Model Output Discussion 12hrs. 01/10/13

[Jonan92]

what does that mean?

 

Well, it's rather improbable, but that setup shows a displaced vortex. If the ride of our side linked up with the one in the artic we will hace a big ride on that side and on the other side the vortex. However, it is too early to see something like that

[snowy weather]

Well, it's rather improbable, but that setup shows a displaced vortex. If the ride of our side linked up with the one in the artic we will hace a big ride on that side and on the other side the vortex. However, it is too early to see something like that

thanks

[J10]

For those in the north and west of England and Wales you wouldn't want the low to shift any further west or next weekend could be pretty miserable for most of the country. The metoffice already have the South east under persistent rain. So what's to say that persistent rain could effect a wider area of the UK.

Shame the south easterlies on most models 48 hours back have gone.

 

We tend to be very sheltered from these types of weather events and even under low pressure we would see the best of the weather, clearly you are speaking as someone badly effected. From a local point of view, would much prefer weather systems to the east rather than the west.

 

How many times have we seen Northerly events such as this, modelled too far west.

Edited October 6, 2013 by J10

[SMU]

another misunderstandin I'm afraid Timmy. ALL models take the data at T+00 and run through to the end of their period using complex maths to solve the almost as complex physics equations, there is NO historical data fed in. Write to UK Met, ECMWF and NOAA to see what they say?

John- within that though there must be somewhere a background pattern to build a program- a base set up, a 'typical' outcome to any one gridpoint - how much of that is factored in ... well- who knows-

 

But irrespective of whats written in - the GFS needs a euro upgrade-

 

S

[Met4Cast]

John- within that though there must be somewhere a background pattern to build a program- a base set up, a 'typical' outcome to any one gridpoint - how much of that is factored in ... well- who knows-

 

But irrespective of whats written in - the GFS needs a euro upgrade-

 

S

 

Was there not a test done where data from the ECM was fed into the GFS computer and the accuracy went up by a fair amount? 

[SMU]

I remember something ages ago... but not much stats etc-

 

We have what we have- just have to make the best of it--- I think its part of the fun second guessing the models..

[Tamara]

It seems as though the GFS has gone from one extreme to the other - it was too far east with the pattern but now it is possibly overcompensating by pulling the trough coming down from Scandinavia too far west. The 12z UKMO has the trough a fair bit further east than the GFS at t96

 

GFS 

 

 

UKMO

 

Edited October 6, 2013 by Tamara תָּמָר

[chionomaniac]

It is worth pointing out how important a meridional flow is for those hoping for cold when looking at the models for this coming winter. We are seeing a classic switch forecast from high 850's  (+12ºC) over Scotland tomorrow being replaced by low 850's by Thurs (-3ºC?) - a 15ºC switch around. This is very difficult to achieve in a zonal flow. Yes, we may be on the wrong side of the ridge in the outer reaches of the modelling in FI, but always be aware that these switcharounds do occur in meridional flows and that by the time that the exact ridge positioning becomes modelled more accurately by days 4/5, the ridge may be better postioned/ orientated bringing colder 850's over an area that this previously looked unlikely.

 

I have learnt to always look for the meridional pattern first and disregard the positioning of the troughs/ ridges until the meridional pattern is established. Normally, when it is established over a period of time, the cold that floods to more southern latitudes will often hit the UK and when it does it can hang around. 

 

So that begs the question - when we are in an established zonal flow, what is necessary to change this to a more meridional flow?

 

And the answer to this is not a straightforward one. It just doesn't occur without some type of driving mechanism. Yes, we need to look at the stratosphere - but if the stratosphere is already cold and a strong polar vortex established then we need to look back into the troposphere. In some years the stratosphere will be more receptive to tropospheric interactions than others ( more discussion for the strat thread) but we will still need a kick start from the troposphere to feedback into the stratosphere. The kick start often will come from the tropics in the form of pulses of convection interacting with slight undulations in the polar vortex which influence the positions of the sub tropical jet stream and polar jet streams respectively. The exact positioning of the large scale undulations ( or Rossby waves) will be influenced by (amongst other things) the pulses of tropical convection ( aka the phase of the MJO) and that is why we monitor that so closely. These waves will interact with land masses and mountain ranges which can absorb or deflect the Rossby waves disrupting the wave pattern further - and this interaction and feedback between the tropical and polar systems is the basis of how the Global Wind Oscillation influences the global patterns. The ENSO state can affect this - giving us the underling atmospheric base state . 

 

If the deflection of the Rossby Wave is great enough then the wave can be deflected into the stratosphere. This occurs a number of times during a typical winter and is more pronounced in the NH due to the greater land mass area. Most wave deflections into the stratosphere do change the stratospheric vortex flow pattern - this will be greater if the stratosphere is more receptive to these wave breaks ( and if they are substantial enough, then a SSW can occur). The change in the stratospheric flow pattern can then start to feedback into the troposphere - changing the zonal flow pattern into something with more undulations and perhaps ultimately to a very meridional flow pattern.

