Model Output Discussion - 28th November

[Weathizard]

06z ens are pretty decent though? I don't really rate the ensembles in complicated scenarios like this but some keep saying that they are more important than OP runs,.

Edited November 28, 2012 by Weathizard

[cpm1962]

Seems the Meto 15 dayer has now updated to a more unsettled but rather cold forecast reflecting the synoptical changes across all models in the past 24-35 hours.

Having laboured through the various model updates during the past 10 days though you have to ask the question whether meduim range forecasting has improved over the past 20-30 years. We have ENSO's ,Rossby Waves, Stratosphere observations, mountain torques and EL NINA & NINOS all consuming Technical and human resources round the clock which has seen gerat improvements in long range global weather patterns, but they still cannot forecast shortwave developments and their implications within 120 hours around the UK shores. You have to laugh dont you

I avidly follow this discussion and all the technical and strat threads. There does seem to be a "disconnect" for a very small geographical area such as the uk, between the overall hemisphere pattern , more acurate than not even at about 15 days out ( and this accuracy does appear to have improved considereably over the last few years or so) and then the fine details that only come into play only in the high resolution period of the models, which factoring in all the local issues and whilst not contradicting the global position, overide them in terms of what the uk weather will actually experience .

[andymusic]

Seems the Meto 15 dayer has now updated to a more unsettled but rather cold forecast reflecting the synoptical changes across all models in the past 24-35 hours.

Having laboured through the various model updates during the past 10 days though you have to ask the question whether meduim range forecasting has improved over the past 20-30 years. We have ENSO's ,Rossby Waves, Stratosphere observations, mountain torques and EL NINA & NINOS all consuming Technical and human resources round the clock which has seen gerat improvements in long range global weather patterns, but they still cannot forecast shortwave developments and their implications within 120 hours around the UK shores. You have to laugh dont you

I'd say - just like in the film "Jaws" - "WE NEED A BIGGER BOAT" - think the met office still need a "BIGGER COMPUTER" for number crunching the model output - I think things have improved over the past couple of years - but we're not quite there yet regarding all the variables and being able to work out all the possible outcomes - and considering the weather which after all is a vast natural gift of "mother nature" - the vast number of possible outcomes must be immense - therefore once we have a little more understanding of the parts that effect the weather and we are able to number crunch enough of the outcomes, I would have thought the forecasting capabilities will steadily improve even more and also further out.

[Frosty.]

I think Gibby was spot on this morning as usual, we are into a rather cold pattern for at least the next few weeks and it will be cold enough for sleet and wet snow at times, especially across northern britain with northern hills and mountains likely to accumulate a decent covering from early next week onwards. Before then we have a cold settled spell for the rest of this week including the weekend with bright or sunny spells, increasingly frosty nights and a growing risk of fog which will turn into freezing fog as the air chills by the day. Into early next week, as rain pushes east it could turn to snow for a time, and again this risk is high for northern hills, then rather cold and showery with a polar maritime flow and showers becoming wintry with widespread frosts again, also a risk of depressions sliding southeast with undercutting which drags even colder air down across the uk from the north/north east. It could turn into a cold month with several shots of very cold snowy weather, probably more likely from mid month.

Edited November 28, 2012 by Frosty039

[NL]

I'd say - just like in the film "Jaws" - "WE NEED A BIGGER BOAT" - think the met office still need a "BIGGER COMPUTER" for number crunching the model output - I think things have improved over the past couple of years - but we're not quite there yet regarding all the variables and being able to work out all the possible outcomes - and considering the weather which after all is a vast natural gift of "mother nature" - the vast number of possible outcomes must be immense - therefore once we have a little more understanding of the parts that effect the weather and we are able to number crunch enough of the outcomes, I would have thought the forecasting capabilities will steadily improve even more and also further out.

Its not so much we need bigger computers but more data input from 'out-there' places. The Atlantic is a very big ocean with few 'data stations' as is the Arctic. In reality we don't do so bad with what we have.

[Troubleatmill]

ECM 00z control on the 15day ensembles looking good for bitter cold, with operational looking like it might follow suite

Edited November 28, 2012 by arron123

[Methuselah]

Its not so much we need bigger computers but more data input from 'out-there' places. The Atlantic is a very big ocean with few 'data stations' as is the Arctic. In reality we don't do so bad with what we have.

But, to handle all that extra data, we'll need bigger, faster computers.

[weather eater]

Not sure any model has a grip on the situation past day 5 at the moment.

The commentary on the upper air modelling for the polar vortex from 06z GFS reads something like this...

pulled apart, squeezed, attempted to reform, split, split into three parts.

