Convective / Storm Discussion - 8th September onwards 2013

[Guest William Grimsley]

Presumably you mean down in Devon? http://www.ukasf.co.uk/storm-forecasts/257 Click on the lightning overlay ha - a very active day, particularly in the early hours through to mid-morning. Sadly very little in this corner of Kent on that particular day.

WOW! There are a lot of lightning strikes over the UK! It must have been through the night and I slept through it, here.

[NO LONGER POSTING]

Going by the NAE this is how I see things... Subject to change at lastminute.com but there we go..

 

Area number one which is Central Devon up in East wales and Further north...

 

 

 

Notice the PPN rates get higher as the area moves north...

 

Area two is Eastern Ireland and up into Western Scotland VERY heavy PPN rates..

 

South east pretty much misses out going by this and TBH I would like us too..

[Coast]

Interestingly the latest GFS has activity in The Channel (French side) tomorrow:

 

There's a lot of rain under that too, will it make a tad further North and disrupt the SE?

 

[Mapantz]

Looking at all the various models that show PPN distribution, the ECM is the only one that i can see which falls closest inline with the MO warnings at the moment. The GFS/WRF/NMM/UKMO/NAE all show different scenarios, so for now, i'm gonna wait to the output later and then just watch the radar.  

[Guest William Grimsley]

Going by the NAE this is how I see things... Subject to change at lastminute.com but there we go..

 

Area number one which is Central Devon up in East wales and Further north...

 

 

 

Notice the PPN rates get higher as the area moves north...

 

Area two is Eastern Ireland and up into Western Scotland VERY heavy PPN rates..

 

South east pretty much misses out going by this and TBH I would like us too..

Tomorrow is going to be a wet day for W England, by the looks of things. Hopefully, this rain band will finish this short lived unsettled period off on a high.

[NO LONGER POSTING]

Looking at all the various models that show PPN distribution, the ECM is the only one that i can see which falls closest inline with the MO warnings at the moment. The GFS/WRF/NMM/UKMO/NAE all show different scenarios, so for now, i'm gonna wait to the output later and then just watch the radar.

 

Not really the NAE suits perfect with it infact its an exact match..

Tomorrow is going to be a wet day for W England, by the looks of things. Hopefully, this rain band will finish this short lived unsettled period off on a high.

 

I cant see it being thundery though :S

[Coast]

NMM now going more with the Westerly flow of precip' tomorrow but still keeps the intensity right through the SW and Western home counties in the early evening tomorrow:

 

 

The convective stuff does seem to be limited to the French side:

 

Edited October 2, 2013 by Coast

[Mapantz]

I cant see it being thundery though :S

 

With potential totals of 20 or 25mm falling in an hour in some locations, i can see it.

[Coast]

Liam Dutton on the rain content of tomorrow potential storm:

 

Warnings issued as heavy rain brings flood risk

 

Following a fine and warm weekend for most of us, the weather has turned more unsettled this week, with the prospect of some intense rain in the next 48 hours. The jet stream has dipped southwards just to west of the UK and is drawing up a plume of warmth and humidity ahead of it. As a result, a south to south easterly wind is going to deliver batches of heavy, thundery rain to most places during Thursday and Friday, with a risk of localised flooding. In these kinds of situations, it is always difficult to pinpoint which locations will see the greatest amounts of rainfall, but the weather computer models are now gaining consensus that western areas will see the wettest weather.

 

Low pressure’s influence

 

At the moment, there is an area of high pressure to the east of the UK and low pressure to the west. Given the way that the wind flows around each, this set up acts as a conveyor belt for very moist air to be pushed over us. However, as low pressure inches ever closer, this allows moist air to rise more readily and form clouds, giving rain. As well as this, there are two other factors that will help to concentrate the heaviest rainfall in particular areas – convergence of winds and orographic enhancement.

 

Convergence of winds

 

When the wind blows, its direction can be subtly influenced by the surface over which it flows. As the sea is smooth and generally uniform, the wind encounters negligible friction and flows freely. So, a southerly wind will continue to be a southerly wind. However, when the wind flows over land it encounters friction. This not only slows it down a little, but alters its direction – causing it to back. Therefore, what was a southerly wind over the sea can become more of a south easterly wind over the land. It’s the clashing (convergence) of these winds from different directions that enhances the rate at which air rises, resulting in more moisture in the clouds and thus greater amounts of rainfall – something that will happen in western areas during Thursday.

 

Orographic enhancement

 

A brisk southerly wind will mean that the very moist air travelling northwards across the UK will encounter hills and mountains. This will cause the moist air to be lifted even higher up in the atmosphere than would be the case if it was moving over flat terrain. The result will be for clouds containing greater amounts of moisture to form over the hills and mountains in the west, enhancing the intensity of the rain that falls – a process known as orographic enhancement.

 

How much rain is expected?

 

Scotland, Northern Ireland, Wales and the western side of England could see 20-30mm falling widely in the next 48 hours. Elsewhere, only 5-15mm of rain is expected. The worst affected areas – Cumbria, eastern parts of Northern Ireland, western Scotland and the mountains of south Wales – could see 50-80mm. Weather warnings have been issued by the Met Office, with localised flooding highlighted as a potential hazard.

 

http://blogs.channel4.com/liam-dutton-on-weather/warnings-issued-heavy-rain-brings-flood-risk/5030#sthash.yU8oqjVs.dpuf

 

[pad199207]

Some Torrential falls of Rain here this afternoon. Got soaked at lunchtime!

 

Some lightning last night, was surprises considering so far inland

 

reached 20 degrees earlier

[Panayiotis]

Feels like the middle of summer here with this humidity, currently 19.4C! Quite a good temperature for October! Hopefully I get to see these storms kick off to the S of me so I can see some action!

