Model output discussion 25th Jan onwards

[russell k]

Quite uninteresting 850 GEFS this morning with low confidence and nothing to extreme temp wise.

there seems a lot of doubt looking at the SLP ens

[East_England_Stormchaser91]

To me this is key to where we go next week to 10 days. I expect wave 2 activity next week will show it's hand more in the trop response. Jet diving south. Big scandi high to force westwards and the mighty canadian vortex weaken . Easy right?!!

Too risky mate. Our luck has just been rotten this winter. Still have not seen one flake, but 50 miles North in Lincoln and 80 miles in Sheffield are seeing snow. Forgetting what snow even looks like with my own eyes! We are just on the wrong side of the extreme this winter, and on the right side is the Southern USA like Myrtle beach and New Orleans believe it or not are getting a pasting!

Edited January 30, 2014 by East_England_Stormchaser91

[Bobby]

A lot of rain to come over the next 72 hours on the NMM. ~50mm in many western areas and ~75mm locally. That's not even 3 days into the next Atlantic onslaught which goes on as far as the eye can see

 

 

GFS 06z rainfall for next 8 days

 

 

SW England to get hit hard again - more than that on high ground, the catchment areas. Floods and more floods it seems. No surprised they've got the army in.

Edited January 30, 2014 by Bobby

[snowflakey]

To me this is key to where we go next week to 10 days. I expect wave 2 activity next week will show it's hand more in the trop response. Jet diving south. Big scandi high to force westwards and the mighty canadian vortex weaken . Easy right?!!

 

I really do hope so, it does seem to me that a Scandy high teens to develop later on in the winter sometimes. I think what we are seeing this year is a very exaggerated setup to what we get quite often in our winters. If and when the steep temp gradient off the eastern see board become weaker, then I believe we maybe looking towards the east for our weather.

Sorry mod if this is slightly off top

[Purga]

Average becoming mild and very unsettled / wet right through until mid Feb.

 

 

Diabolical chart for European coldies

 

This winter is so bad it's noteworthy!

[Summer Sun]

Latest NAO update keeps it positive to at least mid February

 

 

Latest AO update shows it to heading positive during next week and it stays that way to at least mid February

 

[somersetsnow]

They can and have been wrong, but unfortunately this winter its been the undercut and cold block backing west which has failed and failed.  The signals from all types at present, models, strat and us alternatives is 'as you were' and confidence in that is probably higher than in past due to advancements in all.  Get your sand bags ready, it aint going to be pretty for a week or so.  I am still erring on the side for a pressure rise to our southern quadrant down the line, but like the block to our E/NE it may not be influential enough.

 

regards

 

BFTP

Thanks so much for you reply,thought i would be shot down for asking,lol. Not looking forward to this weekend although not bad round here…..at the mo. Julieanne.

[somersetsnow]

Hi,

 

Firstly, it's not a daft question at all - it's a perfectly reasonable one to ask.  The broad answer is 'yes', NWP does indeed get things wrong; indeed, sometimes very wrong.  NWP models - especially those that are stochastic in origin - are highly sensitive and susceptible to variance, the degree to which will depend largely on the integrity of the initialisation data (the 200m odd daily readings that feed into them)  If there are ghost areas of data - and this does happen, albeit not often - then you will often see a fairly dramatic consequential effect.  To counteract that, many variables are parameterised during assimilation and, where required, smoothed-out through applied algorithms (winsoring, outlier factoring)  This essentially 'cleanses' the data, pre-processing; not a perfect option by any means, but nevertheless it calms erroneous signals.

 

You may have heard about the ensemble approach?  This is where small degrees of variance is intentionally introduced to the initialisation data, in order to grow forecast depth.  You can then analyse that depth to ascertain degrees of confidence in the operational forecast.  The ensemble approach has probably been the biggest forward step over the last few years, and that's only really been possible with acceleration of supercomputing power; it takes an incredibly long time to generate forecasts, so you need a LOT of computing power to produce one, let alone an ensemble suite.

