South West England Cold Spell Discussion

[Dartmoor_Matt]

Some downgrades, some upgrades.

Snow all day here and more now. WiB also had heavy snow in N Devon.

[snowking]

Very obvious from the NAE why the warnings are in place...

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/th85/10011212_1012.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/t850/10011212_1012.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/t925/10011212_1012.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/tmax/10011212_1012.gif (MAXIMUM temps - terrific)

And all that translates to - http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/prty/10011212_1012.gif

Snowfall!

And this is why advisory's are in place

Just awaiting 12z FAX now to see how far inland this will push - ireland will get BATTERED if that comes off

SK

[BristolBlizzard]

Battleground into Tuesday latest Bias outlook from my point of view:

X = marks the spot where the potential change-over lies when the initial warm sector erodes and cooler air digs in with PPN intensity of heavier pulses lowering the 0oC isotherm to 100M - areas to the E of the red line carry the most risk

3 = areas where snow would be most likely on latest guidance - although the signal is weak/moderate only and is subject to shift

1 = outside the general model scope but could mark the E extent if the system tracked further E - although the blocking does look too substantial for this to actually happen

I find it interesting that during these kind of set-ups, in the past we have seen that classic cold air battle displacement some-where around the Bristol area or close to or just marginally South of the M4 corridor. Right now model guidance generally show a relatively mild upper level being advected from the continent despite recent low level PBL air being relatively cold. The dew point projections although not to be taken to literally at this early stage are marginal to way out at +2/+3 to the West of the line marked X. The right of the line or to the East it covers Dartmoor/Exmoor intentionally - due to the higher topography and terrain in the these areas - despite marginal overall atmospheric dynamics based on latest guidance. We'll see though. I'm fascinated to see the NAE 12Z guidance -0 although we'll need a good few more runs before we start seeing the overall picture due to the T+48 limitation in the model suite that we get.

thanks tc . might be good chance for bristol . westcountry ect ect.

[Dartmoor_Matt]

Very obvious from the NAE why the warnings are in place...

http://expert.weathe...011212_1012.gif

http://expert.weathe...011212_1012.gif

http://expert.weathe...011212_1012.gif

http://expert.weathe...011212_1012.gif (MAXIMUM temps - terrific)

And all that translates to - http://expert.weathe...011212_1012.gif

Snowfall!

And this is why advisory's are in place

Just awaiting 12z FAX now to see how far inland this will push - ireland will get BATTERED if that comes off

SK

Rain/Sleet on the leading edge before the snow? Seems a bit backwards, but I'll take my 0c for Tuesday thanks

Looking great for this part of the world in the coming days, but its going to be oh so close...isn't it always on a small island surrounded by relatively warm sea?

Oh to be in a consistent place.

[yipikiaye]

thanks tc even metoffice has warnings out now for my area come tuesday and looks like it ll be a all day er with snow up untill late evening

Just wondering what kind of snow depths can we expect if this was to come off.I also think my snow which fell last week should remain another day till this arrives tuesday

Edited January 10, 2010 by yipikiaye

[biggiemauls]

Wiltshire hangs in the balance for snow on tuesday then!? Hopefully the snow already here will last until tuesday at least.. Thanks for the updates everyone.

[Dartmoor_Matt]

I'm a bit concerned tbh... got 7inches at the mo, give or take, so assume maybe a bit of a thaw tomorrow, depending on sunshine etc then it could pretty tricky come Tuesdays and Wednesdays snowfall?

Hmm.

Road out of the village is pretty impassable to anything other than a 4*4 at the moment, god knows what it'll be like by then. Especially with the salt situation. Can't see them gritting up here like they have been.

[Thermohaline Conveyor]

Pleasure guys, I have a vested interest in Bristol, as I used to live there for a while and I've always lived in the West Country - despite currently living in Spain. I do note the subtle difference in the T850 projections between the NAE and GFS. Just a little concerned because the ensembles are relatively tight on the GFS for them to rise reasonably rapidly to the +2 - I guess the devil is in the detail. Also note 2mT (Surface) projections to be +5 with good correlation.

[dogs32]

Very obvious from the NAE why the warnings are in place...

