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Angelici Magiovinium

Scotland Regional Discussion - January 14th 2013>

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Please use this thread for your regional discussions about the current weather or what is being forecast for the next few days in Scotland

Link to the previous one here…

http://forum.netweather.tv/topic/75517-scotland-regional-discussion-january-12th-2013/page__st__820

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watch raintoday.co.uk.. the band to the east has already edged a bit closer to you.. Good Luck!

Aye last few frames look like more easterly movement. We might get lucky here, cold has certainly entrenched itself today.

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Aye last few frames look like more easterly movement. We might get lucky here, cold has certainly entrenched itself today.

Don't know, that wind is still pushing down from the NW.....

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Have a watch at 5 min intervals, definite westeastward trend from the mass out east of Dundee.

http://www.meteorada...imated-12&time=

Westward, no ?

rofl.gif

biggrin.png

Got excited there for a minute - sitting out here in my yacht in the middle of the North Sea... ;)

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Well the roller coaster keeps going :bad: The 12z looks interesting, that low looks nasty I just hope it's not the end of our cold spell.

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Evening peeps! Nae snaw here, a tiny dusting in Portree this morning, rather chilly though 2.4 degrees and falling. Doesn't look as if Skye will see much in the way of white stuff....shame! sad.png

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It has been snowing off and on all day here. Just checked the depth on the garden table and it is sitting at 9 cm. I have exams on Wednesday and Thursday so I am hoping I can drive into them without any major problems. Fingers crossed!

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UW120-21.GIF?14-17

I'd imagine if this chart comes off then the MetO will be issuing some Red weather warnings in places in the UK. Someone somewhere would be in for a remarkable blizzard.

Also, MetO now forecasting some spells of light snow for my location overnight tonight.

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Good model output so far tonight with the likelihood of a big snow event at the end of the week going into the weekend increasing. The UKMO has been very consistent with low pressure off the Atlantic running into the block that's by this time started to establish itself over us from the east. It goes for an approach from sw to ne direction which would give us the greatest chance of remaining in the cold and at the same time reducing the risk of any precip turning to rain. I think this scenario looks favourite just now.

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Also, MetO now forecasting some spells of light snow for my location overnight tonight.

lol in contrast the MetO have now removed all the little snow symbols they did have for Perth for the rest of the week to be replaced with just the clouds.

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lol in contrast the MetO have now removed all the little snow symbols they did have for Perth for the rest of the week to be replaced with just the clouds.

You've got to laugh, the band is getting closer

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lol in contrast the MetO have now removed all the little snow symbols they did have for Perth for the rest of the week to be replaced with just the clouds.

why does this not surprise me :(

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FMS, what's happening here? Thick sleet aka no on now at 0C. WMFS? We still looking good for later in the week?

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The band of ppn moving southwest over Fife appears to be perking up...

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UKMO is very good for the east coast up to +132ish, after that I'd be having another psychological episode regarding uppers and coastal modification but still probably hanging onto snow for the majority in the east and all in central and western parts would see blizzards from +120 onwards, especially given how much there would already be on the ground. GFS is still very snowy but turns to rain from the southwest around +120. Either way a lot of snow for the bulk of Scotland.

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Either way a lot of snow for the bulk of Scotland.

To be honest I'd take half a centimetre lying on the ground. Two years is a long wait.

2.2c, light drizzle outside at present.

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Some super winter sunshine anc clear skies earlier. Another cold day, no snow overnight. For snow here in the next few days, I think I'll be relying on some precipitation in western areas around Wednesday/Thursday. The end of the week is looking very interesting but considering how we've seen last minute changes effect snow prospects, then we'll need to hope that the models maintain the trend. It's too hard to call what will follow this weekend, but I really do hope that we end up with a better cold and snowy period than this following the SSW earlier this month.

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You've got to laugh, the band is getting closer

It is but I don't think it will actually blow any further west than Dundee, I think that band is supposed to 'hug' just along the coast.

What is the precipitation like in Dundee then Dundonian kilters??

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    • By LomondSnowstorm
      Well here we are again folks, that special time of year when the anticipation of Christmas is matched only by the joy of the now annual tradition of the LomondSnowstorm winter forecast. Last winter promised much and delivered some, although on the ground it was generally more of a slushy hinterland than a winter wonderland. So can we continue the trend of generally below average winters which have developed in tandem with a more southerly tracking jet, or will the glorious summer of 2013 usher in another trend bucking warmer than average season? In this forecast I’m going to look at a number of factors, including the El Nino Southern Oscillation, Global Angular Momentum, the Quasi Biennial Oscillation, Arctic Sea Ice, Eurasian snow extent/autumnal gain and Solar Activity to put together a forecast for what the winter of 2013/14 has in store for us. Once again, the usual disclaimer goes out about the low confidence nature of the more detailed parts of the forecast, but it’s good fun and paints a picture more readily for those who don’t have a particularly strong meteorological background.
      [size=6][b]ENSO[/b][/size]
      The El Nino/La Nina state, an index of the Sea Surface Temperature anomaly in the Eastern Pacific, has been shown to be critical to the global circulation pattern, so I’ll address if first. At present, as it has been for about a year now, we’re in a neutral phase (between 0.5 and -0.5 amplitude), and the model outlook suggests that it will stay that way throughout the winter:
      [attachment=191357:enso.jpg]


      Neutral ENSO winters have been shown to have SSWs less frequently than in those with either a clear La Nina or El Nino state (Butler and Polvani, 2011) which would indicate a lower chance of Polar vortex disruption and therefore a higher chance of more ‘normal’ winter conditions than we saw last year. However, neutral/weak ENSO values are also associated with a greater frequency of –ve NAO conditions, which is strongly correlated with below average temperatures.
      [size=6][b]QBO[/b][/size]
      The Quasi Biennial Oscillation is another key factor to consider, with easterly (negative)QBOs encouraging a weakening of the Polar Vortex and westerly QBOs a strengthening. However, it is more complex than that, and a combination of a Westerly QBO and a peak in Solar activity has been shown to increase the probability of a Sudden Stratospheric Warming Event. Currently, the QBO is in a Westerly state and will remain so (given that it’s a two year cycle) for the rest of the winter:
      [attachment=191369:QBO.jpg]
      [size=6][b]Solar Activity[/b][/size]
      This is one of the hottest (if you’ll pardon the pun) areas of meteorological research at the moment, and along with the Stratospheric developments this has contributed a huge amount to the advancement of medium range forecasting in recent years. The interest began when the historically cold winter of 2009/10 occurred during a deeper and more prolonged sunspot minimum than we’ve seen in 100 years:
      [attachment=191377:sunspot.jpg]
      The inevitable upturn in the 11 year cycle has taken place since then which takes us up to near the peak of the cycle this winter, although it’s a peak which is far more akin to those of the freezing Dalton minimum years than those of more recent years, . Nonetheless, remember the linkage between Solar Activity, West QBO and an increased prevalence in SSWs, because it may be critical to the coming winter.
      [size=6][b]Arctic Sea Ice Extent[/b][/size]
      For the unitiated this one might seem a bit strange, but in fact there is a reasonably strong basis for [i]lower [/i]Sea Ice extent being associated with an increase in the prevalence of blocking highs and a subsequent decrease in average temperatures across western Europe. As anyone who pays much attention to environmental news knows, Sea Ice in the Northern Hemisphere has been at historical (at least during the post 1979 satellite age) lows in extent. However, this year has seen something of a comeback for the ice, with the extent so far for the year being the highest since 2006:
      [attachment=191371:sea ice.jpg]
      Still, it remains below the long term average so this can be tallied up as being a slight mark in favour of increased blocking. October [size=6][b]Eurasian Snow Cover/Snow Gain[/b][/size]
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      [attachment=191373:Snow cover.jpg][attachment=191372:snow cover 2.jpg]
      Overall then this index is neutral, with the gain being far less spectacular than it could have been but partly because of a record high starting point.
      [size=6][b]North Atlantic SSTs[/b][/size]
      The feedback between Sea Surface Temperatures in the North Atlantic and the North Atlantic Oscillation, or in other words blocking over our side of the Northern Hemisphere, was shown to have been largely responsible for the record cold December of 2010 (Met Office, 2013). The key signature of a negative NAO is a tripole in the North Atlantic, with a cold section around 30-50 degrees latitude just off the coast of Eastern Canada, with warmer sections to the north and south:
      [attachment=191376:SST correlation.jpg]
      The signal is rather muted but a tripole of sorts has been showing in the North Atlantic in recent weeks, which is a fairly promising sign, although we need to watch to see if this sustains and develops further.
      [attachment=191375:SST 2014.jpg]
      [size=6][b]Arctic Oscillation tendency[/b][/size]
      Two recently developed indices of snow cover and height anomalies respectively have an exceptional record of predicting the Arctic Oscillation tendency - Cohen’s Snow Advance Index, which as previously discussed is indicative of a moderately positive Arctic Oscillation, and the very recently developed October Pattern Index, which can be thought of as the atmospheric effect of the SAI, which is actually at its highest value since 1991/92. Anyway, given the agreement between the two and the high predictability both have, I’d put our chances of seeing a +ve Arctic Oscillation for the winter at 90% plus. This doesn’t necessarily preclude a below average winter, and is less reflective of temperatures at our side of the pond than the North Atlantic Oscillation, but hemispherically it points towards high latitude blocking being generally scarce and does reduce our likelihood of a cold winter. However, this does not imply a permanently positive Arctic Oscillation, and we should bear this in mind.
      [size=6][b]Long Range Forecast models[/b][/size]
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      [size=6][b]Global Angular Momentum[/b][/size]
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      [size=6][b]Composites[/b][/size]
      Having looked at years from 1958 onwards (prior to that the datasets become sketchier and it’s tougher to pattern match) and basing on the criteria outlined above I’ve come up with 11 composite winters which broadly match the likely winter ahead. These were all either ENSO neutral or weakly positive/negative (value less than 1), featured positive QBOs and are ‘weighted’ towards those which are more similar. While some years with negative Arctic Oscillations were counted, years were double weighted based on the Arctic Oscillation value given the likelihood of a positive one this year. The most similar winter was 1990/1991, which is counted four times in the composite charts, with 1971/72, 1980/81, 2001/02 and 2008/09 counted twice and the rest just once. The full list of years are:
      2008/09, 2001/02, 1990/91, 1985/86, 1980/81, 1978/79, 1971/72 ,1966/67, 1961/62 and 1959/60.
      [size=5][b]December[/b][/size]
      [attachment=191365:December height.jpg]
      For December, the Aleutian Ridge and negative height anomalies over the Western side of the Arctic are the most notable features, but otherwise the anomalies are fairly muted, with a positive anomaly out in the mid Atlantic and actually a slight mean trough over Europe.Half of these winters featured either a Canadian Warming or SSW in the first half of winter, with 8/10 featuring a notably cold stratosphere initially, so this may well be the key to our winter once again. The Stratosphere composite looks like this for December:
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      [attachment=191364:Dec the strat.jpg]
      [size=5][b]January[/b][/size]
      Onto January and we have a very different looking anomaly – Greenlandic height rises come into play but with a very strong negative height anomaly stretching right across from NE Canada into southern Europe. Again, this is very far from clearcut, with evidence of some vortex disruption particularly in our neck of the woods but still with negative or neutral height anomalies across the pole:
      [attachment=191368:Jan the strat.png]
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      [attachment=191367:jan strat.jpg]
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      [size=5][b]February[/b][/size]
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      [attachment=191366:feb height.jpg]
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      [attachment=191370:r2Udu38dtx.png]
      [b]Adjustments[/b]
      Given the SST pattern I’d suggest that the mean height anomaly for February is centred somewhat further west over Greenland, while low heights south of 60 degrees north are likely to be confined to southeast Europe through December.

      [size=7][b]2013/14 Winter Forecast[/b][/size]
      [b][size=5]December[/size][/b]
      A very zonal period to start the month following a short, sharp Arctic blast at the end of November, with west-northwesterly winds and very limited blocking. Near constant low pressure systems will bring wind and rain throughout, with only brief drier interludes. Temperatures above average in England and Wales but near or even slightly below average for Scotland, where colder upper air temperatures will bring the odd smattering of snow even to lower levels in spite of a lack of frost, with precipitation above average initially everywhere. Perhaps something along the lines of this:

      From around the 12[sup]th[/sup] onwards things will quieten down, with high pressure building in from the south, bringing a brief spell of very mild southerlies followed by a dry and eventually frosty spell in the run up to Christmas. Temperatures above average everywhere up to the 20[sup]th[/sup] but cooling down towards average from the south as heights transfer northwards, precipitation generally below average away from the far northwest Highlands where they’ll be around average. By Christmas, heights will transfer westwards with an initial spell of rain followed by a genuinely cold northerly blast as low heights dive temporary southeastwards, bringing more widespread snowfall and low temperatures, although with accumulation generally confined to the usual spots (which of course vary depending on the exact wind direction) before the dam breaks and the heights sink once more by month’s end. Temperatures will be generally above average for most of England and Wales, with an initial CET punt of 5.6C, the Scottish mean will sit around average at 3.4C. Precipitation will be marginally above average for all of Scotland and much of northwest England but for southern England and Ireland it will be around or below average. In other words, a fairly typical December.
      [size=5][b]January[/b][/size]
      I’m anticipating a switch around in January, where transient colder snaps brought about by an excessively strong vortex are replaced by a more wintry pattern. Nonetheless, it won’t start off that way – more bog standard Atlantic frontal systems will dominate the first half, with temperatures and precipitation widely above average. However, as the month progresses, mid latitude height rises will ridge northwards, with the jet finally being diverted southwards with colder air encroaching from the east. With still a large chunk of the vortex situated over Canada the height rises will take a week or two to become properly established, with a number of transitional snow-rain-snow events interspersed with more settled milder days, and temperatures will generally be around or slightly below average, but eventually, by around the 25[sup]th[/sup], a cold easterly flow will be established, ushering in one of the main cold spells of the winter. With the centre of the high between Iceland and Scandinavia rather than further east and with still a fairly impressive cold pool over the Arctic the UK could tap into some severely cold uppers if the setup works out. This would bring a period of very low maxima, perhaps sub zero, with the potential for significant snowfall right across the British Isles, but particularly for areas exposed to the easterly wind (including the Forth-Clyde streamer area) where showers would merge into longer periods of snow, although with low heights anywhere in the south of England could see some impressive snowfall totals, perhaps upwards of 8 inches quite widely IF we tap into the cold pool before the flow is cut off. (Note: the timing and severity of this event are very much low confidence, so I’d wait until at least early January before stocking up on tinned goods). Temperatures for the month as a whole will be below average but not massively so – a CET of 3.1C and a Scottish mean of 1.8C are my current bets. Precipitation totals generally around average, with the exception of the Western Isles and Northwest Highlands where it will be somewhat drier than average and southern England where it will be above.
      [size=5][b]February[/b][/size]
      With the easterly flow cut off by the start of the month as heights lower from the north a brief spell of anticyclonic weather will prevail through the first part of February, away from the far south of England where the odd snow shower may remain. Temperatures at the surface would be well below average even without the upper cold pool as the snow fields caused minima to drop like a stone under clear skies. With the southerly arm of the jet still dominant, and the vortex still not really managing to get a foothold east of Canada, a reload of the cold looks likely, with a weak Scandi trough/ weakfish southeast Greenland high providing a possible route, propped up by the strong southerly jet. This would give more snow to eastern parts, with Aberdeenshire in particular taking a bad hit, and temperatures way below average once again. By mid-month the pattern will look to shift westwards, with height rises over Western Greenland, leaving us in a west based –NAO state (think February 2010) with a rather messy cold trough, bringing a rather dour mix of snow, sleet and cold rain from a variety of wind vectors before eventually height rises over southeastern Europe build northwestwards and introduce a milder flow to end the month.
      Precipitation once again above average, although moreso in eastern parts, with temperatures very much suppressed until the very end. My CET punt is a very cold 0.8C, the coldest February since the sub zero 1986 (one of the ‘lesser’ composite years incidentally) with the Scottish mean a positively balmy 1C.
      I hope I haven’t bored/scared you too much, and I’ll be looking to update it throughout the winter and give an honest assessment of if/when it goes completely bust and we end up with a heatwave early February. I’ll be updating this in the next few days too with one or two synoptic charts which maybe give a better representation of my thoughts than the description does.
    • By onemanmows
      View over the carse towards Mentieth Hills and Aberfoyle
    • By Zenarcher
      Please continue to discuss the Scottish weather
      Previous thread
    • By lorenzo
      A new thread for a hopefully snowier outlook as Friday evening progresses... As always if you look in on the thread and haven't posted, please say Hello, we are a nice friendly bunch. Previous Thread here
      Good Luck Folks !
      Here are a couple of images from the NetWeather Radar for this evening show the developing picture well and whet the appetite.
      First image is standard precipitation overlay, social media overlay, wind chill and scale.
      Second image shows weather type and dewpoints.
      Hopefully you can see the other icons for selection on the right hand side of these images.

      Yours for one month for the cost of 349p, goes well with lamp posts.
    • By Angelici Magiovinium
      Please use this thread for your regional discussions about the current weather or what is being forecast for the next few days in Scotland....
      link to the previous one here...
      http://forum.netweat...3/page__st__720
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