South West England Cold Spell Discussion

[dogs32]

yes i think its gone up a notch for some places in the UK..

as anyone noticed how bad the roads are lately,Ice breaking up the surfaces on roads.

Pot hole's appearing in numerous place's I think it is due to the long period of Ice..

edit...just heard some places In Scotland running out of Salt.

and some old people have been stranded in their home's for week's due to the ice..BBC24..

Edited January 4, 2010 by dogs32

[Lynxus]

-1.4c in swindon. Could be an ice day?

Here at work in bath though, we seemed to be inside a snow cloud earlier as the air was thick with ice particles blowing around and leaving a white layer on most things.

Yeah we had freezing fog this morning and a lot of places looked like it had snowed ( but was just extreme frost )

The pavements,trees,grass,roads were covered in white icey snowy suff

Edited January 4, 2010 by Lynxus

[snowking]

Looks like its going to just about be an ice day here, -0.3c now and we're through the warmest part of the day

Looking increasingly to me as though the BBC are forecasting the precipitation to maintain a little more intensity and organisation as it heads through our region now, and i especially like the look of the wrap-round front for tomorrow - looks like its will be sliding SW-wards, which should result in an almost streamer-like movement, slipping slowly southwards, so could well give a few cms fairly widely if indeed it verify's

All eyes on the radar through the early hours

SK

[Ian Fergusson]

G'Day folks and hi Thermo - fab to see you here, mate!

Ok.... as some of the eagle-eyed amongst you may have spotted, we have two primary forecasting issues / changes to discuss:

1. The UKMO's later NAE assessment for tomorrow - which arrived after those of us broadcasting this morning for BBC Breakfast had finished - heralded some changes. The key one, for us at least, is a more coherent look to the frontal progression tomorrow morning, with a broader areal spread of PPN (predominantly snow inland) and some further potential later into the evening. We're not expecting significant accumulations, however - albeit the snow isn't even our major concern anyway; it's the outcome of any PPN falling onto very cold ground that will be the major peril tomorrow morning....

Attached, illustrating the point, are two sets of NAE modified fields (i.e., with expertise and mods from the UKMO Chief Forecaster, not the raw output, I stress); plus the WBFL progression and PPN discrimination (green = liquid).

2. The UKMO GM is remaining ambivalent about end-of-week developments and for this reason, you'll hear little ramping of a major, widespread snow threat (as opposed to more regionalised / sub-regional but still substantial falls in the E and SE later in the week) from UKMO until the model settles and offers reasonable continuity of threat severity / spatio-temporal spread. This is, needless to say, a key change from the GM modelling used by our on-air forecasts yesterday, but that's the nature of our world when delving into the very fluid mid-range stuff...

Current rather elastic thinking, still with very tempered confidence as I understand it, is for potential developments over the weekend from the east - much as earlier anticipated for Friday but still with low certainty. So to summarise, the profound risk of something very newsworthy and bothersome still remains, but rightly, the UKMO will keep powder dry on formal advisories, etc., until we see some continuity that reaches strict bounds of statistical confidence for offering advisories / early warnings on this event/events.

Tomorrow aside, the NAE paints generalised accumulations (using 4km modelling) of snowfall in the West Country totalling ca. 1-3cm by end of Thursday, but without bothering to post the mapping for this, I should stress that the subsequent NAE runs may well modify these values to some respect.

The overwhelming story however, as I stressed in my forecast opening today for BBC ONE, is a good deal of dry and very cold weather in the westcountry, bar these transient spells of snowfall tomorrow / passing showers; but things could turn a good deal more problematic at the end of the week. In only 60sec airtime, it's not possible to offer greater analysis than that, sadly!

Incidentally, the snowgrains widely reported across Bristol this morning were a good example of anthropogenic snowfall, caused primarily by outflow from chimneys at Avonmouth spewing-up a conspicuous Cu and vast amounts of aerosols into the freezing fog; ditto from more local such sources in Bristol itself (e.g., chimney at the hospital near St Michaels Hill). We saw similar effects last February and Didcot Power Station, as many of you might know, is a better studied source of the phenomenon (you can Google the recent interesting paper published on this).

