South West/Central Southern England Regional Weather Discussion 15/12/13 18z ------>

[Sungirl]

All quiet here...... (except someone's fireworks!)

 

The calm before the storm maybe?  Anyone able to update me on this predicted storm and how it may affect me in Berks? I am very behind with the ongoings of the weather atm, due to the forthcoming C event 

[AWD]

Here's my look at the upcoming weather situation for the next 24 hours or so.

Firsty, a brief scour of the 12z High Res model output and where our low is currently.

A look at the Atlantic satellite imagery shows our low starting to form now;

This will rapidly deepen thanks to a strong thermal gradient consisting of both Canadian Arctic air and Atlantic Maritime air, fuelling a strong Jet stream with the UK as it's eastern target;

This therefore, means a "cyclonic bomb" is heading our way;

A look at what the 12z High Res models (primarily the NAE & EURO4) forecast for our region specifically then. We can see the rainfall hitting Cornwall tomorrow morning and spreading to most of the region by midday tomorrow;

You can see there, once the rain arrives, it's with us for most, if not all of the day. The mass of PPN highlighted here;

During the afternoon, to make matters worse, windspeeds will also become more notable, especially around coastal fringes. Winds currently modelled to gust around the 60mph - 80mph mark widely;

I'm not going to dwell too much on the wind side of things though, as I feel windspeeds will be a more local, rather than regional issue and for many of us, rainfall accumulations will be a rather more problematic issue than windspeeds. I'll leave you with this chart courtesy of Meteogroup, which details Windspeed forecasts rather well IMO;

One thing I will say though, is the tornadic possibilities tomorrow strengthen markedly, so be aware of localised structural damage if your in any squall/tornadic activity;

Back to the more pressing issue of rainfall accumulations then and by the end of day tomorrow, both the NAE and EURO4 models show marked rainfall volumes across a large swathe of our region;

Respectable agreement between the two there. If these were to verify, which is looking increasingly likely they will now, then we are certainly looking at flooding issues and river flooding over the Christmas period. With further, although less dramatic, rainfall progged for Tuesday, the 48hr accumulative rainfall charts look startling to say the least;

Before I get onto my personal forecast, I'll leave you with the updated Meto FAX chart for tomorrow;

A sub 930mb low possible tomorrow, centered NW of Scotland with gales/severe gales over much of the UK. Not often you'll see a depression as noteworthy as this over these here shores.

Anyway, here's my summary of where I think we stand regarding tomorrow;

The areas in red are the main areas at risk of high rainfall totals and flooding tomorrow. These include much of Devon, especially the moors, much of Dorset, SE Wiltshire and South Hampshire. Rainfall totals over the next 24/48 hours are expected to exceed 50mm widely within this area, locally much more too. You will notice a black circle over Dartmoor inparticular too. I strongly advise those of you within this black circle to be prepared and take action. Dartmoor and surrounding areas could receive biblical rainfall totals causing serious flooding, structural damage and a possible threat to life. This is no joke, the area within the black circle is in real danger of alarming rainfall totals.

The area in orange, which includes much of Gloucestershire, North Wiltshire, Oxfordshire and also Cornwall will also receive high rainfall totals, although falling just short of those within the red areas. Areas within the orange zones should be prepared for upto 40mm widely, locally a little more. This again could cause flooding problems but hopefully not as severe as those within the red areas.

The yellow area, which includes the Bristol and Somerset areas should get off lightest. Although still very wet, limited minor flooding is likely with many areas just experiencing obese puddles really. Typically 30mm in this area.

That's my take on things anyway. I should be around a little more over the next 48 hours so of you have any questions etc, I'll try to answer them or if I can't, I'll pass it on to someone more knowledgable.

I'll leave you with the latest BBC amber warning area which differs slightly to mine, but is equally, if not more important;

Stay safe all and have a safe Christmas!

Edited December 22, 2013 by AWD

[Nights King]

That gap in your map I assume you created off the NAE map which looks to me like its modelling in the Somerset levels?

 

I expect more than 30mm over mendips that would be like having a bit of patchy drizzle to what we are used too

[AWD]

That gap in your map I assume you created off the NAE map which looks to me like its modelling in the Somerset levels?

