Winter Model Discussion - Cold Hunting -12Z 06/01/13

[SE Blizzards]

do you have a link for those ensembles ?? I.e where I can go find the one for my region ?

http://www.meteociel.fr/modeles/gefs.php

just click the part of map in which u live and the ensembles will come up for your region

[fergieweather]

Ps Shannon entropy at almost record high levels. What a saga! Fair play to folk at Exeter....!

[bradymk]

Hi guys,

So on what scale is this forecasting cold snap - are we talking cold/snow conditions on a level not seen for many-a-year.

Hope you are well,

Thanks BC

Hard to give an answer to that BC as such uncertainty makes the outlook rather unpredictable at the moment. Were continuing to see model flips and not much model agreement however i would say turning colder this weekend with the potential for rain to snow in some areas sat night. Then it gets even more uncertain but a cold pattern likely to remain next week with the potential of it becoming very cold and wintry into final third of month. But to answer your question, really cant say whether we will see that due to uncertainty however i would say it is unlikely but of course possible. Certainly a lot colder than recent weather with snow potential increasing, let the rollercoaster continue.

[Southern Storm]

Very latest UKMO guidance just issued goes for the cold/v cold story predominanting into next week with potential sequence of battleground set-ups of snow to rain and back again in W/SW ; heavy snow potentially in any region; perhaps with a temporary relaxation of pattern but return of cold thereafter (MOGREPS keeping a N'rly well into 10-15d trend period).

Thanks for the insight, I still won't be counting any chickens just yet but

You will have made a few people very happy with that post!

[from russia with love]

@fergieweather Maybe it me being a dunce but what is shannon entropy?

[Southern Storm]

Ps Shannon entropy at almost record high levels. What a saga! Fair play to folk at Exeter....!

Sorry to ask this but could you explain this please, as I haven't got a clue what it means lol

Hope you don't mind.

Edited January 8, 2013 by thunderman24

[from russia with love]

GFS op has backup from CFS!!!! Dust off the sledges!!! The CFS run has been hinting at a low just south of the UK on the 21st of January now for a few runs and GFS now following.

[Barmada Casten]

Hard to give an answer to that BC as such uncertainty makes the outlook rather unpredictable at the moment. Were continuing to see model flips and not much model agreement however i would say turning colder this weekend with the potential for rain to snow in some areas sat night. Then it gets even more uncertain but a cold pattern likely to remain next week with the potential of it becoming very cold and wintry into final third of month. But to answer your question, really cant say whether we will see that due to uncertainty however i would say it is unlikely but of course possible. Certainly a lot colder than recent weather with snow potential increasing, let the rollercoaster continue.

Thanks for taking the time to answer my question.

Appreciated.

[Winter Monsoon]

Sorry to ask this but could you explain this please, as I haven't got a clue what it means lol

Hope you don't mind.

Think he means massive uncertainty al la:- http://en.wikipedia....rmation_theory)

[Southern Storm]

@fergieweather Maybe it me being a dunce but what is shannon entropy?

Snap!

[Paul T]

'shannon entropy' in laymen's terms, in this context, could be 'unpredictability'

All time high shannon entopy is basically an all time high unpredictability in the model forecasts

Edited January 8, 2013 by Paul T

[alijoe]

Great explanation on wikapedia on shannon entropy.

[Southern Storm]

Think he means massive uncertainty al la:- http://en.wikipedia....rmation_theory)

OK thanks for that.

Always learning something new on this site!

[Met4Cast]

@fergieweather Maybe it me being a dunce but what is shannon entropy?

It's a measurement of unpredictability/uncertainty

[Southern Storm]

I remeber someone posted a chat from the last failed cold spell that showed a visual representation

Of when models struggle to pinpoint a particular feature.

For example, we are always questioning the positions of short waves coming out of north america,

And the chart I'm thinking of is like an anomaly map that shows where the most uncertainty is and the Possible downstream knock on effects.

Could someone put me out of my misery and tell me the name of this chat?

As I think it would be a very useful tool in these uncertain times, now possibly a little

Less uncertain after Ian's post.

Edit here it is

Edited January 8, 2013 by thunderman24

[Met4Cast]

I remeber someone posted a chat from the last failed cold spell that showed a visual representation

Of when models struggle to pinpoint a particular feature.

For example, we are always questioning the positions of short waves coming out of north america,

And the chart I'm thinking of is like an anomaly map that shows where the most uncertainty is and the

Possible downstream knock on effects.

Could someone put me out of my misery and tell me the name of this chat?

As I think it would be a very useful tool in these uncertain times, now possibly a little

Less uncertain after Ian's post.

Good question, I forgot about those!

I wouldn't mind having a link to them either

[Southern Storm]

Finaly found it but I Don't think there's a way to copy the original post so here's a link.

Paul explains thing nicely.

Good question, I forgot about those!

I wouldn't mind having a link to them either

[LomondSnowstorm]

Good question, I forgot about those!

I wouldn't mind having a link to them either

Only available on NW extra, here's the +120 chart though:

Considering that the original post by Paul showing that for +144 (which was during another period of model variation) had actually less of a spread than the +120 it's easy to see the models are struggling with this setup.

[syed2878]

hi guys. sorry mods this might be a bit off topic. but for those of u who have been down beet have listen to phillip eden's forecast on 5live's upallnight forecast of snow northeast england and easton scotland for this weekend www.bbc.co.uk/5live

[Met4Cast]

Finaly found it but I Don't think there's a way to copy the original post so here's a link.

Paul explains thing nicely.

http://forum.netweat...40#entry2420607

Cheers for that!

Only available on NW extra, here's the +120 chart though:

Considering that the original post by Paul showing that for +144 (which was during another period of model variation) had actually less of a spread than the +120 it's easy to see the models are struggling with this setup.

Where abouts are they on NW Extra? I have it, I just can't seem to find them anywhere!

[LomondSnowstorm]

Cheers for that!

Where abouts are they on NW Extra? I have it, I just can't seem to find them anywhere!

Go onto the extra ensembles and hit the panel maps tab and you should find it.

[LomondSnowstorm]

Don't worry, you can be assured that as soon as late May/June hits, pressure will rise to the NW and we'll be sat under a cold, wet trough

I say this completely tongue in cheek btw

I don't know about that, it's been a pretty reliable feature at some point in our summer for a few years now. Last year just took the biscuit though, the only time I've ever got sick of a greenie high! It isn't so fun when it's 14C and raining every day.

[Wilxy]

Don't worry, you can be assured that as soon as late May/June hits, pressure will rise to the NW and we'll be sat under a cold, wet trough

I say this completely tongue in cheek btw

Yep that will be the effects of SSW months down the line

[Wilxy]

Better heights towards greenland at very short range with that low further west south of greenland.

[Wilxy]

Wow this could potentially be a upgrade for a easterly if that low sinks south and heights manage to build over the top of it.