Winter Model Discussion - Cold Hunting 08/01/13 00z Onwards

[Snowly does it]

A little confused by the reaction to the model output and the 6-15 dayer, which today suggests a cold and blocked solution Sunday to the latter part of the week followed by attempted breakdown from the west with an uncertain outcome. That's a description of pretty much every cold spell in the UK and is what the GFS shows, albeit with the milder encroachment failing.

We live on an island artificially warmed by the gulf stream, that's what we get.

IMBY wise I am very happy with the output.

[SP1986]

It is true to a certain extent that if there is any uncertainty in the outputs in tends to evolve into a milder scenario, not always though, in the run up to 2010 if you remember rightly, the ECM had a hiccup then too, but then had to revert back to the cold spell. I'm not saying that's what will happen this time, but you would, given all the information we can glean, suggest the cold spell may end up more diluted affair, but that is not necessarily what will happen.

Having looked at the outputs it is almost nailed on that as far west as Holland will see very cold conditions, maybe not too dissimilar to last January/February, but the key is whether they can move over the north sea.

I see a few similarties with last February, although the pattern hasn't established for as long, and it has the potential for being further west.

[Summer Sun]

The problem is that people think cold means heavy snow and -10c temps.

The majority of the last 12 months have returned colder than average CETs - so colder weather is very much a possibility, just as milder than average is.

Indeed quite often bitter cold weather can deliver cold sunny days away from any fog patches (tomorrow will be a perfect example of this away from the south), the best chances of nation wide heavy snow comes from the west with battle ground scenarios, northerlies and easterlies quite often fail to deliver nation wide

Edited January 8, 2013 by Gavin.

[Timmytour]

I wouldn't always go with that Rob. Like you with many years of model watching under my belt i i find it is often a case of the actual outcome being a something of a halfway house between the two and to be honest a if the 06Z gfs came in even half as strong as suggested it would still be quite something.

There might be a halfway house in terms of the impact of the weather in the end, but I'm not sure, with the differences being shown, whether there can be much of a halfway house in terms of the way things progress here. I reckon it's one way or the other....if it goes the way of GFS, it might not end up as severe as the 6z run, but it'll be a point to GFS I'd say. And vice versa of course with ECM

Edited January 8, 2013 by Timmytour

[High Altitude]

Look in the 'Dynamics' Section half way down. It does a better job explaining it then I could!

http://en.wikipedia.org/wiki/Sudden_stratospheric_warming

SM

This is a good link. Thanks SM.

It states that a major SSW occurs every 2 years so why do we not see significant cold periods or outbreaks every other year. Or if SSW is that much of an important factor for UK cold spells then at least every 4 years, especially as minor events according to the text are a seasonal occurrence. In the main the nineties was a relatively mild decade for the UK yet there must have been 4-5 major SSW events and countless minor. This being the case it appears that there is much more variance to the UK receiving cold and other overiding or equally relevant goings on up in the atmosphere must need to come into play at the same time in order for us to have a shot at cold.

Question:

Does a major SSW event gurantee a cold outbreak for somewhere in the northern hemisphere or are other variables at play here as well meaning that a SSW event is just a signal that enhances the probability of cold period but not the defining factor?

[Ian Brown]

No evidence other than 10 years or so of looking at the models! And we know that to get a decent cold outbreak in the UK everything has to be "just so" to overcome the natural mildness of our location. Generally if one of the models spots something that's not quite right then the whole house of cards collapses in short order.

I'm not saying that will necessarily happen, just that I think it is more likely that GFS will flip towards ECM than vice versa. Fingers crossed that I am wrong though!

Absolutely Rob, TEITS was saying the other day that you can’t let past disappointments judge subsequent events but you have to have them at the front and back of your mind.

The frivolity of the weekend aside, is a proper cold spell within T144 ? No.

Do the big 3 models agree at T144 on the building blocks for Northern blocking ? No.

Are the METO bullishly confident or even reasonable confident (they were for late 2010) ? No.

Can this go wrong via the usual route of LP through the corridor of death and lack of heights over Greenland ? Absolutely.

Have the Express run a ‘big freeze’ story ? Yes.

The wrong answer to 1 or 2 of the above would worry me, but thats a full house.

[Rob K]

There might be a halfway house in terms of the impact of the weather in the end, but I'm not sure, with the differences being shown, whether there can be much of a halfway house in terms of the way things progress here. I reckon it's one way or the other....if it goes the way of GFS, it might not end up as severe as the 6z run, but it'll be a point to GFS I'd say. And vice versa of course with ECM

Yes that is what I was thinking. Often there is a halfway house but the GFS and ECM go off at such wildly difficult tracks that the only compromise would be a high sat over the UK with yet more gloom. So quite possible I suppose actually!

[Frosty.]

The Meto update today (6-15 day) is thankfully not following the ECM run from this morning or last night, the ecm shows a less cold/milder trend as next week progresses, the meto says cold all next week with wintry showers and night frosts, my question is, what do they mean by wintry showers..why can't they say snow showers, perhaps it's because it won't be cold enough for snow showers with accumulations, more like a mix of rain/hail/sleet and hill snow? think I just answered my own question.

