Scotland - Weather Chat

[Cheggers]

Oooo, what did I miss?

First time I have the whole festive period off, I get dragged oot shoping.

Really wet morning, peaked at 9C, but now down to 2C

[cscrim]

Just home from a night of Complete Madness in Glasgow. Looks like I have missed some madness in here whilst away. Hope whatever caused it does not stop people posting. Very unusual to see deleted/edited posts in here, more so when a certain other thread survives untouched at times.

[LomondSnowstorm]

Missed the whatever happened earlier stuff as been on trains all day with the worst internet connection going.

 

Hope everything is all resolved and no further editing or deleting needed, very unusual for this thread?

 

Anyhow, for those of you who don't venture into the model thread some of the more extreme ensembles from tonights 18z.

 

Variations on the theme and all kicked off by one ridge over the Pacific and another in Greenland locale, soon to be followed by the Siberian Bear.

 

gensnh-4-1-204.pnggensnh-4-1-252.pnggensnh-5-1-228.png

gensnh-5-1-264.pnggensnh-11-1-240.pnggensnh-13-1-252.pnggensnh-15-1-252.png

 

Result, nothing like last winter and potential game of chase the easterly after throwing out the last of the Turkey.

 

Nothing beats an Easterly cliffhanger on Netweather, it's like 24 and Homeland rolled into one..

 

EDIT - Rab ^^^            

 

Quite an ensemble mean out past the 29th, god knows what the parallel ensembles would've looked like given how progressive the GFS op was tonight:

 

For Inverness an utterly ridiculous set of ensembles for ground temperatures, the mean is pretty much 0C throughout:

 

Other than the GFS op, which looks overly progressive as it often is, it looks a pretty cold outlook for most of us, and with the potential for the Greenland heights to lead to a stratospheric feedback which *could* lock us into a 2009/10 style freeze. 

Anyway, looks like more snow for the Highlands, possibly extending further east tomorrow night into Aberdeenshire:

  

It's a fairly marginal setup, uppers -5/-6C with 950hpa temperatures not consistently negative, but with a bit of shelter from the westerly winds colder air is likely to become embedded at the surface the further northeast you are and lead to some potentially significant falls. Snow accumulation charts out to early Saturday show the risk:

Wouldn't be unreasonable to expect a few of the heavier showers across central and eastern areas to turn to snow through tomorrow either, although with temperatures around 3C it's unlikely to stick unless it's particularly heavy:

But still, pretty decent for a mild spell

[Guest]

It might be my imagination but the charts look well off from where they were a couple of days ago.

[mistyqueen]

Morning all! A bit damp up here, just had a heavy hail shower. Temp currently 3c and a wee breeze along with it. I'm going to stop looking at the charts for a couple of days as I fear I may end up very disappointed. Be lovely if it did come off though..... :w00t:

[Northern Strath]

A covering at the hoose with heavy snow as I left. So a snowy commute to work with heavy showers also for the higher parts of inverness

[Ravelin]

It might be my imagination but the charts look well off from where they were a couple of days ago.

 

It's not your imagination. Wild swings seem to be the theme of the charts at the moment, especially the GFS (both old & new). Of the 12Z I looked at this morning the ECM seems the best, and seems to have been a bit more consistent with it's theme the last day or two. I'm way beyond my level of understanding but at the moment it looks like it any solution from deep freeze to BBQ Turkey is a possibility in a weeks time. I'm pinning my hopes on the "the models always struggle and flip flop when a big change is about to occur" theory some on the MO thread claim.

 

Back to the reality, if I remembered to reset my weather station yesterday then we had an overnight min of -1.5C last night (but really not sure if I did or not). It was a sunny 2.3C at 7:30am this morning and my car windscreen had ice on it (not frost). Still bright and sunny now, coolish, with a breeze.

[Ross B]

It appears to be snowing outside... Wet snow but it's still snow

[101_North]

From out of nowhere - heavy wet snow :-)

[grifter]

Not much to report here, apart from wild temp swings. Very very mild a few days ago, colder now, but the consitent theme was and is showers. Doesn't feel quite like last year, which was balmy and consistent heavy rain. Snow starting to appear on hills again, which was blowtorched away the other day.

Edited December 19, 2014 by grifter

[LomondSnowstorm]

It might be my imagination but the charts look well off from where they were a couple of days ago.

Short term they're a total mess, the low developing out in the Atlantic decides, instead of just heading east, that it's going to come north and phase with a shortwave that otherwise would've been quite helpful, and someone needs to nuke that HP to the south which really doesn't want to leave:

The longer term pattern however (in spite of what the GFS op FI may do to flatten the pattern) still looks likely to be one conducive to a big cold outbreak from the north at some point before the end of the year:

 

The ECM seems to support this, albeit not quite as vociferously as its ensembles, but getting some sort of High-latitude blocking in place is at least half the battle in these setups:

Most of the signals, from the waning of zonal winds over the next week or so to the reduction in angular momentum and movement of the Global Wind Oscillation into active phases having been pretty much dead all month, point to a block setting up in the Greenland vicinity. Both GFS runs almost get there but fail in the low res part of the run, while the ECM still manages to build a block over Greenland, so that should be fairly encouraging. That's not to say we should expect a flip to much better runs this afternoon, but any run which simply collapses the blocking and brings the Atlantic surging back looks suspect.

[Northernlights]

Heavy wet  blustery snow showers and hills very white again.  Currently 1.8c and lying snow level about  900 feet. Icy again after a slight overnight ground frost.