 

In terms of model skill (ie: how accurate are they?) there's been a fairly linear growth, as more powerful supercomputing becomes available. In real terms, the 96hrs forecast is - today - as accurate as the 24hr one, 30 years ago; so, a four-fold increase in skill.  Further advancement of skill comes from better understanding of atmospheric science and modelling and translating the effects back the models.  This is a continual area of research, and where - for example - there's been an up-tick in understanding of the stratospheric~tropospheric relationship.  In addition, ever greater data density (so, more observations / sensors) will only ever be of help to models that rely so heavily on data.

 

There's a few graphs here to show how accurate the forecast are; the final one depicting the linear growth in skill, over the last 30 years.

 

Hope that helps?

 

SB

Wow! Thank you for taking the time to reply,much appreciated.

[Bobby]

This neat animation sums up our problem this winter. The polar vortex bringing exceptionally cold air across north America which then swings eastwards towards blighty igniting powerful cyclones as it crosses the warm Atlantic.

 

 

[Blake]

GFS 12z coming out now, seems that slightly better heights are building over the pole/to the north heading towards Svalbard. Looking a little better to the NE/E too. 10-15mb rise in high pressure north of Scandi. Low out west flattens a bit too which to me would allow blocking to the NE to become stronger as the low weakens.

 

6z

 

 

12z

 

 

And then a bit later, Azores sinks, heights to north head south. HP across the north. LP over northern tip of Scotland now 200 miles further south?

 

I'd say these are quite big changes here.

 

6z

 

 

12z

 

 

8c to 10c changes over northern Scandinavia, on the colder side.

 

6z

 

 

12z

 

Edited January 30, 2014 by GUWeather

[SMU]

http://modeles.meteociel.fr/modeles/gfs/runs/2014013012/gfsnh-0-120.png?12

 

Well, Im beginning to wind down the posts for 2013/14 winter- However im still lurking.

 

 

GFS showing some snow around at day 5 & also shows the cut off High over Scandi like the ECM yesterday-

 

May be a good run.- Pretty good polar flow aligned to slide into Scandi as well

S

[Bobby]

http://modeles.meteociel.fr/modeles/gfs/runs/2014013012/gfsnh-0-120.png?12

 

Well, Im beginning to wind down the posts for 2013/14 winter- However im still lurking.

 

 

GFS showing some snow around at day 5 & also shows the cut off High over Scandi like the ECM yesterday-

 

May be a good run.- Pretty good polar flow aligned to slide into Scandi as well

S

 

The Block vs the Atlantic is like Justin Bieber vs Vladimir Klitschko unfortunately.

[snowking]

The Block vs the Atlantic is like Justin Bieber vs Vladimir Klitschko unfortunately.

 

That's a bit harsh on the block isn't it

[Due South]

Get the first week of Feb out the way, then Dry and Warm Southern England. ( Corbyn ). If it comes off, at least some relief for the flooded communities.

[Iceaxecrampon]

Anyone who thinks "Winters Over" will be in for a reality check.

 

12Z

 

Saturday AM T+39 T+42

 

 

 

I would be inclined to think this is in the near reliable.

 

Ian

 

 

 

 

[Troubleatmill]

Anyone who thinks "Winters Over" will be in for a reality check.

 

12Z

Predominantly over 400m though iceaxe? Ok for me and thee up the fells, but lowland struggling, cold wet with a bit of sleet

 

Saturday AM T+39 T+42

 

h500slp.png

 

uksnowrisk.png

 

I would be inclined to think this is in the near reliable.

 

Ian

[linarite]

Hi,

 

Firstly, it's not a daft question at all - it's a perfectly reasonable one to ask.  The broad answer is 'yes', NWP does indeed get things wrong; indeed, sometimes very wrong.  NWP models - especially those that are stochastic in origin - are highly sensitive and susceptible to variance, the degree to which will depend largely on the integrity of the initialisation data (the 200m odd daily readings that feed into them)  If there are ghost areas of data - and this does happen, albeit not often - then you will often see a fairly dramatic consequential effect.  To counteract that, many variables are parameterised during assimilation and, where required, smoothed-out through applied algorithms (winsoring, outlier factoring)  This essentially 'cleanses' the data, pre-processing; not a perfect option by any means, but nevertheless it calms erroneous signals.

