Model output discussion - heading into 2018

[shaky]

Latest arpege pushes the slider way north and gives snow or much of wales and north west england!

[karyo]

5 minutes ago, tight isobar said:

As most will(12hrs former)..

But using it in compare to ec output...

 

Even when the other models were correcting south, the ICON was keeping it north until very late.

Anyway, it is good to see that it doesn't have the north bias this time around.

[tight isobar]

1 minute ago, karyo said:

Even when the other models were correcting south, the ICON was keeping it north until very late.

Anyway, it is good to see that it doesn't have the north bias this time around.

Classic ec vs gfs...and supporting data.

If 12z today are in same ball park..

I know where my moneys going.

[feb1991blizzard]

6 minutes ago, shaky said:

Latest arpege pushes the slider way north and gives snow or much of wales and north west england!

Edited December 24, 2017 by feb1991blizzard

[Sperrin]

If memory serves me right there was a good bit of debate about the models propensity to gradually move these sort of systems further South and East. 

Here are two images of the slider from a few days ago and this morning providing further support for this theory. Furthermore, the last slider behaved in an almost identical fashion. 

As @northwestsnow has pointed out this has been slightly (to put it mildly) frustrating for us in the NW!

[karyo]

4 minutes ago, feb1991blizzard said:

He talks about the 6z Aprege which is much further north than this.

[Singularity]

Some excellent insightful posts in the past couple of days  

A key issue with long-range guidance based on teleconnections or indeed other methods is that they work with probabilities. The odds of a HLB pattern for Jan essentially peaked near 75% but that still leaves a one in four chance that the trigger phenomenon, in this case tropical convection in the Pacific, will fall short.

Nothing in weather is guaranteed until very short notice and sometimes not even then!

 

Looking at the morning model output and as uninspiring as the tropospheric patterns are beyond the midweek interest, GFS certainly has its festive hat on when it comes to the stratospheric output - but those details are for the appropriate thread

[feb1991blizzard]

2 minutes ago, karyo said:

He talks about the 6z Aprege which is much further north than this.

He must be using a different site / version sorry - its only just come out since - its a midlands jackpot but looks like massively biased ppn type charts towards snow to me.

[karyo]

2 minutes ago, feb1991blizzard said:

He must be using a different site / version sorry - its only just come out since - its a midlands jackpot but looks like massively biased ppn type charts towards snow to me.

I agree! It often overdoes the wintriness.

[feb1991blizzard]

2 minutes ago, Singularity said:

Some excellent insightful posts in the past couple of days  

A key issue with long-range guidance based on teleconnections or indeed other methods is that they work with probabilities. The odds of a HLB pattern for Jan essentially peaked near 75% but that still leaves a one in four chance that the trigger phenomenon, in this case tropical convection in the Pacific, will fall short.

Nothing in weather is guaranteed until very short notice and sometimes not even then!

 

Looking at the morning model output and as uninspiring as the tropospheric patterns are beyond the midweek interest, GFS certainly has its festive hat on when it comes to the stratospheric output - but those details are for the appropriate thread

Even then it doesn't look like its going to do much damage to the vortex - warming just barely flirting with the surf zone, having a look and then saying no thanks.

[Methuselah]

The upcoming slider looks like delivering a right old mess...fifty shades of marginal would be my guess? And that's not allowing for the fact that the depression's track is as yet far from decided.

So here's to a Merry Christmas for all -  and nice clean sidewalks!

[TEITS]

22 minutes ago, Singularity said:

Nothing in weather is guaranteed until very short notice and sometimes not even then!

d

Forgive me for saying but isn't the whole point of using Teleconnections is they are less susceptible to wild swings compared to the NWP. I also think im right in assuming that Teleconnections are generally used more for seasonal forecasting than short term.

Im dubious whether there has been a flip in these teleconnections but rather a misinterpretation. How can we go from the 12th Dec with predictions of blocking and E,lys to the Teleconnections suggesting the opposite only 12 days later. I have seen this so many times. The Teleconnections predict a cold spell which fails to occur and then magically the Teleconnections support the idea of no cold spell. Time and time again these Teleconnections are always predicting a cold spell in the future which fail to arrive. Since I joined this forum this has always been the case and yet nobody spotted the 2009/2010 cold spells via Teleconnections which is ironic.

Weather forecasting has improved since the invention of computers and increased observational data. The future of forecasting will only improve due to increased computing power rather than humans understanding these Teleconnections.

