Convective Storm/Discussion thread - 11/06/16 onwards

[Ben Sainsbury]

3 hours ago, William Grimsley said:

Just been looking at the BBC Weather graphics, to me it doesn't show any sort of area of heavy showers/thunderstorms moving in behind, maybe the convection will be associated with the front? Potentially embedded cells?

Definitely a very complex setup tomorrow in my eyes, got my eye over far SW late tomorrow, for some embedded organised storms. Interesting...

[William Grimsley]

2 minutes ago, Ben Sainsbury said:

Definitely a very complex setup tomorrow in my eyes, got my eye over far SW late tomorrow, for some embedded organised storms. Interesting...

Hopefully the mid level energy will help keep them moving this way, but by no means am I praying for anything. LOL.

[Ben Sainsbury]

7 minutes ago, William Grimsley said:

Hopefully the mid level energy will help keep them moving this way, but by no means am I praying for anything. LOL.

Let me explain, late Tomorrow across the Far SW, there looks be 200-300 J/Kg of CAPE, over run by 60kts of DLS, along with strong SRH, with the trigger being the low pressure system, yet no models suggesting any storm developments, and I lack professional storm knowledge. But it's just my opinion. Thus Significant Tornado Parameter is high too. (The Map below shows current projections in my amateur opinion. Green = Marginal Risk, Grey = Potentially Severe, yet very marginal) I'll update later on my Twitter and here.

Edited June 27, 2016 by Ben Sainsbury

[William Grimsley]

Sounds promising, to me I reckon it'll be something like a very blustery cold front with heavy rain (potential squall line but most likely not) then a brief clearence before heavy downpours with thunder, lightning and hail move through.

[Ben Sainsbury]

Just now, William Grimsley said:

Sounds promising, to me I reckon it'll be something like a very blustery cold front with heavy rain (potential squall line but most likely not) then a brief clearence before heavy downpours with thunder, lightning and hail move through.

Possibly, but very unlikely to happen, there's probably something that I'm missing but not sure what, let's see what ESTOFEX, ConvectiveWeather and other forecasters here say later!

[William Grimsley]

7 minutes ago, Ben Sainsbury said:

Possibly, but very unlikely to happen

The squall line? Yeah, again a very low chance of that, but there's a chance, looks quite vicious.

[Mapantz]

Not seeing it myself. Steepening lapse rates hooking in to the SW later in the afternoon, CAPE is meagre, high PWAT. I'd go for some heavy bursts of rain with maybe the odd rumble mixed in the heavier ppn.

I'd like to be wrong, but I can't envisage anything severe?

[William Grimsley]

Yes, nothing severe but the possibility is there for some hail and/or thunder and lightning in some of the showers.

[Ben Sainsbury]

52 minutes ago, Mapantz said:

Not seeing it myself. Steepening lapse rates hooking in to the SW later in the afternoon, CAPE is meagre, high PWAT. I'd go for some heavy bursts of rain with maybe the odd rumble mixed in the heavier ppn.

I'd like to be wrong, but I can't envisage anything severe?

But does that mean in this situation 60kts of DLS and 350m^2s^2 of SRH have no affect then in the SW?

Because from what I know Strong DLS and Small CAPE can still produce Strong Storms? I do understand with high PWAT, lightning is less likely?

Just trying to learn too!

Edited June 27, 2016 by Ben Sainsbury

[William Grimsley]

2 hours ago, Ben Sainsbury said:

But does that mean in this situation 60kts of DLS and 350m^2s^2 of SRH have no affect then in the SW?

Because from what I know Strong DLS and Small CAPE can still produce Strong Storms? I do understand with high PWAT, lightning is less likely?

Just trying to learn too!

PWAT doesn't have much effect on lightning, except higher PWAT values can mean that showers have to be incredibly intense (rainfall rates of 200 mm/hr +) in order for them to contain lightning whereas lower PWAT values mean that lightning may be able to arise at much lower rainfall rates.