[LomondSnowstorm]

Like this, basically, is what we should be seeing in the output:

 

[Gogoslo]

Morning LS

 

Couple of quick Qs.    Are the models usually this volatile ( if that's the correct word ) in winter ?     In your opinion ,  how far out should we be looking for any degree of certainty in terms of Xmas day / boxing day?  

 

And finally.   Are we in a better position now for a colder / snowier winter than we were at this point last year ?       From memory last year there was a lot of "potential" within the models that never came to fruition.    Could it be the same this year ?

 

many thanks in advance.

[LomondSnowstorm]

Morning LS

 

Couple of quick Qs.    Are the models usually this volatile ( if that's the correct word ) in winter ?     In your opinion ,  how far out should we be looking for any degree of certainty in terms of Xmas day / boxing day?  

 

And finally.   Are we in a better position now for a colder / snowier winter than we were at this point last year ?       From memory last year there was a lot of "potential" within the models that never came to fruition.    Could it be the same this year ?

 

many thanks in advance.

Hi there. The short answer to the first question is no, but it really depends - for the first half of December the models were pretty consistent because we had a 'normal' pattern with fairly strong westerlies and a predictable pattern of highs and lows moving across the Atlantic into Europe. However, when we see a big pattern change, with the vortex shifting further east and weakening and ridging starting to get up into Greenland, the models almost always struggle. The only exception really to this was November/December 2010, with the first spell coming out of a period where high pressure was in place anyway and the second one had such a strong signal for a Greenland high that even fairly large errors still ended up with basically the same result:

 

December 2009 in particular were fraught with model uncertainty, downgrades, having to get a second or third bite of the cherry before things fell into place. So this isn't an uncommon problem when looking at possible cold spells.

For Christmas itself I think we're starting to see a bit more clarity now, with a northerly on Christmas Eve likely followed by a temporary ridge building in on Christmas Day keeping things cold at the surface, and with the potential for a flurry or two:

     

 

After that is where the divergence comes in, although actually the GFS has flipped towards both its own ensembles and moreso the ECMs in going for low pressure around Boxing Day (potentially snow-rain-snow for us) with a proper northerly and Greenland high building in behind. What we now want to see is cross model agreement and interrun consistency. The ECM generally wanted to delay the onset of proper cold by a day or two and it looks like it was right on that, but all roads still seem to lead towards a Greenland high developing and some sort of Arctic sourced cold arriving.

Finally, we're undoubtedly in a better position than last winter - last winter we were starting with some truly horrendous background signals which meant that a strong vortex and westerlies were always the form horse. There was a chance of a switch around in mid-winter to a colder pattern if the strat played ball and it almost came off, but the vortex ended up in the worst place possible for us just west of Greenland and we were just a bit too far southwest to benefit from the blocking that did develop. However, this time, thanks to much better background signals to start off with, the vortex has been far weaker, both at 'ground' level and at the stratospheric level, and we're now looking at an attack on the vortex both from below and from the very top, where some really strong warming is going to take place in the next few days. This means that there's far less resistance to a cold pattern developing than last winter. 

And also, look at where the vortex is centred this time round:

 

compared to last winter:

The lack of purples over Western Greenland means we're far less likely to see anything like the kind of raging jetstream we saw last winter, and if that pattern persists for the rest of the winter we'll have a really good chance of getting some proper cold in.

[Hawesy]

Beautiful day in St Andrews with sunny skies and temp currently 5c. But that's only after chaos on the roads this morning with black ice resulting in cars off the roads and in fields all around NE FIfe.

[Gogoslo]

Many thanks for that LS.   Really appreciated.

[Scottish-Irish Skier]

 

ECM ensemble mean = 

 

 

ECM and GFS ops = 

 

[NorthernRab]

A covering at the hoose with heavy snow as I left. So a snowy commute to work with heavy showers also for the higher parts of inverness

 

Was just down at Clachnaharry (one of the sea-level areas of Inverness beside the shores of the Beauly Firth for those who are reading this but aren't familiar with the area) where it was snowing heavily even there - so some widespread interesting conditions likely this evening I'd wager.

Edited December 19, 2014 by NorthernRab

[Snow Monster]

Interesting met office outlook. Not often your hear them mention risk of significant snow!

[Northernlights]

Heavy wet  blustery snow showers and hills very white again.  Currently 1.8c and lying snow level about  900 feet. Icy again after a slight overnight ground frost.

Some dryer snow showers now with lying snow down to 600 feet just 0.7c here and ground starting to freeze

[Northern Strath]

Was just down at Clachnaharry (one of the sea-level areas of Inverness beside the shores of the Beauly Firth for those who are reading this but aren't familiar with the area) where it was snowing heavily even there - so some widespread interesting conditions likely this evening I'd wager.

Aye I did see that before I headed back up the road after work Rab. Some pretty wild showers being blown in. Pity there is another mild interlude coming our way but I'm hopeful following a decent last 2weeks up here and indications of the cold in the near future consolidating more

[Hairy Celt]

Was just down at Clachnaharry (one of the sea-level areas of Inverness beside the shores of the Beauly Firth for those who are reading this but aren't familiar with the area) where it was snowing heavily even there - so some widespread interesting conditions likely this evening I'd wager.

 

I was at N Kessock early afternoon getting still more wet sleet thrown at me.  Temp's been at 2C to 3C steadily for >24 hours at sea level now so should be a good dollop more even on some lower slopes - if it doesn't get too blown around.

 

I had been thinking of tomorrow for a hill day but MWIS doesn't make it look too wonderful, with gales and snow / rain all day...

[grifter]

Windy + hail/sleet/rain showers here.

[West Highland Storm]

Sleety snow showers, coming from Fort William town centre just there big wet flakes.