[frosty ground]

3 minutes ago, TEITS said:

Forgive me for saying but isn't the whole point of using Teleconnections is they are less susceptible to wild swings compared to the NWP. I also think im right in assuming that Teleconnections are generally used more for seasonal forecasting than short term.

Im dubious whether there has been a flip in these teleconnections but rather a misinterpretation. How can we go from the 12th Dec with predictions of blocking and E,lys to the Teleconnections suggesting the opposite only 12 days later. I have seen this so many times. The Teleconnections predict a cold spell which fails to occur and then magically the Teleconnections support the idea of no cold spell. Time and time again these Teleconnections are always predicting a cold spell in the future which fail to arrive. Since I joined this forum this has always been the case and yet nobody spotted the 2009/2010 cold spells via Teleconnections which is ironic.

Weather forecasting has improved since the invention of computers and increased observational data. The future of forecasting will only improve due to increased computing power rather than humans understanding these Teleconnections.

Confirmation bias is the term you are looking for.

[ACCOUNT DELETED]

Wednesday morning looks interesting with a risk of snow across Wales. Now I know the south coast of Wales had wet snow/sleet/rain on the 10 December with no accumulations. However since then, sea temperatures have dropped another 2C. Despite the mild weather this week, the temperature is now down to 8C the coldest is around 7C in February/ early March and this is the coldest Christmas swims for a good few years. So does that guarantee snow at sea level? NO as there are many other factors that need to be considered but it does help in lowering the freezing level. So if we get the right conditions it could be an interesting Jan & Feb for us, if not we end up with the plain old rain like previous years. Wednesday's snow risk is questionable at the moment. 

[Polar Maritime]

The NetW-wx high resolution shows some wintry potential from Boxing day till weeks end as cold air moves South bringing ground frosts and a sub-zero wind chill over the UK. Possible snow cover for some over the Pennines & Wales especially members at altitude could see some seasonal weather. Something interesting to follow over the Christmas period at least ☺

I would also like to wish all members (That includes all the followers that arnt always active) A Merry Christmas and a Happy Healthy New Year.

 

[SMU]

11 hours ago, comet said:

 

Will it still be a top post if say in a couple of weeks it proves to be totally incorrect like the ones of GP and Tamara plus if things in the tropics can change as quick as that then they can do so again.  Its as  if  these teleconnects and AAM budgets, GWO etc are the holy grail of weather forecasting lol. I am sure they play a part but I have yet to see any reliable long range forecasts on here or anywhere else.  Sure on the face of it the outlook beyond some interest next week does not look great but that can soon change. Also there is never much mention of the strat forecasts in any these musings and yet when the strat and trop are coupled the strat plays a very important part on the tropospheric weather patterns regardless of the above teleconnets etc.

Indeed.

Also I’m not quite sure why it seems to be coming as a surprise to everyone - when it was highlighted many days ago -

when we review & quantify the the net change of the zonal wind from the First week December to the last day of the year then it was blindingly obvious about a week ago that it was going Pete tong.

The zonal wind forecasts have got stronger & stronger over the past 10 days To the point where I highlighted it was getting close to the record breaking Nino from a couple of Decembers ago. 

So any forecast that was released pre 10 days ago relating to ongoing blocking etc is now redundant - is has been a complete burn. ( including my thoughts of persistence based on November’s profiles )

The forecast for zonal weather should now be the headline until at least the midpoint of week 1 Jan - by then the GFS suite has the zonal wind dropping off again.

so that’s where it is today- not in a great place..

 

[mulzy]

24 minutes ago, TEITS said:

Forgive me for saying but isn't the whole point of using Teleconnections is they are less susceptible to wild swings compared to the NWP. I also think im right in assuming that Teleconnections are generally used more for seasonal forecasting than short term.

Im dubious whether there has been a flip in these teleconnections but rather a misinterpretation. How can we go from the 12th Dec with predictions of blocking and E,lys to the Teleconnections suggesting the opposite only 12 days later. I have seen this so many times. The Teleconnections predict a cold spell which fails to occur and then magically the Teleconnections support the idea of no cold spell. Time and time again these Teleconnections are always predicting a cold spell in the future which fail to arrive. Since I joined this forum this has always been the case and yet nobody spotted the 2009/2010 cold spells via Teleconnections which is ironic.

Weather forecasting has improved since the invention of computers and increased observational data. The future of forecasting will only improve due to increased computing power rather than humans understanding these Teleconnections.

