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phil nw.

Model Output Discussions 18z 31/01/2016

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5 minutes ago, blizzard81 said:

Yeah, northern england looks to be the place to be - hopefully lol. You are much higher up than me so you look to be in a prime location :)

Well we might need an upgrade or two, the 850's are not great but we'll see closer the time. :)

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Hope I'm not off topic, but long range forecasts… are really useless, how many times have the MET OFFICE said mild winters ( especially the winters of 09 and 10 ) and look how they turned out!! even there summer ones, I'm sure they have a hat ( for summer or winter )… with 9 mild and 1 cold outlook W… and 1 wet n cool, 9 hot n dry outlook S!!… a chart is only as good as the input, that's put into it!! A week is a long time I weather… and the weather will only do, whatever it does!! It will and does change… a chart for me, what it shows 2day… for a week later, if it shows 75% of what it shows 2/3days later… will be probably be right!! But if not… then start again

Ive always felt the MET OFFICE to be mild rampers, no matter what… but so is MADDEN the cold ramper!! But he will get 1 right, eventually lol

Ps... I say this about long range or medium range because some are throwing the towel in… with still alot of winter left and they will change whether it will be the holy grail cold n snow… or the bloody boring mild… mucka seems to have perked up a bit, when it seemed the towel had been chucked in… :D

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24 minutes ago, Law of averages!! said:

Hope I'm not off topic, but long range forecasts… are really useless, how many times have the MET OFFICE said mild winters ( especially the winters of 09 and 10 ) and look how they turned out!! even there summer ones, I'm sure they have a hat ( for summer or winter )… with 9 mild and 1 cold outlook W… and 1 wet n cool, 9 hot n dry outlook S!!… a chart is only as good as the input, that's put into it!! A week is a long time I weather… and the weather will only do, whatever it does!! It will and does change… a chart for me, what it shows 2day… for a week later, if it shows 75% of what it shows 2/3days later… will be probably be right!! But if not… then start again

Ive always felt the MET OFFICE to be mild rampers, no matter what… but so is MADDEN the cold ramper!! But he will get 1 right, eventually lol

Ps... I say this about long range or medium range because some are throwing the towel in… with still alot of winter left and they will change whether it will be the holy grail cold n snow… or the bloody boring mild… mucka seems to have perked up a bit, when it seemed the towel had been chucked in… :D

Most recently Summer 2012 and Winter 13/14 were both forecasted initially to be respectively hotter and colder than average, dry and settled and look how those turned out.

Long range forecasts are only indicative of what signals at the moment could lead to regarding the weather, but these can always change just as much as the models and the weather itself.

Edited by wishingforsnow

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In case you were wondering:

image.thumb.jpeg.024fcd82764c0fb1fdbd2e2z

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Just Model 'output' discussion please in here, Thanks. 

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7 minutes ago, Daniel* said:

In case you were wondering:

image.thumb.jpeg.024fcd82764c0fb1fdbd2e2z

That will do nicely for me and a large swathe of the UK things do look to be turning the way of the coldie... will we see it continue or will it be all change again tomorrow?? the models apart from December have really struggled this winter so far no real consistency at all and i guessing thats down to how unusual the background signals have been...with the super strong El Nino... well lets just hope for us coldies that we can at the very least get some decent snowfall for many if not all of us....must be able to get at least one decent go...

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MWB, I like your analysis of the amateur and the professionals forecasting competence. I know that there are people on here who can give the models a good run for their money.

You go on to say that the only thread that has not given false hope this winter is the strat thread where it has been made clear all winter that a SSW was a strong possibility, but would only be useful if it occurred in the right way. If that's the best that the strat thread has come up with then we are all in with a chance?

Edited by Weathervane

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h850t850eu.png

It's amazing what a ridge nosing out of Canada can do really. By interfering with the jet, it prevents the two features in the far-western N. Atlantic from merging, and the leading one is able to race across the UK to become an interesting 'runner' that engages with the polar maritime air associated with the mature UK/Scandi trough.

GFS entertains us further by disrupting the second far-w. N. Atlantic low and producing another 'runner' which grazes past the SE of the UK with some marginal snow achieved on the NW flank.

ECM's not interested in round two though - seemingly due to a shortwave west of Iceland (yes there it is again this season! Same problem area!). UKMO also has that feature but it's not as strong so it's hard to say which way that would go.

 

Suggestions longer-term that the polar vortex won't be re-forming over Canada after all, rather making its way toward Siberia. Probably via the Atlantic, with further rough weather for us to contend with. This could be the stormiest February in many years - remember, Feb 2014 calmed down quite a lot after the big Valentines Day Storm.

