Winter Model Discussion - The Hunt For Cold -18z 17/12/12

[nick sussex]

The underwhelming output continues with a possible mini cold blip by the GFS the highlight! even that has the propensity of getting watered down.

The ECM is like watching paint dry till the final frame at 240hrs, looks like a low developing near the Gulf of Mexico could run ne and if it develops sufficiently and stays an inland runner it could help pull the Azores high further west and north with a bit more amplification upstream.

Overall apart from a few skirmishes with some PM air at best it looks largely uneventful from a cold perspective upto 240hrs, however its looking dismal in terms of rainfall for areas that really don't need anymore.

A few more interesting options in the GEFS ensembles but we need to see that Azores high displaced and some big changes to deliver on a more UK wide scale.

Edited December 20, 2012 by nick sussex

[Summer Sun]

There looks to be good agreement for a cold snap just after Christmas this morning going by the ensembles

There are plenty of members trending below zero this morning especially on the Aberdeen ensemble

As ever nothing is set but its a trend continued from last night

This trend to colder and increasingly wintry weather is showing on GFS this morning

It looks like been a slow process the further south you are but something to watch for sure over the coming days

Edited December 20, 2012 by Gavin.

[MR EXTREMES]

The underwhelming output continues with a possible mini cold blip by the GFS the highlight! even that has the propensiity of getting watered down.

The ECM is like watching paint dry till the final frame at 240hrs, looks like a low developing near the Gulf of Mexico could run ne and if it develops sufficiently and stays an inland runner it could help pull the Azores high further west and north with a bit more amplification upstream.

Overall apart from a few skirmishes with some PM air at best it looks largely uneventful from a cold perspective upto 240hrs, however its looking dismal in terms of rainfall for areas that really don't need anymore.

A few more interesting options in the GEFS ensembles but we need to see that Azores high displaced and some big changes to deliver on a more UK wide scale.

ran through the gfs and ecm ukmo by god im more confident now perhaps no white christmas but the charts are getting closer and closer to a colder evolution with ok arctic cold snaps until pressure is sustained over greenland even through this wet and windy spell scotland and northern england more so the hills could do very well.

im very happy with this mornings output and i dont believe in the azores high being a major player or spoiler.

[MR EXTREMES]

Here's hoping for something snowy...otherwise there'll be more than a few 'displaced' headaches on here!

not bothered right now i know january is going to be the starting point for a more intresting colder spell see i have my crystal ball lol oh and my trusty models and my trusty net weather friends lol.

i think over all theres clear indication that something will trend the right way.

[mountain shadow]

Slightly disagree with Gibby's summary of no lowland snow in the model output.

The models do point to a chance in the North and West as nearer the Arctic air although it is precarious as mentioned.

Still at least it gives something to look for.

[Summer Sun]

not bothered right now i know january is going to be the starting point for a more intresting colder spell see i have my crystal ball lol oh and my trusty models and my trusty net weather friends lol.

i think over all theres clear indication that something will trend the right way.

Yes the first task is to block the Atlantic off until we can we are stuck with what we have now, hopefully into next week the pattern will change

[karlos1983]

Another good run required please from the GFS, and "dis-place" could go mad.

[No Balls Like Snow Balls]

Good to see that it's possible xmas day won't be to mild, still a way to go though but fingers crossed models will show temps gradually getting colder.

[nick sussex]

ran through the gfs and ecm ukmo by god im more confident now perhaps no white christmas but the charts are getting closer and closer to a colder evolution with ok arctic cold snaps until pressure is sustained over greenland even through this wet and windy spell scotland and northern england more so the hills could do very well.

im very happy with this mornings output and i dont believe in the azores high being a major player or spoiler.

Lol! you're easily pleased.

First rule regarding cold advection south with no proper Greenland high, ignore the 850's until nearer the time, the GFS in particular over estimates the southwards push of colder air.

If you look at the actual GFS theres little time for those cold uppers to head south and at this timeframe if further shortwaves develop then the cold will get delayed.

Thats why my post may seem rather less enthusiastic than most this morning, we need something to slow low pressure tracking east and the Azores high to retrogress, the ECM 240hrs at least shows that developing low in Canada and thats really needed but we need it to stay inland and run up to the west of Greenland.

[carinthian]

Just a thought. That very cold Russian High has been stagnant in the same place for weeks now with polar continental airmass now entrenched east of the far reaches of the North Sea . A couple of weeks ago this airmass was forecast by the main models to advance westwards and we all know that never happened. Now the model forecasts are for it to collaspse with erosion from the Atlantic. What if these models are wrong again ? Looks like an endless spin cycle and the British Isles in permanent rince hold. My hunch is the Russian high to play havoc with model projections beyond the next 72 hours.

C

[snow drift]

Just a thought. That very cold Russian High has been stagnant in the same place for weeks now with polar continental airmass now entrenched east of the far reaches of the North Sea . A couple of weeks ago this airmass was forecast by the main models to advance westwards and we all know that never happened. Now the model forecasts are for it to collaspse with erosion from the Atlantic. What if these models are wrong again ? Looks like an endless spin cycle and the British Isles in permanent rince hold. My hunch is the Russian high to play havoc with model projections beyond the next 72 hours.

C

I hope that is not the case and I expect it not to be. In that the high will clear off. The models are more in tune with the pattern we are in. If it did turn out the way you are suggesting, then I better get the boat out of the sea and put it on the drive to use to get to work.

[TEITS]

My view of the output is somewhat inbetween the comments this morning. Im not as excited as some but im not as disappointed as others. Between Xmas it does look likely a cool/cold NW/N,ly could develop but again it really depends on where you live. I would be far happier if I lived in Scotland especially with elevation compared to my location which is as flat as a pancake. I always laugh when the Met O refer to high ground in E Anglia in their forecasts!

