mean that the approaching system can be anything other than rain? Sleet if your up on pen y fan in the beacons? 

Fear not, it doesn't even get here on the 06z GFS, it's heading for Spain lol

 

[Polar Maritime]

The GFS 6z shows a 'slightly' colder Northerly flow on Wednesday, With -10c 850's pushing South over Northern England/Scotland giving some hard overnight frosts for the UK.

Edited February 20, 2016 by Polar Maritime

[Tim Bland]

Great continuity between 00z and 06z 

does anyone have snowfall charts from ECM for Weds? Is it just a narrow band along the M4 corridor that may see snow from this? 

[winterof79]

GFS is a cold run i make no bones about that.Snow piling up on the frontal boundary where the trough becomes stationary.We can dream I suppose.

 

Edited February 20, 2016 by winterof79

[winterof79]

That is a seriously good chart with no shortage of cold to tap into.It also could draw in a n/e flow eventually as the Met allude to

Wether its the MJO,warming or the Scud missile,something's got it in for the ageing Vortex.

Edited February 20, 2016 by winterof79

[Lukesluckybunch]

2 minutes ago, winterof79 said:

That is a seriously good chart with no shortage of cold to tap into.It also could draw in a n/e flow eventually as the Met allude to

Yes a nice chart,but is there anything before this to get excited about..?