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

[Ali1977]

Misfit- someone said yesterday the dam line may not be a monorail factor in snow turning to rain due to the cold air in place, hopefully snow all day.

Major factor even

[Troubleatmill]

Great satellite roll showing the cold block to east meeting the atlantic head on. and just how difficult it is for models to nail down excact westerwards or eastwards movements of approaching fronts to the cold block

http://www.yr.no/satellitt/europa_animasjon.html

[phil nw.]

Subtle differences on the timing of the snow coming in Friday.

The Hi Res NMM a bit slower than the NAE at 06Z

No doubt though it`s on it`s way though.

[KDME]

I appreciate that right now, the models are not 100%. Anyone hazard a guess how far east the snow will possibly get?

I run a small retail business in Chelmsford, Essex. So far, this weather has already caused a downturn. Therefore the prospect of snow is giving me the creeps!!

Thanks.

[bradymk]

Subtle differences on the timing of the snow coming in Friday.

The Hi Res NMM a bit slower than the NAE at 06Z

No doubt though it`s on it`s way though.

Yes NMM bit slower with the snow however i would say the NMM is quicker with the main band at 06h

[Orpingtoniceagedec10]

Are any of the models hinting at a breakdown in the cold from sunday like the MO are saying . Or are they all sticking with the blocking pattern ?

[R.P. McMurphy]

Misfit- someone said yesterday the dam line may not be a monorail factor in snow turning to rain due to the cold air in place, hopefully snow all day.

Major factor even

Hi Ali, you don't need the dam line in this current setup as few points will be low from the feed.

[johnholmes]

In frontal situations possibly more than a snowy showery set up the so called magic 528 1000-500mb line is much less important than the 850mb temperature and the 1000-850mb thickness levels. Try the Guide on this it does work quite well. Remember to factor height amsl, and your distance from the nearest coast if it is relevant from the isobar direction or more specifically what the surface wind is showing and predicted to do.

Glenn what do you mean with this or is something spelt wrong?

as few points will be low from the feed.

Edited January 16, 2013 by johnholmes

[Alexis]

I tend to find the 528 dam line is pretty meaningless. I've seen plenty of maritime based setups deliver 100% rain in sub 528dam air.

[Davey80]

Is the front expected to sweep away to the northeast or be dragged down the spine of the country and exiting the south east?

[Andrew snow hope]

I know lets get through Friday first but next week has some epic chance of some bigger snowfall based on GFS. Any thoughts on this?

[liltbrockie]

I know lets get through Friday first but next week has some epic chance of some bigger snowfall based on GFS. Any thoughts on this?

I'd say there's a chance but its still way out there in FI

[Mark Neal.]

In frontal situations possibly more than a snowy showery set up the so called magic 528 1000-500mb line is much less important than the 850mb temperature and the 1000-850mb thickness levels. Try the Guide on this it does work quite well. Remember to factor height amsl, and your distance from the nearest coast if it is relevant from the isobar direction or more specifically what the surface wind is showing and predicted to do.

Glenn what do you mean with this or is something spelt wrong?

as few points will be low from the feed.

I think he meant to say Dewpoints John!

[Boro Snow]

Are any of the models hinting at a breakdown in the cold from sunday like the MO are saying . Or are they all sticking with the blocking pattern ?

I havent seen anywere the mo saying these gunna be a breakdown of the cold, it is mentioned by the mo in its 6-15 day forecast for the end of jan but nothing sooner except for maybe the sw

[LomondSnowstorm]

The NAE looks a bit less progressive with the band this run than the last few:

compared to

[mickpips]

I havent seen anywere the mo saying these gunna be a breakdown of the cold, it is mentioned by the mo in its 6-15 day forecast for the end of jan but nothing sooner except for maybe the sw

the first line of their weather warning states 'As the weather breaks down.. ', I think thats where the question arose as that simple sentence is quite misleading.

[Sweetdream]

With everyone regarding the potential of the snowfall some have forgotten the impact of more flooding in far west areas where it will turn readily to rain.

[snowking]

I know somebody posted the link to this multi-model mean the other day which is superb.