Edited October 2, 2013 by Panayiotis

[Convective]

Don't know what to expect here to be honest. A few sferics within 30 miles. Forecast all night too.

[Supacell]

Pretty nice 'upgrade' on today's NWP output at a glance, mainly in terms of coverage, though GFS models substantial instability overspreading a good portion of the country tomorrow.

 

I'll have a closer look with a cup of tea lol.

 

GFS 12z is a treat with widespread decent CAPE and instability tomorrow evening and into the night. Some of the CAPE values on those charts would be good at night even in midsummer.

 

Looking through the charts on Lightning Wizard I would say there could be quite widespread thundery activity later tomorrow and through the night.

 

During the evening there looks to be a chance of something more organised into the S and SE, with a slight supercell parameter according to the attached chart for 6pm. At this time there is also a risk of hail up to 2cm in diameter. 

 

 

Later in the evening the risk expands north. Take a look at these ELT's and PWAT values for the evening.

 

 

 

And then, even by midnight there is over 500j/kg of CAPE.

 

 

The likelihood if these charts came off that there could be some decent storms, moving up from the continent into the S and SE during the late afternoon and then spreading north through the evening and night. They may lose some intensity as they do, but still likely to retain lightning, thunder and torrential rain along with gusty winds... that's if it ends up like this by the time we get there of course.

[Guest William Grimsley]

It has been dry and cloudy before a torrential downpour with pea size hail hit at 19:21 today, here. High Rainfall Rate Today: 140.4 mm/hr 19:41 High Hourly Rainfall Today: 9.2 mm 19:46 Rainfall Today: 13.0 mm.

Edited October 2, 2013 by William Grimsley

[Evening thunder]

This does look promising too.. http://www.metoffice.gov.uk/public/weather/forecast/egham#?tab=map&map=SignificantWeather&fcTime=1380693600&zoom=8&lon=-0.55&lat=51.43

 

Edit: just realised you will probably have to select the rainfall option and play through the timeslots to see what I mean

Edited October 2, 2013 by Stormmad26

[Andy Bown]

Ian Fergusson's Points West forecast showed thunderstorms within the large mass of heavy rain and he seemed confident of thundery activity.

 

Right now there is plenty of lightning over Northern Spain and Portugal drifting Northwards, so I guess this is the system due to arrive tomorrow.

 

93% humidity this evening!

 

[Jane Louise]

Posted 7.38pm Weds

 

Moderate Risk of Elevated Thunderstorms Early Phase SW UK and Late Phase SE UK

 

A relatively low risk for categorised severe weather though certainly some potential for localised electrical displays.

 

A near 'Spanish Plume' scenario with a very elevated layer of theta expected to slide northward from the continent through Thurs. Looking at the forecast soundings it appears unlikely that any of this lot will be capable of becoming surface based. ML CAPE looks to start from around 700mb upwards. Spanish Plumes are typically very hard to predict timing wise. In this case even more so when the theta looks mixed in with the primary cold front then post frontal surface troughing. Some broad variation within the WRF and GFS models; WRF giving scattered thundery showers primarily early on across the SW whilst GFS concentrates the best instability much further east later in the day. If we look primarily at the GFS we see the strongest risk zone to be Herts through to Suffolk late evening. Whilst this region shows the strongest ascent between an elevated layer at 650mb and 500mb I am not sure if the increase in vertical shear at this level will have any significant effect in isolating any embedded storm cells.

 

http://www.ukweatherworld.co.uk/forum/index.php?/topic/99790-convective-outlook-thurs-3rd-oct-2013/

 

http://www.ukweatherworld.co.uk/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=24759

 

Good luck all.

[dogs32]

nice one jane....................heres hoping...keeping eyes open for toniight early hrs

[Supacell]

So it would be the "late phase" for me then. I may chase tomorrow evening/night as I have now booked Friday off work.

[Jane Louise]

nice one jane....................heres hoping...keeping eyes open for toniight early hrs

Oh hiya Pat,  are you back in Cheltenham yet? if so we can keep each other updated with the storms Lol We've had nothing here again since you've been gone Lol you took them all with you

[MP-R]

That's quite a spike of rainfall between Honiton and Chard on the radar! Anyone under that at the moment or been under it? Would expect some hail within it.

[dogs32]

Oh hiya Pat,  are you back in Cheltenham yet? if so we can keep each other updated with the storms Lol We've had nothing here again since you've been gone Lol you took them all with you

nice to see you girl.........thats a long question....................many times usa.....gloucester...chelt.....midlands derby....too much to say......good to see u  still at it......ive always kept a look out  for uk TS........and while im here will be watching tomorrows potential....... lol..good old times jane ..look promising/.....cameras   got cobwebs  in uk..not  missurio

 

keep us updated

 

try to get on more but difficullt

Edited October 2, 2013 by dogs32

[Jane Louise]

nice to see you girl.........thats a long question....................many times usa.....gloucester...chelt.....midlands derby....too much to say......good to see u  still at it......ive always kept a look out  for uk TS........and while im here will be watching tomorrows potential....... lol..good old times jane ..look promising/.....cameras   got cobwebs  in uk..not  missurio

You too  Lol, Yes , good old times and what a laugh we used to have following and hoping the storms would hit Glos in the early hours especially.  My camera is ready again . I'm hoping tomorrows the day Lol  

[Paul]

Good to see you again Pat, hope life's treating you well

 

Tomorrow could be a lively one - this from the NMM

 

 

 

[dogs32]

You too  Lol, Yes , good old times and what a laugh we used to have following and hoping the storms would hit Glos in the early hours especially.  My camera is ready again . I'm hoping tomorrows the day Lol  

u always make me smile with your ethusism wits,,,,, TS.....try to be on more....got camera ready just in case