I 100% disagree with your post.  Seasonal forecasting will improve as we get a better understanding of teleconnections - it is still an embryonic area of meteorology.  For the foreseeable, it will remain probabilistic rather than saying X will happen, Y will not happen but that is still useful insight - it' still better than nothing or a toin coss.  Yes, better computer processing power will ensure marginal gains in the short to medium term NWP.  However longer term forecasting will be very dependent on teleconnections - the few friends I have in meteorology are excited (and sometimes frustrated) by this area of meteorology.  Exciting times ahead!

Edited December 24, 2017 by mulzy

[booferking]

14 minutes ago, Steve Murr said:

Indeed.

Also I’m not quite sure why it seems to be coming as a surprise to everyone - when it was highlighted many days ago -

when we review & quantify the the net change of the zonal wind from the First week December to the last day of the year then it was blindingly obvious about a week ago that it was going Pete tong.

The zonal wind forecasts have got stronger & stronger over the past 10 days To the point where I highlighted it was getting close to the record breaking Nino from a couple of Decembers ago. 

So any forecast that was released pre 10 days ago relating to ongoing blocking etc is now redundant - is has been a complete burn. ( including my thoughts of persistence based on November’s profiles )

The forecast for zonal weather should now be the headline until at least the midpoint of week 1 Jan - by then the GFS suite has the zonal wind dropping off again.

so that’s where it is today- not in a great place..

 

I remember last year quite a few were going for blocky weather while you were having none of it, you mostly use zonal winds as your forecast and time & time again you get it right teleconnects and AAM are a complete bust they are as useless as a chocolate fireguard for are small Island.

Edited December 24, 2017 by booferking

[feb1991blizzard]

8 minutes ago, booferking said:

I remember last year quite a few were going for blocky weather while you were having none of it, you mostly use zonal winds as your forecast and time & time again you get it right teleconnects and AAM are a complete bust they are useless as a chocolate fireguard for are small Island.

Whilst I agree with your praise of Steve last year - it should have been written off a long time before some accepted it was bust, I disagree wrt AAM - AAM is related massively to zonal winds.

EDIT : in fact although I am not knowledgable as far as I am aware the AAM is the total sum of the force of all the winds (zonaly averaged)

Edited December 24, 2017 by feb1991blizzard

[tight isobar]

7 minutes ago, booferking said:

I remember last year quite a few were going for blocky weather while you were having none of it, you mostly use zonal winds as your forecast and time & time again you get it right teleconnects and AAM are a complete bust they are useless as a chocolate fireguard for are small Island.

Fully agree with this and SM.

its also stark when ops and the like cannot decipher our 48/72 hrs scenario with the current slider situ...

Such a tiny island -and being/- maritime ocean dependant telecons have minimal shout imo!!!

Edited December 24, 2017 by tight isobar

[Methuselah]

14 minutes ago, mulzy said:

I 100% disagree with your post.  Seasonal forecasting will improve as we get a better understanding of teleconnections - it is still an embryonic area of meteorology.  For the foreseeable, it will remain probabilistic rather than saying X will happen, Y will not happen but that is still useful insight - it' still better than nothing or a toin coss.  Yes, better computer processing power will ensure marginal gains in the short to medium term NWP.  However longer term forecasting will be very dependent on teleconnections - the few friends I have in meteorology are excited (and sometimes frustrated) by this area of meteorology.  Exciting times ahead!

I agree with the bulk of what you're saying there, mulzy...My one quibble is that, as far as I can see, unless humanity can invent a computer whose computing power is infinite and have access to every last shred of data there is, long-range weather forecasting will be forever probabilistic...?

IMO, we will never be in a position from which we can know everything...?

Edited December 24, 2017 by Ed Stone

[N/A]

20 minutes ago, Draig Goch said:

Wednesday morning looks interesting with a risk of snow across Wales. Now I know the south coast of Wales had wet snow/sleet/rain on the 10 December with no accumulations. However since then, sea temperatures have dropped another 2C. Despite the mild weather this week, the temperature is now down to 8C the coldest is around 7C in February/ early March and this is the coldest Christmas swims for a good few years. So does that guarantee snow at sea level? NO as there are many other factors that need to be considered but it does help in lowering the freezing level. So if we get the right conditions it could be an interesting Jan & Feb for us, if not we end up with the plain old rain like previous years. Wednesday's snow risk is questionable at the moment. 

