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Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

Hello.

Can one of the more knowledgeable folk answer a question of mine please. :hi:

This evening, I witnessed a shower that skirted my area which went from puffy cumulus through the developmental stages to an eventual anvil.

My question then is why was there no electrical activity from this smallish cell in spite of visible glaciation and can a glaciated shower still actually produce NO actual THUNDER and LIGHTNING?

What are the processes involved and am I right in thinking that perhaps I was simply seeing lofted hail?

Questions Questions. :help:

TIA

gottolovethisweather

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Posted
  • Location: Camborne
  • Location: Camborne

Hello.

Can one of the more knowledgeable folk answer a question of mine please. :hi:

This evening, I witnessed a shower that skirted my area which went from puffy cumulus through the developmental stages to an eventual anvil.

My question then is why was there no electrical activity from this smallish cell in spite of visible glaciation and can a glaciated shower still actually produce NO actual THUNDER and LIGHTNING?

What are the processes involved and am I right in thinking that perhaps I was simply seeing lofted hail?

Questions Questions. :help:

TIA

gottolovethisweather

I’m glad you didn’t come up with any difficult questions :whistling:. Electrification of clouds, in particular Cbs, has been the subject of much research over the years and I’m not sure that it has still been satisfactorily resolved. Some thoughts on the processes.

Two general hypotheses have been developed to account for thunderstorm electrification. One involves the induction mechanism, the other non inductive charge transfer. As an example of the first category, since the ionosphere at 30-40 km altitude is positively charged (owing to the action of cosmic and solar ultraviolet radiation in ionization) and the earth's surface is negatively charged during fine weather, cloud droplets can acquire an induced positive charge on their lower side and negative charge on their upper side. Non-inductive charge requires contact between cloud or precipitation particles.

The typically observed distribution of charges in a thundercloud is shown in attached thumbnail. The separation of electrical charges of opposite sign may involve several mechanisms: raindrop break-up (large droplets retaining positive charge, the surface spray carrying negative ions), or the selective capture of negative atmospheric ions by falling cloud particles are possible factors, but they do not appear to create sufficiently large charges. A third mechanism is the splintering of ice crystals during the freezing of cloud droplets. This operates as follows. A supercooled droplet freezes inwards from its surface and this leads to a negatively charged warmer core (OH-ions) and a positively charged colder surface due to the migration of H+ ions outwards down the temperature gradient. When this soft hailstone ruptures during freezing, small ice splinters carrying a positive charge are ejected by the ice shell and preferentially lifted to the top of the convection cell in updraughts. This theory can explain the charge distribution attached, which shows that the upper part of the cloud (above about the -20 °C isotherm) is positively charged. Equally, the negatively charged hail pellets fall towards the cloud base. However, the ice-splintering mechanism appears to work only for a narrow range of temperature conditions, and the charge transfer is small.

According to J. Latham, the major factor in cloud electrification is non-inductive charge transfer. This involves collisions between splintered ice crystals and warmer pellets of soft hail. Previous accretion of supercooled droplets on the hail pellets produces an irregular surface, which is warmed as the droplets release latent heat on freezing. The impacts of ice crystals on this irregular surface generate negative charge, whereas the crystals acquire positive charge. Negative charge is usually concentrated between about -10 and -20 °C in a thundercloud, where ice crystal concentrations are large, due to splintering at about the -5C level and then ascent of the crystals in upcurrents. Radar studies show that lightning is associated with both ice particles in clouds and rising air currents causing upward motion of small hail. The origin of small positive areas near the cloud is still under discussion. They could arise through the action of convective updraughts carrying positive charge. It is likely that the very varied electrical properties of thunderclouds (from cloud to cloud and within individual clouds as they develop) cannot be explained by any single theory of charge generation.

Source: Roger G. Barry and Richard J. Chorley, “Atmosphere, Weather & Climateâ€, seventh edition.

Now all that’s fairly straightforward :D but does it answer the question? Many Cbs have anvils and don’t produce thunderstorms so I’m assuming they don’t satisfy the electrification criteria for some reason or other (I don’t think lofted hail has anything to do with it). We had a couple down here yesterday that had anvils but they weren’t huge cells and the base was quite high, plus I did notice the tropopause was very low at around 400mb so I’m wondering whether the Cb cell, although appearing to satisfy storm conditions, isn’t in fact fully developed and doesn’t in fact contain sufficient energy to accomplish electrification. I think the point I'm trying to make is that not a huge amount of the Cb is in fact positively charged.

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Posted
  • Location: Hessen, GERMANY
  • Location: Hessen, GERMANY

How about this one?

http://lynn_mills.tr...ning/index.html

Some interesting ideas in this I think... though it does date back to 1997.

I imagine that the reason for the lack of static build-up is down to the structure of the clouds in terms of net areas of condensation and evaporation not being marked enough, therefore meaning the potential difference doesn't build to sufficient levels to cause more than the odd discharge occasionally, if you accept the premise of the above writing.

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Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

Many Thanks to the the both of you. :hi:

I did think that I may have been asking a stupid question that guaranteed a stupid answer but evidently not! :rofl::fool:

I'll have to have a better read of those links too when my brain is up for it.

Cheers

gottolovethisweather

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Posted
  • Location: Bangor, Northern Ireland (20m asl, near coast)
  • Weather Preferences: Any weather will do.
  • Location: Bangor, Northern Ireland (20m asl, near coast)

It could be linked to cloud depth.

I mean I always assumed that different days have restrictions on cloud height (cap) and when the cloud reaches its highest point within the restraint it begins to spread out and produce what we know as the Anvil, but on many occasions the distance between the base and the top or Anvil is not sufficient enough to produce the needed buildup of static to create lightning.

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Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

It could be linked to cloud depth.

I mean I always assumed that different days have restrictions on cloud height (cap) and when the cloud reaches its highest point within the restraint it begins to spread out and produce what we know as the Anvil, but on many occasions the distance between the base and the top or Anvil is not sufficient enough to produce the needed buildup of static to create lightning.

Thanks The watcher.

Indeed, that certainly sounds logical enough but I doubt, as in most things meteorological it will be as straight forward as just as you stated.

KInd Regards

gottolovethisweather

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Posted
  • Location: Bangor, Northern Ireland (20m asl, near coast)
  • Weather Preferences: Any weather will do.
  • Location: Bangor, Northern Ireland (20m asl, near coast)

Thanks The watcher.

Indeed, that certainly sounds logical enough but I doubt, as in most things meteorological it will be as straight forward as just as you stated.

KInd Regards

gottolovethisweather

Yes, there is alot more to it than that basic explanation, but it is a base to start from, an understanding to gather more information on.

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  • 3 weeks later...
Posted
  • Location: Camborne
  • Location: Camborne

In this months Weatherwise mag. there is an interesting interview with lightning expert Ron Holle. A small extract from the interview courtesy Weatherwise http://www.weatherwise.org/#.

Where are our biggest gaps in understanding of lightning?

We need datasets very badly in other countries. We don't have a really good idea of how many deaths and injuries there are around the world. I've estimated 24,000 deaths and 10 times as many injuries per year in the world, but I don't know whether that's good within a factor of 10. As for lightning itself, we still have a gap in understanding just how it starts in the cloud-exactly what is the mixture of water, ice particles, and supercooled raindrops-at what temperature, at what updraft speed. We sort of know, but it's not very precise. I'm hoping that with the new dual polarization radar we may be able to answer some of that. We'll know where the hail is in the cloud, and also where some of the small hail and the graupel and those things are.

Then there's a lot of new high speed video that's come out in the last couple of years showing us things we've never seen before. There are lightning features shown in the videos that, well, we don't even know what they are. It's not as simple as we thought.

One of the things I would love to know, and I'm never going to know is this: There are 25 million cloud-to-ground flashes in the United States every year. What do they hit? How many of them hit trees, and how many of them hit buildings? How many hit open land, and how many hit water? There are a lot of unknowns. You take that and the sociological issues, and it keeps me interested when I come into work every day.

I rather like his throwaway line, "it's not as simple as we thought". :o

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Posted
  • Location: Newbury, Berkshire. 107m ASL.
  • Weather Preferences: Summer:sunny, some Thunder,Winter:cold & snowy spells,Other:transitional
  • Location: Newbury, Berkshire. 107m ASL.

Thanks WS.

A very interesting topic of research it seems.

Kind Regards

gottolovethisweather

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