 

Plenty to sort out before then - this weekend is still un-forecastable beyond the broad theme of unsettled, wet and windy, thanks to the models being unable to agree or be consistent with the tracks and intensity of the secondary low Sat/Sun and the either very intense or fairly shallow feature Sun/Mon. The differences with that second one are downright ridiculous!

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19 minutes ago, fergieweather said:

There's a key issue here: UKMO don't issue seasonal forecasts. They issue *probabilistic assessments* spanning 3-month periods. These have been pretty accurate the last two winters since GloSea5 was introduced. This winter (D-J-F) called for mild, often wet/windy weather 1st half; greater (but not definitive) potential for colder weather 2nd half, with Feb the only month in output more likely to see -ve temp anomalies *but* this reliant on SSW, all set against El Niño signature and W'rly QBO. So far, these broadscale pointers have proved a good guide since November, and it's worth noting commercial forecast organisations (eg WSI, MeteoGroup, Metra etc) all had fairly similar expectations across this season. I actually think this winter has been a pretty good one for seasonal forecast specialists and for key tools, eg EC Seasonal/EUROSIP/GloSea5.

I agree Ian, so far this winter has been pretty well forecasted. The predictions from more than one major forecasting centre based on model outputs and background signals such as El Nino did call for a predominantely mild, wet and unsettled winter and they were spot on. 

Edited by wishingforsnow

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Still that colder trend showing for next week in the charts tonight as the Atlantic trough digs se into Europe.The ens have been consistent on this for a few days as pm air becomes more prevalent as lows track further south.Gefs 850's and mean chart T144hrs

850.thumb.png.b35f85c64d84d5df76763b0ece 56b262e86abe1_viewimage(5).thumb.png.5f1

 quite a cold westerly pattern setting in for a few days.

A colder looking ECM Op chart too at T144hrs,some -5C uppers getting well south.

ecmt850.144.thumb.png.fadbaa180cc6ded194 

Disappointing for cold and snow fans that we don't see Arctic blocking but it is what it is so we get the minor prize of a more southerly tracking jet and a colder Atlantic setup.No great freeze but a chance of some snowfall anywhere,especially with elevation.If we get a little runner(secondary wave depression) move across at the base of the main trough,such as showing in the GFS op around T156hrs,some places could well get a surprise snow event.

 

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21 minutes ago, fergieweather said:

There's a key issue here: UKMO don't issue seasonal forecasts. They issue *probabilistic assessments* spanning 3-month periods. These have been pretty accurate the last two winters since GloSea5 was introduced. This winter (D-J-F) called for mild, often wet/windy weather 1st half; greater (but not definitive) potential for colder weather 2nd half, with Feb the only month in output more likely to see -ve temp anomalies *but* this reliant on SSW, all set against El Niño signature and W'rly QBO. So far, these broadscale pointers have proved a good guide since November, and it's worth noting commercial forecast organisations 

I would agree Ian I think ye have done quite well this year. Of course most lrfs outside of the Meto try to get something of note into their forecasts esp cold/snow. The default pattern is mild and wet which is bore fest to most of us. It isn't much fun reading a prediction of mild and wet winter ahead tbh even if it's a correct call.

What does surprise me is how poor the gfs/ukmo/ecm perform at times. They haven't improved their accuracy over the last 10 years and have if anything gotten worse

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1 minute ago, January Snowstorm said:

I would agree Ian I think ye have done quite well this year. Of course most lrfs outside of the Meto try to get something of note into their forecasts esp cold/snow. The default pattern is mild and wet which is bore fest to most of us. It isn't much fun reading a prediction of mild and wet winter ahead tbh even if it's a correct call.

What does surprise me is how poor the gfs/ukmo/ecm perform at times. They haven't improved their accuracy over the last 10 years and have if anything gotten worse

Evidence please?

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For the talk of long range FC the January Hurricane had huge impacts as it pushed in to the Arctic and no LRF could foresee that and it had huge implications on the pattern after so IMO LRF aren't really up to much. Most of the time the weather will be mild wet and windy so to say a chance of cold at the end of winter and mild before that is nothing to get excited about in terms of verification. Anyway hopefully all areas see some snow this upcoming week

 

Edited by Abyss

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Some higher resolution model output to examine possible outcomes with the weekend features:

arpegeuk-2-78-0.png?03-18 arpegeuk-2-114-0.png?03-18

This is ARPEGE and it looks rough N. Half of UK Sat evening and overnight, then the south is in the firing line from the second system, but not until Monday based on extrapolation from the end of this run.

nmmuk-2-72-0.png?03-18 icon-0-77.png?03-12

WRF and ICON have the parent low further SW but with the secondary disturbance clearly identifiable as that kink in the isobars. It is notable that the level of development along the frontal boundary has generally trended toward something less compared to the 00z runs.