Edited January 8, 2013 by Frosty039

[Bobby]

This is a good link. Thanks SM.

It states that a major SSW occurs every 2 years so why do we not see significant cold periods or outbreaks every other year. Or if SSW is that much of an important factor for UK cold spells then at least every 4 years, especially as minor events according to the text are a seasonal occurrence. In the main the nineties was a relatively mild decade for the UK yet there must have been 4-5 major SSW events and countless minor. This being the case it appears that there is much more variance to the UK receiving cold and other overiding or equally relevant goings on up in the atmosphere must need to come into play at the same time in order for us to have a shot at cold.

Question:

Does a major SSW event gurantee a cold outbreak for somewhere in the northern hemisphere or are other variables at play here as well meaning that a SSW event is just a signal that enhances the probability of cold period but not the defining factor?

Have a look at this

Which suggests that based on 54 SSW events over the decades on average a SSW leads to warmer weather rather than cold

"From a total of 54 SSW events compared with 1940-2012 CET anomalies

1-20 days following SSW is 0.038°C warmer than the 20 days preceding SSW.

7-28 days following SSW is 0.116°C warmer

15-45 days following SSW is 0.089°C warmer."

[weather eater]

What I dont understand is the METO update was cold or very cold with snow last night from yesterdays 12z. Yesterdays evenings ECM wasnt what we wanted with regards to cold, and they didn't use that output as part of their update. So what were they using, the GFS? Now they wont even consider the GFS and are going with the ECM.

So it seems ignore any output from the GFS until it matches the ECM

I rather suspect that the MO know just as well as we do that there is no point looking much past 120hrs at anytime, especially at the moment. Out to the point of between120hrs to 144hrs the GFS and ECM are not miles apart, so siding with the ECM doesn’t mean that much; people really need to stop thinking that runs are likely to verify in their entirety and that correspondingly that’s the MO thinking as well. Then there is the Shannon Entropy, how I read that is that model synoptic evolutions are at, shall we say maximum unpredictability. The MO also talk of battle ground events I can’t see where they are going to come from on the recent ECM operationals.

[No Balls Like Snow Balls]

Absolutely Rob, TEITS was saying the other day that you can’t let past disappointments judge subsequent events but you have to have them at the front and back of your mind.

The frivolity of the weekend aside, is a proper cold spell within T144 ? No.

Do the big 3 models agree at T144 on the building blocks for Northern blocking ? No.

Are the METO bullishly confident or even reasonable confident (they were for late 2010) ? No.

Can this go wrong via the usual route of LP through the corridor of death and lack of heights over Greenland ? Absolutely.

Have the Express run a ‘big freeze’ story ? Yes.

The wrong answer to 1 or 2 of the above would worry me, but thats a full house.

But equally you could ask them questions about a mild weather pattern and the answer would still be no. So what you are spouting on about is a load of old cobblers really because the simple fact is that no one really knows for certain what will happen. I appreciate that you have been looking at the models for many years. I have been playing football for many years, but that doesn't make me Wayne Rooney does it!!!

Edited January 8, 2013 by No balls like Snow Balls

[SP1986]

Karl, I suspect wintry in this scenario means a mix of snow, sleet and hail.. don't forget they may initially start of less wintry and become more and more tending to snow later. Plus hail might be prevalent, given the potential instability in eastern areas.

Not sure about the past disappointments comment, I'm pretty sure if there have been many disappointments in the past, there is pretty good reason for it!

Edited January 8, 2013 by SP1986

[chionomaniac]

Absolutely Rob, TEITS was saying the other day that you can’t let past disappointments judge subsequent events but you have to have them at the front and back of your mind.

I think though Ian, there can become a problem if you let previous disappointments override your objectivity. And I would say that it appears that you may be coming close to that, no matter what the outcome.

[TAFKAP]

Either that or you're taking some posts too seriously

Fair enough, but that said I thought the post a few pages back about snow in Jerusalem and Palestine was taking the Michael but looks to be some truth in it http://www.israelnationalnews.com/News/Flash.aspx/259224

(NB Fun fact, although you might not think it, Jerusalem gets snow pretty much each year)

[frosty ground]

No evidence other than 10 years or so of looking at the models! And we know that to get a decent cold outbreak in the UK everything has to be "just so" to overcome the natural mildness of our location. Generally if one of the models spots something that's not quite right then the whole house of cards collapses in short order.

I'm not saying that will necessarily happen, just that I think it is more likely that GFS will flip towards ECM than vice versa. Fingers crossed that I am wrong though0!

What about the situations which had model disagreement and still turned out cold....... FYI every cold spell / Snap that has come to pass has had model disagreement in the lead up to such events. The disappointment in missing out what was forecasts is probably remembered more than an actual events coming to pass, who cares about disagreement when the situation resolves itself?

Hence the mild always wins argument is clearly snake oil.......

PS I've seen the models for the last 10 years also!