Best

Ian

Edited January 4, 2010 by Ian Fergusson

[Jonesywilliteversnow]

thanks Ian interesting week ahead then!

had an ICE day today here in Nailsea temps peaked at -0.1 failing down again now

P.s currently revising Sub-glacial erosion process's

Edited January 4, 2010 by Jonesywilliteversnow

[Iceberg]

Thanks Ian that will do for tomorrow, I much appreciated the time took to write it and the output below.

Any comment on the ECM ?, it seemed to show a lot of precip for the first half of this week, particularly for the south. ?

[Dartmoor_Matt]

Thanks Ian,

Not looking too good for my area then, seems to be a wall around S'ern/Central Devon regarding snow.

Oh well.

[Ian Fergusson]

thanks Ian interesting week ahead then!

had an ICE day today here in Nailsea temps peaked at -0.1 failing down again now

P.s currently revising Sub-glacial erosion process's

Yes, -8 this morning at Filton - brrr. I can't stress enough how I see the potential tomorrow evolving for some extremely dangerous road and pavement conditions. I think it could becme a major story, locally.

[BristolBlizzard]

thanks ian . all take care in the ice to as it can be so dangerous .

[Lynxus]

Thanks again Ian, good stuff.

The next week or so will certainly be good fun

[chapmanslade]

Yes, -8 this morning at Filton - brrr. I can't stress enough how I see the potential tomorrow evolving for some extremely dangerous road and pavement conditions. I think it could becme a major story, locally.

With correctly recorded air temps of -9C this morning the ground temperatures will be substatially lower and take the road salt / grit out of it's working range. It was largely dry this morning so not too many problems - it will be very different on Tuesday morning.

-2.3C here at the moment which is going to be one of the coldest days since 1981/2 when I lived in the Chilterns particularly as it is bright sunshine

Edited January 4, 2010 by chapmanslade

[Iceberg]

Yep, read in my local paper that there were 150 accidents in the space of 30 mins in the run up to Christmas, and a 40 car pile up on the A35 I think it was.

I have to unfortunately travel 50-60 miles tomorrow, so hoping it won't be too bad until the evening, just got new tyres though.

[Ian Fergusson]

Thanks Ian that will do for tomorrow, I much appreciated the time took to write it and the output below.

Any comment on the ECM ?, it seemed to show a lot of precip for the first half of this week, particularly for the south. ?

Yeah, it's interesting. The medium-range guys at Exeter are watching this one: main snow singal is again E/SE but their briefing to us at midday stresses potential, for the weekend, of snowfall spreading further into southern-central England. But they suggest heavy snow signal starts reducing broadly from Monday, with exception for a day or so longer in SE; thereafter a good deal of dry and very cold weather in the W / central England. In the 10-15 day scheme of things, a minority of members want to suggest a S/SW flow establishing late in this period, but between now and then the continuation of cold (and increasingly anticyclonic) theme dominates the story, at least so far as the Exeter boffins are concerned.

[Dartmoor_Matt]

Temps seemed to have levelled off at -1.2C with DP falling below -5C again and pressure dropping quite steeply, and trending downwards, still a lovely sunny afternoon.

Think it'll be a NO event tomorrow here though... does reverse psychology affect the weather?

[Ian Fergusson]

Yeah, it's interesting. The medium-range guys at Exeter are watching this one: main snow singal is again E/SE but their briefing to us at midday stresses potential, for the weekend, of snowfall spreading further into southern-central England. But they suggest heavy snow signal starts reducing broadly from Monday, with exception for a day or so longer in SE; thereafter a good deal of dry and very cold weather in the W / central England. In the 10-15 day scheme of things, a minority of members want to suggest a S/SW flow establishing late in this period, but between now and then the continuation of cold (and increasingly anticyclonic) theme dominates the story, at least so far as the Exeter boffins are concerned.

