General Model Output Discussion

[yamkin]

Given all the output so far this morning we should hopefully see the low track taken further south on the gfs 06hrs run, the ecm ensembles also show some room for taking the low a touch further south. The ukmo for some reason overdid the Xmas celebrations and is suffering from a hangover!

Nick, Last year around Xmas time the models seemed to be on a hangover mode at times. Is there a reason for the hangover mode over the Xmas period?

[MR EXTREMES]

If only we could see the MetO's private model as they are strongly indicating Heavy Snow from Wednesday onwards :cold: (BBC24 News Forecast by Susan Powell)

watch bbc 24 weather 3 am this morning and yes he did say it gonna get snowy but midlands north on tuesday wed here in the south 11c very wet.

so looks like it gone boobs up for us in the south.

can anyone tell me if this cold is like to cover the uk in time?

cheers.

[yamkin]

watch bbc 24 weather 3 am this morning and yes he did say it gonna get snowy but midlands north on tuesday wed here in the south 11c very wet.

so looks like it gone boobs up for us in the south.

can anyone tell me if this cold is like to cover the uk in time?

cheers.

The following is from TWO Forum courtesy of Chris.........

Morning all,

Lovely runs again this morning and the Siberian high link up Steve M was talking about shows up in nearly all the models!!!!!!

http://www.wetterzentrale.de/pics/Recm1681.gif this is great to be seeing at this time scale and is a trend that could potentially develop and bring some prolonged deep cold to the UK.

As for the Westcountry Blizzard watch (Cotswolds) still plenty of data to get excited about I especially like the GME this morning,

Low perfectly placed http://www.wetterzentrale.de/pics/Rgme841.gif

Nice south easterly wind http://www.wetterzentrale.de/pics/Rgme844.gif

UKMO still wants to bring the low further north, ECM doesn't develop the Low as much (but still snowy I think) and GFS is heavy rain turning to heavy snow. Overall not much cross model agreement but very exciting potential.!!!!

And the models in general are simply outstanding in the so called even larger teapot, it's cold with mild snaps (just) not the other way round lol!!!!

[snowmadchrisuk]

yeah chris i remember this also, the data coming in was less as not all stations reported data , its only one run and the 12 previous were all good for cold coming back, mind due it hasnt ever left us up here and we are on the coast, we had snow again last night on top of the snow we had on the ground since last friday

Stop it , your making me jelous , I dremt about moving to Scotland last night . The 6z has the low further South on Monday compared to the previous 2 runs.

[Guest North Sea Snow Convection]

Nick, Last year around Xmas time the models seemed to be on a hangover mode at times. Is there a reason for the hangover mode over the Xmas period?

I didn't see the models yesterday, but judging from some of the comments I have quickly read this morning from yesterday, I would say overall the models look like they have been consistent enough. I think that at any time they would struggle with the track of a low pressure system such as this with such extensive blocking to the north. On that basis, it gives some hope for southern most parts that the modelling of the cold air to the north is being underplayed as the track of the low is shifted a little further south - and some of these shortwave link ups are being overdone too.

However, I wouldn't expect too much snow in Croydon as a given if I were you Yamkin. South of the M4, but most especially the south east corner looks the least favoured area to see snow as things stand this morning.

Btw - have read Steve M's summary, and it is a very good analysis indeed of what happened with the last cold spell and I think it is very true that we need the 'Siberian' element to come into play to get the least marginal cold air across the greater part of the BI. That looks possible from the current modelling - if the troughs to our south, south west and also to our north east allow it to without getting in the way

Edited December 26, 2009 by North Sea Snow Convection

[nick sussex]

Nick, Last year around Xmas time the models seemed to be on a hangover mode at times. Is there a reason for the hangover mode over the Xmas period?

Well this has caused some debate over the last few days in terms of data issues as to whether fewer Xmas flights have lowered the accuracy because of less flight data. Regarding the gfs 06hrs run so far the cold air hanging on better in the south here. A better orientation to the low here which is a good sign.

[BARRY]

Well this has caused some debate over the last few days in terms of data issues as to whether fewer Xmas flights have lowered the accuracy because of less flight data. Regarding the gfs 06hrs run so far the cold air hanging on better in the south here. A better orientation to the low here which is a good sign.

[/quote

don't like as much now

Edited December 26, 2009 by BARRY

[Mark Parsons]

If only we could see the MetO's private model as they are strongly indicating Heavy Snow from Wednesday onwards (BBC24 News Forecast by Susan Powell)

Yes that is what she said but it looks like only being likely in central areas atm and that could and probably will change, imo the charts are still all over the place and who knows where we will be by the middle of next week!

