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phil nw.

Model Output Discussions 18z 31/01/2016

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4 minutes ago, Cloud 10 said:

Day 8 GFS 06z snow depth anyone?:laugh:

192-780UK.thumb.GIF.990611421c86618cfe1d

 

Well I very much hope that occurs as I would be burried:DI may wait for the 12z output to assess further.GFS is usually correct when it goes against the other output,except it's usually showing the warmer scenario.Here's hoping.

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2 minutes ago, winterof79 said:

Well I very much hope that occurs as I would be burried:DI may wait for the 12z output to assess further.GFS is usually correct when it goes against the other output,except it's usually showing the warmer scenario.Here's hoping.

You would get 15cm and I would get just 1cm according to that!

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Some people are on the pitch...they think it's all over!!...not according to the Gfs 6z it ain't ...Boom..Bank:cold-emoji::D:bomb:

06_132_preciptype.png

06_138_preciptype.png

06_177_preciptype.png

06_183_preciptype.png

06_216_preciptype.png

06_144_uk2mtmpmin.png

06_180_uk2mtmp.png

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Never gonna happen, but nice to look at nonetheless. The inevitable shortwave will scupper the passage of cold air southwards and leave those south of Scotland cool but wet, much like today.

Either that or the cold upper air will get downgraded nearer the time. It's the story of the winter so far and I haven't seen anything in the charts today to persuade me it's set to change anytime soon. So enjoy the cold looking FI charts, but realise they've less than a 10% chance of actually coming off.

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Its a messy set up but the overall broad theme all models agree on is a westerly airstream reigning supreme, but more north of west rather than south. Temps levelling out very near average northern half of the country, a bit above further south. In these set ups expect short term developments, and it is very much borderline snow to low levels territory for the north, thicknesses hovering around the 528 dam line from Monday onwards for the foreseeable.

Its not far off a wintry cold pattern, but shortwave activity to the NW looks like preventing a clean northerly source for the time being at least... we do have a very cold pool of air set to develop over NE Canada this will spawn low pressure and it is where and how low pressure systems and troughs develop in the mid atlantic which will determine how much polar air we can inject into the country.

Indeed we are not far off seeing a similar pattern to late Jan/early Feb last year which for some was quite a cold wintry picture with transitory snowfalls and a run of frosts..

 

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Excellent post by Damianslaw, we are very close to having a quite wintry spell and as he mentions as I and others have the Short wave activity to our NW prevents the cold air flooding down. However, I think as we are very close it isn't off the table.  Not the favourite but the southerly tracking lows are putting us within a shout.  If I'm wrong so be it but we are in early Feb and we are in a situation of being in with a shout.  Synoptic ally I'm generally pleased the way it's turned out.  I suggested this being a cold wintry period of winter because in a set up like this it's normally a win win. But it's this 'funny' winter and it is the UK.  So let's hope that the tweaking keeps heading colder 

 

regards

 

BFTP

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Well, I refuse to get carried away just yet, regarding the bit about twenty-foot snowdrifts, but I'll tentatively suggest the possibility of some folks seeing some nacreous clouds??:D 

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Some good points BFTP, but im not picking up that towel.......................................yet;-)

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3 minutes ago, Ed Stone said:

Well, I refuse to get carried away just yet, regarding the bit about twenty-foot snowdrifts, but I'll tentatively suggest the possibility of some folks seeing some nacreous clouds??:D 

Yes the famous nacreous clouds that delivered a snow shower with temps of 6 celsius, one learns a lot in the moaning thread!:D

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35 minutes ago, BLAST FROM THE PAST said:

 However If I'm wrong so be it but we are in early Feb and we are in a situation of being in with a shout.  Synoptic ally I'm generally pleased the way it's turned out.  I suggested this being a cold wintry period of winter because in a set up like this it's normally a win win.

