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lorenzo

Scotland Regional Discussion - Autumn 2013

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So how low will the snow fall & lie next week?

 

OK, since I'm currently addicted to the model output thread I'll take a guesstimate at this. Assuming we're talking at low levels, not just on the bigger hills, snow falling currently looks most likely from early hours Tues, through Wed. As for actually hanging around on the ground, I'd say not for that long. It's November, the ground isn't that cold yet and we're looking at it being relatively mild tomorrow & Sat so no help there. Temps Tue & Wed, although low for the time of year aren't likely to stay sub-zero during the day from what I've seen. After that the models are a bit unsure but even if it does stay cold after Wed it looks more likely to be a dry cold than a wet cold.

 

Basically it's an appitiser, not the main course.

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Would you mind explaining to the ickle kiddiwinks about Debbie Harry's effect on all males in existence in the early 80s, please? Posted Image

 

Were there not largely 2 reasons...or should that be 2 large reasons? Not sure any more detail than that is appropriate on a family friendly forums such as this, and anyway a quick Google will provide adequate illustration.

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That's the snow tyres on again so now it will probably turn mild until March. Posted Image

 

Anyone else fitted the old winter tyres and if so what? I got two fronts fitted for £170. They are Yokohama W Drive 205/55/16 V91 M+S (made in Japan).

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OK, since I'm currently addicted to the model output thread I'll take a guesstimate at this. Assuming we're talking at low levels, not just on the bigger hills, snow falling currently looks most likely from early hours Tues, through Wed. As for actually hanging around on the ground, I'd say not for that long. It's November, the ground isn't that cold yet and we're looking at it being relatively mild tomorrow & Sat so no help there. Temps Tue & Wed, although low for the time of year aren't likely to stay sub-zero during the day from what I've seen. After that the models are a bit unsure but even if it does stay cold after Wed it looks more likely to be a dry cold than a wet cold.

 

Basically it's an appitiser, not the main course.

 

If only the 850's were lower the chance of snow sticking below 300m would be greatly enhanced.

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Were there not largely 2 reasons...or should that be 2 large reasons? Not sure any more detail than that is appropriate on a family friendly forums such as this, and anyway a quick Google will provide adequate illustration.

 

 Is this the picture?

Posted Image

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It's a lovely day outside, but feeling chilly in the breeze:

 

post-2844-0-02757900-1384433623_thumb.jppost-2844-0-55218700-1384433903_thumb.jp

 

I still can't believe we're moving again in three weeks, if I thought this place was going to be bad for snow then the new house is going to be a disaster. The things we do for the people we love, Mrs Catch you have no idea :lol:

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In fairness, I think most of my generation at least know who Debbie Harry is, if not quite the significance she had on guys in the 70s.

Anyway, slight issue (and one we really didn't have last March) is the lack of deep cold uppers to tap into. The northerly itself looks like bringing circa -8 uppers to our shores but after that any of the 'cobra run' setups that I've seen have involved a flow from the continent which is barely any colder than Scotland. Thus, the ECM setup of a decent northerly which is followed by a cold high sitting over us is for me the best option in terms of overall weather enjoyment and actually also in terms of chances of decent cold. 4C with endless Stratocumulus isn't my idea of fun, so a bitter but dry holding pattern while Eurasia gradually cools is for me a better bet than something synoptically impressive but actually pretty tame (unless we can get proper troughing into Scandinavia). Low heights over Europe are the key - if we keep those it really doesn't matter how close the high gets to sinking because it won't actually sink.

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couple of nice GEFS anomalies charts from the 0z and 6z posted by MATT HUGO on twitter

 

post-18233-0-92583300-1384435730_thumb.ppost-18233-0-21964000-1384435746_thumb.p

 

also goes to show the trouble the GEFS is having with placing the high pressure

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You really can't beat Scotland in winter so here's a quick video to follow up the photo that Netweather kindly shared on their Facebook page yesterday.  Last week I got three wonderful snowy walks in Torridon but this one, on Sunday just gone, was probably the highlight:

 

 

Fabulous views, but you're braver than me going over the Horns in snow.

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I think parts of the north of Scotland are on for getting pasted at the start of next week, Altnaharra for a foot Posted Image

 

Edit: I wanted to be the first to mention it, here's hoping for a polar low at some point this winter...

Edited by CatchMyDrift
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Fabulous views, but you're braver than me going over the Horns in snow.

