South West & Central Southern England Regional Weather Discussion 28/08/13 00z ------------------>

[Guest William Grimsley]

My forecast for Friday, Saturday and Sunday for SW England:

 

Friday Morning: During the morning it will be a cloudy and possibly damp start, turning slowly turning brighter towards lunchtime. Friday Afternoon: During the afternoon heavy and possibly thundery showers will move in, continuing into the evening before dying away overnight.Saturday Morning: During the morning it will be dry but mainly cloudy. Saturday Afternoon: During the afternoon again heavy and possibly thundery showers will move in, continuing into the evening before dying away overnight.

 

Sunday Morning: During the morning it will be dry but mainly cloudy. Sunday Afternoon: During the afternoon there might be 1 or 2 showers which will be light.

Edited September 5, 2013 by William Grimsley

[MP-R]

Yes, but these showers over Devon and Cornwall are likely to turn out heavy and thundery on Friday Afternoon. I saw some turrets earlier today...

 

There were indeed turrets for a time this afternoon, a lot of castellanus and floccus with some undulatus around Bristol earlier but that seemed to dissipate and a more uniform line of altocumulus/altostratus has straddled the western skyline since about 5pm.

 

We now have high cloud moving SSW-NNE and a few stratocumulus clouds moving more NW-SE.

[jtay]

Looking west and here comes the end of summer over the horizon.

[AWD]

Tomorrow's forecast map;

A complex frontal wave initiates with the warm air over the Southern portion of the country, re-energising an area of PPN and spawning a "cut off" low pressure system over the UK, setting us up for a cooler and more disturbed period of weather. Our area may be one of the luckier areas in escaping the worst of any rainfall however.

First, here is tomorrow's FAX chart;

Along the cold front shown there is where the area of PPN is expected to spawn and intensify. This process will start to happen overnight tonight, but for clarity and ease, my forecast is only for the daytime period tomorrow and not for any overnight period.

To my red area first then. The area of intensifying PPN along the cold front should be sitting somewhere across Hampshire towards Sussex by dawn. Therefore, some moderate rainfall is likely across east Hampshire and Berkshire inparticular first thing tomorrow morning. This should quickly clear east/north east though.

We then see the low pressure move west, with the PPN wrapped around it's eastern flank. By tomorrow night the low pressure sits somewhere over the Irish Sea, off the north Wales coast, as shown here by the FAX for midnight tomorrow night;

This is why our region never sees much in the way of persistent, heavy rainfall with the exception of the red area I described above. The "eye" of the low never pulls far enoug west to bring the heavy PPN further westwards. Instead the PPN wraps itself around the eastern flank of the low and then around it's northern flank as the low continues to spin anticlockwise.

Onto my other two main areas for tomorrow then. The green area, which includes north Cornwall, Devon, Somerset, Bristol, BANES and Gloucestershire will see a scattering of showers come in off the Bristol Channel. These showers will be blustery and some of them may be heavy in the afternoon. Below is a clear convergence line, showing the likelihood of a frequent flow of showers setting up on this convergence line;

An unknown distance either side of this line may see few, if any showers, whilst other areas directly on this convergence line may see frequent showers. This is how some large rainfall differentials may be recorded across a small part of the region. Showers will also hit the north Devon coast, with the bigger ones making there way a fair bit inland.

The blue area, which includes the far south of Cornwall and the Isles of Sicily may see some heavy rain later tomorrow afternoon and evening as a band of heavy rain heads down from the north west into the English Channel. There is some uncertainty on this part of the process however.

The areas favoured to stay driest tomorrow, with just a isolated shower possible, are Dorset, Wiltshire into Oxfordshire. Although cooler, these areas could see a dry day with good sunny spells. It will be breezy everywhere however.

After the early rainfall clears Hampshire and Berkshire, these areas could also see a bright, dry day too, with few, if any showers making it that far inland.

So to summarise below;

- Early moderate, persistent rainfall clearing East Hampshire and Berkshire tomorrow morning. After this has cleared, a bright but breezy day here.

- Showers developing in the Bristol Channel, pushing into Devon, Somerset, Gloucestershire and the Bristol area as the day progresses. Some heavy, blustery showers possible later in the day. As ever in such a set up, not all places will see the showers with some remaining dry. With a convergence line expected to form tomorrow, this will especially be the case.

