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Model Output Discussion - The Start Of Winter

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30 second model summary - Strong agreement to see Azores High Pressure influencing the UK this week with mostly settled conditions. Chances of frost at night if skies clear, but with cloudier, drizzly periods for places as well, mostly towards South. Brighter to North with odd shower. Temperatures struggling to reach double digits. Likely chilly Polar Maritime flow late this week with wintry showers towards North-West. Some doubts about what happens beyond. Though some possibilities of seeing a more unsettled Westerly pattern with Azores high hangin' about to the West or South-West, maybe with Lows to North-West dropping South-East towards UK with Azores high amplifying to West and Northerly winds resulting. 00Z GEM particularly notable of this. Maybe a chance of even pulling in some ridging over the top of a sinking trough/low with a flow from the East/North-East being another possibility (but probably unlikely for now... although yesterday's 00Z GFS run had showed the idea of Low Pressure dropping to our South with heights building to the North. And considering Rodger J Smith goes for something colder from mid-month in his Winter forecast with snowfall possible towards the East (https://forum.netweather.tv/topic/72635-the-seasonal-forecast-thread/?p=3077871), it's probably still something not to be totally ruled out). But perhaps if Vortex becomes a little too menacing to North (along with little upstream amplification), then maybe something a bit more flatter and zonal like on the GFS operational model with wettest conditions to North. Either way, maybe a fairly Westerly driven pattern with occasional amplification to our West delivering Polar Maritime/Arctic Maritime flows from time to time is probably the best bet for now. Edit: Suppose the flattish/zonal Westerly pattern would also fit in with what FergieWeather is suggesting.

Edited by DiagonalRedLine
Added in link to RJS's Winter Forecast
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Shaky, re your query in the last thread: "i guess with nothing certain in the mid range anything that does happen within that time will have an effect there after (10 to 15 day range)!! If you dont mind me asking what is the uncertainty in the mid range fergie? !" - It's regarding how pronounced the cold snap into Fri-part of Sat will be, with UKMO-GM more pronounced in this respect versus EC DET (all due to evolution and model differences over next couple of days, traceable way out west over Alaska).  But short-lived, either way (with no significant snow accumulations expected in grand scheme of things), with confidence good for more zonal set-up into the following week.

nice one mate!! At least we got an interesting couple of days this week!! Hopefully we get more of a high pressure influence over the uk with the zonal set up allowing for some cold and frosty weather!! Noticed some -4 uppers around england on Friday/Saturday in a very slack flow and also after a couple of frosty and cold nights! With surface cold in place i do wonder whether some places could see some wintry precipitation unexpectedly?
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Quite like the updated 3 & 4 week ensemble mean maps from CFS. Nice cold festive period if these verified :cold:

Notice the trend for the troughing down into Europe on week 4

 

I remember GP referring to these maps quite a lot :good:

 

post-12941-0-26329300-1417444447_thumb.g

Edited by blizzard81
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UKMO resolutely sticking to its colder air digging further south than the GFS and GFS P at T96hrs:

 

 

UKMO

 

post-1206-0-36165100-1417450612_thumb.gi

 

GFS P

 

post-1206-0-12436900-1417450648_thumb.pn

 

That's really a big difference at that timeframe.

 

The ECM so far over the last few days has been closer to the GFS solutions and I'm surprised this divergence has lasted this long.

 

We'll see who the ECM sides with later.

Edited by nick sussex
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Crazy differences at just 96 hours between gfs and ukmo! ! Gfs flatter and ukmo still going for the northerly and infact after taken a look at yesterday's 120 hours chart and comparing it to todays 96 hour chart it looks like the northerly is even more potent!!! Somethings gota give now!!

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Crazy differences at just 96 hours between gfs and ukmo! ! Gfs flatter and ukmo still going for the northerly and infact after taken a look at yesterday's 120 hours chart and comparing it to todays 96 hour chart it looks like the northerly is even more potent!!! Somethings gota give now!!

The change is due to how each model handles the PV and you'll see upstream how the UKMO develops a shortwave in Arctic Canada, further on that next low looks like having quite an active cold front on it with a steep temperature gradient over a relatively short area.

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UKMO resolutely sticking to its colder air digging further south than the GFS and GFS P at T96hrs:

 

 

UKMO

 

attachicon.gifUN96-21.gif

 

GFS P

 

attachicon.gifgfsnh-0-96.png

 

That's really a big difference at that timeframe.

 

The ECM so far over the last few days has been closer to the GFS solutions and I'm surprised this divergence has lasted this long.

 

We'll see who the ECM sides with later.

I suspect ECM will go somewhere inbetween with regards to the mini-northerly.

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The GFS(P) has trended slightly towards the UKMO solution in the last 24 hours but still quite a large divergence as Nick says:

gfsnh-0-96.png?12 gfsnh-2014113012-0-120.png?12vUN96-21.GIF?01-17

(yesterday's GFS in the middle)

Also, good to see the new GFS hasn't given up on its tendency to blow up lows to apocalyptic levels:

gfsnh-0-192.png?12

Some quite awesome blizzards for upland Scotland if that verified:

gfsnh-1-192.png?12

 

Worth adding also that even the GFS (P)'s half hearted attempt would still give some wintriness even to relatively modest elevations in Scotland, the Lake District and Ireland:

90-779PUK.GIF?01-12

Edited by LomondSnowstorm
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GFS, GFS P and GEM are all in pretty good agreement and are not going for the northerly like UKMO this afternoon

 

gfs-0-96.png?12gfs-0-96.png?12gem-0-96.png?12

 

UKMO still going for the northerly

 

UW96-21.GIF?01-17

 

All over to ECM now to see which one it will back

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Quite like the updated 3 & 4 week ensemble mean maps from CFS. Nice cold festive period if these verified :cold:

Notice the trend for the troughing down into Europe on week 4

 

I remember GP referring to these maps quite a lot :good:

 

attachicon.gifwk3_wk4_20141130_z500.gif

 

Yes, I think he was the last person to wheel them out!