I expect more than 30mm over mendips that would be like having a bit of patchy drizzle to what we are used too

Don't the the boundaries or figures too literally, they're just there for a broad brush story of where both the wettest and least wettest places are likely to be tomorrow. Only you will know your environmental nuances that can affect rainfall accumulations local to yourself. Edited December 22, 2013 by AWD

[AWD]

From Ian;

"W COUNTRY Rain establishing from SW/W across region from Mon AM will continue - aside temporary drier interludes - through to early hrs Tues. Rainfall totals widely 10-40mm; highest (potentially circa 40-60mm) in S areas, e.g. SE #Somerset, #Dorset, S #Wiltshire. Very windy Mon too; a lot of local variation but strongest gusts to S'rn districts, potentially 60+mph e.g. Dorset/S Wilts. Winds widely gusting 40-50+mph elsewhere across region. Combined with many hrs rainfall, sig travel issues/disruption likely."

[Sainsbo]

Absolutely fab post there AWD, I'd agree with you about the main problem being the rain. The River Avon is very close to topping its banks as it is, without the rainfall expected tomorrow

[karlos1983]

great post AWD

[Beast of Plympton]

Here's my look at the upcoming weather situation for the next 24 hours or so.

Firsty, a brief scour of the 12z High Res model output and where our low is currently.

A look at the Atlantic satellite imagery shows our low starting to form now;

image.jpgimage.jpg

This will rapidly deepen thanks to a strong thermal gradient consisting of both Canadian Arctic air and Atlantic Maritime air, fuelling a strong Jet stream with the UK as it's eastern target;

image.jpg

This therefore, means a "cyclonic bomb" is heading our way;

image.jpg

A look at what the 12z High Res models (primarily the NAE & EURO4) forecast for our region specifically then. We can see the rainfall hitting Cornwall tomorrow morning and spreading to most of the region by midday tomorrow;

image.jpgimage.jpgimage.jpg

You can see there, once the rain arrives, it's with us for most, if not all of the day. The mass of PPN highlighted here;

image.jpg

During the afternoon, to make matters worse, windspeeds will also become more notable, especially around coastal fringes. Winds currently modelled to gust around the 60mph - 80mph mark widely;

image.jpgimage.jpg

I'm not going to dwell too much on the wind side of things though, as I feel windspeeds will be a more local, rather than regional issue and for many of us, rainfall accumulations will be a rather more problematic issue than windspeeds. I'll leave you with this chart courtesy of Meteogroup, which details Windspeed forecasts rather well IMO;

image.jpg

One thing I will say though, is the tornadic possibilities tomorrow strengthen markedly, so be aware of localised structural damage if your in any squall/tornadic activity;

image.jpg

Back to the more pressing issue of rainfall accumulations then and by the end of day tomorrow, both the NAE and EURO4 models show marked rainfall volumes across a large swathe of our region;

image.jpg

image.jpg

Respectable agreement between the two there. If these were to verify, which is looking increasingly likely they will now, then we are certainly looking at flooding issues and river flooding over the Christmas period. With further, although less dramatic, rainfall progged for Tuesday, the 48hr accumulative rainfall charts look startling to say the least;

image.jpg

image.jpg

Before I get onto my personal forecast, I'll leave you with the updated Meto FAX chart for tomorrow;

image.jpg

A sub 930mb low possible tomorrow, centered NW of Scotland with gales/severe gales over much of the UK. Not often you'll see a depression as noteworthy as this over these here shores.

Anyway, here's my summary of where I think we stand regarding tomorrow;

image.jpg

The areas in red are the main areas at risk of high rainfall totals and flooding tomorrow. These include much of Devon, especially the moors, much of Dorset, SE Wiltshire and South Hampshire. Rainfall totals over the next 24/48 hours are expected to exceed 50mm widely within this area, locally much more too. You will notice a black circle over Dartmoor inparticular too. I strongly advise those of you within this black circle to be prepared and take action. Dartmoor and surrounding areas could receive biblical rainfall totals causing serious flooding, structural damage and a possible threat to life. This is no joke, the area within the black circle is in real danger of alarming rainfall totals.

The area in orange, which includes much of Gloucestershire, North Wiltshire, Oxfordshire and also Cornwall will also receive high rainfall totals, although falling just short of those within the red areas. Areas within the orange zones should be prepared for upto 40mm widely, locally a little more. This again could cause flooding problems but hopefully not as severe as those within the red areas.

The yellow area, which includes the Bristol and Somerset areas should get off lightest. Although still very wet, limited minor flooding is likely with many areas just experiencing obese puddles really. Typically 30mm in this area.

That's my take on things anyway. I should be around a little more over the next 48 hours so of you have any questions etc, I'll try to answer them or if I can't, I'll pass it on to someone more knowledgable.

I'll leave you with the latest BBC amber warning area which differs slightly to mine, but is equally, if not more important;

image.jpg

Stay safe all and have a safe Christmas!