Argh - sorry - thought you were meaning next week, not this one!! Apols!!

[Duane S.]

G'Day folks and hi Thermo - fab to see you here, mate!

Ok.... as some of the eagle-eyed amongst you may have spotted, we have two primary forecasting issues / changes to discuss:

1. The UKMO's later NAE assessment for tomorrow - which arrived after those of us broadcasting this morning for BBC Breakfast had finished - heralded some changes. The key one, for us at least, is a more coherent look to the frontal progression tomorrow morning, with a broader areal spread of PPN (predominantly snow inland) and some further potential later into the evening. We're not expecting significant accumulations, however - albeit the snow isn't even our major concern anyway; it's the outcome of any PPN falling onto very cold ground that will be the major peril tomorrow morning....

Attached, illustrating the point, are two sets of NAE modified fields (i.e., with expertise and mods from the UKMO Chief Forecaster, not the raw output, I stress); plus the WBFL progression and PPN discrimination (green = liquid).

2. The UKMO GM is remaining ambivalent about end-of-week developments and for this reason, you'll hear little ramping of a major, widespread snow threat (as opposed to more regionalised / sub-regional but still substantial falls in the E and SE later in the week) from UKMO until the model settles and offers reasonable continuity of threat severity / spatio-temporal spread. This is, needless to say, a key change from the GM modelling used by our on-air forecasts yesterday, but that's the nature of our world when delving into the very fluid mid-range stuff...

Current rather elastic thinking, still with very tempered confidence as I understand it, is for potential developments over the weekend from the east - much as earlier anticipated for Friday but still with low certainty. So to summarise, the profound risk of something very newsworthy and bothersome still remains, but rightly, the UKMO will keep powder dry on formal advisories, etc., until we see some continuity that reaches strict bounds of statistical confidence for offering advisories / early warnings on this event/events.

Tomorrow aside, the NAE paints generalised accumulations (using 4km modelling) of snowfall in the West Country totalling ca. 1-3cm by end of Thursday, but without bothering to post the mapping for this, I should stress that the subsequent NAE runs may well modify these values to some respect.

The overwhelming story however, as I stressed in my forecast opening today for BBC ONE, is a good deal of dry and very cold weather in the westcountry, bar these transient spells of snowfall tomorrow / passing showers; but things could turn a good deal more problematic at the end of the week. In only 60sec airtime, it's not possible to offer greater analysis than that, sadly!

Incidentally, the snowgrains widely reported across Bristol this morning were a good example of anthropogenic snowfall, caused primarily by outflow from chimneys at Avonmouth spewing-up a conspicuous Cu and vast amounts of aerosols into the freezing fog; ditto from more local such sources in Bristol itself (e.g., chimney at the hospital near St Michaels Hill). We saw similar effects last February and Didcot Power Station, as many of you might know, is a better studied source of the phenomenon (you can Google the recent interesting paper published on this).

Best

Ian

Well that pretty much sums up the next few days then! A fantastic and very insightful post, so much info summerised in just a few paragraphs. You should be a TV weather forecaster Ian!

[Iceberg]

Argh - sorry - thought you were meaning next week, not this one!! Apols!!

No probs I was trying not too look to far away(but the period you mentioned is very interesting, at least for those in Dorset maybe not Devon)

[dogs32]

Cheers Ian,A lot to take in there,I gather this all will get upgraded or down graded in the next 48hrs,

What's the chance of a second trough or band of shower's being more potent than this first one coming down tomorrow?

Laura Tobin not mentioning rain anymore but sleet or snow,also for North Midland's 5cm-10cm.

But didn't go into great detail further South,though saying there would be sleet or snow for us.

