Model output discussion - 5th December 2016 - Into Winter we go

[Banbury]

12 minutes ago, fergieweather said:

What's unsavoury? 18z GFS offers one heck of a chilly block. And effectively dry. Bear in mind 850hPa temps unrepresentative of surface temps in those set-ups (subsidence inversion/continued radiative cooling). Fog could be a real issue however, especially if there's any longevity of continental slack flow and resultant import of higher aerosol levels.

NB Note v different sense of direction further into 12z GFS PARA. Fine balance... etc. 

Ian ...just a quick question, over on TWO there is a debate about " missing data" over the xmas period and that it effects  the output being shown and that we wont see a true reflection until the holiday period is over?

 

Thoughts....................if any?

[bluearmy]

1 minute ago, Banbury said:

Ian ...just a quick question, over on TWO there is a debate about " missing data" over the xmas period and that it effects  the output being shown and that we wont see a true reflection until the holiday period is over?

 

Thoughts....................if any?

If the output was consistent since Xmas eve then you might be able to understand that debate but given the swings in the patterns, run to run in the mid range, I can't see the relevance. 

[legritter]

Hi gang ,the weather past about 7 to 8 days is currently hard to put detail on for the UK, but we do have many things going in our favour , UK met are on board so is ecm and gfs ,there will be swings day to day but let's look at the models more day to day same time for comparison .remember how Dec 2010 went big let downs one day Stella runs the next .

Winter snow and cold doesn't come easy to our shores ,many of our classic winters IF now around now with our modern technology  computers etc  would still give us a roller coaster ,collapsing high pressure being one of them (end of January 63 )high to our north collapsed south allowing Atlantic in for two days ,then new high formed ,icy blast continued .apart from the thrill of deep snow ,my interest is how would modern day Britain cope ,how would the Media respond , social media ,government , and how soon would our models forecast a mayor snow storm , the wording of forecasts etc on tv ,it's great when we get people like Fergie weather pop in to our forum ,and I would love to hear him say Big snow south of M4 corridor, and of course north , well I, m very happy with current prospects but must admit a bit uneasy until we get a few more runs ,gosh I, m hanging  cheers gang .

[Banbury]

Just now, bluearmy said:

If the output was consistent since Xmas eve then you might be able to understand that debate but given the swings in the patterns, run to run in the mid range, I can't see the relevance. 

That's my take as well , I don't buy into this missing data rubbish

 

Now watch Ian shoot me down

[feb1991blizzard]

The biggest concern of mine is that the 12z's downgraded and although the EC46 sounds great, it was derived from 0z starting conditions, which pumped out a stonking ECM, perhaps the 12z's is the start of the usual downgrades.

[Ali1977]

GEFS look better than the Op, the spoiler low not so prevalent south of Greenland at day 8 with many showing a better tilted high NW SW, open to more WAA towards GReenland bringing in Northerlies

edit - some belters by day 10. No downgrade here

Edited December 26, 2016 by Ali1977

[Nick F]

7 minutes ago, Banbury said:

Ian ...just a quick question, over on TWO there is a debate about " missing data" over the xmas period and that it effects  the output being shown and that we wont see a true reflection until the holiday period is over?

 

Thoughts....................if any?

That old chestnut comes round every year! Was waiting for someone to mention that.

A lot of the data, probably most of that used and simulated by NWP, is derived from satellites as far as I'm aware, also automated weather stations, radiosondes and from aeroplanes and ships play a crucial role if less in number. So can't see how there would be much less data over Christmas as satellite data makes up the majority of data.

Edited December 26, 2016 by Nick F

[fergieweather]

Just now, bluearmy said:

If the output was consistent since Xmas eve then you might be able to understand that debate but given the swings in the patterns, run to run in the mid range, I can't see the relevance. 

Meteorological trade runs 24-7 even over Christmas(!); the satellite data keeps churning; many aircraft providing data... etc. I've never heard such a 'theory' espoused anywhere before.

[fergieweather]

1 minute ago, Nick F said:

That old chestnut comes round every year! Was waiting for someone to mention that.

A lot of the data, probably much of that used by NWP, is derived from satellites as far as I'm aware, also automated weather stations and from aeroplanes and ships play a crucial role if less in number. So can't see how there would be much less data over Christmas as satellite data makes up the majority of data.

Snap! Agreed Nick. It's clearly some modern mythology.

[Hairy Celt]

1 minute ago, fergieweather said:

Snap! Agreed Nick. It's clearly some modern mythology.

I've heard that the latest advanced GPS on Santa's sleigh actually draws power from the satellites it uses for tracking, so the weather data is degraded before uploading... 

[Banbury]

4 minutes ago, fergieweather said:

Snap! Agreed Nick. It's clearly some modern mythology.

