Winter Model Discussion 12Z 15/1/13 onwards.

[shuggee]

Last Friday the GFS modelled that the Atlantic would break through the block on Wednesday (i.e. now).

On Monday the GFS modelled that the Atlantic would break through the block on Saturday.

Today the GFS is modelling that the Atlantic will break through the block on Tuesday.

Isn't this typical "hopecasting" behaviour?!

[Brad lough]

Hi thanks for the reply swfc

[Yarmy]

Last Friday the GFS modelled that the Atlantic would break through the block on Wednesday (i.e. now).

On Monday the GFS modelled that the Atlantic would break through the block on Saturday.

Today the GFS is modelling that the Atlantic will break through the block on Tuesday.

Isn't this typical "hopecasting" behaviour?!

Hopelesscasting.

[DartmoorSnow]

Like This

Glacier Point

Today, 11:51

I think we need to start to plan contingencies for a potentially sustained and very severe spell of wintry weather, of which Friday could just be the start.

NWP is presenting a number of potential snow events next week, which could well provide substantive accumulations.

The longwave trough migrating eastwards off the eastern coast of North America is consistently being modelled by ensemble means as cutting through a developing mid Atlantic ridge mid to late next week. That provides an eddy in the flow which is likely to enhance the easterly flow off an already frigid land mass to our east and north-east.

Thereafter, the ridge could retrogress towards the NE Atlantic and Greenland bring in another surge of Arctic air from the NE. That would give us a sustained period (with snowcover for much of the UK) of below normal temperatures.

I've grabbed the 06z GEFS at day 13 which depicts the synoptic pattern with a trough firmly ensconsed over Europe and high pressure to the north.

[Wayneywoo]

I have little doubts the GFS is underestimating the strength of this cold block that is over Scandinavia feeding us the cold continental air, coupled with the LP that is stuck over Europe that is keeping the block propped up. 12z starts off well and then resets to default with the Jet running SW/NE and giving us mild SW'lys.

I'd like to think this is a mild outlier, we will see...

And the good news is.........

The London 12Z GFS ensembles go on the mild side of the run from 21st onwards

Looking at the ensembles, you can see the temp prediction of the run is a mild outlier however the precip prediction is nearer the middle of the ensembles

[SL7]

Complete newby here: at what point or time can there be certainty in what's going to happen on Friday and the weekend. Or will it keep changing?

[Carlrg]

I often ask myself why I love severe gales and atlantic zonality! Really guys, looks like an epic 2 weeks plus for snow and some very low night time temps. we could have not asked for more, better than 12 degrees and drizzle innit. I suspect, going off current output there will be no trees putting out early blossom this year like last.

All I ask is that folks look out for the birds, 2 to 3 weeks sub zero is tough if your a sparrow, give em a water source n some fatballs!

Here, Here very well said. With 2m charts as cool as these they will need all the help they can get.

http://www.meteociel.fr/modeles/bome_cartes.php?ech=6&code=0&carte=0&mode=8&archive=0

I know it in FI but temps showing even cooler to the end of the run!!!!!!

And before anyone pulls me up, i know its the BOM but it was developed by the UKMO so that's good enough for me.

[johnholmes]

Complete newby here: at what point or time can there be certainty in what's going to happen on Friday and the weekend. Or will it keep changing?

probably by 12z tomorrow but it would help if you dropped your town in your avatar please-welcome to Net Wx, lots to enjoy, have a look round, son't be afraid to ask questions.

[Summer Sun]

Complete newby here: at what point or time can there be certainty in what's going to happen on Friday and the weekend. Or will it keep changing?

Things for Friday will firm up during tomorrow

As for the weekend your looking at Friday really

Welcome to netweather as well

Edited January 16, 2013 by Gavin.

[johnholmes]

Like This

Glacier Point

Today, 11:51

I think we need to start to plan contingencies for a potentially sustained and very severe spell of wintry weather, of which Friday could just be the start.

NWP is presenting a number of potential snow events next week, which could well provide substantive accumulations.

The longwave trough migrating eastwards off the eastern coast of North America is consistently being modelled by ensemble means as cutting through a developing mid Atlantic ridge mid to late next week. That provides an eddy in the flow which is likely to enhance the easterly flow off an already frigid land mass to our east and north-east.

Thereafter, the ridge could retrogress towards the NE Atlantic and Greenland bring in another surge of Arctic air from the NE. That would give us a sustained period (with snowcover for much of the UK) of below normal temperatures.

I've grabbed the 06z GEFS at day 13 which depicts the synoptic pattern with a trough firmly ensconsed over Europe and high pressure to the north.

and your input please?

[matty40s]

Complete newby here: at what point or time can there be certainty in what's going to happen on Friday and the weekend. Or will it keep changing?

Well you can be sure that most places will see snow on Friday, how much and for how long is still not completely clear......but it could be a lot for a lot of people.

You will notice that there are no weather warnings out yet for Saturday or Sunday, this is because the Met Office still have no real idea of what Fridays progression will lead to, and it may be late tommorow, or even Friday when this becomes more clear.