Edited January 8, 2013 by frosty ground

[No Balls Like Snow Balls]

The below is from Twitter

Australia BOM had to adjust their temperature scale for extreme heat wave event - colours for 50-52°C & 52-54°C added

LOL, I reckon the GFS will be adjusting it's temperature scale to -50 850 temps by the time this SSW has panned out

Edited January 8, 2013 by No balls like Snow Balls

[chicken soup]

Whats the betting that the gfs12z moves towards ecm, then a couple of hours later the ecm moves towards the previous gfs, leaving us even more bamboozled than we are now.

[Yarmy]

Have a look at this http://forum.netweat...80#entry2463540

Which suggests that based on 54 SSW events over the decades on average a SSW leads to warmer weather rather than cold

"From a total of 54 SSW events compared with 1940-2012 CET anomalies

1-20 days following SSW is 0.038°C warmer than the 20 days preceding SSW.

7-28 days following SSW is 0.116°C warmer

15-45 days following SSW is 0.089°C warmer."

The CET is not a proxy for the entire Northern Hemisphere.

[Tamara]

You can't make up fixed rules about weather patterns - each one has to be taken and assessed on its own merits using the best available model output and data that is available at that given time. This is a continually moving programme, continually subject to change. The current pattern evolution, and potential avenues that the pattern may take are rife with uncertainties with the atmosphere in such flux over the polar stratosphere field. On that basis the process of using best available data at a given time takes on a higher level of necessity than usual. Of course weather forecasting always has this requirement 24/7 - it is just that predicting the way forward in such a set-up as this is a permanent updating 'now-cast' on the biggest of usual scales! No wonder we get an insight into the head scratching that is going on at the METO - not an enviable task with so much model chopping and changing and lack of agreement

The GFS alludes to a progressive -NAO scenario as head through the rest of the month - this fits the predicted background pattern and would also plausibly also fit any less cold interlude that the ECM may allude to as well, as polar vortex energy is transported across the pole from Canada to Siberia.

[UV-RAY]

It becomes back to my theory about the NAO refusing to go negative for reasons that need researching in spite of the background signals being otherwise.

We can get cold without the benefit of –NAO but events such as Jan 1987 and Feb 1991 are rare beasts.

What about December 2009, January and February 2010, December 2010, not forgetting the winter of 1996 Ian.

[Weathizard]

Hope the 12z GFS sticks to its guns with regards to heights to the NW, it must stick to its guns. If it switches its a bit of a disaster, but knowing the models recently the GFS will switch to mild and the ECM will go for the next ice age!

Best case scenario we got some agreement tonight or the ECM moves towards the GFS. Worst case GFS gives in and folds to the ECM

[Paul]

We need to keep it to discussing the models in here - if your opinion is that whatever the models show is irrelevant because of one reason or another, then perhaps this isn't the best thread to be taking part in?!

[mcweather]

Timmytour, on 08 January 2013 - 14:36 , said:

There might be a halfway house in terms of the impact of the weather in the end, but I'm not sure, with the differences being shown, whether there can be much of a halfway house in terms of the way things progress here. I reckon it's one way or the other....if it goes the way of GFS, it might not end up as severe as the 6z run, but it'll be a point to GFS I'd say. And vice versa of course with ECM

Yes that is what I was thinking. Often there is a halfway house but the GFS and ECM go off at such wildly difficult tracks that the only compromise would be a high sat over the UK with yet more gloom. So quite possible I suppose actually!

of course the other halfway house between the ECM pushing the Atlantic through and the GFS pushing the arctic evolution through could be the battle ground scenario that the Meto keep alluding to.

[fergieweather]

The Meto update today (6-15 day) is thankfully not following the ECM run from this morning or last night, the ecm shows a less cold/milder trend as next week progresses, the meto says cold all next week with wintry showers and night frosts, my question is, what do they mean by wintry showers..why can't they say snow showers, perhaps it's because it won't be cold enough for snow showers with accumulations, more like a mix of rain/hail/sleet and hill snow? think I just answered my own question.

The latter is the guidance I've been given (messy mix of rain, sleet, snow).

Incidentally - after an interesting conversation about where we may be heading, with my learned mentor this morning (!), he suggests take a look at Dec 1990 for what he considers a close analogy to what we have currently developing. He suggests I pull up the archives for this, but will do so when I get a moment.

Cheers

Ian

[Rob K]

The Meto update today (6-15 day) is thankfully not following the ECM run from this morning or last night, the ecm shows a less cold/milder trend as next week progresses, the meto says cold all next week with wintry showers and night frosts, my question is, what do they mean by wintry showers..why can't they say snow showers, perhaps it's because it won't be cold enough for snow showers with accumulations, more like a mix of rain/hail/sleet and hill snow? think I just answered my own question.

The Met Office seem to have an allergy to the word "snow" in their text outlooks, I think because they are worried about causing panic. They almost always say "wintry" instead, either "wintry showers", or in frontal situations "rain turning wintry". Just one of those quirks...

I remember one of the most notable things about the run up to Nov/Dec 2010 was that the Met updates actually included the word "snow" with no qualifiers. I commented on it at the time...

Edited January 8, 2013 by Rob K