[TEITS]

I will say that if the 06Z verified then Wales/ W Midlands would be the first to see heavy snow. This risk then extends further S/E as the day progresses although I don't think snow would fall in SE/E Angia.

[nick sussex]

Absolutely,the low is more west to east than SW to NE,another 50 miles south would make a hell of a difference

This is very important, the ukmo had the low alligned sw/ne yesterday and this could cause trouble, we want to see it west/east or even wnw/ese and elongated. We see here the cold air about 100 miles further south than for the same time on the gfs 00hrs run.

Edited December 26, 2009 by nick sussex

[East Herts Snow]

Well out to +102 and everything shunted South by about 100 miles.

Southern Wales and South West Midlands look best for snow thus far....

Edited December 26, 2009 by North Londoner

[BristolBlizzard]

I will say that if the 06Z verified then Wales/ W Midlands would be the first to see heavy snow. This risk then extends further S/E as the day progresses although I don't think snow would fall in SE/E Angia.

is bristol to far south to be affected !

[Mark Parsons]

The following is from TWO Forum courtesy of Chris.........

Morning all,

Lovely runs again this morning and the Siberian high link up Steve M was talking about shows up in nearly all the models!!!!!!

http://www.wetterzen...cs/Recm1681.gif this is great to be seeing at this time scale and is a trend that could potentially develop and bring some prolonged deep cold to the UK.

As for the Westcountry Blizzard watch (Cotswolds) still plenty of data to get excited about I especially like the GME this morning,

Low perfectly placed http://www.wetterzen...ics/Rgme841.gif

Nice south easterly wind http://www.wetterzen...ics/Rgme844.gif

UKMO still wants to bring the low further north, ECM doesn't develop the Low as much (but still snowy I think) and GFS is heavy rain turning to heavy snow. Overall not much cross model agreement but very exciting potential.!!!!

And the models in general are simply outstanding in the so called even larger teapot, it's cold with mild snaps (just) not the other way round lol!!!!

cant see where the cold air will come from to turn this rain to snow.

[john mac]

fantastic we need the low to come in on a more west to east angle which will help us get the cold further south

[nick sussex]

The snow risk extends here as theres less sea modification, the gfs 00hrs run had a more ne flow this is more ene,again here if you're in the se it would help if the low alligns more wnw/ese this would pull in a more easterly flow with lower dew points undercutting the precip. We're still some way from calling the low track however but the gfs 06 hrs run so far is a step in the right direction.

Edited December 26, 2009 by nick sussex

[snowmadchrisuk]

fantastic we need the low to come in on a more west to east angle which will help us get the cold further south

This is good for the cold lasting a little longer , but looks a repeat of Monday 21st Dec , where the ppn would struggle to get North of Northampton.

[Altostratus]

If the whole pattern was shifted a couple of hundred miles south along with those nuisance troughs which are cutting off the coldest air from arriving across the greater part of the BI then the models this morning would get the perfect '10'. Taken at face value they are very much spoiled by these lows which stop an amazing easterly right across the UK and on a transatlantic trip to the states and Canada. Very frustrating.

The exception is the GEM which has the less cluttered straightforward evolution to the main low staying and passing to the south with no subsequent messy spoiling link ups with the trough over the Baltic and the lows to the south west which appear to cut off the properly cold air.

Faultless blocking to the north - hopefully the models are just over complicating things and that cold air gets far enough south, before it is whisked away again.

The ECM looks rather suspect to me from t144 onwards - and over progressive. However, hoping for better this evening. Very good outlook further north, but less so in southern and south eastern most parts, where the cold air looks to be struggling to arrive and the sledges are not ready to come out yet.

I agree with you. The initial channel low is too far north to deliver anything to southern areas – it looks like an all rain event here tbh. People in the south shouldn’t be expecting much from this. There is still time for a shift southwards, but this is looking unlikely IMHO. In the medium to long run, synoptically brilliant, yet failing to deliver to most southern areas. This morning’s charts have also highlighted a potential spoiler, with a ridge of high pressure building from the south. The output is excellent throughout for the north, but lacklustre for southern areas. There is still plenty of time for things to change and the general trend is certainly excellent, with blocking in all the right areas. From an IMBY perspective, I hope we don't have a similar outcome to Feb 2001, whereby the coldest air never quite made it to southern areas - It was tantalisingly close. I'm refeering to the infamous 'Kettley' cold spell for those that remember.