The broad gist from ensemble means holds sway though.. anomalous ridge in the North Atlantic, deep troughing over much of Europe, below average temperatures over a sustained period with the potential for attacks of more colder air coming from the north, north-east and east.

The upper air volatility is interesting to watch though - signal that the pv is coming under more pressure from below and registering all the way up to 30 hPa.

I hope so GP and if I'm wrong you won't hear me complaining that’s for certain.

Edited November 28, 2012 by weather eater

[dragan]

15 day ensembles for ECM 00z control looks like its going to go for very cold outcome.

[Catacol]

06z ens are pretty decent though? I don't really rate the ensembles in complicated scenarios like this but some keep saying that they are more important than OP runs,.

The more complicated the scenario, the more important the mean runs. To plump for one run when the models are struggling is no good at all. When there is general model agreement out to T144 or even beyond (which is rare) then the single op run is worth a look.

[PolarWarsaw]

As I stated last night- 1% chance of ECM coming true is about right-

More solutions, more options today-

If we take todays output alone, we have chilly conditions-poor in the S if you like the white stuff, northern hills/mountains from Yorkshire N might get a sprinkling.

Might be time to take 10 days away from the models-

I forsee nothing interesting in that period.

[johnholmes]

Not sure any model has a grip on the situation past day 5 at the moment.

The commentary on the upper air modelling for the polar vortex from 06z GFS reads something like this...

pulled apart, squeezed, attempted to reform, split, split into three parts.

The broad gist from ensemble means holds sway though.. anomalous ridge in the North Atlantic, deep troughing over much of Europe, below average temperatures over a sustained period with the potential for attacks of more colder air coming from the north, north-east and east.

The upper air volatility is interesting to watch though - signal that the pv is coming under more pressure from below and registering all the way up to 30 hPa.

I agree with your post Stewart and especially the last paragraph

[Mark Bayley]

Next week to day 10 is the period i am looking Frosty and it looks pretty Atlantic driven to me.

I can see that as the trough disrupts further south a little later we could get a cyclonic type of north easterly-but further into week 2.

I wonder if the more short term (next week or so) could be partly due to the MJO briefly progressing through phase two (although low amplitude), as shown by the UKMO and GFS ensembles? (Edit, corrected maps to add GFS)

Although i note these two models are keen on perhaps progressing it into phase one. Which gives a composite not to dissimilar to the NAEFS mean.

As GP noted the stratospheric output is still promising, with the PV continuing to be strained. With support for higher pressure in the North Atlantic

Which is supported by the long range ensemble means for both the ECM and GFS, which also show below average 850hpa temps, and below average surface temps

ECM

GFS

The long range ensembles continue to support both a -NAO and -AO, well into December.

AO

NAO

Given that there is no sign of a more organised and strong PV, and support for higher pressure out in the NA is strong, as well as -NAO as we head into and through December, i would be very surprised if we did not see a decent shot at much colder spell

Edited November 28, 2012 by Mark Bayley

[Interitus]

Its not so much we need bigger computers but more data input from 'out-there' places. The Atlantic is a very big ocean with few 'data stations' as is the Arctic. In reality we don't do so bad with what we have.

The lack of data is not as important as the processing as pointed out in this white paper from NOAA outlining their plans to catch the ECMWF by 2014 -

http://www.esrl.noaa.gov/psd/people/tom.hamill/global_HPC_whitepaper_hamilletal.pdf

The computing power is not solely for increased model resolution, just as important is the data assimilation - how the information is parameterised eg going from 3D-Var to 4D-var requires 10-100x more processing power.

The author notes that -

"These improvements are much larger than the improvement that can be expected by dedicating the same amount of resources to augmenting the observing system."

[Dean E]

I'm starting to think that we are going to see a rather slow transition to a colder conditions rather than a more rapid cool down. With this slow transition would come mild blips for most southern areas and a more colder pattern further north, closer to the block. To me, from the models and ensembles at the moment, this seems to be the most likely outcome.

But I think we can safely say, backing from the CFS and 500mb anomoly, December could well be a month to remember.

And then there's the rest of winter...

SM

[Weathizard]

Could anyone explain the reason for the risidual polar votex spitting out lows in high resolution? Is this due to high pressure to the north, I'm not as clued up on all this as some so thought I'd ask the question? Just thought because the Vortex is weak over Greenland we'd be less susceptible to these barreling low pressures? I assumed its to do with the Jet?

Edited November 28, 2012 by Weathizard

[Interitus]

I wonder if the more short term (next week or so) could be partly due to the MJO briefly progressing through phase two, as shown by the GFS and ECM ensembles?

They are borderline weak, but also about a week away and the MJO takes 10-12 days to affect North Atlantic weather regimes.

