Convective Storm/Discussion thread - 16/07/16 onwards

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Thu 21 Jul 2016 - 05:59 UTC Fri 22 Jul 2016

ISSUED 05:02 UTC Thu 21 Jul 2016

ISSUED BY: Dan

A rather messy picture with areas of dynamic and convective precipitation developing later today and overnight, giving a rather broad low (but non-zero) risk of lightning during Thursday / Thursday night. Greatest risk appears to be over parts of Northern Ireland / Ireland this afternoon with the aid of some diurnal heating generating a few hundred Jkg-1 CAPE, with some sporadic lightning possible - elsewhere lightning is possible (especially later today and overnight) but considered too low, or coverage at least will be quite low, to warrant any threat levels at this time.

http://www.convectiveweather.co.uk/forecast.php?date=2016-07-21

[Windblade]

10 hours ago, staplehurst said:

@Supacell

 

What I will say is, though, once you go to America you'll be hooked and want to go again and again - my first was in 2012, but I've been back every year since, and no sooner have I landed back in the UK after each trip that I'm already looking forward to the following year...

Yeah. My favourite weather is a tornado (although I'm yet to see one). I'm fascinated by them (although at the same time I hate the destruction they cause and don't want to see people getting hurt). The Usa is where its at for that kind of thing so will have to plan a trip over there at some point I think.

 

Meanwhile just took a look at the forecast for the south east for the next few days. Initial reports had this heatwave ended by today (although still warm) but I see its still going to be relentlessly sunny, hot and almost 30 degrees lasting until next week. As I said last night this bloody heatwave just WILL. NOT. GO. What is incredibly frustrating is this is the hottest place in the country and we have a lot of instability at the moment but just no convection while a lot of other cooler places have had lots of rain and storms to cool things off. These pics were taken this morning at 7am.

[East_England_Stormchaser91]

A couple of satellite images of the east Anglian beast yesterday. Clearly defined overshooting top on it! 

Remerkable stuff . Within the UK range according to blitzortung, over a 24 hour period, 109,000 strikes were registered!! Very concentrated in specific areas, but when they did occur, the lightning rates were phenomenal for UK standards. 

[Flash bang flash bang etc]

Frankly surprised at no convective potential for London today

[Methuselah]

15 hours ago, Norfolk Sheep said:

Oh I saw it coming, trust me, the anvil was huge radar said direct hit right up to barely 10 miles out. However it literally split as it approached, you could see it happening. Now why that happened I have no idea, but it's not unusual for storms (big or small) to suddenly divert north or south of here. Must be some sort of local topography (which in a relatively flat county is hard to conceive!) 

It was truly immense, NS... Maybe the biggest anvil I have ever seen.

Edited July 21, 2016 by Ed Stone

[Methuselah]

15 hours ago, Norfolk Sheep said:

Oh I saw it coming, trust me, the anvil was huge radar said direct hit right up to barely 10 miles out. However it literally split as it approached, you could see it happening. Now why that happened I have no idea, but it's not unusual for storms (big or small) to suddenly divert north or south of here. Must be some sort of local topography (which in a relatively flat county is hard to conceive!) 

After yesterdays evening's fireworks, one or two non-thunder days will make a change...

PS: quote function is playing-up again!

[Windblade]

Me too. So much energy around and nothing to do anything with it.

[BrickFielder]

Slight chance of a few thunderstorms tomorrow as upper level troughs (occluded front) move across the UK.

Looks like very slack winds until you reach the very top of the clouds, so slow moving with heavy downpours might be the order of the day. Could be good for photographers. Very slight risk of spout development (very weak spin ups) due to convergence zones developing. Dry air aloft should enhance storm severity slightly.

Too far out to put much more detail on things at the moment, but key risk might be localized flooding.

[Windblade]

33 minutes ago, BrickFielder said:

Slight chance of a few thunderstorms tomorrow as upper level troughs (occluded front) move across the UK.

Looks like very slack winds until you reach the very top of the clouds, so slow moving with heavy downpours might be the order of the day. Could be good for photographers. Very slight risk of spout development (very weak spin ups) due to convergence zones developing. Dry air aloft should enhance storm severity slightly.

Too far out to put much more detail on things at the moment, but key risk might be localized flooding.

Thanks for the forecast. I'm a bit rubbish at reading the charts. Can you explain the chart please if you have time?

Edited July 21, 2016 by Windblade

[Flash bang flash bang etc]

So today in London do we ignore the heat that has built up during the day, the apparent convergence zone drifting about overhead and the slow advance of an area of relatively heavy PPN moving in from the SW?

i know I don't get the science but it seems if that were the case in the midlands or out over Lincs we would be looking at more thunderstorms!

...or is it just because I've got my cameras back?

I'm not ready to sit back and put up with another weather lull before the next plume in September - I haven't had my fix yet!

[Windblade]

Yes, there is a lot of low level convection going on in London right now. I bet it doesn't amount to anything though. The heat is relentless. Its supposed to be cooler today but it feels just the same to me.

[NO LONGER POSTING]

1 minute ago, Windblade said:

Yes, there is a lot of low level convection going on in London right now. I bet it doesn't amount to anything though. The heat is relentless. Its supposed to be cooler today but it feels just the same to me.

Looks warm in south for the foreseeable future 

 

[Windblade]

16 minutes ago, Surrey said:

Looks warm in south for the foreseeable future 

 

Don't I know it! 

