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Model output discussion - 1st December onwards

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1 minute ago, Polar Climate said:

No

gensnh-1-1-120.thumb.png.9f3692b21b8dbdegensnh-4-1-138.thumb.png.b40dc1808bee099gensnh-5-1-132.thumb.png.0cac298acbe678fgensnh-6-1-126.thumb.png.c1ad246b562b9d4gensnh-10-1-114.thumb.png.cec8f613583defgensnh-11-1-126.thumb.png.b7086bba2d3820gensnh-13-1-120.thumb.png.ce736aff0be196

Good answer, PC. I won't ask you for the short version!:yahoo:

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Bottom line, with such a huge surge of warm air into the Arctic circle (as is currently underway) expect the unexpected.

The only thing I do expect is very little consistency from the models in the coming days, I can see a situation with them running with one mid-term outcome for a few runs, then suddenly ditching it and going with a very different one!

 Whether short term we can squeeze out a cold spell I am not so sure but 2nd half onwards of Jan is getting more and more interesting.

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I always feel that the more the minor models and GEFS members are posted on this thread, the less cold/hot the actual outcome will be.  

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2 hours ago, nick sussex said:

The NAVGEM normally is cannon fodder because it picks out a solution which isn't supported by the other operational runs however its increase in amplitude over the ne USA is now being supported by the UKMO/ECM although the latter doesn't turn out as favourable. The GFS 06hrs run is also trending that way over the ne USA in the earlier timeframe, the models will now have a difficult balancing act caught between two stools, eject the UK low as a clean feature or stick with elongated shortwave energy, as you can see by the GFS 06hrs its now confused as to what to do.

I'm not saying that the chips will fall kindly but its clear that theres a lot of volatility in the outputs for the detail over the UK.

The latest NAVGEM is coming out shortly, who knows it might now drop the idea which wouldn't surprise me which would be somewhat ironic given the UKMO now backs it!

Many thanks Nick! Really enjoy your words and have learnt so much from you. Incidently what did the 12z navgem have to say for it self then?

 

 

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1 hour ago, Glacier Point said:

The MJO cruising through the Pacific has triggered a pattern change to a notable -AO and more neutral NAO, although in reality the NAO is more positive still due to a residual trough signal in the North-east Atlantic. Fundamentally the game has changed as angular momentum has been moved upwards and the consolidation of the MJO in the next week is going to take it to the heady heights of +3SD. For an angular momentum junkie like me, these are rarified times and emphasises the lofty company we're keeping - only 1997/8 and 1982/3 witnessed such high levels of global westerly wind balance. GEFS product below is off the scale !

 

 

Neither of those years saw the peak in January though.... the closest Nino year with a peak in AM in Jan is 2009/10. But the momentum peak was around half of what you are forecasting here Stewart. 

Hmmmm.........

Edited by Catacol

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As expected varying degrees of difference between the models continues, the usual theme though intact, i.e. GFS sticking out on its own, with the UKMO and ECM siding together. GFS tends to perform less well when it comes to developments to our NE, if it was the other way around and ECM was dislodging their influence but GFS not so, I'd be inclined to suggest the chances of colder air from the NE feeding into northern parts next week are limited, alas I don't think we can dismiss the chances of this happening. Indeed UKMO has been very bullish sticking with the theme of trough disruption early next week.

Lots going on in the short term which will have knock on implications for later next week.

The longer term trend remains an increasingly colder outlook with heights to the north becoming more influential against the atlantic.

A word on this evening - wow we have a frost forecast, and temps tomorrow look cold, around the 1-3 degree mark.. quite a shock to the system.. winter looks like arriving a month late.

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2 minutes ago, Catacol said:

Neither of those years saw the peak in January though.... the closest Nino year with a peak in AM in Jan is 2009/10. But the momentum peak was around half of what you are forecasting here Stewart.

Hmmmm.........

Closest is 1982/83 but I think we are marginally ahead timing wise...

