Model Output Discussion - 12th December Onward

[Weather-history]

Why do you think it looks odd?

Between the two main lows you would expect some kind of ridge but instead there is a low and to the north of it, nothingness. Its looks like the three body problem.

[I remember Atlantic 252]

The 06z is never the most reliable of the 4 daily runs, but the evolution IMO beyond the weekend is a very safe bet given the NH profile.

if the 06Z was showing hairdryer SW'lys, you would be saying 'the 06Z is the most reliable run'

[Weather-history]

if the 06Z was showing hairdryer SW'lys, you would be saying 'the 06Z is the most reliable run'

It really is a dumbass term "hairdryer" to describe it. Ask any place that suffers orthographic rainfall in this set-up from it.

ECM 12z has the Thursday night low across southern parts again

[Summer Sun]

GEM hardly brings any storm on Friday

http://www.wetterzen...cs/Rgem1081.gif

ECM takes acorss the south heading in to the south east by mid-day Friday

http://www.wetterzen...ics/Recm961.gif

Edited December 12, 2011 by Gavin D

[Interitus]

It really is a dumbass term "hairdryer" to describe it. Ask any place that suffers orthographic rainfall in this set-up from it.

ECM 12z has the Thursday night low across southern parts again

Orographic - ironically orthographic relates to correct spelling

[Cheese Rice]

I'm supprised there isn't more discussion on the snow potential tonight and tomorrow!? Can any experts give their view? This is the latest forecast for central areas tomorrow from the met at 1530;

Showers, sometimes as snow to low levels, with some settling on hills. Some more persistent snow in western areas. Eastern areas drier and brighter.

Understandably its been overshadowed by the storm but yes the potential is there, providing you see some PPN.

Here looks prime position for some snowfall, but we shall see...

Heavy showers will fall as snow over hills above about 100 m, and at times to low levels too. Accumulations of 10 cm or more are possible on hills, and there may also be some slushy accumulations at low levels. As a result some roads will become icy at times.

Very strong winds will accompany the showers at times, notably across Northern Ireland and southern and western Scotland.

The public should be aware that travel may be disrupted as a result of the bad weather, notably over high ground where combination of strong winds and snow could lead to temporary blizzard conditions.

[Paul White.]

It really is a dumbass term "hairdryer" to describe it. Ask any place that suffers orthographic rainfall in this set-up from it.

ECM 12z has the Thursday night low across southern parts again

I agree but the phrase that really bakes my noodle is "Blowtorth SWs" As for tonight's models nothing set yet, it's North its South (Fridays Storm) Maybe we should a all play a game a bit like spot the ball but this one we pin the low's centre and we can lobby Net Weather to provide 6 months worth of Extra

[A.J]

It really is a dumbass term "hairdryer" to describe it. Ask any place that suffers orthographic rainfall in this set-up from it.

ECM 12z has the Thursday night low across southern parts again

Yes the 12z runs of the GFS & ECM very similar out to T96 so far, still though at odds with the UKMO which has the LP exiting the UK further north. Even a small variation in track would have a significant effect in wind strengths and affected areas, indeed also on PPN spread/type in areas where flooding might be an issue

GFS12z

ECM12Z

UKMO12z

[Weather-history]

Orographic - ironically orthographic relates to correct spelling

Oops.... yes :lol:

[OldMetMan]

It seems the models are having some trouble with the Friday low, in terms of its complexity. They all seem to have picked up on the fact that there will likely be warm frontal waves running ahead of the system but the attached 72 UKMet chart shows the front-runner as the deeper, with a shallower wave following behind.

The NOGAPS on the other hand, shows a warm front wave followed by a much more vigorous low, with a strong pressure surge behind it - such as would give a spell of intense NW winds.

In particular, the GFS seems to be sticking with the idea of a fairly shallow wave running across the very south of the UK.

Given the sparse data in the area of predicted development of this low, I think satellite data will be crucial nearer the time. Rapidly developing secondary lows can be dangerous beasts - remember October 1987!

[Cloud 10]

Not one,but two depressions due to cross southern parts this week if the 12z gfs is to be believed.

Must be quite a while since that's happened!

[Summer Sun]

ECM in FI brings in some rather mild air

http://www.wetterzentrale.de/pics/Recm2162.gif

http://www.wetterzentrale.de/pics/Recm2402.gif

[NickyB]

ECM in FI brings in some rather mild air

http://www.wetterzentrale.de/pics/Recm2162.gif

http://www.wetterzentrale.de/pics/Recm2402.gif

A little bit of straw clutching going on I think

[casparjack]

ECM in FI brings in some rather mild air

http://www.wetterzentrale.de/pics/Recm2162.gif

http://www.wetterzentrale.de/pics/Recm2402.gif

I've just gone over to TWO to get away from your spamming of this thread, only to find you posting exactly the same there almost simultaneously!!

Life's too short...

[January Snowstorm]

Whilst this week could be fun from an active weather point of view, it's hard to ignore the ominous look of mild leading upto Christmas. Next week is looking like a damp squib!

[Mark Parsons]

Whilst this week could be fun from an active weather point of view, it's hard to ignore the ominous look of mild leading upto Christmas. Next week is looking like a damp squib!

