Model Output Discussion 18th Nov.2013-12z onwards.

[Skyraker]

We might just get to see a fabled polar low..... unicorns are more common.

 

 

*edit* IIRC thse are pretty much nowcast situations as the models rarely pick them up. ie) the first you'll know about it is when it shows on the sat image.

Edited November 28, 2013 by Skyraker

[SMU]

So who wants to take the baton on this-

 

Ensemble watch- this was done successfully on TWO by Retron & it is a bit of fun-

 

Whats needed is someone who may not at want to contribute to much to the discussion but feels they have a bit of time to make a graph or a plot for us.

 

Im setting the bench mark ensemble for Aberdeen @ -10c. This is easy to measure on the ensembles.

 

All you have to do for EACH run of the GFS ensembles is produce a graph to how many of the ensembles reach -10c within the timeframe of December 6th-10th - this timeline should cover the error of the timing..

 

 

Anyone wants to do it thanks a lot it takes I guess around 15 mins each run after set up-

 

Ive chosen Aberdeen as I think the amount of -10s we will get for London is to low, even if the stella Northerly arrives we may only get -9c. So Aberdeen is a good bet..

 

I hope someone can do the challenge of the loads of people viewing on here.....

S

Edited November 28, 2013 by Steve Murr

[nick sussex]

The debate re which is better ensembles or operationals is really down to what kind of set up you are dealing with. There are some set ups in which the ensembles give a good broad picture and other times when they are really not upto much.

We often see this with easterly set ups because they often entail undercutting shortwave energy, the ensembles are reluctant to undercut, they will often prefer to take energy more east than se,its for this reason that you rarely see the ensembles projecting an easterly at long range, 99 times out of a 100 its the operational run which will pick this first followed by a slow jumping on board of the ensembles as the timeframe gets closer.

With set ups where theres not much middle ground ie easterlies the ensemble mean is useless because if you blend an undercutting scenario with one of energy riding over the top you end up with a very misleading picture.

The current set up is a northerly toppler with an added complication by way of that possible shortwave, however broadly speaking theres another element of difficulty as the PV is expected to head back west to Canada after any northerly if this verifies.

We shouldn't assume just because the UKMO says one thing that this is a fact rather than simply a forecast, that forecast changes as quickly as the models do, no output at this stage will be comfortable with the complications caused by that moving PV and also what it encounters in the eastern USA.

There is uncertainty even to get to the northerly and after this we may well see the high sink but this is not a given especially if you look at both the ECM and GFS at 240hrs.

We'll just have to see whether we can overcome the first hurdle to get the northerly, I'd be more worried about that than a forecast for milder conditions over two weeks away.

[Gavin Hannah]

Just for you Frosty!

 

 

Another banker on the GFS 06Z run!

 

[Skyraker]

Steve said 'Its highly unlikely the resolution of the ensembles is better than the operational- you may want to check that.'I'm sure I've seen somewhere that the GFS ensembles run at a lower resolution to the opp but the resolution does not drop after 192 hours like the opp run. If true this means that you give added weight to the opp until 192 then go with the ensemble 'trends'. This makes sense from a logic viewpoint.The opp is often the mildest run which assuming the above is correct makes sense as it tends to default quickly back to zonality once low res kicks in.Jason

 

 

 

 A T382L64 high resolution control  out to 7 days, after which this run gets truncated and is run out to 16 days at a T126L64 resolutionA T190L28 control that is started with a truncated T382L64 analysis and run out to 16 days, labeled as 20 perturbed forecasts each run out to 16 days at T190L28 horizontal and vertical resolution. The initial perturbations are generated using Ensemble Transform with Rescaling (ETR) method.

 

Source http://www.emc.ncep.noaa.gov/GEFS/mconf.php 

[Gael_Force]

CC, whether there is a northerly or not the METO are detailing the likely evolution thereafter; a toppling with the Atlantic rolling in over the top. Depending on how far the High sinks, then as we know we can see very mild SWerlies from this set-up.

 

Long term climatology would point to this scenario but in recent years, when a deep trough extends into western Europe, the tendency has been for the base to become cut- off and low heights are in place rather than the high sinking and setting up a long term residence. It may be that this year the patterns return to more traditional mode but it is not what I expect to see.

[Skyraker]

Long term climatology would point to this scenario but in recent years, when a deep trough extends into western Europe, the tendency has been for the base to become cut- off and low heights are in place rather than the high sinking and setting up a long term residence. It may be that this year the patterns return to more traditional mode but it is not what I expect to see.

 

Cut off low inflating the high north... ? It's not imposssible.