Edited June 27, 2016 by William Grimsley

[viking_smb]

no rain please, boating in sea cadets tomorrow eve lol, I don't think they will be any storms tomorrow night,

[Ben Sainsbury]

42 minutes ago, William Grimsley said:

PWAT doesn't have much effect on lightning, except higher PWAT values can mean that showers have to be incredibly intense (rainfall rates of 200 mm/hr +) in order for them to contain lightning whereas lower PWAT values mean that lightning may be able to arise at much lower rainfall rates.

Oh I see that's how it works, sorry now I understand!

[Chris.R]

1 hour ago, William Grimsley said:

PWAT doesn't have much effect on lightning, except higher PWAT values can mean that showers have to be incredibly intense (rainfall rates of 200 mm/hr +) in order for them to contain lightning whereas lower PWAT values mean that lightning may be able to arise at much lower rainfall rates. 

 Is that right I just thought PWAT  values were an indicator of the potential rainfall intensity or  total rainfall amount for a given cell,  precipitable water. I didn't think it had  anything to do with lightning at all but after the torrential downpours that had no lightning for some reason last week, I see what you mean.

 For some reason last week, I see what you mean.

We are all learning. :-)

:-)

Oh bugger, I missed a penalty  while typing this which is why it went wrong. lol

Edited June 27, 2016 by Chris.R

[William Grimsley]

I think your reply is a bit screwed up. PWAT values itself don't effect lightning amounts, but higher PWAT values can leave you saying "Why isn't this cell electrifying?!"

[Ǝssex Ǝasterly]

3 minutes ago, William Grimsley said:

I think your reply is a bit screwed up. PWAT values itself don't effect lightning amounts, but higher PWAT values can leave you saying "Why isn't this cell electrifying?!"

 

Or they can leave you saying, the weather will do what it does and I can carry out my daily business without worrying over something I have no control over 

[Chris.R]

6 minutes ago, William Grimsley said:

I think your reply is a bit screwed up. PWAT values itself don't effect lightning amounts, but higher PWAT values can leave you saying "Why isn't this cell electrifying?!"  Sorry it's this phone as well, it's ridiculous. I totally get you now, makes sense. I'll  Watch out for that in the future. :-) 

 

[<<Ryan>>]

Some big storms around here on Saturday. Must have had 3-4 separate storms during the day. Hail the size of marbles in the worst.
Got a pic of the first shower that popped up - started producing thunder 20 minutes after I took this photo. 

Some places nearby had it much worse: http://www.kentonline.co.uk/gravesend/news/heavy-rain-causes-havoc-97994/

Edited June 27, 2016 by <<Ryan>>

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Tue 28 Jun 2016 - 05:59 UTC Wed 29 Jun 2016

ISSUED 20:25 UTC Mon 27 Jun 2016

ISSUED BY: Dan

A complex situation for Tuesday, with a broad upper vortex situated across the North Atlantic, and various disturbances running around its periphery. One such feature will bring a spell of showery rain on the forward side of an upper shortwave, this generally tracking eastwards across southern half of Britain through the day. A messy mix of dynamic/frontal precipitation with elements of mid-level instability is expected, the latter likely to erupt on the forward side (N Wales - N Midlands - N England - East Anglia), albeit with limited depth and hence questionable as to how much, if any, lightning activity may occur with this activity. A broad LOW threat has been issued to cover this potential.

Once early showery rain has cleared SW England / S Wales, modest heating of a residual SMZ with Tds 12-15C through the afternoon (assuming sufficient cloud breaks) will yield 200-500 Jkg-1 MLCAPE in a highly sheared environment. There is scope, therefore, for some elements of deep convection (heavy showers) to develop, perhaps focussed along distinct lines parallel to the mean flow.

Dry intrusion in the mid/upper levels will limit convective depth somewhat, so given the uncertainty surrounding the true lightning potential we have remained with just a LOW threat level at this stage. However, any convection that does develop will benefit from strong shear, and perhaps also local backing of the surface winds - given relatively low LCLs, there is scope for a tornado to occur. This situation needs monitoring but relies very much on a good overlap of parameters in a relatively short window, hence the uncertainty at this stage. Potential also for some strong wind gusts, this risk extending north into mid-Wales with any stronger convection that manages to develop, especially so on the wrap-around feature.