You may also fing that the Regional thread for your area gives you more localised information, on here is mainly the whole of the UK model analysis

Edited January 16, 2013 by matty40s

[Long haul to mild]

Absolutely no reason at present to buy into the quick breakdown modelled by GFS tonight, certainly while it has so support yet from other models and precious little from its own ensembles either. Blocks rarely get smashed away this quick. GFS in in deep love with the Azores high and always tries to get it back into the UK picture as soon as possible!

All I know is the breakdown just gets put back all the time and therefore it doesn't give any reason to make us believe in it. Eventually the block will break down and someone will say "well done GFS for calling it right" but it would hardly be a coup in the UK to get a prediction of zonal correct eventually!

I expect the GFS to back down or (more likely) continue with its habit of delaying the breakdown. Remember, we were supposed to be in mild SW'lys by now if last week's GFS runs were to be believed!!

[michail]

That littlle low just entering the ukmo T144 chart from the left, would that be a spoiler or would it flatten out the Azores high even further? Any hope for ireland?

[phil nw.]

Yes as we expected/hoped,lol GFS op goes mild against the ens mean next week in sending more energy northwards and flattening the blocking.The T144hrs ens spread shows the uncertainty with the area off the Canadian vortex and into into the Atlantic.

The ens mean at T168hrs looks more like the expected evolution

following the trend in reducing the strength of the Canadian vortex and showing more of a tendency to raise hts towards Greenland/Iceland later.

The main emphasis in directing that main Atlantic energy south east and extending low pressure towards the UK and France showing.

This is the key element of this cold setup at the moment.

I think the next few days is the period where our cold pool looks a little vunerable as it get`s attacked by the disrupting Atlantic trough at least twice but most models favour the undercutting and renewal of cold from the east with quite modest heights further north so for now that`s ok.

I would be far happier with longer term prospects though if we can see a solid upper high to our north appeariing in the models soon out of the wreckage of the remaining vortex.

[SL7]

probably by 12z tomorrow but it would help if you dropped your town in your avatar please-welcome to Net Wx, lots to enjoy, have a look round, son't be afraid to ask questions.

Thanks!

I'm in Leicester.

Will update my profile.

[Ian Brown]

Thanks Phil, the GFS loves to smash the jet through with associated height rises over Southern Europe and it's OP stands alone tonight as we wait for the ECM.

It's been a generally poor episode for the GFS.

[SL7]

Well you can be sure that most places will see snow on Friday, how much and for how long is still not completely clear......but it could be a lot for a lot of people.

You will notice that there are no weather warnings out yet for Saturday or Sunday, this is because the Met Office still have no real idea of what Fridays progression will lead to, and it may be late tommorow, or even Friday when this becomes more clear.

You may also fing that the Regional thread for your area gives you more localised information, on here is mainly the whole of the UK model analysis

Thanks for your reply. Yep, looking at met office and then following the forum has lead to some confusion for me I.e the other day there was massive excitement over possibilities of snow for fri and met office was showing nothing of the kind. But it's totally understandable why met office didn't do so prematurely.

[Barry12]

Thanks!

I'm in Leicester.

Will update my profile.

You'll get snow probably 5cm minimum, 10cm plus likely.

[michail]

That littlle low just entering the ukmo T144 chart from the left, would that be a spoiler or would it flatten out the Azores high even further? Any hope for ireland?

http://www.wetterzentrale.de/pics/Rukm1441.gif

[shawng]

Metoffice have warnings out for sat and Sunday for pretty much the whole country

now

[ChartViewer]

ECM T48 850's nice

T72

Edited January 16, 2013 by ChartViewer

[bluearmy]

T72 FAX and we have the third offering of front and shortwave placement from exeter within 18 hours. basically a shortwave develops on the occlusion and runs up the channel whilst the occlusion pivots back west. how far east will the precip get and will it become enhanced in the se of the uk by the shortwave ???

[Frosty.]

Absolutely no reason at present to buy into the quick breakdown modelled by GFS tonight, certainly while it has so support yet from other models and precious little from its own ensembles either. Blocks rarely get smashed away this quick. GFS in in deep love with the Azores high and always tries to get it back into the UK picture as soon as possible!

All I know is the breakdown just gets put back all the time and therefore it doesn't give any reason to make us believe in it. Eventually the block will break down and someone will say "well done GFS for calling it right" but it would hardly be a coup in the UK to get a prediction of zonal correct eventually!

I expect the GFS to back down or (more likely) continue with its habit of delaying the breakdown. Remember, we were supposed to be in mild SW'lys by now if last week's GFS runs were to be believed!!

I think the gfs has got the angle of a hypothetical breakdown all wrong next week, west to east would bring a change to milder but the most likely outcome is for the cold block to the northeast to remain strong and begin to extend southwest rather than weaken and keep the uk locked in the freezer.

Edited January 16, 2013 by Frosty039

[cobby]

You'll get snow probably 5cm minimum, 10cm plus likely.

But maybe not level snow if the wind causes drifting

[Jayces]

Metoffice have warnings out for sat and Sunday for pretty much the whole country

now

for ice, not snow.