I agree with this. There's a gloom on this thread at the moment but it's only 6th February, we are not in spring yet (although much of winter thus far has seemed like it). As always we will need to throw a couple of double sixes but this mornings 6z has certainly got my attention.

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so todays upgrade is at T168 rather than T240 FI so how much more likely is it or is it just another R Herring .  I ask again how can supposed weather model computers be so srong so often , if I made this many mistakes in my job I would have been super duper down a long time ago , so lets hope for once they are correct

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The models still seem to be struggling with any mid Atlantic trough disruption.

There does however seem a trend to re-amplify the flow near the ne USA for a time which helps to pull the PV chunk further west and allow the Azores high a brief window to ridge north.

Both the ECM and GFS agree on this which is a positive. The toppling of the ridge however is in line with an expected flattening again of the upstream pattern.

Given the set up the UKs chances of cold and possible snow improves in relation to the amplitude of the pattern in the east/ne USA.

On two fronts more amplified less deep lower heights head into the Atlantic, more chance of a more southerly tracking low and then later more re-amplification of that flow leads to a stronger ridge north of the Azores high to the west and better cold advection into the UK from the ne.

 

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Nice to see some interesting evolutions spewing out from the high res runs this morning. OK, there aren't cold blocks showing, that would bring prolonged cold weather, but what's potentially on offer from mid-week is much of an improvement on the current mild mush for coldies. 

There's a lot of energy in the upper flow across the Atlantic, with the strong 200mph+ jet across the Atlantic as the signature. But, it's shifting further south than we've seen recently and certainly compared to back in December. I think the big blocking high over Russia/Siberia is helping the jet dive SE towards the Mediterranean later next week too and carving a deep trough over Europe.

eps_z500a_nh_33.thumb.png.2856299ec71fe1

Be interesting to see, later this month/early March, if the MJO wave through to 7 shown by many of the extended model runs, such as the EC32, has much effect on the upper wave pattern seeing as the the path shown is less amplified than the previous run through 7/8 back in Jan. Certainly hints of mid-latitude blocking appear on the extended runs now from GFS and ECM.

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1 hour ago, Tim Brawn said:

so todays upgrade is at T168 rather than T240 FI so how much more likely is it or is it just another R Herring .  I ask again how can supposed weather model computers be so srong so often , if I made this many mistakes in my job I would have been super duper down a long time ago , so lets hope for once they are correct

What you are looking at now is in all likelihood about as good as it will get in my view, chaos theory will see to that. The impossible task of having to understand the drivers, their current influence on the atmosphere and most impossible of all, their interactions with each other, i.e. what overrides what, under what circumstances and to what degree. The 'to what degree' is the important part as each degree, and part of, will set us off in a different  direction. Difficult enough if we only had 2 drivers on the go but when we have the number we have, forget it, ain't going to happen, ever.

Advancements in the future will come in the form of more accurate probability forecasting. 

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1 hour ago, Tim Brawn said:

so todays upgrade is at T168 rather than T240 FI so how much more likely is it or is it just another R Herring .  I ask again how can supposed weather model computers be so srong so often , if I made this many mistakes in my job I would have been super duper down a long time ago , so lets hope for once they are correct

This has been explained many times before. Computer models (not just for weather but any predictive model) aren't sentient beings who 'make mistakes' like some sort of badly skilled employee. They're merely forecasting tools that generate likely outcomes from a set of initial data and probabilistic algorithms, programmed to the best of current human understanding of weather physics...across three different, massively complicated environments (atmosphere, land, marine). 

Atmospheric dynamics and chaotic systems are enormously complex, and our understanding of their processes and interactions (all the factors at play) is still being developed. Models are not infallible oracles or some sort of superpowers that 'should know better' or are just not pulling their fingers out. And, as always, if anyone feels they can do better there's nothing stopping them from developing their own weather models :D

And it's important to remember that this winter has been even more complex, with a variety of different drivers and influences that may not otherwise be at play. Every time you hear the words 'unusual' or 'rare' or 'unprecedented' logically it gives a clue that the models' performance may be affected. 