 

It is looking like the loss of summer sea ice in the Arctic ( and corresponding increased  autumnal snowfall further south) in recent years may be contributing to the pattern of the jet stream being less zonal - with more undulations due to the baronclinicity zone possibly being displaced further south - but there are other factors such as the SST's influencing whether the flow is more zonal.

 

And these are all the things that we need to monitor in the coming weeks and during winter - especially if a zonal flow becomes established.

[Summer Sun]

Anyone else having problems loading UKMO at t120 and t144?

[Cloud 10]

Anyone else having problems loading UKMO at t120 and t144?

 

Its okay on meteociel now SS

 

meteociel.fr - modèle UKMO pour la France, resolution 1.25 degré

[nodrog]

Anyone else having problems loading UKMO at t120 and t144?

No. It's all good.

[johnholmes]

John- within that though there must be somewhere a background pattern to build a program- a base set up, a 'typical' outcome to any one gridpoint - how much of that is factored in ... well- who knows- But irrespective of whats written in - the GFS needs a euro upgrade- S

I hoenstly don't know Steve, all I do know is what was valid when I was forecasting with UK Met. Then there was no background built in whatever. I really would suggest someone writes to the 3 main centres, explain what we are curious about and why and ask politely if they can help. Who knows perhaps there are background signals fed in. It seems unlikely to me but it would be good to know the real answer would it not?

[Captain Shortwave]

The UKMO wants to take the trough into central Europe instead of into northern France like the GFS/GEM

Apart from a few showers the east from Thursday onwards, the outlook would not be too bad here.

Lets see what the ECM comes up with, though this mornings run was similar to the GFS/GEM runs

Edited October 6, 2013 by Captain shortwave

[Summer Sun]

Its okay on meteociel now SS

 

meteociel.fr - modèle UKMO pour la France, resolution 1.25 degré

 

 

No. It's all good.

 

Cheers guys I wasn't loading before past t120 all is fixed now though

 

 

Pretty much as you were with the high starting to drift east

 

[Captain Shortwave]

ECM following the GEM/GFS for the developments of that low

Friday looks like a rank old day for the south if that verifies.

Western Scotland. Ireland and North west England look like the places to be

Edited October 6, 2013 by Captain shortwave

[Frosty.]

This is what I had been waiting for..it now feels like winter is coming when you see the first big blue mass covering the uk..and who better to deliver this wonderful news than Mr Darren Bett, notice how unhappy he is to bring the nation this news that most of us on here had been waiting for, and delivered without even a semblance of a smile throughout... enjoy the cold snap ladies and gents..the first of many between now and next april. 

[SMU]

Nice post Chiono-

 

ECM looks spot on tonight to what I think will be the final picture from 48-120....

 

 

Post that ALL models have lost the Greenland height signal at 192 - I wonder if the ECM will try & retrograde tonight which will be very rare for Oct but will ensure the snowcover starts pushing into Scandi at day 8-10

 

S

 

PS the UKMO looks to have had a wobble tonight-

Edited October 6, 2013 by Steve Murr

[I remember Atlantic 252]

This is what I had been waiting for..it now feels like winter is coming when you see the first big blue mass covering the uk..and who better to deliver this wonderful news than Mr Darren Bett, notice how unhappy he is to bring the nation this news that most of us on here had been waiting for, and delivered without even a semblance of a smile throughout... enjoy the cold snap ladies and gents..the first of many between now and next april. 

 

And just think this time last week we were looking at 22°C and sunny all week

[DAVID SNOW]

This is what I had been waiting for..it now feels like winter is coming when you see the first big blue mass covering the uk..and who better to deliver this wonderful news than Mr Darren Bett, notice how unhappy he is to bring the nation this news that most of us on here had been waiting for, and delivered without even a semblance of a smile throughout... enjoy the cold snap ladies and gents..the first of many between now and next april. 

 

Welcome home Frosty , you have been away far too long in the warm wilderness

[SMU]

Big retrograde AHOY on the ECM- would be a cracking winter pattern- very unusual-

 

S

[Summer Sun]

Looking at the big 3 and UKMO is on its own again this evening with the position of the high those in the south who don't want cold rain will be hoping UKMO is on the right path

 

 

Compared to GFS and ECM

 

 

Again at t144 with have differences

 

UKMO

 

 

GFS and ECM

 

[Captain Shortwave]

Something very cold for October could be coming here 

[Cheshire Freeze]

Something very cold for October could be coming here 

 

I guess the 192 hours chart will reveal all.

[Summer Sun]

t192 from ECM

 

 

Some very low uppers building to our north and north east, northern Scotland looks to be the warmest place in the UK looking at the uppers

Edited October 6, 2013 by Summer Sun

[Jonan92]

Amazing set up - quite unusual for this time of the year