 

Hmm, I was in two minds about it.  Because I had to drive home afterwards I didn't really want a huge day in the hills, so initially thought I'd go only as far as the first horn.  That would still have been a great walk with grand views.....but once up there with Sgurr Mhor rearing up ahead I just couldn't resist Posted Image

 

post-10976-0-73641400-1384438414_thumb.j

 

That said, clambering over those pinnacles under conditions like that is probably at the limit of what I feel comfortable with without ropes and other people with me.

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Amazing views.  I live in Lochcarron which is near Torridon I have been up the hills but not quite as far as you have.  Thanks for sharing.

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Hmm, I was in two minds about it.  Because I had to drive home afterwards I didn't really want a huge day in the hills, so initially thought I'd go only as far as the first horn.  That would still have been a great walk with grand views.....but once up there with Sgurr Mhor rearing up ahead I just couldn't resist Posted Image

 

Posted ImageDSC09747.jpg

 

That said, clambering over those pinnacles under conditions like that is probably at the limit of what I feel comfortable with without ropes and other people with me.

Nice one. One of my favourite hills, and the one where I got my intro to winter hill conditions rather a long time ago. You got better conditions than I did then - piles of melting slush up to about 800m then rime ice everywhere!

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Nice one. One of my favourite hills, and the one where I got my intro to winter hill conditions rather a long time ago. You got better conditions than I did then - piles of melting slush up to about 800m then rime ice everywhere!

 

Gawd, can't say I fancy those steep slopes in slush and ice.  What a savage introduction!

 

In other news, beautiful sunset here in Fife.  Nice and still.  It has that wintry feel about it.

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small question LS with regards to snow as i'm not as clued up on what perameters we need.

 

if we are under the 528 dam or lower do we still need to have the uppers so low for snow or can we get away with slightly warmer uppers and still get snow.

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small question LS with regards to snow as i'm not as clued up on what perameters we need.

 

if we are under the 528 dam or lower do we still need to have the uppers so low for snow or can we get away with slightly warmer uppers and still get snow.

 

850s up to(but not above) 0C are technically fine for snowfall under certain circumstances, mostly if the cold is deeply embedded at the surface and is cooling the lower layers of the atmosphere up to around 900hpa. 950hpas upwards MUST be sub 0C for snow to fall, which is why that's the parameter I tend to use, unless pressure is extremely low i.e. the Braer storm where 950s were probably around 1-2C but 950hpa was pretty much ground level. 528 dam thickness is probably a better indicator than -5C uppers, 1290 on the 850-1000 thicknesses is even better (anything below that and snowfall is almost guaranteed) and dewpoint at or below 0C/Wet bulb temperature below about 1C are also fine indicators but none are entirely fullproof so it's just a case of checking all the variables and seeing if they all tick the box. And then we have to hope there's some precipitation around.

 

I'll run through a quick example for Lerwick on Monday midday based on the 12Z GFS:

Uppers -6C *check*:

Posted Image

 

Thickness 522 dam *check*:

Posted Image

 

DP sub 0C *check*

Posted Image

 

850-1000 around 1295 *passable*:

Posted Image

 

Now we check the skew-t for any nuances between 850hpa and surface level that might lead to a problem for snowfall, including it being too dry:

post-9298-0-81166100-1384448840_thumb.pn

Confirms DP is sub 0C (actually -1.9C), Temperature is a bit high *but* 0C line is about 950hpa so it should be ok, along with the fact that the cloud level is very low (maybe 900hpa, check out John Holmes' guide on the learning area for how to read skew-ts) and the CAPE is extremely promising (cloud development above 500hpa) so showers would be very, very likely to form, with a high chance of troughs embedded in the flow. Given this tendency for heavy showers air temperatures would be pushed down readily during showers since the relatively high air temperature is a function of ground heating by the sun so we'd expect pretty much all precipitation there to fall as snow, although probably not lie given the high initial air temperature.

So, in summary, it dependsPosted Image

Edited by LomondSnowstorm
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Lol humorous ending but great analysis LS :)

OTR no one speaks any more keich than me so followed u will be....I love the short sharp nature of twitter and there are lots of weather people to follow...just click on who Matt Hugo follows and select some...I will tweet u some people later to follow if I get the 4 strong posse to bed with some energy still left!!

Great potential for many but IMBY not too much excitement to be gained from northerlys as always dies out over the hills unless it is a major front coming down....anyway there's always a first time to see decent snow from the north!!

Oh and I was Madonna not Debbie Harry....had the Lacey bra like a virgin poster on my wall #goodtimes

Edited by edodfc
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Just arrived in Carrbridge, central highlands. Log fire on. Dinner cooking. Cold beer in hand.

