Convective/Thunderstorm Discussion : Spring/Summer 2017

glightning

Another video from Plymouth. Good action from mid way through the video!

https://www.youtube.com/watch?v=RTJ8MB2v4oc

Meteorite58

Been in some intense storms but never seen or heard anything like that before, the flash that set off the alarm at 6.23 and the boom after!

glightning

Rougies wrote: »

Jpmarn wrote: »

I feel sort of jealous that northern England is getting some active thunderstorms. The extofex chart on the last page posted around 0300 didn't indicate that much thunder for England showing most of outside the light yellow 15% boundary. Extofex indicated more activity for the Island of Ireland but so far very little so far.

That chart was only valid until 6am this morning and it was spot on for SW England. Here's the chart for 6am Sat - 6am Sun.

I thought Estofex called the whole situation pretty well to be honest...

The correctly predicted the storms in the far NW of Ireland on Friday (even getting the timing right between 4pm and 6pm). They also called out the direction of the storm motion well predicting it to track to the N / NE and that CAPE over NW Ireland would fall away quickly after 6pm which it indeed did.

They also predicted widespread and intense storms for the SW of England tracking North over Wales, etc. They never predicted anything for eastern Ireland.

Overall they got it spot on in my opinion and it's why we really should pay attention to these forecasts along with short range models such as RIPWRF and NMM to avoid shattered hopes. In fact, I had little hope for this setup for NI based on the short range model output.

pedigree 6

Meteorite58 wrote: »

Been in some intense storms but never seen or heard anything like that before, the flash that set off the alarm at 6.23 and the boom after!

I wonder what exactly set it off?

Anyway there was a strong thunderstorm last year here in wexford.
I was out waiting for it to come up my way from south in the county and I was just about to go back inside and I heard a small crack either from a tree or the electric fence wire and about a second after, the lightning came down with the thunderclap straight away. I thought I was a goner.:p

That same thunderstorm broke lorry weighbridges in about a 5 mile radius all around Clonroche. I couldn't exactly tell you the science but it seems an opposite charge builds up in the earth during a thunderstorm and because this one was so strong it put the weighbridges out of action.

glightning

With lightning, the charge flows from positive to negative (as per standard electrical behaviour).

The earth (ground) is positively charged. Also, due to the updrafts in the thunderstorm (hail collision with water droplets rising in the cloud), the anvil (at the top) becomes positively charged and the base becomes negatively charged.

What then happens, is that as the base becomes increasingly negatively charged, the earth (ground) sends up positive streamers towards the base of the cloud (which is why you might feel static in the air or hear a crackling). The base of the cloud starts "reaching down" towards those streamers. Once any one of the streamers connects with the pull from the base of the storm a CG (cloud to ground) strike occurs.

The CC (cloud to cloud) or infra cloud lightning occurs between the positive and negatively charged parts of the cloud.

Meteorite58

I wonder what exactly set it off?

I think it is caused by the electromagnetic pulse from the lightning ( can also set off smoke detectors in a house ) and also the vibration sensor in the car alarm can be triggered by the thunder, especially sensitive ones .

glightning

So in other words when lightning occurs it doesn't actually go from the cloud to the ground. What actually happens is it comes from the ground to the cloud to neutralise the negative charge at the base of the storm

Trebor176

I vaguely remember this night in 1997 (I was only 11, though). Around 9:45 is when it really gets bad. The above video reminded me of it with the alarms going off!

glightning

Here is a photo of positive streamers coming up from objects caught on camera

https://s-media-cache-ak0.pinimg.com/236x/bb/4b/ce/bb4bcec5625f4f5e7a0421238cecdb22.jpg

In this case where you can see them, the actual lightning discharge has just occurred. But it didn't connect with either of these streamers. However they light up due to the huge discharge occurring nearby

pedigree 6

glightning wrote: »

With lightning, the charge flows from positive to negative (as per standard electrical behaviour).

The earth (ground) is positively charged. Also, due to the updrafts in the thunderstorm (hail collision with water droplets rising in the cloud), the anvil (at the top) becomes positively charged and the base becomes negatively charged.