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/th85/10011212_1012.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/t850/10011212_1012.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/t925/10011212_1012.gif

http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/tmax/10011212_1012.gif (MAXIMUM temps - terrific)

And all that translates to - http://expert.weatheronline.co.uk/daten/proficharts/en/nae/2010/01/10/basis12/ukuk/prty/10011212_1012.gif

Snowfall!

And this is why advisory's are in place

Just awaiting 12z FAX now to see how far inland this will push - ireland will get BATTERED if that comes off

SK

SK or TC what do you reckon of our chances mate..

and how much,sorry to put you on the spot

for Cheltenham

edit..sorry havent been following the thread currently working

Edited January 10, 2010 by dogs32

[Lynxus]

Temp. +1.3c and dropping.

Still light drizzle, however the water from the slight thaw has started to freeze again.

I think god really is the only one who will know what what happens now, And im willing to belive in him/her/it if him/her/it gives me an answer.

[BristolBlizzard]

Pleasure guys, I have a vested interest in Bristol, as I used to live there for a while and I've always lived in the West Country - despite currently living in Spain. I do note the subtle difference in the T850 projections between the NAE and GFS. Just a little concerned because the ensembles are relatively tight on the GFS for them to rise reasonably rapidly to the +2 - I guess the devil is in the detail. Also note 2mT (Surface) projections to be +5 with good correlation.

thanks tc .

[Iceberg]

I have to say, I'm also very lost with the very latest MO 60% weather warning that has been issued for the South West. There is a risk that as the warm sector clears a cooler slot digs South and at the same time PPN projections are intense. I can also see the strong mixing eventually destroying the front as it battles against the strong dominant high. The T850 boundary at the point of cooling is +1/0 to around -1/-2 - there is a possibility that heavy PPN will drag down this cooler boundary close to the surface. I'm not saying that there is not a possibility that some transient snow will be possible across areas close to Somerset/N Devon to higher ground, but on current guidance I don't see snow being the main problem here. Maybe Ian can shine some light on the latest NAE, GM and MOGREPS take on this.

I agree with everything you've just said. METO must be over doing it with the 60%.

Looking at the 12Z raw NAE, it too turns the band readily to snow, even across Cornwall, which is frankly unbelievable.

I can only conclude that NAE is underplaying the 950 temps and the coldnest of the boundary later. It's currently going for -1's across Cornwall with G temps of 0 and I don't believe this for an instant.

This is happening at midday, with a strong modification of the lowest layers as it moves over a relatively warmer Channel, its possible that some of the highest ground over the moors, might see a couple of hours of snow before it turns to rain, but's the best I am afraid. I think this time tommorrow G temps will be raise to approx 2C and 950's to 1C. 1000-850 thicknesses will then be up accordingly.

Currently the 1000-850 thickness shows how marginal it is.

It will be interesting to hear Ians views on this, but I can't help but feel that it's a bad call by the METO.

[snowking]

SK or TC what do you reckon of our chances mate..

and how much,sorry to put you on the spot

for Cheltenham :lol:

edit..sorry havent been following the thread currently working

Hi mate

Well latest GFS is absolutely PERFECT for glos, wilts, bristol and eastern somerset (possibly dorset too) - keep things there mr. weather

Dews - conductive (0 to -1c but with intense precip snow no problem)

Temps - 0c - fine

850's - max -1c - marginal but with heavy precip fine

Thicknesses - fine

We also have the heaviest part of the precip over us as the front stalls

If things were to play out like that then some places would be looking 20cm+ in the space of 12 hours (possibly more for mendips and cotswolds along with welsh hills)

SK

[leon]

For Tue it might start as as snow and turn quickly into rain. It look to me as well very very border line with these temperatures... I hope I am wrong of course.

Leon

[Dartmoor_Matt]

I agree with everything you've just said. METO must be over doing it with the 60%.

Looking at the 12Z raw NAE, it too turns the band readily to snow, even across Cornwall, which is frankly unbelievable.

I can only conclude that NAE is underplaying the 950 temps and the coldnest of the boundary later. It's currently going for -1's across Cornwall with G temps of 0 and I don't believe this for an instant.

This is happening at midday, with a strong modification of the lowest layers as it moves over a relatively warmer Channel, its possible that some of the highest ground over the moors, might see a couple of hours of snow before it turns to rain, but's the best I am afraid. I think this time tommorrow G temps will be raise to approx 2C and 950's to 1C. 1000-850 thicknesses will then be up accordingly.