[Buriedundersnow]

Remember, there is still lots of time for change. A model that shows this is the NAM, which for a second consecutive run has the deep low in a very different and better position than all the other models. It would result in more WAA being drawn north. And remember, its a high res model, so its something to keep an eye on IMO.

NAM:

GFS:

does anybody know how accurate the NAM is compared to the GFS

[Mark Bayley]

They are borderline weak, but also about a week away and the MJO takes 10-12 days to affect North Atlantic weather regimes.

Yes, i noted it was quite low amplitude. Still, quite a promising outlook these next few weeks!

Edited November 28, 2012 by Mark Bayley

[Weathizard]

does anybody know how accurate the NAM is compared to the GFS

I believe it is a higher resolution model which SHOULD make it more accurate, not certain how accurate it is though

Edited November 28, 2012 by Weathizard

[Frosty.]

I forsee nothing interesting in that period.

I assume you are joking? since the next 10-15 days + are going to be cold with widespread frosts, a risk of some snow, freezing fog and beautiful crisp early winter sunshine and a risk of wintry showers of hail/sleet and snow as opposed to mild with swly winds and drizzle!

Nothing interesting

[Suburban Streamer]

As I stated last night- 1% chance of ECM coming true is about right-

More solutions, more options today-

If we take todays output alone, we have chilly conditions-poor in the S if you like the white stuff, northern hills/mountains from Yorkshire N might get a sprinkling.

Might be time to take 10 days away from the models-

I forsee nothing interesting in that period.

fair enuff - see u in 10 days

i am enjoying watching the pv split getting serious - i think this one may end in divorce

[phil nw.]

I wonder if the more short term (next week or so) could be partly due to the MJO briefly progressing through phase two, as shown by the GFS and ECM ensembles?

Although i note these two models are keen on perhaps progressing it into phase one. Which gives a composite not to dissimilar to the NAEFS mean.

As GP noted the stratospheric output is still promising, with the PV continuing to be strained. With support for higher pressure in the North Atlantic

Which is supported by the long range ensemble means for both the ECM and GFS, which also show below average 850hpa temps, and below average surface temps

ECM

GFS

The long range ensembles continue to support both a -NAO and -AO, well into December.

AO

NAO

Given that there is no sign of a more organised and strong PV, and support for higher pressure out in the NA is strong, as well as -NAO as we head into and through December, i would be very surprised if we did not see a decent shot at much colder spell

I am not to sure i would take too much from the weak MJO signals at the moment Mark.

However i agree wrt to the vortex under pressure etc but unfortuanetly for the UK the core of lower heights is being pushed this side of the pole-at least for now.

This is what`s flattening our blocking somewhat in the next few days.We can see this from the ECM mean T48 and then T144hrs

The good thing from a cold pov is we get a cold Atlantic flow because of the southern tracking jet but not any stable block to advect the deep cold from the Arctic once our current ridge is flattened.

I am of course aware of the current wave breaking in the Strato.which, as GP alluded too, will continue to undermine the vortex.I am sure this will cause more distortion and fragmentation to it and then we could well get another chance of more substantial northern blocking.

[Mark Bayley]

I am not to sure i would take too much from the weak MJO signals at the moment Mark.

However i agree wrt to the vortex under pressure etc but unfortuanetly for the UK the core of lower heights is being pushed this side of the pole-at least for now.

This is what`s flattening our blocking somewhat in the next few days.We can see this from the ECM mean T48 and then T144hrs

<snip>

The good thing from a cold pov is we get a cold Atlantic flow because of the southern tracking jet but not any stable block to advect the deep cold from the Arctic once our current ridge is flattened.

I am of course aware of the current wave breaking in the Strato.which, as GP alluded too, will continue to undermine the vortex.I am sure this will cause more distortion and fragmentation to it and then we could well get another chance of more substantial northern blocking.

Yes, goes to show that despite blocking, it doesn't always guarantee much colder weather for the UK, if the blocking and PV fragments don't always fall into the right place. With regards to the MJO, i agree that it is probably not of great use given the low amplitude, although i note that GFS is keener on something a little stronger (which i see i did not attach to my original post!) as we head into December.

Edited November 28, 2012 by Mark Bayley

[TonyH]

Interesting to just have a quick look back at the MO thread from a week ago. Lot's of hope-casting and talk of the blocking getting more established, cold NE air arriving by December, etc. To be fair, also a fair bit of challenge to this too, injecting a bit of realism.

So one week on, we are entering a half hearted cold snap, then a cool zonal outlook for early December, very little sign of wintry weather or real cold.

Edited November 28, 2012 by TonyH