What then happens, is that as the base becomes increasingly negatively charged, the earth (ground) sends up positive streamers towards the base of the cloud (which is why you might feel static in the air or hear a crackling). The base of the cloud starts "reaching down" towards those streamers. Once any one of the streamers connects with the pull from the base of the storm a CG (cloud to ground) strike occurs.

The CC (cloud to cloud) or infra cloud lightning occurs between the positive and negatively charged parts of the cloud.

I understand you now but I wonder have you the positive and negative charges the wrong way around?

What do you think of this lecture?
http://www.atmo.arizona.edu/students/courselinks/spring15/atmo589/ATMO489_online/lecture_1/lect1_global_elec_circuit.html

I never thought the science behind thunderstorms could be so interesting.:)

Edit: Don't mind me you have it correct. Apologies.

pedigree 6

Meteorite58 wrote: »

I think it is caused by the electromagnetic pulse from the lightning ( can also set off smoke detectors in a house ) and also the vibration sensor in the car alarm can be triggered by the thunder, especially sensitive ones .

Would it be the polarity of the electrical device changing for a split second before the lightning bolt hits the ground.

Say the device works by the positive charge (electricity) going to the negative.
But just before the bolt hits a charge greater than the one coming from the brown wire (ESB) comes from the earth or neutral wire and it shuts down the device for a split second.

pedigree 6

Here's a mad thought that just occurred to me.:pac:

Say you know the case of sea based thunderstorms producing sferics and then when they come to land they go quiet.

Could one reason be that the sea water is a better conductor than soil (the earth).
The thunderstorm might not be charged up enough to start producing lightning bolts over land but just enough to produce them over sea.
We've said before that the charge comes from ground, water, sea, etc, Planet Earth anyway and it's easier for it to come through the sea water and then escape through the air to meet the charge coming from the cloud.

I know with all thunderstorms you have a warm moist inflow and a cool fast downdraft and when the inflow gets cut off that the thunderstorm starts to die but maybe the increased conductivity of sea water could also be a factor?

Anyway that's something to chew over.:pac:

glightning

One thing I left out earlier....

What actually happens (if you watch in slow motion) is that multiple exchanges occur between the cloud and ground. There will be different parts of the cloud that have become negatively charged at the same time and therefore each will trigger a stroke (all happens within a second or so). Hence the lightning "flicker". Basically as per the laws of nature everything is trying to balance out and become a steady state just like the way the atmosphere does every single day! Therefore multiple parts of the cloud can discharge to each other AND to the ground - all within milliseconds of each other.

The biggest, loudest, and most powerful lightning strikes come right out of the top of the anvil all the way to the ground (well ground to anvil really). These are the ones that create window rattling booms. We had one last summer here and I felt the shockwave on my face!! These huge anvil discharges start with a massive BANG rather than a rolling clap.

pedigree 6

Then as well the actual lightning bolt itself.
Why is there light off it?

It's because of the resistance of the air itself. The cloud is fine because it can move through the water and moisture itself but when the charge travels through tlhe resistant open air it glows bright like electricity going through a resistant coil in an old fashioned light bulb.

glightning

Yes, the lightning actually causes the air around it to ionize which as you say then creates the glow.

Here's some text from online that describes the process :-

The strong electric field causes the air around the cloud to "break down," allowing current to flow in an attempt to neutralize the charge separation. ... The electric field causes the surrounding air to become separated into positive ions and electrons -- the air is ionized.

pedigree 6

This might also be worth a look at glightning.

(Apologies mods if you think this is clogging up the thread say so)
But I think it may interest people.

You can see how the ground in normal weather conditions has both positive and negative charge (both in equal proportions) but during a thunderstorm overhead the positive charge gets pulled up to the surface in quantities equal to the negative charge overhead.

This clip he has then will freak you out.

He has to explain then how lightning rods get struck sometimes then.:D
He could of just said the lightning comes from half a mile away in the cloud and not directly overhead.:p

I won't post any more on it but it's very interesting.

pad199207

Another night of fun and games for the UK, while we just get crappy cloud and mush!

gugsy

If you think Plymouth storm was massive look at French storms atm, over 230 strike per min

pad199207

Storm over Brittany atm looks even more spectacular than the one that was in SW UK Friday night.