Currently the 1000-850 thickness shows how marginal it is.

It will be interesting to hear Ians views on this, but I can't help but feel that it's a bad call by the METO.

Don't they have access to alot more information than we do?

Plus that rather impressive CO2 producing computer

I seem to remember a similar situation last Feb when they said snow to rain, and looked what happened then.

Edited January 10, 2010 by Dartmoor_Matt

[dogs32]

Hi mate

Well latest GFS is absolutely PERFECT for glos, wilts, bristol and eastern somerset (possibly dorset too) - keep things there mr. weather

Dews - conductive (0 to -1c but with intense precip snow no problem)

Temps - 0c - fine

850's - max -1c - marginal but with heavy precip fine

Thicknesses - fine

We also have the heaviest part of the precip over us as the front stalls

If things were to play out like that then some places would be looking 20cm+ in the space of 12 hours (possibly more for mendips and cotswolds along with welsh hills)

SK

cheers mate,

I will keep an eye on any update's you have for us all.

trying to get back to normality by working :lol:

large amount's!!! and if it stall's oh hell...lol

Edited January 10, 2010 by dogs32

[Wilxy]

Cloudy and a few flakes of snow just started.

[yipikiaye]

wow major upgrades this evening for my area and i almost given up of seeing anything this evening

Weathercoxy u had any snow today or is this the first time today.I still think this easterly winds going to get up

temp now 0.0c

[Wilxy]

wow major upgrades this evening for my area and i almost given up of seeing anything this evening

Weathercoxy u had any snow today or is this the first time today.I still think this easterly winds going to get up

temp now 0.0c

yes had some this morning and was actally heavy for a few mins before becoming light again.

[BristolBlizzard]

Hi mate

Well latest GFS is absolutely PERFECT for glos, wilts, bristol and eastern somerset (possibly dorset too) - keep things there mr. weather

Dews - conductive (0 to -1c but with intense precip snow no problem)

Temps - 0c - fine

850's - max -1c - marginal but with heavy precip fine

Thicknesses - fine

We also have the heaviest part of the precip over us as the front stalls

If things were to play out like that then some places would be looking 20cm+ in the space of 12 hours (possibly more for mendips and cotswolds along with welsh hills)

SK

wow sounds great thanks

[rowieboyz]

Just seen the latest BBC forecast with Dan C and he was giving out heavy snow for Devon and Cornwall on tuesday including lower levels. I am struggling to see how this will happen, I would have thought it would be mor of a rain event. I am expecting a downgrade by them tomorrow.

Jase

[Thermohaline Conveyor]

I think if you were going to put any money on the upcoming evolution with the state of the model guidance as it is at the moment you'd tout the battleground line between marginal transient to transient some-where close to the classic Bristol/Somerset area and in and around that dreaded M4 Corridor cliché. The 0oC 2mT temperature simulated by NAE is obviously for snowfields across higher MSL in Dartmoor and perhaps Exmoor - so it's feasible that should the current temperature profile be realised a period of snow would certainly be possible across these areas. Ian has a higher degree of chart access concerning the NAE, GMC and MOGREPS and it will be interesting to see his take on the current guidance that he is receiving. Personally it is rather premature to start issuing approximate accumulation estimates - until the precise tracking and evolution of this low pressure system is simulated with a higher degree of consistency. The GFS take on things would be in the region of 10 - 20cm with locally higher totals across higher topography eg. Wales. These values are by no means to be taken as a literal forecast, they are merely indicative markers of the current projections based on the intensity phasing and tracking over a mean of 4 GFS runs and combining this with 2 ECM mean tracking biases.

[leon]

wow major upgrades this evening for my area and i almost given up of seeing anything this evening

Weathercoxy u had any snow today or is this the first time today.I still think this easterly winds going to get up

temp now 0.0c

What upgrade are you talking about?

Leon

[Dartmoor_Matt]

Plenty of showers around on the radar at the moment over Devon.

and some heavy ones over Cornwall, anyone know if thats falling as snow down there?

[Lynxus]

Ill be glad to step off this winter roallercoaster. Its killing me. I just cant stop watching the charts and radars and forum.

Then again, ill get about 1 month off then we all hop on the stormcoaster. <_<