Thanks for the post AWD.... Very good!! I hope that I don't have to worry too much being on a big hill.... How much total rainfall accumulations are we talking about here??

[karlos1983]

think we could be looking at widespread 40-60mm

[Beast of Plympton]

think we could be looking at widespread 40-60mm

 

I see... pretty damaging then. Thanks for the info mate.

[karlos1983]

I see... pretty damaging then. Thanks for the info mate.

judging by the NAE anyway. looks concerning

[festivalking]

Thanks for the post AWD.... Very good!! I hope that I don't have to worry too much being on a big hill.... How much total rainfall accumulations are we talking about here??

 

Indeed but its getting to the top of the hill that is the issue. The road from Yelverton to Dousland was in all sense and purposes a river on wednesday, then again we had 3 inches of rain in an afternoon!!! Not looking forward to the drive back from work tomorrow night!

[Costa Del Fal]

All the latest forecasts for Cornwall, the Isles of Scilly and the Channel Islands now available at http://www.cciweather.co.uk for tomorrow!

[BARRY]

will be an interesting drive back from plymouth tomorrow

[Beast of Plympton]

Indeed but its getting to the top of the hill that is the issue. The road from Yelverton to Dousland was in all sense and purposes a river on wednesday, then again we had 3 inches of rain in an afternoon!!! Not looking forward to the drive back from work tomorrow night!

You are right, and as you go further on toward Princetown it can get pretty bad there. I have to go and get my boy from Plymouth tomorrow morning then I am staying up on the hill for the day! Edited December 22, 2013 by Beast of Dartmoor

[Polar Bear]

http://m.bbc.co.uk/news/uk-25484998

Looks like they read your post AWD... Oh eck.

[AWD]

Latest from Ian;

"W COUNTRY Latest met office assessment indicative of widespread 50-60mph gusts inland tomoro with potential to 70mph as far N as M4 corridor. However, rainfall tally gives greatest concern: 25-50mm looking fairly broadscale, especially further S where totals highest. 60+mm feasible over uplands of e.g. Dorset Downs; S Wiltshire, etc. Expect locally to ca. 40+mm over Mendips/Cotswolds. Many of you asking re air travel tomorrow. Cannot pre-judge this, so please follow @OfficialBRS for any guidance/status tomorrow."

[rich1974]

Anyone know what sort of time these winds get going here in Berkshire? And at what time they'll be at there worst? I'm driving to Bristol tomorrow and need to be there at 12 mid day, i'll be heading home (up the M4) an hour later so only a quick trip but one that must be done.

[dec10snow]

In a completely different direction to tomorrow's weather, if any of you are having snow withdrawal symptoms;

http://braemarscotland.co.uk/snowgate-webcam/

[kernowman]

Wind picking up here in the far South West, gave the radar a quick glance, holy smoke, this is going to be a rough ride.

[kumquat]

Yep, kernowman a quick glance at the radar tells it like it is. Not good.

 

Rich1974, Crosswinds of 25 - 40/50 knots between 0900 and 1500, worse as you come across the Wiltshire Plains. Gusts even harsher. Look out for South/North cross carriageway gusts. Lots of surface water and spray. Be careful!

 

Edit: Actually longer into the evening also with the ppn right up the M4 corridor. I'd give it a miss tomorrow if I could get away with it.

Edited December 23, 2013 by kumquat

[kumquat]

Don't the the boundaries or figures too literally, they're just there for a broad brush story of where both the wettest and least wettest places are likely to be tomorrow. Only you will know your environmental nuances that can affect rainfall accumulations local to yourself.

 

On Mullie's little hill, I'd expect a few mills of drizzle and maybe a couple of stones of hail on the lee side. His cider cans will have more of an impact on the local community. 

Edited December 23, 2013 by kumquat

[AWD]

From Ian;

"W COUNTRY 0550GMT UPDATE F'cast remains consistent re earlier advisories. Add potential 50+mm rain totals Forest of Dean #FOD to previous. Rain establishes from W into AM rush-hr & no widespread relaxation of wet weather until early hrs Tues. Winds pick-up later this morning & into midday. Considerable localised flux on gust strength/impacts but to 50-60mph fairly widely."

[somersetsnow]

Going to be an interesting day

[lettice]

Is it calm before the storm?

We have had no rain here since late yesterday afternoon and lighter winds

Will be walking down to Waitrose mid morning, to get some last minute shopping for the Christmas break.

But looking on the radar, its looks to be on its way soon, so will be a wet and blustery walk.