[Wilxy]

is bristol to far south to be affected !

i hope so warnings so close yet so far

[East Herts Snow]

Only downside in the short term is the colder air pushing more South is that the ppn has moved into Northern France at +108 onwards.

Overall a colder, but dryer run for Southern areas, although Tuesday/Wednesday snow event has been upgraded, especially for South Wales and West Midlands.

Edited December 26, 2009 by North Londoner

[TEITS]

Just want to clear a few things about this possible snow event.

The 06Z sends a SW across the S. Now with this SW the upper temps look to be around -5C. Now this is just cold enough for Wales/Midlands/Possinly parts of the SW. However this isn't cold enough for E Anglia/SE due to the warming effects of the N Sea. Now beyond this and the main LP system remains to the S but is pulling in ever increasing cold upper temps. So although the SE/E Anglia miss the snow event, the focus switches to these regions as snow showers move in from the NE.

[Mark Parsons]

I agree with you. The initial channel low is too far north to deliver anything to southern areas – it looks like an all rain event here tbh. People in the south shouldn't be expecting much from this. There is still time for a shift southwards, but this is looking unlikely IMHO. In the medium to long run, synoptically brilliant, yet failing to deliver to most southern areas. This morning's charts have also highlighted a potential spoiler, with a ridge of high pressure building from the south. The output is excellent throughout for the north, but lacklustre for southern areas. There is still plenty of time for things to change and the general trend is certainly excellent, with blocking in all the right areas. From an IMBY perspective, I hope we don't have a similar outcome to Feb 2001, whereby the coldest air never quite made it to southern areas - It was tantalisingly close. I'm refeering to the infamous 'Kettley' cold spell for those that remember.

completely agree,it is looking just that way and I hope it is wrong but you cant get away from the fact that the south generally is less likely to be effected by snow and prolonged cold.

[Guest North Sea Snow Convection]

The 06z looks a little better, but I think the problem stems from the fact that there is no properly cold air in situ, away from the more northern parts, just prior to the arrival of this low. If there was dense cold air meeting the low as it heads in from the south west approaches then I think that we might see a more favourable orientation and track of the low as it would disrupt more NW-SE against the cold air and is forced on a much morre southerly track. Jan 82 was an example of this where very cold air was sitting just to the north east of the LP system and undercut the ppn immediately to the south. This is missing in the first analysis, and a bigger trigger is need to the NE to get the cold air further southwards. The Scandi trough is also actually hindering this process by keeping the coldest air to the NE of us

[Guest North Sea Snow Convection]

I agree with you. The initial channel low is too far north to deliver anything to southern areas – it looks like an all rain event here tbh. People in the south shouldn't be expecting much from this. There is still time for a shift southwards, but this is looking unlikely IMHO. In the medium to long run, synoptically brilliant, yet failing to deliver to most southern areas. This morning's charts have also highlighted a potential spoiler, with a ridge of high pressure building from the south. The output is excellent throughout for the north, but lacklustre for southern areas. There is still plenty of time for things to change and the general trend is certainly excellent, with blocking in all the right areas. From an IMBY perspective, I hope we don't have a similar outcome to Feb 2001, whereby the coldest air never quite made it to southern areas - It was tantalisingly close. I'm refeering to the infamous 'Kettley' cold spell for those that remember.

I totally agree with all of that - and the Feb 2001 situation does come to mind here

[Matt12]

Judging by the ensembles, I wouldn't even say it's a given that Northern parts of the UK will stay in a prolonged cold spell i.e. beyond 3rd/4th of Jan. Look at the huge scatter, and the GFS operational and GEFS control are well above the mean in many northern locations, including northern England/Scotland, from around the 3rd onwards!

I still think it's all to play for for everywhere, including Northern parts - if you want anything beyond a short cold snap, that is.

[Wilxy]

Just want to clear a few things about this possible snow event.

The 06Z sends a SW across the S. Now with this SW the upper temps look to be around -5C. Now this is just cold enough for Wales/Midlands/Possinly parts of the SW. However this isn't cold enough for E Anglia/SE due to the warming effects of the N Sea. Now beyond this and the main LP system remains to the S but is pulling in ever increasing cold upper temps. So although the SE/E Anglia miss the snow event, the focus switches to these regions as snow showers move in from the NE.

Unlucky but things can still change and will do whether there good or bad but either way at least u had loads of snow the other week.