 

Clearly they are 500m temp anomalies, but does anyone know what does the scale numbering refers to?

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Is this the major wind storm (sometime in December) that Chio refers to in the winter forecast ?

Misses most of the UK on this run but it's track may change and I wonder if it will herald a major

pattern change ?

 

post-12941-0-10562100-1417452461_thumb.p

 

I say it misses us but it may actually hit us later in the run!

Edited by blizzard81

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Yes, I think he was the last person to wheel them out!

 

Clearly they are 500m temp anomalies, but does anyone know what does the scale numbering refers to?

 

They're 500hPa height anomalies, with the scale in m.

Edited by Nick L
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What will it take to blast those low heights over Greenland!!

 

post-12941-0-15160200-1417452737_thumb.p

 

 

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UKMO is no real supprise given what Fergie Said earlier.  A good chance of some snow showers to end the week over Scotland and wintry showers over Northern areas on the latest UKMO. Either way though it seems even if the UKMO is on the money they still expect "more zonal set-up into the following week."
 

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UKMO seems on its own re that Northerly as even the King of amplification, the GEM even says no: post-14819-0-85867800-1417452067_thumb.p

 

Apart from that a pretty lack lustre 16 days ahead with a slightly flatter GFS in our sector. However good to see that the US ridge(s) are back in FI compared to the 0z and 06z and although of little consequence before mid month does tie in with my hope for heights in the Atlantic later in December:

 

post-14819-0-72177400-1417452204_thumb.p 06z: post-14819-0-77809400-1417452222_thumb.p

 

Different modelling of the Atlantic storm on the 12z and the outcome is that it blows up & flattens the UK HP early week 2:

 

post-14819-0-26911800-1417452331_thumb.p  Parallel more so: post-14819-0-26703000-1417452411_thumb.p

 

As I said this may not resolve till near the weekend. GEM's infamy at blowing up LP systems is seen again on the 12z:

 

post-14819-0-85422500-1417452519_thumb.p

 

Just a matter of watching at the moment as there are plenty of variations on the theme as the models cope with the Atlantic storm and the US ridging in week 2.

 

 

 

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They're 500hPa height anomalies, with the scale in m.

 

Oh, thanks, I had completely misread them as I thought they were temps!

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UKMO seems on its own re that Northerly as even the King of amplification, the GEM even says no: attachicon.gifgem-0-90.png

 

Apart from that a pretty lack lustre 16 days ahead with a slightly flatter GFS in our sector. However good to see that the US ridge(s) are back in FI compared to the 0z and 06z and although of little consequence before mid month does tie in with my hope for heights in the Atlantic later in December:

 

attachicon.gifgfsnh-0-360.png 06z: attachicon.gifgfsnh-0-372-2.png

 

Different modelling of the Atlantic storm on the 12z and the outcome is that it blows up & flattens the UK HP early week 2:

 

attachicon.gifgfs-0-192.png  Parallel more so: attachicon.gifgfs-0-180.png

 

As I said this may not resolve till near the weekend. GEM's infamy at blowing up LP systems is seen again on the 12z:

 

attachicon.gifgemnh-0-222.png

 

Just a matter of watching at the moment as there are plenty of variations on the theme as the models cope with the Atlantic storm and the US ridging in week 2.

The GEM is however very similar to the GFS P at that timeframe.

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GFS P carrying on it's trend to develop low heights over the eastern/central med in the post 10 day period

with high pressure over the top ridging over to the mother high over Russia. GFS P 06z showed this and now

the 12z is remarkably similar.

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I think TBH the models today is showing a continued stalemate between the colder air and milder air just like a couple of weeks ago. It reminds me of WWI when neither side gaining an upper hand. So the UK is still stuck in No Man's Land.

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The GEM is however very similar to the GFS P at that timeframe.

 

Yes but the GFS blows up the Atlantic storm, whilst the GEM blows up the lower heights sinking SE from the Canadian PV, though admittedly a similar outcome (as the Pros have said a period of more zonal weather likely). The Atlantic storm is therefore barely a blip (shortwave) as it mixes with that LP system. Highly unlikely IMO.

 

post-14819-0-21909700-1417453650_thumb.p

 

The Control is also worrying for Scotland: post-14819-0-25923600-1417454243_thumb.p

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The UKMO really sticking to its guns regarding the Northerly for the end of the week,and seems to have bonded with the NAVGEM. :laugh:

 

UKMO 96 hrs..  NAVGEM 96 hrs..

 

 

Not exactly winter armageddon on the way,but could give an enhanced risk of wintry precipitation for some areas which will make for some tricky forecasting for the pro's.

 

 

Just to add some support from NASA. :D

 

Edited by Cloud 10
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