[Paul]

So who wants to take the baton on this-

 

Ensemble watch- this was done successfully on TWO by Retron & it is a bit of fun-

 

Whats needed is someone who may not at want to contribute to much to the discussion but feels they have a bit of time to make a graph or a plot for us.

 

Im setting the bench mark ensemble for Aberdeen @ -10c. This is easy to measure on the ensembles.

 

All you have to do for EACH run of the GFS ensembles is produce a graph to how many of the ensembles reach -10c within the timeframe of December 6th-10th - this timeline should cover the error of the timing..

 

Ensemble watch.jpg

 

Anyone wants to do it thanks a lot it takes I guess around 15 mins each run after set up-

 

Ive chosen Aberdeen as I think the amount of -10s we will get for London is to low, even if the stella Northerly arrives we may only get -9c. So Aberdeen is a good bet..

 

I hope someone can do the challenge of the loads of people viewing on here.....

S

 

We could probably automate this quite easily - will ask karl.

[SMU]

cool-

 

Paul can update on / remind on the 20 GFS ensembles what the 'sway' put on each of the runs.

 

S

[johnholmes]

Having read some comments in posts mentioning my name this morning and in recent days it still seems a little unclear what my reports are all about. For most people on here and certainly those that read them via my website are only interested in whether it's going to rain or snow or not and it's these folks that my reports are directed towards. The sciences are drawn by many knowledgeable posters much more educated and qualified people than me and illustrated on this and other forums well. Remember my reports are posted across from my website and are compiled with my websites readers in mind and not any forum. If people on here think that I just use to blanket an approach perhaps it might be better just for me to provide a link to my website for the report each day and to not clutter up forum space. What do you think?

 

 

continue posting Gibby but please doing it yourself rather than via SS would be my request? Many on here wish for the same basic guidance and a look at what may happen according to each model which is what you provide. For those wanting to do their own interpretation of what they think the models mean/will do, I cannot quite see why they make comment about your forecast interpretations but then we all different and have to try and rub along together without getting too uptight with one another. It is after all simply the weather. It has a wonderful gift of making everyone of us looks chumps at times.

[bluearmy]

there is an existing thread on model resolution which answers most questions.

[IDO]

My view is that the mixed ensembles are solid with regard to an amplified long wave pattern giving a meridional flow from the US trough to the Atlantic ridge into a Euro trough. Why the ensemble mean is not seemingly much use when we have a trigger pattern changer is that, as in the case of the GFS 06z 11 of the 22 members fail to ridge the Atlantic, to one extent or another, at the crucial time, eg:

At T204:

So assuming no short wave drama and the NH profile that is most lkikely (Atlantic Ridge), by T240 we can see how many of the remaining members currently give us a cold flow...

...9 out of 11; so high confidence of a cold flow if the LW pattern is established.

So what about longevity. Again looking at the members who had the initial Atlantic Block, at T288, a small minority keep the cold flow (early days and well into FI, so could change):

Many go with Fergieweather's Met update; a milder flow, SW/W. Interestingly the runs left out (crosses) have a 50:50 split as to cooler or average at the same time frame! On this run the medium term potential may be better for the coldies if a short wave does flatten the pattern!

The London ECM 0z ens:

A similar mix as the GEFS with plenty of spread, so likely no great variance to the possibilities between the two. Therefore a zonal outlook is not currently figuring in the short to medium term.

[Average Joe]

Having read some comments in posts mentioning my name this morning and in recent days it still seems a little unclear what my reports are all about. For most people on here and certainly those that read them via my website are only interested in whether it's going to rain or snow or not and it's these folks that my reports are directed towards. The sciences are drawn by many knowledgeable posters much more educated and qualified people than me and illustrated on this and other forums well. Remember my reports are posted across from my website and are compiled with my websites readers in mind and not any forum. If people on here think that I just use to blanket an approach perhaps it might be better just for me to provide a link to my website for the report each day and to not clutter up forum space. What do you think

 

 

 

For the non-technically minded folk who DO wish to follow this site purely to gain an understanding as to whether it’s likely to rain, sleet, snow or blizzard at this time of year rather than worrying about splitting PV’s or whatever else it is they do, please please continue posting Martin. Personally I find your comments and non-biased summary an extremely useful tool amongst some of the excitement that occurs from time to time. On behalf of the silent types that enjoy reading them, thank you!! 

[tempestwatch]

For the non-technically minded folk who DO wish to follow this site purely to gain an understanding as to whether it’s likely to rain, sleet, snow or blizzard at this time of year rather than worrying about splitting PV’s or whatever else it is they do, please please continue posting Martin. Personally I find your comments and non-biased summary an extremely useful tool amongst some of the excitement that occurs from time to time. On behalf of the silent types that enjoy reading them, thank you!! 