Hopefully it dies over the channel, nothing worse seeing those brits getting all the fun!

pedigree 6

Anyone got any links to good webcams?

This one is from Brighton Beach.
You can see the lightning on the horizon.

http://magicseaweed.com/Live-Brighton-West-Pier-Webcam/67/

Edit: Here's a better one.

http://www.vision-environnement.com/live/webcam/webcam-trouville.php

Rougies

pad199207 wrote: »

Storm over Brittany atm looks even more spectacular than the one that was in SW UK Friday night.

Hopefully it dies over the channel, nothing worse seeing those brits getting all the fun!

Looks like they'll be getting another serious light show in south UK. Here's what estofex has to say about tonight.

Confidence in more widespread CI increases during the night with the development of a diffuse/weak LL vortex over the W-English Channel in response to the approaching upper trough. This vortex pushes a wavy front east and a cluster of organized thunderstorms is forecast to evolve over NW-France and/or SW-UK. Forecast soundings reveal more elevated convection with MUCAPE of 1 kJ/kg and 20 m/s DLS. Also, 0-3 km shear increases to 15-20 m/s over far S-UK. Expect thunderstorms to grow upscale into a cluster of storms while crossing S-UK from WSW to ENE.

http://www.estofex.org/

The MCS crossing the English channel now is is a beast!

Nibs05

Webcam wise for London, I keep a eye on the Tottenham ground development, in the last few days cam4 was moved and now faces south, London skyline is in the distance and may make for some good viewing later on.

https://youtu.be/Kq3g-KPM1W0

Rougies

Found a really nice couple of webcams for Brighton, seeing some nice forks already!

https://www.skylinewebcams.com/de/webcam/united-kingdom/england/brighton/brighton-pier.html

https://www.skylinewebcams.com/de/webcam/united-kingdom/england/brighton/brighton.html

pedigree 6

She's sailing up the English Channel. Ha.:p

Edit: I'll say it'll be a tight squeeze but she'll make it.;)

Rougies

pedigree 6 wrote: »

She's sailing up the English Channel. Ha.:p

Edit: I'll say it'll be a tight squeeze but she'll make it.;)

They're sick over on the netweather forums and I don't blame them. Glad it doesn't only happen to us though

pedigree 6

Torrential rain in Hastings.

https://www.beaming.co.uk/company/hastings-pier-webcam/

Stevecw

Good webcam here from Dover Beach:

https://www.skylinewebcams.com/en/webcam/united-kingdom/kent/dover/dover-beach-kent.html

Gonzo

pad199207 wrote: »

Another night of fun and games for the UK, while we just get crappy cloud and mush!

that's always gonna be the way. Ireland just does not have the right conditions for storms, rarely ever. The last thunderstorm that I have witnessed here that was in any way decent was in August 1985, since then noting more than 15 minute 'storms' with a few cracks of thunder and even those are rare, often year's apart.

Clonmel1000

Gonzo wrote: »

that's always gonna be the way. Ireland just does not have the right conditions for storms, rarely ever. The last thunderstorm that I have witnessed here that was in any way decent was in August 1985, since then noting more than 15 minute 'storms' with a few cracks of thunder and even those are rare, often year's apart.

Kinda like snow really.

pedigree 6

Gonzo wrote: »

that's always gonna be the way. Ireland just does not have the right conditions for storms, rarely ever. The last thunderstorm that I have witnessed here that was in any way decent was in August 1985, since then noting more than 15 minute 'storms' with a few cracks of thunder and even those are rare, often year's apart.

If you were to pick a favoured spot for thunderstorms in this country it would be the Northwest.
Usually High Pressure is to our east and Low Pressure is to our west and with just the right air pressure there and southerly winds building the "heat of the day" showers up over the country before they get there coupled with moisture from the Shannon makes Cavan, Leitrim and Fermanagh lucky buggars.:pac: