Scottish Cold Spell Discussion 19:

[Guest]

Major black ice here this morning. really nasty driving conditions. roads closed and road accidents all over! Decided not to venture far today as there has been a pile up on the road i was planning to go on! Nasty.

Anyhow charts are amazing again, looks like we will see snow at some point if not Thurs then maybe even by the weekend - all to play for. Off to have another look at the charts.

That is SOME chart SP!!!

The 06z has certainly thrown a wobbly there, it will be interesting to see what the ensembles spit out. If there is any support for that run then expect a full meltdown on NW later...

Black ice was fairly bad here earlier, I didn't realise until I got in from the walk to school how cold it was! 1C and not one of us had gloves or hats on!! Don't tell MrsCatch :lol:

[Snowplough33]

The 06z has certainly thrown a wobbly there, it will be interesting to see what the ensembles spit out. If there is any support for that run then expect a full meltdown on NW later...

Black ice was fairly bad here earlier, I didn't realise until I got in from the walk to school how cold it was! 1C and not one of us had gloves or hats on!! Don't tell MrsCatch

I dont really uderstand the emsembles, so once they are out, a short post be nice please. Surely that 06z run will downgrade massively today..........and if not, then as you say, caos here tonight. It looks a very slack flow, which I guess is not good for snow anyway is it, but severe cold be nice anyway!!

[Guest]

I dont really uderstand the emsembles, so once they are out, a short post be nice please. Surely that 06z run will downgrade massively today..........and if not, then as you say, caos here tonight. It looks a very slack flow, which I guess is not good for snow anyway is it, but severe cold be nice anyway!!

I'm not the best person to explain ensembles, I could have a go but would probably make a mess of it

NW guides are always good though

http://forum.netweather.tv/topic/25663-guide-to-ensembles/

Edited January 19, 2010 by CatchMyDrift

[snowy owl]

Looks like the GFS run was a cold outlier - but there are still a lot of cold possibilities. I think we should expect a change in the later run to something less extreme!

It still looks pretty cold though whereever you look but i'm only going as far as the weekend at the most as its all still a bit topsy turvy.

CMD - better keep those hats and gloves out!!

Edited January 19, 2010 by snowy owl

[Blizzardo]

The 6-15 day Met Office forecast looks a bit colder than recently and seems to indicate that they believe that the Easterly as shown in some models this morning will be brief with more of a Polar Maritime influence afterwards.

Its a bit vague and covers a few bases but in general it does look as though they feel the trend is towards a colder spell.

UK Outlook for Sunday 24 Jan 2010 to Tuesday 2 Feb 2010:

Rather cloudy for many parts, with showers or longer spells of sleet or snow likely in the east and over high ground at first, with outbreaks of light rain further west. From Wednesday (27th) wintry showers are expected to ease in the east, with rain, sleet or snow developing across western and northwestern parts. Temperatures are expected to be below normal, and perhaps very cold in the east, with overnight frosts likely and an associated risk of ice in places. There is a lot of uncertainty regarding the end of the period, but a continuation of unsettled weather is likely with spells of rain, sleet and snow, and a risk of strong to gale force winds mainly across western parts. Temperatures probably remaining below normal.

Updated: 1226 on Tue 19 Jan 2010

[Guest]

Although I would say that a good start is to head here:

http://www.netweather.tv/index.cgi?action=ensviewer;sess=

Select your local area and 850 temps and it should bring up a chart like this:

The green line shows the normal (non-ensemble) operational run which we see as the main GFS run. The blue run is the control for the GEFS (ensemble) run and the thick red is the mean of the ensemble runs. The thin lines are just individual ensemble runs which use the same data as the main GFS run but with minor tweaks here and there (see the NW guide for more info on that!).

To me the two most important aspects are firstly, how many of the thin lines follow the green line (i.e. how many ensemble members support the ideas of the main run), or to look at it from the opposite point of view, where the lines scatter away from the green line which shows weak support for the ideas of the main run.

Secondly, what does the red line show, if there is a dip in the mean later in the time period does this indicate a trend to a cold spell? This is where you need to compare several of the same time runs over several days (i.e. all the 12z runs for 5 days).

I am sure someone can correct what I have posted, I will probably find fault in it myself too

Edit: And that's just the time series graphs, there are panel maps and all sorts to play with!!!

Edited January 19, 2010 by CatchMyDrift

[Snowplough33]

Although I would say that a good start is to head here:

Select your local area and 850 temps and it should bring up a chart like this:

The green line shows the normal (non-ensemble) operational run which we see as the main GFS run. The blue run is the control for the GEFS (ensemble) run and the thick red is the mean of the ensemble runs. The thin lines are just individual ensemble runs which use the same data as the main GFS run but with minor tweaks here and there (see the NW guide for more info on that!).

To me the two most important aspects are firstly, how many of the thin lines follow the green line (i.e. how many ensemble members support the ideas of the main run), or to look at it from the opposite point of view, where the lines scatter away from the green line which shows weak support for the ideas of the main run.

Secondly, what does the red line show, if there is a dip in the mean later in the time period does this indicate a trend to a cold spell? This is where you need to compare several of the same time runs over several days (i.e. all the 12z runs for 5 days).

I am sure someone can correct what I have posted, I will probably find fault in it myself too

Edit: And that's just the time series graphs, there are panel maps and all sorts to play with!!!

Thats great CMD........explained fine for me.

Thankyou.

[Blizzardo]

Just to add my own view on the ensembles to Catch's very good explanation.

I think they can be a good trend spotter as they measure the probability of a certain forecast actually happening by running a number of different forecasts each with a slightly different scenario.

Each day throughout winter I normally have a quick check of the ensembles and my focus is on the 850 temps (the temperature at approximately 1.5 km) and then air pressure. For me the air pressure gives a clue to a pattern change and the 850's tell how cold it may be.

I tend to focus on the ensemble mean (average) which gives an indication of the most likely forecast from that model run.

At the moment, using the GFS 06z for example the ensemble trend is for pressure to start building from around 23rd (Easterly) and and then fall away after a couple of days (probably Polar Maritime North Westerly influence as the temperature doesnt rise much).

There is reasonable agreement for the initial rise is pressure but a bit less for the pressure drop from the 26th.

[sunny starry skies]

Hi,

For the sun spots, there does seem to be some relationship. Not something that should be dismissed so easily anyway. I'll be annoying by asking the simple question that as the sun warms us from -273 to + 20 C, would an 0.1% change in output not be 0.3 C for a direct correlation of output vs T? Some suggest variation of 0.2%, so 0.6 C? Of course it is not as simple as that but hope you get my point.

Apologies for the off topic divergence.

Will keep this brief as it's off topic and you don't want to debate in the right forum. To your question: The sun heats us from -273C to about -19C (the Moon provides the analogue here), the greenhouse effect of certain gases in our atmosphere raise that by ~33C to ~+14C. The radiative forcing of the 0.1% change in solar irradiance is too small to account for recent climate changes, and all Sun-climate correlations have broken down in the last 30 years. The enhanced greenhouse effect can explain the observed changes and their magnitude. The short answer to your question is in part - it's not as simple a system as that!

Back on topic, cheers for the summaries LS, and it's still looking interesting here for late Wed into Thurs. Though the next system does look to be powering through on Friday as rain, so anything white and wintry will be short-lived this time.

sss

[Mondy]

and all Sun-climate correlations have broken down in the last 30 years

...which in the grand scale of things is miniscule in Sun-climate correlations, yes?

Anyway, where's this snow?

[Snowplough33]

...which in the grand scale of things is miniscule in Sun-climate correlations, yes?

Anyway, where's this snow?

Apparently on the 12z +144 UKMO chart

But this morning it was GSF that was number 1, so we will change to suit as the days go by!!

[LomondSnowstorm]

http://charts.netweather.tv/gfsimages/gfs.20100119/12/30/prectypeuktopo.png

Nice UKMO, with a cold easterly setting in: http://www.wetterzentrale.de/pics/Rukm1441.gif

The ECM isn't too bad, though the easterly never really gets going http://www.wetterzentrale.de/pics/Recm1441.gif http://www.wetterzentrale.de/pics/Recm1921.gif

Charts of the day - GEM http://91.121.94.83/modeles/gem/run/gem-0-144.png GFS 06Z http://charts.netweather.tv/gfsimages/gfs.20100119/06/171/h850t850eu.png

Crazy chart of the day - The japanese model defying the others http://www.meteociel.com/modeles/jma/run/JN192-21.GIF?12-12

FI appears to be around 96 hours now, with the charts above differing totally. The NAO looks neutral to perhaps slightly negative, meaning it'll be a bit harder for the high to move west, but the MJO appears to be moving into a phase which encourages greenland highs in about 5-10 days time, so perhaps the NAO outlook will change given this.

Anyway, North Sea warming in action this evening, with temperatures up to 3.5C due to cloud and light rain having moved in.

LS

[Scottish-Irish Skier]

Will keep this brief as it's off topic and you don't want to debate in the right forum.

Ha ha ha. I don't want to debate at all, although it seems you do I just thought the guy's presentation was interesting would be fun to show on a thread which I feel is domintated by people searching for snow and longing for colder winters. I can guess why GW folk get irked by him. If you want to debate kinetic hydrate inhibitors, I'm all for it (doubt there is a suitable forum though!), but if you want to fight the GHG corner vs sunspots, I suggest you contact Mr Archibald. Thanks for the wee addition to my sun intensity; apparently I wasn't far off for a total guess. One last thought; would you stake your house on the IPCC projections? I imagine if the IPCC did that it would quickly convince the unbelievers and of course, as the IPCC is right, what is there to lose; they'd make millions. Wonder what odds William Hill is offering... Think I'll hedge my bets for now.

As usual, thnx to LSS for the summaries. Interesting times ahead. We had a hard frost last night (-4.5 C) and down to 2.2 C now. Still a good 6" lying in sheltered/north facing aspects in these parts. Figure I'll have a wee head start in the garden when the next snow arrives. That's what, 34 days of lying snow - whoocha.

Edited January 19, 2010 by scottish skier

[Guest]

FI appears to be around 96 hours now, with the charts above differing totally. The NAO looks neutral to perhaps slightly negative, meaning it'll be a bit harder for the high to move west, but the MJO appears to be moving into a phase which encourages greenland highs in about 5-10 days time, so perhaps the NAO outlook will change given this.

Anyway, North Sea warming in action this evening, with temperatures up to 3.5C due to cloud and light rain having moved in.

LS

Cracking summary as always LS! I like the JMA chart and who knows, it must come good one of these times surely??!!

[Snowplough33]

.

Anyway, North Sea warming in action this evening, with temperatures up to 3.5C due to cloud and light rain having moved in.

LS

Thanks again LS. Great summary considering how up in the air it all is.

[shuggee]

Yes that JMA is interesting. There has been talk of upstream signals hinting at the splitting of the polar vortex and one part falling into Scandinavia. Of course, the block to the east needs to lessen its grip first of all and there's precious little sign of that happening yet. So maybe that JMA chart could come true at T+300...

[LomondSnowstorm]

Cracking summary as always LS! I like the JMA chart and who knows, it must come good one of these times surely??!!

The talk on the model thread is of a dry easterly, though how they can look at precipitation amounts in detail with such changes between models is beyond me! The NAO and AO forecasts have been changing constantly in the last few days, which I suppose is natural given that they are merely the products of the same computer models which are struggling with the pattern at the moment!

Anyway, just spotted this from the 12Z ECM http://www.meteogroup.co.uk/meteo/ecmwf/NSea/2010011912/NSea_2010011912_thgt850_120.png

-7 uppers with a shortwave across us, which surely means a decent shot at some frontal snow! Anyway, the main thing is getting the cold uppers back - the snow will surely follow yet again if we can get that!

Catch, I think you were right to like the look of that JMA http://www.meteociel.fr/modeles/jma/run/J192-7.GIF?19-12 http://www.meteociel.fr/modeles/jma/run/J192-21.GIF?19-12 Something like that could be 93esque, though the other models really don't support it at the moment.

[Guest]

The talk on the model thread is of a dry easterly, though how they can look at precipitation amounts in detail with such changes between models is beyond me!

And as we all know after the last cold spell, once the cold is in place anything can and will happen. Almost all of the snowfall in our cold month was last minute nowcasting snow. Stuff the forecasts of "it'll be dry", just give us some cold and then we'll find out where the precip is coming from. The snow will come if we have cold.

As for memories of '93....mmmmmmmmmmmm. If only :)

[snowy owl]

Bit of Easterlies Dramarama - worse than Eastenders!!!

Dry only easterly, or maybe no easterly at all - everything is still uncertain the tiniest tweak and they are off again!!lol! madness.

Anyhow looks like more chance of some initial rain to snow for tmrw/Thursday in some parts?

Can anyone with more knowledge give their opinion on probabilities for temps/precipitation for thurs?

[Mondy]

Ha ha ha. I don't want to debate at all, although it seems you do I just thought the guy's presentation was interesting would be fun to show on a thread which I feel is domintated by people searching for snow and longing for colder winters. I can guess why GW folk get irked by him. If you want to debate kinetic hydrate inhibitors, I'm all for it (doubt there is a suitable forum though!), but if you want to fight the GHG corner vs sunspots, I suggest you contact Mr Archibald. Thanks for the wee addition to my sun intensity; apparently I wasn't far off for a total guess. One last thought; would you stake your house on the IPCC projections? I imagine if the IPCC did that it would quickly convince the unbelievers and of course, as the IPCC is right, what is there to lose; they'd make millions. Wonder what odds William Hill is offering... Think I'll hedge my bets for now.

As usual, thnx to LSS for the summaries. Interesting times ahead. We had a hard frost last night (-4.5 C) and down to 2.2 C now. Still a good 6" lying in sheltered/north facing aspects in these parts. Figure I'll have a wee head start in the garden when the next snow arrives. That's what, 34 days of lying snow - whoocha.

I wouldn't stake my house on anything the IPCC say http://news.bbc.co.uk/1/hi/sci/tech/8468358.stm

Where's my snaw?

[Guest]

Bit of Easterlies Dramarama - worse than Eastenders!!!

Dry only easterly, or maybe no easterly at all - everything is still uncertain the tiniest tweak and they are off again!!lol! madness.

Anyhow looks like more chance of some initial rain to snow for tmrw/Thursday in some parts?

Can anyone with more knowledge give their opinion on probabilities for temps/precipitation for thurs?

Does the precip even reach us yet??

[LomondSnowstorm]

Bit of Easterlies Dramarama - worse than Eastenders!!!

Dry only easterly, or maybe no easterly at all - everything is still uncertain the tiniest tweak and they are off again!!lol! madness.

Anyhow looks like more chance of some initial rain to snow for tmrw/Thursday in some parts?

Can anyone with more knowledge give their opinion on probabilities for temps/precipitation for thurs?

Sure. Maxima around 2-5C for most of Scotland with a few showers dying out in the northeast. The main band arrives at 9pm, though with uppers above freezing the best (and perhaps the word best here is distinctly masochistic in this instance!) we could hope for is freezing rain if the surface air is cold enough. Tomorrow night though is a distinct possibility for snowfall, with temperatures between 0-3C and dewpoints just below freezing http://charts.netweather.tv/gfsimages/gfs.20100119/18/27/ukpaneltemp.png with some convective showers around http://charts.netweather.tv/gfsimages/gfs.20100119/18/24/ukprec.png .

[Guest]

On closer inspection:

[Cheggers]

Great updates again LS and like CMD I like the JMA. Last time I saw blues and purples like that was her indoors after a sledging session near Mugdock Park

Edited January 19, 2010 by Cheggers

[LomondSnowstorm]

Oh joy! The ECM 12Z was a mild outlier, so game on for a decent easterly. Or is the ECM 12Z merely the next trend setter...??