DuncanK,

I mirror your remarks and find Martins un biased comments extremely useful. I am on a steep learning curve and when I look at the charts and make notes, i compare them to martins to see if Iam on par or in the right ball park. Please keep posting Martin!!!

Edited November 28, 2013 by tempestwatch

[legritter]

Plenty of interest and possible outcomes next week ,i for one totally enjoy any charts data summarys that are posted by any poster ,the best forum in northern hemisphere by far .so going by current charts it looks like some fun and games later next week ,beyond that it all depends where any high pressure sets up ,but hey things are looking up ,and come tonight it could be even better .

[karlos1983]

Plenty of interest and possible outcomes next week ,i for one totally enjoy any charts data summarys that are posted by any poster ,the best forum in northern hemisphere by far .so going by current charts it looks like some fun and games later next week ,beyond that it all depends where any high pressure sets up ,but hey things are looking up ,and come tonight it could be even better .

that's done it 

[SomeLikeItHot]

Having read some comments in posts mentioning my name this morning and in recent days it still seems a little unclear what my reports are all about. For most people on here and certainly those that read them via my website are only interested in whether it's going to rain or snow or not and it's these folks that my reports are directed towards. The sciences are drawn by many knowledgeable posters much more educated and qualified people than me and illustrated on this and other forums well. Remember my reports are posted across from my website and are compiled with my websites readers in mind and not any forum. If people on here think that I just use to blanket an approach perhaps it might be better just for me to provide a link to my website for the report each day and to not clutter up forum space. What do you think?

 

Personally I think your summaries are excellent and balanced view of what the main NWP models are saying. Some may like to go beyond the models and try and argue to why we should prefer diferent soluions and that's good also, but on days when I am too busy to trawl through a range of models I always refer to them to get and idea of what is happenning. Would be disappointed to see them go.

[Jax]

Having read some comments in posts mentioning my name this morning and in recent days it still seems a little unclear what my reports are all about. For most people on here and certainly those that read them via my website are only interested in whether it's going to rain or snow or not and it's these folks that my reports are directed towards. The sciences are drawn by many knowledgeable posters much more educated and qualified people than me and illustrated on this and other forums well. Remember my reports are posted across from my website and are compiled with my websites readers in mind and not any forum. If people on here think that I just use to blanket an approach perhaps it might be better just for me to provide a link to my website for the report each day and to not clutter up forum space. What do you think?

Keep the reports/posts coming, I mean, how can you clutter up a weather forum with weather related posts?

[SnowObsessor90]

As has been printed out we've here so many times before, personally I was expecting worse from the output this morning but that could simply be yet  another case of them attempting to pull the wool over peoples eyes, let's see what they show later....

[mincemeat]

For the non-technically minded folk who DO wish to follow this site purely to gain an understanding as to whether it’s likely to rain, sleet, snow or blizzard at this time of year rather than worrying about splitting PV’s or whatever else it is they do, please please continue posting Martin. Personally I find your comments and non-biased summary an extremely useful tool amongst some of the excitement that occurs from time to time. On behalf of the silent types that enjoy reading them, thank you!! 

 

one of the more sensible posts that i have come across of late!

my humble opinion is that when things are to busy at work to go through all the posts, i go to Gibbys for a quick analysis.

[Barry12]

As has been printed out we've here so many times before, personally I was expecting worse from the output this morning but that could simply be yet  another case of them attempting to pull the wool over peoples eyes, let's see what they show later....

 

Could you give any reasons why you think this, backed up with charts? or is this just your 'gut' feeling?

[itsnowjoke]

Keep the reports/posts coming, I mean, how can you clutter up a weather forum with weather related posts?

Here here exactly. Whats the point in Weather forums otherwise.Keep up the good work.And Sorry Mods.

[Cold Winter]

6z GFS ensembles show cold air over the UK from 5th Dec to 9th Dec, so currently looking like a fairly short-lived cold snap. After then there's a wide scatter in the various members but none are as cold as what is being suggested for the end of next week.

 

The operational is yet again the coldest for the 5th-9th Dec period which is interesting as it's trended colder than the rest for the last few runs. Perhaps the others will fall in line with it soon, or it could just be a cold outlier.

 

Edited November 28, 2013 by Cold Winter

[SnowObsessor90]

Could you give any reasons why you think this, backed up with charts? or is this just your 'gut' feeling?

Oh I dunno, maybe due the fact that all of the overriding signs are going against ECM and GFS 00z OP's showed, if  we couldn't get anything of note last December when those background signals did appear to be more favorable then I fail to see see how that's in any way a positive for this time around.

[Summer Sun]

Other than a few days next week NAO shows little sign of going negative for any lengthy period