- Small risk of some more persistent, heavy rain in the far south of Cornwall and Isles of Sicily later in the day. Uncertainty around this though.

- Driest and brightest areas tomorrow are likely to be Dorset, Wiltshire and Oxfordshire.

Temperatures tomorrow will be notably cooler than previous days this week. Most of us not getting above the 12c - 16c range although a few exceptions are possible either side of this.

[Guest William Grimsley]

Tomorrow's forecast map;

image.jpg

A complex frontal wave initiates with the warm air over the Southern portion of the country, re-energising an area of PPN and spawning a "cut off" low pressure system over the UK, setting us up for a cooler and more disturbed period of weather. Our area may be one of the luckier areas in escaping the worst of any rainfall however.

First, here is tomorrow's FAX chart;

image.jpg

Along the cold front shown there is where the area of PPN is expected to spawn and intensify. This process will start to happen overnight tonight, but for clarity and ease, my forecast is only for the daytime period tomorrow and not for any overnight period.

To my red area first then. The area of intensifying PPN along the cold front should be sitting somewhere across Hampshire towards Sussex by dawn. Therefore, some moderate rainfall is likely across east Hampshire and Berkshire inparticular first thing tomorrow morning. This should quickly clear east/north east though.

We then see the low pressure move west, with the PPN wrapped around it's eastern flank. By tomorrow night the low pressure sits somewhere over the Irish Sea, off the north Wales coast, as shown here by the FAX for midnight tomorrow night;

image.jpg

This is why our region never sees much in the way of persistent, heavy rainfall with the exception of the red area I described above. The "eye" of the low never pulls far enoug west to bring the heavy PPN further westwards. Instead the PPN wraps itself around the eastern flank of the low and then around it's northern flank as the low continues to spin anticlockwise.

Onto my other two main areas for tomorrow then. The green area, which includes north Cornwall, Devon, Somerset, Bristol, BANES and Gloucestershire will see a scattering of showers come in off the Bristol Channel. These showers will be blustery and some of them may be heavy in the afternoon. Below is a clear convergence line, showing the likelihood of a frequent flow of showers setting up on this convergence line;

image.jpg

An unknown distance either side of this line may see few, if any showers, whilst other areas directly on this convergence line may see frequent showers. This is how some large rainfall differentials may be recorded across a small part of the region. Showers will also hit the north Devon coast, with the bigger ones making there way a fair bit inland.

The blue area, which includes the far south of Cornwall and the Isles of Sicily may see some heavy rain later tomorrow afternoon and evening as a band of heavy rain heads down from the north west into the English Channel. There is some uncertainty on this part of the process however.

The areas favoured to stay driest tomorrow, with just a isolated shower possible, are Dorset, Wiltshire into Oxfordshire. Although cooler, these areas could see a dry day with good sunny spells. It will be breezy everywhere however.

After the early rainfall clears Hampshire and Berkshire, these areas could also see a bright, dry day too, with few, if any showers making it that far inland.

So to summarise below;

- Early moderate, persistent rainfall clearing East Hampshire and Berkshire tomorrow morning. After this has cleared, a bright but breezy day here.

- Showers developing in the Bristol Channel, pushing into Devon, Somerset, Gloucestershire and the Bristol area as the day progresses. Some heavy, blustery showers possible later in the day. As ever in such a set up, not all places will see the showers with some remaining dry. With a convergence line expected to form tomorrow, this will especially be the case.

- Small risk of some more persistent, heavy rain in the far south of Cornwall and Isles of Sicily later in the day. Uncertainty around this though.

- Driest and brightest areas tomorrow are likely to be Dorset, Wiltshire and Oxfordshire.

Temperatures tomorrow will be notably cooler than previous days this week. Most of us not getting above the 12c - 16c range although a few exceptions are possible either side of this.

That is a very accurate forecast, AWD. I agree with your forecast, entirely. Showers in Devon/Somerset/Bristol with rain in Hampshire is correct. I hope we get some showers here, tomorrow. We have a good chance of getting some showers here and if we get some they could be heavy and possibly thundery.

Edited September 5, 2013 by William Grimsley

[Mapantz]

Despite what the radar has been showing falling here in the last hour, it's bone dry.

[AWD]

Can definetly notice the lengthening of darkness hours now.

I was at the train station both yesterday and today for the 06:30 train into work. Yesterday, with a beautiful sunrise, it was not far off full light by 06:30.