If we take a look at the mean 850's out to 192:

Still sub -4c (as they are throughout the run) and with a mean E'ly cyclonic flow:

Plenty of fun and games to be had in the next 7 days or so at least

SK

[snowwonder]

Just had this from someone at Luton airport!!! Bit off topic but thought worth sharing!!

What follows is the early view of what the end of this week might look like for the UK. Temperatures are expected to continue to fall as we move in to the second part of this week. Day time temperatures will barely climb above freezing (except for the far south west and Ireland) and overnight we will see -4 to -6 falling to -8 to -10 by Fri/Sat.

**SEVERE ICING RISK**

UK - As forecast we have seen large accumulations of snow across far eastern parts of the UK over the last few days which mostly missed LTN & STN, but ice is now affecting many other areas of the country. The next 2 days look much drier and brighter but still very cold, giving us some respite from potentially disruptive wintry weather but a continued risk of severe frost and ice and plenty of de-icing activity. However, towards the end of the week it looks as though there will be a transition to more unsettled conditions spreading from the west. Over the last few days the UK has seen a battle between cold air to the east and north-east, and milder, moist air to the west. Cold air has certainly won the battle for the moment but milder air in the west is trying to push against it all the time. This is creating very difficult conditions to forecast. The current thoughts are that a band of rain will push in from the west on Friday, hit cold air and turn to snow that could produce significant accumulations for much of the UK. The main risk areas initially are Northern Ireland, Wales, northwest England, the West Midlands and southwest England but it is likely that these conditions will move east over the course of Friday and into the weekend. However, considerable uncertainty remains in exactly how the band of precipitation will then position itself, whether it continues northeast or stalls over western Britain. In the extreme west, snow is likely to turn back to rain but we could see large accumulations of snow in places. Amounts of snow are highly uncertain but there is currently a moderate risk of severe disruption to our operation. Over the weekend further outbreaks of rain, sleet and snow are expected to push in from the west but there is still considerable uncertainty as to how quickly this might happen and whether or not we will see slightly less cold conditions despite the above predictions.

London Airports LTN/STN/LGW/SEN - The weather outlook for today and tomorrow is very cold with visibility issues due to freezing fog and then low cloud. Temperatures are set to stay below freezing over the next few days. There is a threat of substantial snowfall for Friday afternoon with a 50-60% risk of snow from the west making its way across to the London Area. If any snow does fall on Friday it is expected to arrive mid morning (however, it is too early to tell with any certainty at this early stage) and be with us for most of the afternoon into early evening. If the snow does eventuate, there is 40-50% probability of accumulations of up to 10cm's.

Due to the nature of the forecast OCC will be providing daily updates and will be in regular contact with the Met office.

** Would all relevant business areas ensure they are fully prepared for this next cold weather event? **

[Sweetdream]

I know somebody posted the link to this multi-model mean the other day which is superb.

If we take a look at the mean 850's out to 192:

Still sub -4c (as they are throughout the run) and with a mean E'ly cyclonic flow:

Plenty of fun and games to be had in the next 7 days or so at least

SK

Hi sk looking through the models my concern is the far SW corner being hit with more flooding. My elderly aunt lives in padstow.

[MKN]

The precip is roughly 150miles further west on the 12z NAE compared to the same time on 06z by +33

[Catacol]

The precip is roughly 150miles further west on the 12z NAE compared to the same time on 06z by +33

Well - I'm liking the sound of that. :-) Not unexpected - observational history suggests that computer models tend to underestimate the power of a block. Where are you seeing the NAE? Hasnt updated on weatheronline yet... EDIT - yes it has. Definite westward adjustment. The folks in Devon better get up at 0600 and open their curtains: it may snow down there after all...

Edited January 16, 2013 by Catacol_Highlander

[MKN]

Poor NAE overall not as far east and precip alot weaker

[Radiating Dendrite]

Poor NAE overall not as far east and precip alot weaker

Good job it is usually wrong then

I am sure things will change a lot in the next 24 hours.

[Met4Cast]

Poor NAE overall not as far east and precip alot weaker

Sorry but..

Weaker? If you're complaining about this you need your head examining