Edited by Glacier Point
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Not great but I guess looking too far ahead we may miss what's right under our noses! Nothing mild about these charts 12hrs away! lol 

gfs90.thumb.png.4e1de29d3dde6ca6661ed7bagfs91.thumb.png.325b2c2c7fcc8c68e2cb4e10gfs92.thumb.png.cb60751d38222f173e240e26gfs93.thumb.png.7b76ea90738d089c9689180b

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27 minutes ago, TSNWK said:

Many thanks Nick! Really enjoy your words and have learnt so much from you. Incidently what did the 12z navgem have to say for it self then?

 

 

Thanks that's nice of you.

The NAVGEM 06hrs run has come out and its the same as the earlier 00hrs run and its had this same output now for about two days. Very strange, normally it picks an outlier solution and would have dropped it by now. Hopefully we'll get a resolution to this tonight.

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8 minutes ago, nick sussex said:

Thanks that's nice of you.

The NAVGEM 06hrs run has come out and its the same as the earlier 00hrs run and its had this same output now for about two days. Very strange, normally it picks an outlier solution and would have dropped it by now. Hopefully we'll get a resolution to this tonight.

Nick can you imagine the reaction on here if the navgem was right all along!!expect the unexpected i say!!its defo been consistent over the last 48 hours!!ukmo sort of joins the navgem aswell!!

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16 minutes ago, nick sussex said:

Thanks that's nice of you.

The NAVGEM 06hrs run has come out and its the same as the earlier 00hrs run and its had this same output now for about two days. Very strange, normally it picks an outlier solution and would have dropped it by now. Hopefully we'll get a resolution to this tonight.

The NAVGEM does overblow pressure over the N/NW, a known bias, so that is no surprise it has been trending that way for a few days (Proviso: Thats not to say it's wrong). The latest bias for our region:

Navgem bias: NOAA_NWS_NCEP_WPC_MODEL_DIAGNOSTIC_-_INT  UKMO568532d84c2d4_NOAA_NWS_NCEP_WPC_MODEL_DI  GFS568532d783773_NOAA_NWS_NCEP_WPC_MODEL_DI

Funny enough the UKMO has been consistently doing this of late as well, where as GFS is more subdued in this region for bias height anomalies. That is likely to be reflected in the current output. The above is for 10 days 0z runs at T144.

Edited by IDO
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3 minutes ago, shaky said:

Nick can you imagine the reaction on here if the navgem was right all along!!expect the unexpected i say!!its defo been consistent over the last 48 hours!!ukmo sort of joins the navgem aswell!!

There are some subtle differences on the 6z NAVGEM though compared to previous runs as the low over N France is further north and the colder air pushed back NE, bit worried with the UKMO sort of siding with the measly NAVGEM, much rather it was UKMO & ECM/GFS or all 3!!! Plenty more twists and turns to come no doubt... :) 

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7 minutes ago, Man With Beard said:

Well let no-one say next Monday/Tuesday/Wednesday is done and dusted in terms of snow or storms, whatever may be. The models have now come far enough to give us confidence that a mild/cold division will get extremely close to the UK in that timeframe, and the division could quite possibly be over the UK as well as the North Sea. We're now dealing with the fine lines of frontal systems, so this could go right down to T24 in any part of the UK.  The variance between models is no more than you'd expect when two substantially different air types are clashing and the various ops cover all the possible outcomes IMO.

To see where the dividing line really is, this is one of the rare occasions where the precipitation charts is useful. First, the most pessimistic - the JMA. See the pressure chart and compare to the precipitation chart; you'll see a band of rain roughly matching a line on the pressure chart which can be traced if you go from the centre of the tiny low over NE Scotland down to where the lines come to a point over W Germany. The rain/snow divide will be somewhere along that line of precipitation, probably slightly on the northern side of the line. So only the Shetlands gets the snow here.

J156-594.GIF?30-0J156-21.GIF?30-0

The other runs all have snow for at least part of the UK.  For the ECM, draw a line between the centre of the low next to Ireland and the low centred over Germany and then go up about 200 miles for the probable snow line - so all of Scotland gets snow away from the immediate coast, and parts of N England are at risk too.