A mean below -5C for Aberdeen is fairly impressive and i've seen alot worse model output.

http://cdn.nwstatic....erdeenshire.png

Edited December 20, 2012 by THE EYE IN THE SKY

[Shunter]

Just a thought. That very cold Russian High has been stagnant in the same place for weeks now with polar continental airmass now entrenched east of the far reaches of the North Sea . A couple of weeks ago this airmass was forecast by the main models to advance westwards and we all know that never happened. Now the model forecasts are for it to collaspse with erosion from the Atlantic. What if these models are wrong again ? Looks like an endless spin cycle and the British Isles in permanent rince hold. My hunch is the Russian high to play havoc with model projections beyond the next 72 hours.

C

I tend to agree, although no models back this up, I cant see this airmass retreating at the rate forecasted. Where does this leave us?. I still think the HP cell will retrogress towards iceland.

[Village]

Yeah, doesnt look as if there is any real winter weather on the cards over the holiday season for the bulk of us. GFS and ECM seem to be pretty much in agreement that an upper cold pool will slip down into Scotland where it will produce more snow for the upland regions. But thats about it.

We should look again after the weekend and see how these models develop the situation.

What usually happens in these instances is that the upper cold air can sink down to the east of England as H/P builds north out in the Atlantic. That will bring a cold northerly down across the UK and wintry showers down the east coast for a time....but this wont be until the first few days of January, so we will have to watch the models.

[karlos1983]

This isn't looking as good for the cold blast at the moment, low is further west.

+102 06z

+102 00z

[Ian Brown]

Lol! you're easily pleased.

First rule regarding cold advection south with no proper Greenland high, ignore the 850's until nearer the time, the GFS in particular over estimates the southwards push of colder air.

If you look at the actual GFS theres little time for those cold uppers to head south and at this timeframe if further shortwaves develop then the cold will get delayed.

Thats why my post may seem rather less enthusiastic than most this morning, we need something to slow low pressure tracking east and the Azores high to retrogress, the ECM 240hrs at least shows that developing low in Canada and thats really needed but we need it to stay inland and run up to the west of Greenland.

Yes, there is no blocking so anything will be fairly transient and often nearer the time in these situations, secondary features develop that end up pulling the jet Northward so that you need to be in the very far North and/or on the highest ground to see any snow.

[carinthian]

I tend to agree, although no models back this up, I cant see this airmass retreating at the rate forecasted. Where does this leave us?. I still think the HP cell will retrogress towards iceland.

Yes, that a minority thought, but I am tending to think along those lines this morning.

C

[TEITS]

Yes, there is no blocking so anything will be fairly transient and often nearer the time in these situations, secondary features develop that end up pulling the jet Northward so that you need to be in the very far North and/or on the highest ground to see any snow.

Im not sure that is true. We have a displaced bartlett HP over Greenland/Canada and a displaced Siberian HP over the Azores. Furthermore we have a displaced Arctic HP centred over Australia.

[No Balls Like Snow Balls]

At T120 the GH is strong no?, stronger than than the UKMO and ECM, this can only be a good thing.

I don't understand how this is not considered blocking?????

[492]

Yes, that a minority thought, but I am tending to think along those lines this morning.

C

The models maintains the block to the east for the next two days and temperatures in the low countries are already down to around 3C. The very cold Russian air has been advancing across Poland overnight and it looks like continuing to advance westwards over the next couple of days. Confidence in the models seems quite high in an Atlantic dominated pattern but it is still facsinating to watch the mild advancing from the southwest at the same time as the cold is advancing from the east. In some of the earlier decades I would have backed the cold to win not but I'm not so sure these days.

http://www.metoffice.gov.uk/data/education/chart_latest.gif

[Dampdorset82]

At T120 the GH is strong no?, stronger than than the UKMO and ECM, this can only be a good thing.

I don't understand how this is not considered blocking?????

There isnt a strong enough ridge over the atlantic so there isnt a strong enough block. Agreed heights are strong but need that ridge in the atlantic

Edited December 20, 2012 by Dampdorset82

[-uksnow-]

We really do need to see that Russian high just bugger off to see anything remotly sustained of cold weather post christmas and new year, it only seems to build stronger again on the 06z, however although FI now is leading to a potential split vortrex at T288

Edited December 20, 2012 by -eded-

[WhiteFox]

At T120 the GH is strong no?, stronger than than the UKMO and ECM, this can only be a good thing.

I don't understand how this is not considered blocking?????

It's a surface high; Greenland is so cold that whenever there is not a low pressure system moving across, pressure builds rapidly at the surface due to the dense cold air. Any low pressure apporaching that high will break through easily. You need to see more green and orange on that chart which would indicate a high pressure with more depth which would be able to withstand the approach of a low pressure.

[Methuselah]

Im not sure that is true. We have a displaced bartlett HP over Greenland/Canada and a displaced Siberian HP over the Azores. Furthermore we have a displaced Arctic HP centred over Australia.

One potential fly-in-the-ointment, however, could be posed by the continued 'displacement' of the Channel low...What if it stays out near Iceland?

[No Balls Like Snow Balls]

It's a surface high; Greenland is so cold that whenever there is not a low pressure system moving across, pressure builds rapidly at the surface due to the dense cold air. Any low pressure apporaching that high will break through easily. You need to see more green and orange on that chart which would indicate a high pressure with more depth which would be able to withstand the approach of a low pressure.

Let's hope for some yellows and oranges then :-)