[weather09]

Agree with BF on well scattered storms tomorrow, despite unfavourable profile aloft.  Relatively poor mid-level lapse rates with weak 500mb heights, however good heating of reasonably moist surface air mass (temps low 20s; dewpoints low-mid teens) will build possibly several 100J/kg CAPE inland, with slack converging winds in advance of the occlusion together with sfc heating likely to develop a few storms during afternoon.  Light winds throughout the profile, so shear will be non-existent.  As mentioned, possibility of funnels with stronger updrafts given low cloud ceiling, steep low-level lapse rates, converging sfc winds and slack winds aloft.

[Harsh Climate]

A huge storm looks head on for munich, might be worth a watch

http://www.earthtv.com/en/camera-destination/munich-germany/

[BrickFielder]

1 hour ago, Windblade said:

Thanks for the forecast. I'm a bit rubbish at reading the charts. Can you explain the chart please if you have time?

So the Forecast SkewT has two main lines on it. The left one is the dew point  (The temperature at which moisture turns into water)  with height and the right one the temperature with height. So you look at the dewpoint at the surface and then work out at what height a rising parcel of air turns to water (I have marked that in purple). You then look at the adiabatic rate the green lines and work out when a parcel of air stops rising (thats the thick green line I have added).

The other chart is the humidity (moisture content of the air) at 300hPA (which would be thunderstorm top height). This tells me that there is drier air aloft where the blue is on the chart. Drier air usually means colder air which would shift the right hand line on the skewt leftwards meaning air parcels can rise higher where there is cold dry air aloft.

[Nick L]

17 hours ago, staplehurst said:

@Supacell

 

What I will say is, though, once you go to America you'll be hooked and want to go again and again - my first was in 2012, but I've been back every year since, and no sooner have I landed back in the UK after each trip that I'm already looking forward to the following year...

I hear you there. I booked 2017 while I was still out there! Only guarantee of actually getting thunderstorms seeing as it's a seemingly 1-in-5 year event to get something half decent here.

[matty40s]

3 hours ago, Harsh Climate said:

A huge storm looks head on for munich, might be worth a watch

http://www.earthtv.com/en/camera-destination/munich-germany/

looks like a nice bow echo on that front..

[carl1980]

Heavy showers approaching now, looks black to the south and west,local forcast said could be a thundery mix 

[Allseasons-Si]

9 hours ago, Summer Sun said:

Day 1 Convective Outlook

VALID 06:00 UTC Thu 21 Jul 2016 - 05:59 UTC Fri 22 Jul 2016

ISSUED 05:02 UTC Thu 21 Jul 2016

ISSUED BY: Dan

A rather messy picture with areas of dynamic and convective precipitation developing later today and overnight, giving a rather broad low (but non-zero) risk of lightning during Thursday / Thursday night. Greatest risk appears to be over parts of Northern Ireland / Ireland this afternoon with the aid of some diurnal heating generating a few hundred Jkg-1 CAPE, with some sporadic lightning possible - elsewhere lightning is possible (especially later today and overnight) but considered too low, or coverage at least will be quite low, to warrant any threat levels at this time.

http://www.convectiveweather.co.uk/forecast.php?date=2016-07-21

NW England looks like having some heavy showers at the moment,maybe the odd sferic in them,quiet slow moving too compared to recent days,so if you are underneath one you will certainly know about it.

[carl1980]

2 minutes ago, Allseasons-si said:

NW England looks like having some heavy showers at the moment,maybe the odd sferic in them,quiet slow moving too compared to recent days,so if you are underneath one you will certainly know about it.

There's no wind very still here showers not far away

[Flash bang flash bang etc]

Southern England have some showers too! Or has everyone forgotten about us 

Still think there is room for some sparks down our way despite nobody mentioning it anywhere.

Could someone explain the mechanisms at work today inhibiting thundery activity around London if poss?

The sky is milky grey with very high level cloud but it does look a little stormy to me

 

[Darren Bown]

Going dark to my SW. A surprise downpour expected soon, but nothing electrical!

[staplehurst]

26 minutes ago, Flash bang flash bang etc said:

Southern England have some showers too! Or has everyone forgotten about us 

Still think there is room for some sparks down our way despite nobody mentioning it anywhere.

Could someone explain the mechanisms at work today inhibiting thundery activity around London if poss?

The sky is milky grey with very high level cloud but it does look a little stormy to me

 

Frustratingly there are very few 12z soundings available for the UK, but if we take the Larkhill ascent from this afternoon and adjust the surface temperature to 25C with a dewpoint of 12C (which seems reasonable for the London area this afternoon etc), you can see that there is some convective potential, but it becomes capped off around 750mb (or approx 2.5km above the ground) due to warmer layers above - in fact it becomes even more capped off at 700mb (3km up), thus severely limiting the potential depth of convection.

Farther north, I suspect this capping in the mid-levels is slightly weaker, allowing parcels to achieve greater heights, but still capped off to a certain extent and hence the presence of some heavy showers over Merseyside recently, but with next to no lightning - it's not totally out of the question, but it's quite a low potential today.

[Flash bang flash bang etc]

9 minutes ago, staplehurst said:

Frustratingly there are very few 12z soundings available for the UK, but if we take the Larkhill ascent from this afternoon and adjust the surface temperature to 25C with a dewpoint of 12C (which seems reasonable for the London area this afternoon etc), you can see that there is some convective potential, but it becomes capped off around 750mb (or approx 2.5km above the ground) due to warmer layers above - in fact it becomes even more capped off at 700mb (3km up), thus severely limiting the potential depth of convection.

Farther north, I suspect this capping in the mid-levels is slightly weaker, allowing parcels to achieve greater heights, but still capped off to a certain extent and hence the presence of some heavy showers over Merseyside recently, but with next to no lightning - it's not totally out of the question, but it's quite a low potential today.

That's actually really well explained! Thanks for the info, I'll keep my unbrella handy just in case ;-)