Today, with cloudy and murky skies, the street lights are still on and it's only just semi-light at best.

A cool feel to the morning too. First time in months I've had to wear my coat into work. At least it's dry though.

[Guest William Grimsley]

It looks like that Devon could see a rather big amount of showers, today! One shower has sat over Newquay Weather for the past 90 minutes! Newquay Weather Rainfall Today: 12.4 mm (Rainfall Today: 11.9 mm recorded from the shower)!

Edited September 6, 2013 by William Grimsley

[Guest William Grimsley]

WOW! Look at this for here this evening! I can't wait! 

 

UK precipitation. Valid: Fri 06/09 18:00.

 

 

UK storm risk. Valid: 06/09 18:00.

 

UK CAPE+Lifted Index. Valid: 06/09 18:00.

 

[Coast]

WOW! Look at this for here this evening! I can't wait! 

 

 

William, are you running a boat-building business or trading on-line in raincoat and umbrella supplies??? :lol:

[Guest William Grimsley]

William, are you running a boat-building business or trading on-line in raincoat and umbrella supplies???

Probably the second one instead running a hoping for showers business!!!

Edited September 6, 2013 by William Grimsley

[Mapantz]

Pretty much as i thought for here,  and 15.2C 

 

Despite a cooler feel, i'm still in shorts and a t-shirt, it's quite pleasant as there's hardly any breeze.

 

 ELT's  really come down in the South West & South Wales through this afternoon, ranging from -20C to -40C in Cornwall, certainly good enough for hail production in those showers, and in turn, lightning.  

Edited September 6, 2013 by Mapantz

[A.J]

Pretty much as i thought for here,  and 15.2C 

 

Despite a cooler feel, i'm still in shorts and a t-shirt, it's quite pleasant as there's hardly any breeze.

yep, not too bad here either, a little overnight rain, but essentially dry now....chance of the odd shower this afternoon, but nothing too drastic. Larger chance of heavier showers affecting north and westward facing coasts and penetrating more inland as the afternoon progresses, but not the washout/storm armeggedon some might have you think....

[Lyn-M]

Yes, pleasant here too.  Currently sunny intervals and 15C.  Overnight rainfall amounted to 3.5mm.

[Sainsbo]

Temperatue onle 12.3C here, need a jumper on outside for the first time in a long time.

Edited September 6, 2013 by Sainsbo

[SunnySouthCoast]

Well didn't get much rain here, just 2mm between 6 & 9am! Though it is colder now than it was last night at 16C.

[MPG]

Some very big shower clouds now heading into North Somerset as forecasted.

[AWD]

Some very big shower clouds now heading into North Somerset as forecasted.

Yup. Just about to post this rather humorous one to my west now;It looks more menacing than what it actually is there. Most of the clouds here are light.Some good cloud structures here. Edited September 6, 2013 by AWD

[Andy Bown]

Yup. Just about to post this rather humorous one to my west now;

image.jpg

It looks more menacing than what it actually is there. Most of the clouds here are light.

Some good cloud structures here.

Is that really your photo AWD?

 

I seem to recall seeing that image in last weekend's Sun newspaper!

[Cakie]

Radar has some interesting developments over Cornwall and out to sea to the North swirling around. Going to be watching that with interest this afternoon. Feeling quite muggy here

[Coast]

Radar has some interesting developments over Cornwall and out to sea to the North swirling around. Going to be watching that with interest this afternoon. Feeling quite muggy here

 

GFS and NMM had the Northern coast of Cornwall and Devon highlighted for rain and possible storms later, likewise South Wales

[Evening thunder]

I was watching that stuff on radar too, a couple showers formed over south Devon recently gradually moving this way which I can see to the SW now.

 

My station is recording a dewpoint of 6-7c, and Exeter Airport 4c, odd to have the best convective potential for a while with the driest air for ages here..

Edited September 6, 2013 by Stormmad26

[Costa Del Fal]

Yay im back in Falmouth till Christmas now. (Though in Woolacombe, Devon next week only). Thundery showers lingering off the coast. One fairly close to the Scilly Isles though.

[ARTDEMOLE]

Lots of sun. A few clouds. Light breeze. 18.0c.

[Mapantz]

It is currently 19.3C here with plenty of sunshine, it may be 7C lower than yesterday but it certainly isn't like the picture painted by the forecasts, it's goregeous!