Thanks for clearing that nonsense up

[Paul_1978]

2 hours ago, shotski said:

And it's mental !!!!!!

not sure what to say about this....

At T+300 not a lot!

[Connor Bailey Degnan]

Hi Everyone, not posted for a while and given the way December went, I'm very surprised but urged myself to be more cautious.

My thoughts on January: Probably colder than average. A brief cold snap star of next week with snow in the North and east for a temporary time, dry elsewhere.  Turning drier frosty into the middle of next week but nothing in terms of snow.  I think we need to look towards mid month! 

[Catacol]

Well - I dunno. I've done a lot of surfing and reading today, and I have to say the signals for upcoming cold and long term cold are not strong. However we have some positives that I'll highlight here. 

Firstly the vortex profile shows a moderate wave 1 event over the north pacific - pushing the vortex towards Russia. I wouldnt say that this is a particularly violent movement, nor is it really kicking the vortex off its perch... but it will provide a degree of support to height rises to our NW and possibly to the movement of cold air westwards out of Russia.

The ridge is noticeable from 10hpa

down to 100hpa

with signs at 240 hours of the mid atlantic ridge to the west of the UK.

The MJO heading towards phase 2 produces a composite suggesting heights to the NE - though not directly supportive of low heights to the south which is really what we need. However - get the heights to the NE and perhaps we can still get that pull of cold. Note this is a very averaged chart over many years and many amplitudes of MJO - so only a very general guide at best.

 

And the last bit of interesting info is in regard to the PNA flagged by IanF earlier today. The PNA is forecast to go negative for what appears to be a sustained period:

ftp://ftp.cdc.noaa.gov/Public/gbates/reforecast2/teleconn/4indices.png

Trawling through the PNA archives revealed one interesting correlation. If we accept that Jan 79 and Jan 63 were the two coldest and snowiest Januarys overall in recent decades then guess what? Both had a sustained spell of -PNA. In both 1979 and 1963 the PNA was negative for 25 days in January. 1st Jan 79 (blizzards and the all time Cornish minimum record of -16.... cold enough even to freeze Sidney's nuts) and 13 Jan 79 (coldest recorded daytime maximum in the UK in the 1970s) were both famous days in UK weatherlore - note the prominence of the pacific ridge on both dates:

And how about the start of the most severe week of the most severe winter on modern times - 17th Jan 1963? Take a look - you get the picture. Perhaps the -PNA comment from the Met might be a key factor going forwards...

 

 

Edited December 26, 2016 by Catacol

[Nick F]

A look at the 12z EC London ens spread suggests the det warmer than the average of the spread by day 10, the average temp maxing at 5C from 5th to 10th Jan - which is not that mild and what appears to be a tight cluster of cold members in there in that day range. Could be a lot worse and looks slighty below norm temp wise, at least, for the SE at least for beginning of Jan

[Ali1977]

On 26/12/2016 at 23:40, Catacol said:

Well - I dunno. I've done a lot of surfing and reading today, and I have to say the signals for upcoming cold and long term cold are not strong. However we have some positives that I'll highlight here. 

Firstly the vortex profile shows a moderate wave 1 event over the north pacific - pushing the vortex towards Russia. I wouldnt say that this is a particularly violent movement, nor is it really kicking the vortex off its perch... but it will provide a degree of support to height rises to our NW and possibly to the movement of cold air westwards out of Russia.

The ridge is noticeable from 10hpa

down to 100hpa

with signs at 240 hours of the mid atlantic ridge to the west of the UK.

The MJO heading towards phase 2 produces a composite suggesting heights to the NE - though not directly supportive of low heights to the south which is really what we need. However - get the heights to the NE and perhaps we can still get that pull of cold. Note this is a very averaged chart over many years and many amplitudes of MJO - so only a very general guide at best.

 

And the last bit of interesting info is in regard to the PNA flagged by IanF earlier today. The PNA is forecast to go negative for what appears to be a sustained period:

ftp://ftp.cdc.noaa.gov/Public/gbates/reforecast2/teleconn/4indices.png

Trawling through the PNA archives revealed one interesting correlation. If we accept that Jan 79 and Jan 63 were the two coldest and snowiest Januarys overall in recent decades then guess what? Both had a sustained spell of -PNA. In both 1979 and 1963 the PNA was negative for 25 days in January. 1st Jan 79 (blizzards and the all time Cornish minimu record.... cold enough even to freeze Sidney's nuts) and 13 Jan 79 (coldest recorded daytime maximum in the UK in the 1970s) were both famous days in UK weatherlore - note the prominence of the pacific ridge on both dates:

And how about the start of the most severe week of the most severe winter on modern times - 17th Jan 1963? Take a look - you get the picture. Perhaps the -PNA comment from the Met might be a key factor going forwards...

 

 

Nice post, and as you say the link is there and we don,t need there crazy NH blocks to bring some exceptional cold air to the UK.

