Model Output Discussion - 5th December - 11th December

[Mark Neal.]

Well I responded to one of Johns' posts which was, for some reason, a response to me. I know who he is/was and I presume he knows how people use pre warnings from the Met Office for their forwards planning so I wasn't sure why it was a response to my need to do that, I was agreeing with him about going with the overall picture and I, myself, was frustrated with those who had changed their mind after just one run, as he was. I presumed I was agreeing with him!

I presumed that people paid as much attention for similar reasons i.e. that they need to look further ahead so that they can be forewarned. Thankfully after the weekend it's Christmas holidays so the only thing I'm looking for then isn't any students that I'm in charge of (loco parentis stuff) but whether I can get up north to see the family!

Anyway, the ECM may have shifted things a little but it looks pretty similar for the South East compared to previous; unusually Friday's system seems to have been predicted to be further south through today, it's something I'm going to have to keep an eye on before as we break up Friday afternoon.

I break up for half-term aswell on Friday, looks like a wet n windy end to the term. Certainly a stormy period of weather, great to hear Nick Sussex's Views on where go in the further outlook, things look a little brighter than a few weeks ago. Still plenty of time for Cold & Snow to arrive, we have got until February.

[Eskimo]

I break up for half-term aswell on Friday, looks like a wet n windy end to the term. Certainly a stormy period of weather, great to hear Nick Sussex's Views on where go in the further outlook, things look a little brighter than a few weeks ago. Still plenty of time for Cold & Snow to arrive, we have got until February.

We have until April really, just obviously less intense

[Mark Neal.]

We have until April really, just obviously less intense

That is true to a extent, i just feel that by February the days are getting considerably longer and when is the last time we have seen a long period of cold & snow during March & April- especially down South, i can't remember one, though i'm only 17 years old. Back to the models, i feel we will have a easterly forming just after the new year, something Nick S has also hinted at.

Mark

[Nick F]

Don't think anyone's posted the t+120 fax for 12z Friday yet?

Looks similar in track to 18z GFS with strongest winds on southern flank for central and southern Britain, then a steep gradient across northern Britain as it exits across the North Sea.

[Aaron]

Well goodness me, if this storm hits the South then we'll never hear the end of it!

[Robbie Garrett]

Don't think anyone's posted the t+120 fax for 12z Friday yet?

Looks similar in track to 18z GFS with strongest winds on southern flank for central and southern Britain, then a steep gradient across northern Britain as it exits across the North Sea.

Well goodness me, if this storm hits the South then we'll never hear the end of it!

Quick question guys, I live 100ft up in a new building (metal/glass) - what's the windspeed likely to be?

[Liam J]

Quick question guys, I live 100ft up in a new building (metal/glass) - what's the windspeed likely to be?

We won't know until mid week, lot's of twists and turns to come in the outputs, complex situation with different scenarios being toyed with.

[Robbie Garrett]

We won't know until mid week, lot's of twists and turns to come in the outputs, complex situation with different scenarios being toyed with.

Well also for tomorrow, with a surface wind gusting of 50mph+, I know the upper winds will be something like 80mph at 2-3000ft but what about 100ft?

[Liam J]

Well also for tomorrow, with a surface wind gusting of 50mph+, I know the upper winds will be something like 80mph at 2-3000ft but what about 100ft?

I would say similar values at 100ft as its not that high, 50-70mph perhaps with the latter over exposed areas and coasts obviously.

[Robbie Garrett]

I would say similar values at 100ft as its not that high, 50-70mph perhaps with the latter over exposed areas and coasts obviously.

Let's just put it this way, I wont be going flying this week! I went up on Friday as Pilot in command and as passenger on Saturday very turbulent at the moment for some reason. Going to bring back memories down south tomorrow listening to the howling sounds.

[TEITS]

Some interesting comments tonight. I shall explain how I view the models to help any newcomers because I disagree with some of the comments tonight.

When you have a potential storm as suggested by the models then you DO need to follow every run. Comparing say the 12Z with yesterday is a pointless exercise. You may ask why and I shall explain. These models are fed huge amounts of data and the complex nature of our climate and the computer modelling means data that is 24hrs old is rendered useless. Following each run means they are using the latest observation data and because of this you will have a clearer picture with regards to this possible storm. The only timeframe I would agree with John H is with regards to the F.I output but certainly not upto +144 which is the timeframe this possible storm could occur. Also worth mentioning that I do know professional forecasters who do follow every run!

At the end of the day this forum consists of many different types of members with a varied knowledge of meteorology. Now if someone wants to comment on each run then thats their choice. I feel some need to chill out and appreciate this forum isn't only for the serious pro forecasters.

[alijoe]

Just check the met office site and now Everywhere is Yellow for Friday for wind.

[Aaron]

Just check the met office site and now Everywhere is Yellow for Friday for wind.

They're playing it safe for now.. many options as to where the storm will track and just about anywhere could be in for severe gales..

[Mark Neal.]

Well goodness me, if this storm hits the South then we'll never hear the end of it!

Oi, Im a southerner... Anyway i can't remember the last storm we had winds of 80-90mph in the South, anyone know? It's not everyday we experience these weather conditions that the models are throwing up, so obiviously we are going to talk about it for a long time, if a serious event did take place.

[ZONE 51]

If anyone could add something to this thread at some point that would be great - http://forum.netweat...ing-wind-gusts/

ive read alot of posts asking about how wind speed is affected by the land/hills/height and that.

Thanks.

Edited December 12, 2011 by ElectricSnowStorm

[Mark Neal.]

Oi, Im a southerner... Anyway i can't remember the last time a storm brought winds of 80-90mph in the South, anyone know? It's not everyday we experience these weather conditions that the models are throwing up, so obiviously we are going to talk about it for a long time, if a serious event did take place.