 

You may have heard about the ensemble approach?  This is where small degrees of variance is intentionally introduced to the initialisation data, in order to grow forecast depth.  You can then analyse that depth to ascertain degrees of confidence in the operational forecast.  The ensemble approach has probably been the biggest forward step over the last few years, and that's only really been possible with acceleration of supercomputing power; it takes an incredibly long time to generate forecasts, so you need a LOT of computing power to produce one, let alone an ensemble suite.

 

In terms of model skill (ie: how accurate are they?) there's been a fairly linear growth, as more powerful supercomputing becomes available. In real terms, the 96hrs forecast is - today - as accurate as the 24hr one, 30 years ago; so, a four-fold increase in skill.  Further advancement of skill comes from better understanding of atmospheric science and modelling and translating the effects back the models.  This is a continual area of research, and where - for example - there's been an up-tick in understanding of the stratospheric~tropospheric relationship.  In addition, ever greater data density (so, more observations / sensors) will only ever be of help to models that rely so heavily on data.

 

There's a few graphs here to show how accurate the forecast are; the final one depicting the linear growth in skill, over the last 30 years.

 

Hope that helps?

 

SB

If there was a 'required reading list' for new members, this would have to be on it!

[snowmadchrisuk]

The 12z gives us plenty of Snow chances, Next week could be one of them weeks where Snow could pop up anywhere at any time, Sat Morning and Tuesday Morning currently look very good for Snow falling but that is assuming it is right, I prefered the 6z for Saturday as the warmer 850's were further North. In FI though we are starting to come up with some Colder outcomes , take the chart below , It gives us a continental influence under low pressure , which no doubt would drag in some unstable air from the North sea ... 

 

 

[Blizzardof82]

Saturday not without interest for some of the white stuff, air looks cold enough and there is precipitation in my neck of the woods

[Summer Sun]

UKMO Euro 4 out to Saturday 06z today has potential doesn't look much on that chart but its what the one's further into the day will show for that we'll have to come back tomorrow

 

[Joe Levy]

Just thought I'd compare the uppers shown across Britain for Saturday morning, according to various models. This will be one of the factors in terms of wintry precipitation, though by no means is it the main or only factor!

EURO4 (6z)

UKMO (12z)

GME (0z)

GFS (12z)

[Blizzardof82]

Euro4 6z shows the little snow interest as well

[snowmadchrisuk]

Euro4 6z shows the little snow interest as well

 

 

Yes Interesting that of all the places that could actually see some Snow falling is SW England, Mind you it could Snow for a week and not settle here, due to all the flooding

 

Edit: More worrying tomorrow's storm is combing with 13m Tides here in Weston, That really is a bad situation to be in at the moment , especially in Somerset.

 

Weston-Super-Mare

High Tide 07:50 (13.00m) Edited January 30, 2014 by snowmadchrisuk

[Joe Levy]

 

Yes Interesting that of all the places that could actually see some Snow falling is SW England, Mind you it could Snow for a week and not settle here, due to all the flooding

 

Edit: More worrying tomorrow's storm is combing with 13m Tides here in Weston, That really is a bad situation to be in at the moment , especially in Somerset.

 

Weston-Super-Mare

High Tide 07:50 (13.00m)

 

It has the potential to cause major flooding issues upstream as well I would imagine, as any storm surge would slow the release of flood water which, combined with existing flooding, saturated ground and heavy rainfall, would be very damaging indeed. 

[snowmadchrisuk]

It has the potential to cause major flooding issues upstream as well I would imagine, as any storm surge would slow the release of flood water which, combined with existing flooding, saturated ground and heavy rainfall, would be very damaging indeed. 

 

Yes I agree with you there, I live on the sea front myself and we have the environment agency assessing the situation at the moment . Sandbags again ...