 

Drive up was good with the A9 quiet northbound. Leon was allowed a good bit of freedom...

 

The views were absolutely stunning with the sun setting. Largely clear, deep orange skies really lit up the autumn colours of the forests around Blair Atholl. Then there was the snow capped peaks to follow at Drumochter. Quite a site to behold. God's own country to coin the phrase. As far as I'm concerned one of the most beautiful countries on earth.

 

Bloody camera was in the boot though.

 

While the borders is lovely, Edinburgh a cool city... coming home (was born and grew up in Carrbridge) to the Highlands is always special. 

 

Chilly oot; was 3 C when I exited the car.

 

 

EDIT. Not now obviously, but gets some great snaw. Not sure I'd be brave enough to jump off it now (in the summer!).

 

Posted Image

 

Oh, and this is how we deal wi snaw here:

 

Posted Image

 

Quality

Edited by scottish skier
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note caution for anyone thinking we are in a good position from the 12z runs because we might not be and will be hoping for a either a second bite at the cherry or things can go horribly wrong in a hurry

 

Greenland or bust

 

 

here I will show you from the ECM 12z and note the bit I have circled in this first chart and this is our killer for getting deep cold with this first bite and why we don't want Scandinavia

 

Posted Image

 

now if we do see the heights heading for Scandinavia the two highs will link and as we can see from the arrow in this chart it will clearly cut off the cold uppers

 

Posted Image

 

this is why we have been seeing anomalies charts like these over the past while because of that big high pressure out toward Russia which only leaves us with a window to deep cold through a Greenland high as the high to our east will kill everything else and will leave us looking for a second bite at the cherry if one ever comes along as it will sink any height rises over Scandinavia.

 

Posted Image

 

so we want Greenland people and nothing else for a chance at prolonged deep cold at this stage

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Greenland or bust

 

Greenland or bust? GOB it is then, I think you've just coined a new term BUS :good: along the lines of "we want plenty of GOB this winter". I love it.

 

12z GFS certainly gives a good shot at keeping the high swinging off the bottom tip of Greenland, very good charts for any time of year and cracking to see before the start of winter proper :)

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to show is the ECM against the GEM and for you CATCH the GFS even though I don't rate it

 

ECM

 

post-18233-0-63431200-1384458952_thumb.gpost-18233-0-22973300-1384458960_thumb.gpost-18233-0-31511500-1384458970_thumb.g

 

GEM

 

post-18233-0-25235400-1384458985_thumb.ppost-18233-0-25742500-1384458994_thumb.ppost-18233-0-18334000-1384459007_thumb.p

 

GFS

 

post-18233-0-01965800-1384458715_thumb.ppost-18233-0-46149200-1384458723_thumb.ppost-18233-0-52248600-1384458733_thumb.p

 

to me the ECM looks worse and might sink the high where the GEM and GFS has it looking better and for once I hope the GEM and GFS is closer to the mark and ECM is having a wobble towards the end and not trying to lead like it does a lot

 

hopefully sorted so can flip through charts instead of it changing screen

 

Edited by Buriedundersnow

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You're right BUS, that was basically what I was warning about earlier - amazing synoptics for January aren't any use unless there's a cold pool to tap into. However, it's still worth keeping the heights around because sooner or later they're bound to try and set up for another go at the retrogression (although the GFS is inching ever closer to achieving that in one go, which would be nice). Otherwise, it's just a case of whether it's crisp and cold with a very limited chance of any snowfall or an easterly which squeezes every last drop of our cold pool until there's nothing left and have a slight chance of getting something epic if it holds. Either is excellent in terms of the longer term synoptics but the latter would feel like such a waste, to a much greater extent than the very cold and quite snowy but 'so gutted it wasn't 6 weeks earlier or it would've been worse than '47, '63 and December 2010 combined' spell this March.

How it could redeem itself is by doing this:

Posted Image

 

Which would make the week of dank drizzly 'North Sea' airmass worthwhile, but at the moment it looks like some kind of holding pattern will be required if we are to get retrogression to Greenland.

It's worth remembering that we had a similar build up to November 2010, with a not all that cold easterly to start with before the cavalry showed up from the Siberian Arctic. This chart, for example, is pretty similar to much of what the ECM has churned out in its later stages:

Posted Image

 

Posted Image

 

This was made irrelevant by the vortex dropping into Russia and two days after the verification date of that chart we were staring down the barrel of an exceptional cold spell:

Posted Image

 

Anyway, there's little point worrying about FI for the moment when we're looking at a good 4 day cold spell at the very least Monday-Thursday next week.

Edited by LomondSnowstorm
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