[nick sussex]

I'm not sure if people have been keeping upto date with the strat thread but we may now be seeing the end of the deep PV, this was running well below average in terms of temps but is set to improve.

In the mean time whilst we're in this holding pattern waiting to get our sledges out whats the best we can hope for in terms of synoptics, well as we've seen the December so far has been much more palatable in terms of a seasonal feel than we may have expected just looking at the teleconnections, as I've often said these aren't an exact science, just as we sometimes miss out on cold even with good teleconnections, the reverse can also apply.

The one thing though that we know with much more certainty is that whilst we may get some colder snaps out of a cold strat we won't get proper northern blocking and the chances for a sustained period with cold and snow UK wide.

So we're going to have to wait a while longer for that, what we can possibly get is an easterly or keeping the Azores high sufficiently west to keep things a bit more interesting, one variable that seems to be entering the scene is that Russian high, this may help lock in lower heights over Europe if it can ridge sufficiently nw.

In terms of an easterly we can only sustain this so long with the jet running ne over the top, to get sustained cold you'd need some background signal for blocking, as we saw in recent winters our easterlies were often shortened because the atmosphere was retrogressing the pattern, so we went easterly, northerly back to easterly but you need proper blocking over Greenland to do this.

Looking towards the Xmas/ New Year period I think theres a good deal of uncertainty and you could make a case for several scenarios, I'd view the Azores high with an often used American term, three strikes and you're out!

It's wanted to move in but been thwarted, it will probably try again one more time after that brief north/nw flow, if it doesn't manage to ridge into southern Europe then thats 3 strikes and out IMO.

The improving background signals should then see a more interesting picture begin to develop as we head towards the New Year, could we squeeze out some interest around Xmas?

I think we'll know by the middle of next week.

[ZONE 51]

Don't think anyone's posted the t+120 fax for 12z Friday yet?

Looks similar in track to 18z GFS with strongest winds on southern flank for central and southern Britain, then a steep gradient across northern Britain as it exits across the North Sea.

Everywhere has just gone on yellow alert.

[Ruzzi]

When you have a potential storm as suggested by the models then you DO need to follow every run. Comparing say the 12Z with yesterday is a pointless exercise. You may ask why and I shall explain. These models are fed huge amounts of data and the complex nature of our climate and the computer modelling means data that is 24hrs old is rendered useless. Following each run means they are using the latest observation data and because of this you will have a clearer picture with regards to this possible storm.

I agree! Surely the only way to spot a trend is to look at as much runs (DIfferent data inputs) as possible to spot a trend and detect an average within the models, i'e which is most likely to occur.

[kumquat]

ECMWF is tredding dangerous ground tonight, If It's wrong It's a pretty epic fcuk up. If It's right and the other models, ENS and all follow then Kudos to the ECM.

I will point out though, If ECM is right in dismissing this storm and the other players rapidly follow then this tells me that ALL models use the same raw data and theres no overall REAL difference between GFS NOGAPS ECM BOM ect ect at all.

I'm very open to correction if you think i'm talking out of my backside here

Of course, they should all use the same raw data as boundary conditions at the start of the run. It's what they do with them afterwards that counts. Are there real data points of temp and pressure that the models are not using? What are the inputs and do some models get better start point data than others? I think we verge into the commercial weather world with these questions.

[kumquat]

The so-called 'science' of tele-connections has been way hyped here IMO. The signs of warming to the stratospheric layer have been creeping up over the past couple of weeks. Any amount of jet-swing or "amplification of the upstream patterns" to coin a couple of favoured phrases here will result in slowing of the W-E PV flow. It's no surprise to me that this would result in a warming strat.

Edited December 12, 2011 by kumquat

[leicesternosnowzone]

The GFS 00z has I think further reduced the central pressure of friday's storm, approximately 970-975mb with the track of the low further south, and windspeeds now predicted to be lighter and probably unlikely to cause as much damage. Perhaps potential disruption from tuesday's winds is now more likely, the south coast and south east corner could be potentially quite gusty 50-60mph(?) (please feel free to correct me I'm still getting used to the models). The northerly toppler still being predicted for next sunday/monday (a bit slower getting started than earlier runs due to friday's low pressure becoming almost stationary, although still deepening in the eastern North Sea.

I would suggest anything after friday's system is still definitely FI but high pressure over Europe (1040mb seems to build in quite quickly(?)) is what the GFS is thinking tonight- and mild SW winds for much of the +200-360hrs timescale.

[weathe20]

Seems to be better ridging on the 0z run, and the -5 line seems to hang around a lot longer after next week compared to recent runs (newbie).

[snowmadchrisuk]

The GFS 00z has I think further reduced the central pressure of friday's storm, approximately 970-975mb with the track of the low further south, and windspeeds now predicted to be lighter and probably unlikely to cause as much damage. Perhaps potential disruption from tuesday's winds is now more likely, the south coast and south east corner could be potentially quite gusty 50-60mph(?) (please feel free to correct me I'm still getting used to the models). The northerly toppler still being predicted for next sunday/monday (a bit slower getting started than earlier runs due to friday's low pressure becoming almost stationary, although still deepening in the eastern North Sea.

I would suggest anything after friday's system is still definitely FI but high pressure over Europe (1040mb seems to build in quite quickly(?)) is what the GFS is thinking tonight- and mild SW winds for much of the +200-360hrs timescale.

Yes on this mornings GFS the strongest winds would be on channel coasts with the really strong winds reserved for France .

[shotski]

ECM looking better for cold at the moment after fridays event.

Edit: short lived cold

Edited December 12, 2011 by shotski