Wow that's a fair drop for just a fortnight ago! Bristol / English Channel, Irish Sea and  especially Irish coasts have also dropped a couple of degrees despite this very mild week. It's getting more exciting now, all we need are the right conditions and we'll have a good chance of at least a dusting of snow on the coast, perhaps as early as Wednesday morning  for starters? 

[Singularity]

37 minutes ago, TEITS said:

Forgive me for saying but isn't the whole point of using Teleconnections is they are less susceptible to wild swings compared to the NWP. I also think im right in assuming that Teleconnections are generally used more for seasonal forecasting than short term.

Im dubious whether there has been a flip in these teleconnections but rather a misinterpretation. How can we go from the 12th Dec with predictions of blocking and E,lys to the Teleconnections suggesting the opposite only 12 days later. I have seen this so many times. The Teleconnections predict a cold spell which fails to occur and then magically the Teleconnections support the idea of no cold spell. Time and time again these Teleconnections are always predicting a cold spell in the future which fail to arrive. Since I joined this forum this has always been the case and yet nobody spotted the 2009/2010 cold spells via Teleconnections which is ironic.

Weather forecasting has improved since the invention of computers and increased observational data. The future of forecasting will only improve due to increased computing power rather than humans understanding these Teleconnections.

Not all teleconnections are the same; some like the La Niña state this winter are very stable compared to model behaviour, while others such as the MJO are still highly unpredictable.

Since late Nov we have essentially seen a sequence of ‘La Nina likely means cold early Dec then more zonal later unless MJO can provide contrary forcing which looks possible but not likely’, ‘MJO forcing looking more likely to do the trick after all as atmosphere joes signs of cooperating’, ‘unfortunately as close as it’s coming it doesn’t quite look to be enough and the La Niña forcing looks to regain supremecy after all, at least for a little while’.

So different levels of predictability making for a complex picture as usual.

[knocker]

12 minutes ago, feb1991blizzard said:

Whilst I agree with your praise of Steve last year - it should have been written off a long time before some accepted it was bust, I disagree wrt AAM - AAM is related massively to zonal winds.

EDIT : in fact although I am not knowledgable as far as I am aware the AAM is the total sum of the force of all the winds (zonaly averaged)

Quote

Angular momentum is of course a measure of the turning force in the winds, so could perhaps be considered a measure of the strength of low pressure systems, but also relates to how much the jetstream undulates and how much blocking we have.

The budget of angular momentum goes up and down as energy is lost as weather systems crash into mountains and increases as cold air meets warm. Each phase of increasing and decreasing momentum suggests different types of weather for the UK. Looking at the current GWO plot we see a liklihood of going into phases 3 and 4 based on how it usually cycles round.

This implies increasing angular momentum as the various torques including mountain torque diminish (i.e those things which take energy out are not active).

This is certainly true of mountain torque.

For frictional torque and gravity wave torque then the jury is out.

Overall it looks like global angular momentum is on the increase.

The tendecy during december has been upwards.

Short term I think we are looking at phases 3-4 and more of an Atlantic influence. What I am guessing at though is that low pressure systems crossing the US will increase mountain torque, equally the jet stream across india is not a weak flabby one which might increase asian mountain torque. The strong jet in the western pacific along with OLR charts suggest strong trade winds with a stationary high to the north east of Australia and convectional activity to the north west of Australia. So back to phase 1-2 fairly quickly I think afterwards.

All maps are available in the link below.

PSD Map room for AAM

I am sure GP will tell us what he expects from the MJO and convectional activity in the pacific and how and if he expects rossby wave development as a result. It is those Rossby waves which in part will affect the stratospheric vortex and the low angular momentum could be linked to a more blocked pattern and sea ice build up to our north which I talked about in associated threads.

What we should always remember though that this a complex interaction of parts of which the stratosphere plays a large part during the winter.

https://www.netweather.tv/forum/topic/52083-gwo-and-global-angular-momentum/

May also be of interest

 

mjo and gwo.pdf

Edited December 24, 2017 by knocker

[Bruegelian]

It is fascinating the way the weather always takes us by suprise, even if it is want you don't personally want. I remember in late Nov/Early Dec when there was a lot of HLB in the troposphere, but the stratosphere was pretty cold, and most people thought that the strat would propagate down and obliterate the blocking. However, that didn't happen, and in fact the reverse happened with the trop changing the strat. And then more recently, we thought that things were looking odds on for blocking, but there has been a suprise flip in proceedings. It can always catch us out!