The Meto say we are going to have much the same on there outlook for next week, maybe not the intense storms though.

Anyway as many have said the outcome of our weather will not be defined at all until these storms have gone through, anything could happen!!

[Nick F]

It seems the models are having some trouble with the Friday low, in terms of its complexity. They all seem to have picked up on the fact that there will likely be warm frontal waves running ahead of the system but the attached 72 UKMet chart shows the front-runner as the deeper, with a shallower wave following behind.

Given the sparse data in the area of predicted development of this low, I think satellite data will be crucial nearer the time. Rapidly developing secondary lows can be dangerous beasts - remember October 1987!

Yes, the newly updated t+72 fax goes along the same lines as the UKMO global rather than the much shallower wave solution from ECM and GFS for the same time, obviously Exeter sticking with their own model operational run.

With regards to snow potential tomorrow, GFS shows dew points falling away to around 0C tomorrow afternoon across much of Ireland, northern and central Britain - so snow perhaps getting to lower levels in the north and west in the heavy showers blowing in, though wet bulbs look rather high at lower levels, so I suspect settling snow could be the reserve of higher ground.

[nick sussex]

Putting aside the earlier timeframe and looking towards the weekend and into next week we see the Azores high making an attempt to ridge into southern Europe.

One could look at the later output and think its a slam dunk! However the big 3 outputs at 144hrs could offer something different, the UKMO and GFS eject some energy east and the ECM holds the European troughing.

The Azores high can not move east if the Russian high locks in low heights over central Europe, before some in here get their t-shirts and barbecues out again I'd wait a while longer.

[feb1991blizzard]

Yes, the newly updated t+72 fax goes along the same lines as the UKMO global rather than the much shallower wave solution from ECM and GFS for the same time, obviously Exeter sticking with their own model operational run.

With regards to snow potential tomorrow, GFS shows dew points falling away to around 0C tomorrow afternoon across much of Ireland, northern and central Britain - so snow perhaps getting to lower levels in the north and west in the heavy showers blowing in, though wet bulbs look rather high at lower levels, so I suspect settling snow could be the reserve of higher ground.

Sorry to be a pain and be thick but is there actually a meteorological definition of what classes as 'High ground' and if so what is it, this has been bugging me for years now but never got around to finding it out.

[jonnybradley]

Interesting that all the models seemed in agreement about the Thursday/Friday out in low res but are playing out slightly different scenarios now the feature is into high res. Really is overload for a noob here.

I keep on seeing people say "due to the complexity" of Fridays system. Could anyone elaborate a bit more on the complex factors involved? Would be nice to try to understand and follow some of these factors building into it.

Many thanks

Jon

p.s I saw a forecast for Chamonix in the Alps today, is curently perdicting over 1m of snow for the 24hr period over Fri - clearly subject to change....

[casparjack]

Putting aside the earlier timeframe and looking towards the weekend and into next week we see the Azores high making an attempt to ridge into southern Europe. One could look at the later output and think its a slam dunk! However the big 3 outputs at 144hrs could offer something different, the UKMO and GFS eject some energy east and the ECM holds the European troughing. The Azores high can not move east if the Russian high locks in low heights over central Europe, before some in here get their t-shirts and barbecues out again I'd wait a while longer.

I was just looking at the T240 frames from the 12z ECM and exactly the same occurred to me, the build in pressure to the East is very apparent, as is the Azores high, in between we have a real squeeze going on; any number of outcomes are possible from here, though one of them could be mild...

Edited December 12, 2011 by casparjack

[kmanmx]

Interesting that all the models seemed in agreement about the Thursday/Friday out in low res but are playing out slightly different scenarios now the feature is into high res. Really is overload for a noob here.

I keep on seeing people say "due to the complexity" of Fridays system. Could anyone elaborate a bit more on the complex factors involved? Would be nice to try to understand and follow some of these factors building into it.

Many thanks

Jon

p.s I saw a forecast for Chamonix in the Alps today, is curently perdicting over 1m of snow for the 24hr period over Fri - clearly subject to change....

Not sure where you saw that. Must of the alps are in for a good dumping, 30 to 50cm on friday across most parts, which is alot, but obviously not rare in the mountains at those heights. I can't see anywhere that is getting 1meter though.

I suspect the snow levels will decrease across the alps if the UKMO is right with the track of the storm, I think those snow levels are assuming it takes a track closer to the channel.

[nick sussex]

Sorry to be a pain and be thick but is there actually a meteorological definition of what classes as 'High ground' and if so what is it, this has been bugging me for years now but never got around to finding it out.

I don't think there is a clear definition of high ground, but if I had to go for a cut off point I'd say ground above 500 feet.

[Nick F]

Sorry to be a pain and be thick but is there actually a meteorological definition of what classes as 'High ground' and if so what is it, this has been bugging me for years now but never got around to finding it out.

I'm not aware of a definition as such, but for the sake of tomorrow, probably 100-150m in the north and west for snow to settle.

[feb1991blizzard]

I'm not aware of a definition as such, but for the sake of tomorrow, probably 100-150m in the north and west for snow to settle.

Thanks Both Nicks.

Edited December 12, 2011 by feb1991blizzard