The severe weather threat is essentially from the front itself, this looking to have a convective element (squall) as evident in the ARPEGE precip output:

arpegeuk-1-71-0.png?03-18 arpegeuk-25-59-0.png?03-18 arpegeuk-25-83-0.png?03-18

The middle and right images show the accumulated precip up to 00z Sat and then to 00z Sun. Looks like 25-30 mm could be dropped by that frontal system as it stalls for a time due to the lowering of heights 'behind' it (to the NW of it). Slow moving squall lines can deliver very high totals (more than 30 mm) in n a short space of time locally so it's something to watch given the already saturated ground. ARPEGO also suggests 40+ mm over high ground which is notable but rather overshadowed by the effect of air being piled up at great speed against the mountains of Scotland for example. Cumbria and NW might also be in trouble... again.

- and that's just from the first act of what looks to be a seriously wet week or so. Here's the 12z GFS accumulations to day 9 (essentially showing net result for the 7 days starting Saturday):

216-777UK.GIF?03-12

Down here in the far south, I'm wary of those high totals int he Channel and far SW, as they suggest convective activity training in on the strong winds, and the inland penetration of these does tend to be underestimated when the winds are strong.

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25 minutes ago, wishingforsnow said:

I agree Ian, so far this winter has been pretty well forecasted. The predictions from more than one major forecasting centre based on model outputs and background signals such as El Nino did call for a predominantely mild, wet and unsettled winter and they were spot on. 

I'm sure if we go back through seasonal threads we will see GloSea5 went for a considerable cold weighting for just to the west of Ireland, emerging in January and getting stronger in February - and the UK on the edge of things. That has not happened. It's not my intention to slate the model but it's important to tell the story properly.

Sorry for keeping this going mods but I think if we are to learn from the models we need to look back as well as forward, hope that's OK.

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Back to the operationals, GFS interestingly showing a ridge developing out of NE Canada and into W Greenland which importantly prevents low heights coming out of the USA from phasing with the deep scandi-Uk trough, conversely we end up with shortwave activity dropping to our SE engaging the cold polar maritime air - hence perhaps some surprise snowfalls. ECM doesn't do this and instead develops a straightforward westerly flow.

GFS does often perform well when it comes to shortwave activity to our NW.. so will be interesting to see if maintains the colder outlook compared to ECM.

Its a very volatile set up, lots of unsettled weather.

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21 minutes ago, damianslaw said:

Back to the operationals, GFS interestingly showing a ridge developing out of NE Canada and into W Greenland which importantly prevents low heights coming out of the USA from phasing with the deep scandi-Uk trough, conversely we end up with shortwave activity dropping to our SE engaging the cold polar maritime air - hence perhaps some surprise snowfalls. ECM doesn't do this and instead develops a straightforward westerly flow.

GFS does often perform well when it comes to shortwave activity to our NW.. so will be interesting to see if maintains the colder outlook compared to ECM.

Its a very volatile set up, lots of unsettled weather.

UKMO has signs of the runner too

UW144-21.GIF

GFS

gfs-0-144.png

Please remember not to over analyse consecutive GFS runs though:wink: 

Edited by winterof79

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18Z back on the storm hunt - from an IMBY point of view this would be a little close for comfort, with near 60mph mean winds not far off in the channel

gfs-14-102.png?18

Still think it won't turn out like this. I'm waiting to see if the D8/D9 north atlantic ridge of the past two GEFS runs can be repeated, though.

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hmmm 18z a good couple of degrees milder than the 12z early next week.

Hope thats reversed in the morning!

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1 hour ago, January Snowstorm said:

 

What does surprise me is how poor the gfs/ukmo/ecm perform at times. They haven't improved their accuracy over the last 10 years and have if anything gotten worse

statistics provided by these centres suggest that comment is incorrect

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Its very difficult to have too much confidence in the detail at longer range as these runner lows that might appear are likely to come and go between outputs.

The set up does look condusive to one or more turning up but the exact track and whether these could give some marginal snow is up in the air this far out.

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Some nice looking charts on the face of it on the 18z, but where has all the cold air gone? ECM was onto something it seems, GFS over cooking that cold Westerly.

gfs-0-156.png

gfs-1-156.png

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5 minutes ago, johnholmes said:

statistics provided by these centres suggest that comment is incorrect

Hi John

Have you ever heard the phrase lies, darn lies and statistics. Perhaps your right but bear in mind 2 recent events.

1) all three models went for the projected very cold spell towards the end of Jan (inc their ensembles) All three were well off the mark

2) as close as only yesterday all three projected a vicious storm hitting southern areas over this coming wknd. 24hours later it's disappeared. That's less than 5 days where they called it wrong

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