South West/Central Southern England Regional Discussion 21/01/13 6z Onwards

[Blizzardof82]

No, its been changed to the rights and wrongs of eating meat!! Didnt you know?? Arguements on both sides im sure.

Anyway, back on topic. I know this winter is no comparison to 1963, but I was watching something on tv about this and the nation were fooled into a false sense of security by mild air creating a thaw (then floods) only for 3 days later to be hit even harder by blizzards.

Does anyone think this is happening due to the SSW? Thoughts please!!

I was led to believe having read more expert posters remarks in the mod thread back in late December early January that the effects of the SSW would not be seen in troposphere until around 26th January however I do believe its early down dwelling in to troposphere has caused the current setup. Therefore if the more cleverer people on netweather are to be believed the best is yet to come as we go in to February with the forming of a Greenland high pressure. Also if you look at METO longer range forecast they seem to be hinted at this so all to play for IMO.

[Argyle1980]

Small snow shower over Truro and still cold here

[AWD]

ok, NMM06z run out, and it's a step towards the NAE IMO....stronger snow signal tomorrow for Devon/Somerset/Dorset/Wilts especially towards the evening.....

No charts at the moment because I'm feeling lazy...lol

Yes, definetly a move towards the NAE compared to its 0z output. A couple of snapshots;

Many different and interesting chart types available with this model. Really recommend getting it, you won't regret it!

[Beast of Plympton]

I was led to believe having read more expert posters remarks in the mod thread back in late December early January that the effects of the SSW would not be seen in troposphere until around 26th January however I do believe its early down dwelling in to troposphere has caused the current setup. Therefore if the more cleverer people on netweather are to be believed the best is yet to come as we go in to February with the forming of a Greenland high pressure. Also if you look at METO longer range forecast they seem to be hinted at this so all to play for IMO.

Thanks Blizzard, got the same sort of impression. GP in the mod thread seems to think february is going to be interesting.

[Mark Neal.]

Yes, definetly a move towards the NAE compared to its 0z output. A couple of snapshots;

Many different and interesting chart types available with this model. Really recommend getting it, you won't regret it!

And if that could nudge just a bit more north-eastwards that would be lurvelly!!

[AWD]

Thanks Blizzard, got the same sort of impression. GP in the mod thread seems to think february is going to be interesting.

He isn't the only one. There are a whole load of experts/knowledgable members who are going for a cold February.

[Argyle1980]

Both sky and bbc hint that we are only having a mild blip before we enter another cold spell

[Mark Neal.]

He isn't the only one. There are a whole load of experts/knowledgable members who are going for a cold February.

Including me! Though expert/knowledgeable members probably dosn't describe me!

[iceman1991]

Can tell me on here if nw hants mite get some snow tormorrow ??

[rockhopper]

Very slow thaw back in progress, light snizzle most of the morning currently 0.7c. The icicles are coming along nicely

[Coast]

Can tell me on here if nw hants mite get some snow tormorrow ??

http://www.netweather.tv/index.cgi?action=will-it-snow;sess=

[Blizzardof82]

The sun has really come out here now temp holding steady at 0.9c though.

[Beast of Plympton]

He isn't the only one. There are a whole load of experts/knowledgable members who are going for a cold February.

Thanks AWD, didn't know that. I only tend to read his as people seem to mention him a fair amount. I find if I try to read to many things can get confusing!! Incidently, your clever, what are your thoughts?

[Wilxy]

Well im off for a haircut, sun starting to break through now thaw should take place soon.

0.1°C

DP -1°C

[Blizzardof82]

Thanks AWD, didn't know that. I only tend to read his as people seem to mention him a fair amount. I find if I try to read to many things can get confusing!! Incidently, your clever, what are your thoughts?

Yes that is true you have the pessimists the realists and the optimists and it can get very confusing if you don't know how to read charts.

[DanDorsetUK]

Not sure where this snow risk is coming from? nothing on radar yet apart from the section going into france. Weird!

[Frosty_wsm]

This is all very thrilling, will it our won't it snow tomorrow, if it did and dumps another 5-10cm then that would be just as good as Friday's event for round here!

[RachN]

Sorry if this is already on here, but just picked this up on the MetCheck website..........

There is growing confidence that an intense pulse of heavy snow could affect North Devon, South Wales, Bristol area, Dorset as well as Salisbury Plain, Mendips and Cotswold Hills later tonight and into the early hours of tomorrow morning.

There is a potential for an additional 10cm of snow falling within a 3hr period which will lead to rapid accumulations on already fallen snow.

The area of snow is tied in with a rather fragmented and messy upper air picture to the South-west of the UK and as this upper vortex drifts East there is the potential for more intense small scale snow events along the South of England during Tuesday and Wednesday.

We will be watching developments to the South-west this afternoon and updating this risk based on convection appearing in the Celtic Sea around 5pm this evening.

[Blizzardof82]

Not sure where this snow risk is coming from? nothing on radar yet apart from the section going into france. Weird!

If you look at netweather radar there is a heavy area of precipitation over North west France, I think that is it?

[Thermohaline Conveyor]

Taking into account a blend of the latest NAE, UKMO and ECM guidance the strongest PPN signal for potentially disruptive snowfall is across North/South Somerset, North Dorset, South East Wales, potentially the Forest of Dean, all these regions now fall within my 60% probability catchment areas. There still remains a considerable amount of uncertainty over PPN totals and snowfall amounts due to a wide disparity in data, however ECM00Z projects a strengthening PPN signal, along with NAE with weaker signals from GFS. All guidance concludes that the greatest PPN spread, -4/-5oC T850 frontal deviation sits within the counties of Somerset and North Dorset and South Wales.