ECM1-144.GIF?31-12

The band of rain/snow is more NW/SE on the GEM, so possibilities of snow all up the east coast here (again, away from the immediate coastline)

gem-2-144.png?00

The NAVGEM has the band of rain/snow right through N England, so snow from the borders north - though with the rain band running west to east, more chance of it sinking as it passes through, bringing N England and maybe even the midlands into the snow band - and as this front is more affected by an easterly feed, more it will be snow too:

navgem-2-132.png?31-12   navgem-0-138.png?31-12

We can see the UKMO is similar by looking at the western and eastern most extremities of the low pressure over S England:

UW144-21.GIF?31-06

but the low on both NAVGEM and UKMO looks likely to clear SE on Wednesday morning, pulling the snow line further south (slight difference between NAVGEM 00Z and 06Z but not big enough to make the 06Z much different). Perhaps not much in the way of precipitation left on the front by then, but SE corner at risk of snow showers to start the day:

navgem-0-150.png?31-08

So there you go, based on today's charts, all parts of the UK at risk of going white next Tuesday/Wednesday, if I had to guess, something like 60% chance for Scotland, 40% for N England / N Ireland, 30% for Midlands/N Wales/E Anglia and 15% for the south. And I don't see this being resolved particularly soon. Keep watching!

 

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=6

 

the  gfs  says buckets  of   rain

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11 minutes ago, Man With Beard said:

Well let no-one say next Monday/Tuesday/Wednesday is done and dusted in terms of snow or storms, whatever may be. The models have now come far enough to give us confidence that a mild/cold division will get extremely close to the UK in that timeframe, and the division could quite possibly be over the UK as well as the North Sea. We're now dealing with the fine lines of frontal systems, so this could go right down to T24 in any part of the UK.  The variance between models is no more than you'd expect when two substantially different air types are clashing and the various ops cover all the possible outcomes IMO.

To see where the dividing line really is, this is one of the rare occasions where the precipitation charts is useful. First, the most pessimistic - the JMA. See the pressure chart and compare to the precipitation chart; you'll see a band of rain roughly matching a line on the pressure chart which can be traced if you go from the centre of the tiny low over NE Scotland down to where the lines come to a point over W Germany. The rain/snow divide will be somewhere along that line of precipitation, probably slightly on the northern side of the line. So only the Shetlands gets the snow here.

J156-594.GIF?30-0J156-21.GIF?30-0

The other runs all have snow for at least part of the UK.  For the ECM, draw a line between the centre of the low next to Ireland and the low centred over Germany and then go up about 200 miles for the probable snow line - so all of Scotland gets snow away from the immediate coast, and parts of N England are at risk too.

ECM1-144.GIF?31-12

The band of rain/snow is more NW/SE on the GEM, so possibilities of snow all up the east coast here (again, away from the immediate coastline)

gem-2-144.png?00

The NAVGEM has the band of rain/snow right through N England, so snow from the borders north - though with the rain band running west to east, more chance of it sinking as it passes through, bringing N England and maybe even the midlands into the snow band - and as this front is more affected by an easterly feed, more it will be snow too:

navgem-2-132.png?31-12   navgem-0-138.png?31-12

We can see the UKMO is similar by looking at the western and eastern most extremities of the low pressure over S England:

UW144-21.GIF?31-06

but the low on both NAVGEM and UKMO looks likely to clear SE on Wednesday morning, pulling the snow line further south (slight difference between NAVGEM 00Z and 06Z but not big enough to make the 06Z much different). Perhaps not much in the way of precipitation left on the front by then, but SE corner at risk of snow showers to start the day:

navgem-0-150.png?31-08

So there you go, based on today's charts, all parts of the UK at risk of going white next Tuesday/Wednesday, if I had to guess, something like 60% chance for Scotland, 40% for N England / N Ireland, 30% for Midlands/N Wales/E Anglia and 15% for the south. And I don't see this being resolved particularly soon. Keep watching!

 

Nice analogy MWB

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A heads up folks- i will be starting a new thread in a few minutes so hold off from posting just while i get it up and running,

Cheers.

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