[Ripeberry]

Thanks for the warning Ian. Now just 0.9c here and the fog has finally rolled back and left a

winter wonderland. The trees look strange all white against a blue sky. Not looking forward to

tomorrow if it's going to be only ice Attached some photos

[Lynxus]

With correctly recorded air temps of -9C this morning the ground temperatures will be substatially lower and take the road salt / grit out of it's working range. It was largely dry this morning so not too many problems - it will be very different on Tuesday morning.

-2.3C here at the moment which is going to be one of the coldest days since 1981/2 when I lived in the Chilterns particularly as it is bright sunshine

I'm not sure what the salt working range is, However as far as I know. 0F is when saline water freezes, So

0 degrees Fahrenheit = -17.7777778 degrees Celsius

Considering grit/salt is not as saturated i would expect the freezing temp to be lower ( Well higher? yano.. closer to 0c lol ).

So yea, It looks like over the coming week or so we may start to see gritted roads turning increasingly icy.

Plus, Im not a fan of the way we just keep gritting.

With LOTS of grit on roads this can also be a hazard. Not just from stonechips but from loosing traction under such a gritty road + ICE isnt going to help at all.

Edited January 4, 2010 by Lynxus

[kaz]

thanks everyone for there very informative post's.. As my job takes me all over north Devon Cornwall and Somerset i am sorta pleased that there is no snow risk for my neck of the woods.. I work from 2200 until 0700 so as you can imagine driving at night in snow is a flipping nightmare, but i have to get out to the patients theat need me so dont have much choice .. Last yr i got stuck with a patient and family untill 12 noon so very glad thats not going to happen again..

kaz x

[Ian Fergusson]

thanks everyone for there very informative post's.. As my job takes me all over north Devon Cornwall and Somerset i am sorta pleased that there is no snow risk for my neck of the woods.. I work from 2200 until 0700 so as you can imagine driving at night in snow is a flipping nightmare, but i have to get out to the patients theat need me so dont have much choice .. Last yr i got stuck with a patient and family untill 12 noon so very glad thats not going to happen again..

kaz x

Howdie Kaz, I think suggesting 'no' snow risk is perhaps taking things too far the other way..... a snow risk of sorts, yes, but with innumerable caveats and not least biased around exactly where you are at what point, as it's a tricky call in this set-up. What I do urge - very seriously - to contemplate and heed the ice risk, irrespective of how it emerged (rain, sleet or snow), and take very special care on the roads (and pavements).

Best wishes

Ian

[Mark Parsons]

I'm not sure what the salt working range is, However as far as I know. 0F is when saline water freezes, So

0 degrees Fahrenheit = -17.7777778 degrees Celsius

Considering grit/salt is not as saturated i would expect the freezing temp to be lower ( Well higher? yano.. closer to 0c lol ).

So yea, It looks like over the coming week or so we may start to see gritted roads turning increasingly icy.

Plus, Im not a fan of the way we just keep gritting.

With LOTS of grit on roads this can also be a hazard. Not just from stonechips but from loosing traction under such a gritty road + ICE isnt going to help at all.

I was told by a county council guy that salt grit becomes inaffective below -3!

[caz100]

Ive just been to the beach with the dog, and family, and the sand was frozen (dry sand) never seen frozen sand at the beach before, very werid must be sooo cold.......

[kaz]

Howdie Kaz, I think suggesting 'no' snow risk is perhaps taking things too far the other way..... a snow risk of sorts, yes, but with innumerable caveats and not least biased around exactly where you are at what point, as it's a tricky call in this set-up. What I do urge - very seriously - to contemplate and heed the ice risk, irrespective of how it emerged (rain, sleet or snow), and take very special care on the roads (and pavements).

Best wishes

Ian

hi ok will do.. I had the same problem the week before Christmas so expecting the same sort of thing this week, I hate driving on ice because you cant see it and i spend most of my time on back roads that have not been treated. i can see this falling as sleet maybe snow up on Exmoor but hitting the ground and freezing making my job even harder than it is. thanks again for everyones post's they are invauble to people who have to be out and about in it.

kaz