[Paul_1978]

54 minutes ago, Changing Skies said:

The trend is clearly not being our friend not seeing the second bite of the cherry as seen in 12z with that lobe of vortex off the coast of Newfoundland.

Disheartening, lets see what the morning brings...

Hmmm it's strange isn't it. Only a few hours ago we had "Boom" and "Get set its coming", but people should be tempering their expectations I reckon. It's far from nailed. Ill be the first to jump up and down if we get great charts within T+144 or less!

[stewfox]

18 minutes ago, Banbury said:

Thanks for clearing that nonsense up

I cant find the link but someone who work in air traffic control posted details once here , about 4yrs ago over this 'myth' . There are less Transatlantic flights on xmas day but looking at all data sets worked out the impact was under 0.002%.

[Allseasons-Si]

Just managed to sneak on here while our lass has gone to bed,shuuuuuussshhh!!!

Kent (snow) clipper by the 3rd of jan

http://www.myweather2.com/synop/player.aspx?synop=2

run it through

ice days forecast from the 2nd Jan here.

 

Edited December 27, 2016 by Allseasons-si

[Tamara]

58 minutes ago, Nick F said:

That lack of deep cold threat from the 12z EC and now 18z GFS high res runs a product of what happens when you lose the cross polar ridging, and movement SE of the upper high

 

 

I hope no-one minds me saying so as an ordinary member, but a theme I have been putting forward for some time now (circa 4 weeks) and gets construed at times as "glass half empty"

As stated and reasoned last night, and several times previously, downstream amplification is not assured in terms of being sustained if there is not the latent supply in the atmospheric circulation to ensure it so.

My own eyes continue to be on the GSDM (tropical and extra tropical budgets) and how they are best interpreted with the troposphere/stratosphere relationship - and it is from there that I attempt appraisal of the NWP

 

Edited December 27, 2016 by Tamara

[Geordiesnow]

ECM kind of sums up the problem we seem to have these days when it comes to attempted ridging into Greenland when even a good enough ridge looks like it should come off, it does'nt and the whole thing slowly collapses, on first glance its actually hard too see any spoiler shortwaves so it is odd however the trends has been for any attempted ridging not to manisfest into a Greenland high.

Today's runs have nosed up the Northerly a bit and I am liking the trend of Scandi turning quite cold(instead of western Russia as per earlier on in the winter) so Im for one not dissapointed with this afternoon runs. The details will vary alot and those flat charts that some GFS runs and the UKMO runs shown yesterday has so far not appeared on any latest output so surely thats got to be a positive but its still something to be wary of when looking at any future output.

[Jason M]

36 minutes ago, Paul_1978 said:

Hmmm it's strange isn't it. Only a few hours ago we had "Boom" and "Get set its coming", but people should be tempering their expectations I reckon. It's far from nailed. Ill be the first to jump up and down if we get great charts within T+144 or less!

Wise advice I feel. Some people are getting way ahead of themselves. All I've really seen in the charts in the last couple of days is a straightforward topple and the hint of something more out in the far reaches of FI. The main plus point really is that there is at least the opportunity for something decent as opposed to the zero prospects in the charts last week.

At present, my own hunch is no more than a 20% chance full on easterly / northeasterly. Hopefully some good runs in the morning can improve those odds

[Banbury]

48 minutes ago, Paul_1978 said:

Hmmm it's strange isn't it. Only a few hours ago we had "Boom" and "Get set its coming", but people should be tempering their expectations I reckon. It's far from nailed. Ill be the first to jump up and down if we get great charts within T+144 or less!

you better start now then , how is that not a great chart ??

I'm struggling with some comments to be honest

[Allseasons-Si]

This as far as i will look on the gefs charts and so should others,we know the game here

144hrs

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=144

and they all show a NE'ly of sorts

that is a good spread

night.

 

Edited December 27, 2016 by Allseasons-si
spell check

[mountain shadow]

42 minutes ago, Tamara said:

I hope no-one minds me saying so as an ordinary member, but a theme I have been putting forward for some time now (circa 4 weeks) and gets construed at times as "glass half empty"

As stated and reasoned last night, and several times previously, downstream amplification is not assured in terms of being sustained if there is not the latent supply in the atmospheric circulation to ensure it so.

My own eyes continue to be on the GSDM (tropical and extra tropical budgets) and how they are best interpreted with the troposphere/stratosphere relationship - and it is from there that I attempt appraisal of the NWP

 

Rather than take the models at face value, I have tried to take Tamara's lead ( I hope) and try and see whether some model runs predicting cross polar flows fit in with the teleconnections such as the AAM and MJO.

The reality is neither have showed much tendency to support any extreme polar incursions into our area of interest.

Indeed I would argue they were pointing towards a UK High and I believe that will be nearer the mark.

Cold...yes, just not snowy cold.