Those areas that have greatest potential to be upgraded are surrounding counties, the remainder of much of Dorset away from the coast initially, the remainder of Somerset and down into parts of Northern, Western and Eastern Devon, especially to higher ground. Other counties included in the 40% probability are South East Wales, Herefordshire and much of Gloucestershire. There remains some uncertainty on the Eastern extent across West Wilts and currently we have removed the 40% and have issued a 20% here, subject to change should a slight deviation exist in the model output today.

Areas in the 20% are less certain, either due to the extent of the PPN North and Eastwards across North Wales, Central Wales, Wilts, East Glos and Hampshire or due to the rain/snow line undulating across parts of West Devon and Eastern Cornwall. There remains potential in a slight Easterly focus to include West Wilts and East Glos and perhaps parts of Hampshire. As does the snowline to the South across Devon and Cornwall, this could be extended, but on current guidance a mix of rain, sleet and perhaps patchy snow would seem the most probable outcome.

• Slight downgrade from 40% to 20% for parts of Wilts
  
• Slight upgrade from 40% to 60% for parts of N/S Somerset
  
• Slight upgrade from 20% to 40% for parts of East and South Devon away from the coast initially
  
• W extremities of Glos remain in 60% although very marginal between 60% and 40%
  

Included is the original risk map issued yesterday:

The latest risk map issued today:

Conclusion

Confidence remains low to partially moderate for snowfall distribution and intensity of PPN ie. snowfall amounts. The risk of significant snowfall is still probable. The biggest disparity in guidance is with the GM GFS with wild fluctuations and a significantly weaker PPN signal, especially for the Northern most extent of the warning area. We will be looking for some consistencies and growing confidence from the GFS12Z in particular, and a stronger comparative ECM12Z to the ECM00Z which showed a strengthening PPN signal. Should ECM12Z and NAE continue to project stronger signals, an amber could be issued, especially if UKMO displays greater willing. A strong uniform set of runs, with broader and more comprehensive agreement is needed before a higher confidence than 60% is issued for any part of the region.

[Nights King]

I feel like we might be close to a good snow event on high ground somerset although would be nice to see it nudge another 10 miles north.

Steady thaw in place here in whitchurch and a slight thaw starting to take place at home with temperature now 0.5c so we need a top up!

[Mapantz]

Not sure where this snow risk is coming from? nothing on radar yet apart from the section going into france. Weird!

The shortwave has taken the precip further south than the models suggested.

[Costa Del Fal]

Thaw setting in here now. Risk of snow showers later today and more organised rain/sleet/snow tomorrow here in Cornwall?

[lfcdude]

Taking into account a blend of the latest NAE, UKMO and ECM guidance the strongest PPN signal for potentially disruptive snowfall is across North/South Somerset, North Dorset, South East Wales, potentially the Forest of Dean, all these regions now fall within my 60% probability catchment areas. There still remains a considerable amount of uncertainty over PPN totals and snowfall amounts due to a wide disparity in data, however ECM00Z projects a strengthening PPN signal, along with NAE with weaker signals from GFS. All guidance concludes that the greatest PPN spread, -4/-5oC T850 frontal deviation sits within the counties of Somerset and North Dorset and South Wales.

Those areas that have greatest potential to be upgraded are surrounding counties, the remainder of much of Dorset away from the coast initially, the remainder of Somerset and down into parts of Northern, Western and Eastern Devon, especially to higher ground. Other counties included in the 40% probability are South East Wales, Herefordshire and much of Gloucestershire. There remains some uncertainty on the Eastern extent across West Wilts and currently we have removed the 40% and have issued a 20% here, subject to change should a slight deviation exist in the model output today.

Areas in the 20% are less certain, either due to the extent of the PPN North and Eastwards across North Wales, Central Wales, Wilts, East Glos and Hampshire or due to the rain/snow line undulating across parts of West Devon and Eastern Cornwall. There remains potential in a slight Easterly focus to include West Wilts and East Glos and perhaps parts of Hampshire. As does the snowline to the South across Devon and Cornwall, this could be extended, but on current guidance a mix of rain, sleet and perhaps patchy snow would seem the most probable outcome.

• Slight downgrade from 40% to 20% for parts of Wilts
  
• Slight upgrade from 40% to 60% for parts of N/S Somerset
  
• Slight upgrade from 20% to 40% for parts of East and South Devon away from the coast initially
  
• W extremities of Glos remain in 60% although very marginal between 60% and 40%
  

Included is the original risk map issued yesterday:

The latest risk map issued today:

Conclusion

Confidence remains low to partially moderate for snowfall distribution and intensity of PPN ie. snowfall amounts. The risk of significant snowfall is still probable. The biggest disparity in guidance is with the GM GFS with wild fluctuations and a significantly weaker PPN signal, especially for the Northern most extent of the warning area. We will be looking for some consistencies and growing confidence from the GFS12Z in particular, and a stronger comparative ECM12Z to the ECM00Z which showed a strengthening PPN signal. Should ECM12Z and NAE continue to project stronger signals, an amber could be issued, especially if UKMO displays greater willing. A strong uniform set of runs, with broader and more comprehensive agreement is needed before a higher confidence than 60% is issued for any part of the region.

Im in the 60 percent.. So all is well...Feel this one though... Is more like... How good is your luck...

[Thermohaline Conveyor]

Im in the 60 percent.. So all is well...Feel this one though... Is more like... How good is your luck...

If you're in Devizes the latest graphics I've done probably puts you in 40%, the first 60%. This suggests that the general trend has been for the shift of more significant snowfall to move away from the far East of the warning areas and everything to shift slightly South and West. I wouldn't put Devizes in 60% on latest guidance.