Elsewhere, a more classic situation of diurnally-driven showers given cold mid-levels and surface heating, yielding 300-600 Jkg-1 MLCAPE, especially across Ireland. Hence a scattering of showers and a few thunderstorms can be expected, with the best lightning potential within the SLGT areas. Hail up to 1.5cm in diameter may accompany the strongest cells. Overall a better overlap of relatively higher instability and better shear suggests lightning will be more widespread in the Ireland SLGT area.

http://www.convectiveweather.co.uk/forecast.php?date=2016-06-28

[Greeny]

1 hour ago, William Grimsley said:

I think your reply is a bit screwed up. PWAT values itself don't effect lightning amounts, but higher PWAT values can leave you saying "Why isn't this cell electrifying?!"

It does look rather interesting for your neck of the woods William. Seems also to be potential for Ireland and later on in the day for Scotland. Equilibrium level for the southwest isn't as high (20 - 25000ft) but skew-t for Newton Poppleford has around 600j/kg of CAPE build up by 1800 with the current run. Lightning wizard has significant tornado parameters and up to 300 SRH although county of Devon skew-T has 191SRH at 12z down to 40 at 18z but that is still enough I think. It is a small area however and SRH may drop before storms finally get going so not sure how it would transpire if anything does fire there. Lightning wizard insists SRH for right movers will still be 200-300SRH at 18z. We shall have to see. Worth looking to any low cloud bases that you may be able to see for rotation and good luck!

Edited June 27, 2016 by Greeny

[Ben Sainsbury]

3 minutes ago, Greeny said:

It does look rather interesting for your neck of the woods William. Seems also to be potential for Ireland and later on in the day for Scotland. Equilibrium level for the southwest isn't as high (20 - 25000ft) but skew-t for Newton Poppleford has around 600j/kg of CAPE build up by 1800 with the current run. Lightning wizard has significant tornado parameters and up to 300 SRH although county of Devon skew-T has 191SRH at 12z down to 40 at 18z but that is still enough I think. It is a small area however and SRH may drop before storms finally get going so not sure how it would transpire if anything does fire there. Lightning wizard insists SRH for right movers will still be 200-300SRH at 18z. We shall have to see. Worth looking to any low cloud bases that you may be able to see for rotation and good luck!

If you didn't see my post from earlier this is exactly what I was saying, decent CAPE, 300 SRH, 60kts of DLS, I'm just not sure!

[Ben Sainsbury]

Thunderstorm Forecast: Slight Risk of Thunderstorms for 28th June 2016! (Poss upgrade in SW if storms initiate!)

[Greeny]

2 minutes ago, Ben Sainsbury said:

If you didn't see my post from earlier this is exactly what I was saying, decent CAPE, 300 SRH, 60kts of DLS, I'm just not sure!

Yes I did see it thats what prompted me to take a look. Its interesting for me to see what happens with this forecast and it being a small area, its a learning curve. The deep layer shear is coupled with nearly 30knts of low layer shear. Would be well interested with this setup myself. Can understand the tornado risk. I looked at the surface winds and they were quite strong which prompted me to check the LLS. As always I would be cautious to get too excited but would be looking around with interest

[Supacell]

There was lightning detected somewhere in the UK on 12 of the first 14 days of this month and on 21 days of the month to this point. Some of these days saw widespread storms, some saw disruptive storms. That is pretty good going by anyone's standards and has been in my opinion the most active June since I started chasing in 2004.

This time 4 years ago we were staring down the barrel of what would go on to become one of the biggest storm days of the last decade

Edited June 27, 2016 by Supacell

[Chris.R]

 Please don't mention that day lol

[Supacell]

1 minute ago, Chris.R said:

 Please don't mention that day lol

Maybe not for all