FWIW, I think the models' behaviour this winter will only help to improve understanding and increase accuracy in the future. 

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36 minutes ago, Daniel* said:

 8)

image.thumb.jpeg.10db9edacf538ee4c59fc15image.thumb.png.fec329ecc2fc264817e9492f

I like that chart, Snow coming back to South sweden again and London may see first snow this Winter, and both GFS and ECMWF shows more meridional flow from 12th February and after

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Back we come down the garden path with the 12z GFS....Shocking consistency.

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_gfs-1-174.png

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2 hours ago, Nick F said:

Nice to see some interesting evolutions spewing out from the high res runs this morning. OK, there aren't cold blocks showing, that would bring prolonged cold weather, but what's potentially on offer from mid-week is much of an improvement on the current mild mush for coldies. 

There's a lot of energy in the upper flow across the Atlantic, with the strong 200mph+ jet across the Atlantic as the signature. But, it's shifting further south than we've seen recently and certainly compared to back in December. I think the big blocking high over Russia/Siberia is helping the jet dive SE towards the Mediterranean later next week too and carving a deep trough over Europe.

eps_z500a_nh_33.thumb.png.2856299ec71fe1

Be interesting to see, later this month/early March, if the MJO wave through to 7 shown by many of the extended model runs, such as the EC32, has much effect on the upper wave pattern seeing as the the path shown is less amplified than the previous run through 7/8 back in Jan. Certainly hints of mid-latitude blocking appear on the extended runs now from GFS and ECM.

This is where my money is. Look at the GEFS ensembles, and you'll see heights very strong to our west / south west, and very few heights into Europe. It's setting up for a push of heights north in the Atlantic once the low pressure train hits a problem. So I'm predicting a cold phase at some point between D10 and D20.

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Just now, winterof79 said:

Back we come down the garden path with the 12z GFS....Shocking consistency.

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_gfs-1-174.png

think it's just a complicated set of lows/shortwaves - so the general theme is there and stays the same but as it's marginal it'll flip one way or the other - but the general idea is there and looking very promising

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The GFS is all over the place with what the PV does and where those deep low heights go in the Atlantic. Each run takes a different view so its hard to have much confidence in it.

The UKMO seems a bit more consistent with keeping the PV further to the nw.

NCEP's comments reflect the differences between the outputs especially in relation to that troughing in the ne USA:

MODEL EVALUATION/PREFERENCES... THE FORECAST STARTED WITH A GENERAL COMPROMISE BETWEEN A RELATIVELY AGREEABLE 00Z GFS/ECMWF/GEFS MEAN/ECMWF ENSEMBLE MEAN. SLIGHTLY LESS WEIGHT WAS GIVEN TO THE GFS SINCE IT REMAINED ON THE FASTER SIDE OF MODEL SPREAD WITH LIFTING A SURFACE LOW AWAY FROM THE NORTHERN MID-ATLANTIC COAST ON TUESDAY...BUT NOISE IN THE ENSEMBLE MEMBERS STILL SUGGESTS A LOT OF UNCERTAINTY WITH THIS SYSTEM. OTHER AREAS OF UNCERTAINTY IN THE FORECAST INCLUDE THE EXACT AMPLITUDE OF A BROAD TROUGH OVER THE EASTERN U.S. LATE NEXT WEEK AS WELL AS THE TIMING/EVALUATION OF AN UPPER TROUGH SLIDING INTO THE WESTERN U.S. NEXT SATURDAY.

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Mother of all northerlies out in FI.  Ooops, wrong attachment, meant this one

gfsnh-0-276.thumb.png.777a4862cdba6b79af

 

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The problem with the models everything is in FI and every day it gets pushed out further the snow on the 06z on the 12th is gone at this rate it will be over before its started lack of post says it all I'm afraid us poor coldies are suffering this winter! 

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