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Powerful March Convective Clouds

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martinastro
Martin Mc Kenna
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« on: March 07, 2009, 01:43:49 pm »

On March 4th I seen the best convective clouds I have ever witnessed in early March from N. Ireland. Why the best?, to cut a long story short these cbs and cu towers where huge, solid, and crisp. A line before sunset even had an overshooting top (s). The boiling updraughts where erupting skyward so fast that they looked notably different each sec. I could see this motion on a sequence of images I took of one cu tower when I flicked through the images on the LCD screen, with continuous shots at 240/sec it was amazing to see such explosive updraughts in that time frame. I never seen this in early march before, in fact, it was the caliber of an intense Summer day.

Here's a report with more.

http://www.nightskyhunter.com/Solid%20Spring%20Convection%20-%20March%204th%2009.html



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JohnC
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« Reply #1 on: March 08, 2009, 11:15:31 am »

Now that's what I call brilliant - it's jot just a good  photo of powerful updraught, it's 'an education' in it's own right too... brilliant, brilliant.  Smiley

These Cb's are a lovely sight with the orange of the setting sun on them,  some of my favourite US photos are like this.

You've done a great job here, Martin.
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martinastro
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« Reply #2 on: March 08, 2009, 01:07:38 pm »

Thanks very much John for your comments  Smiley, much appreciated. I was hoping the first photo would be educational for some because I know there are many on here who don't know the main features of a convective system. That white cu/cb was beautiful to watch and so big, so far the convection here today is a very sorry sight in comparison to the above.

I really enjoyed trying to shoot those distant cells at sunset, always a great time for light isn't it. It would have been so nice to have seen some lightning flickering in there!!. Thanks again John, looks like the storm season has already begun!  Smiley
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Roman White
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« Reply #3 on: March 08, 2009, 02:31:16 pm »

Nice colourful shots, Martin!  Smiley
The convective weather here usually starts later - in April-May, but maybe there'll be some t-storms in March (I had one in March 2008)

I have one question to your #1 image: how did you detect the tropopause? Imho it must be much higher...  Huh
(that Cb looks like 3-5km in height to me)
« Last Edit: March 08, 2009, 02:32:56 pm by Roman White » Report Spam   Logged

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martinastro
Martin Mc Kenna
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« Reply #4 on: March 10, 2009, 07:02:53 pm »

Hi Roman, sorry about the delay in getting back to you. The height of the troposphere varies with the season due to the difference in temp. During the Summer the troposphere is much higher hence we get some really huge storm cells, during Winter they are smaller and are sometimes known as low-topped cells. The ceiling of the troposphere is called the tropopause. The top of a cb (cumulonimbus) cell always stops growing when it hits the tropopause, this when you will see the distinctive anvil flattening out along this ceiling. So just by looking at the cb top you can tell where this is to some degree of accuracy. There are different types of cb though, some ,like the one on that annotated image, have such strong updraughts that the top can look solid like a brick or mountain, sometimes they can look like solid towers, these are the cumulonimbus capillatus species. So the line marks the approx position of the tropopause and serves as useful enough for educational purposes. I hope this helps  Smiley
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Roman White
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« Reply #5 on: March 10, 2009, 08:44:17 pm »

I agree with you, Martin, but I can't see any anvils in the first image (?). The grey cloud in the upper part of it looks more like a closer patch of Cu fra. So, imho again, that Cb hasn't reached tropopause at the time of image capture.
The top of a cb (cumulonimbus) cell always stops growing when it hits the tropopause, this when you will see the distinctive anvil flattening out along this ceiling.

Well, I just cannot stay away while other post here images of convective weather...   Roll Eyes

Here are two shots from last May, captured in the countryside not far from Poltava.
...A nice summer day (temperatures +20...+25C) with plenty of Cu, Cb clouds and several T-storms travelling in the neighbourhood...
This Cb was 10...15km away (actually, there was a good t-storm passing by, you can see the darkness below). My rough estimate of cloud's height is 7-8km, maybe higher - it was developing enormously quick. There is no anvil from this cloud, but those Cs clouds were possibly anvils from more distant Cb cells, so the tropopause was certainly above 10km there...


At the same time a similar freak was closer to me (to the right - E), possibly it was smaller than the more distant one. I remember, when we caught a bus several minutes later, it went east - and we appeared just under that cloud... heavy enough rain followed, along with a t-storm. But I guess it was very moderate comparative to the more distant one


« Last Edit: March 10, 2009, 08:48:00 pm by Roman White » Report Spam   Logged

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martinastro
Martin Mc Kenna
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« Reply #6 on: March 10, 2009, 09:37:21 pm »

As I mentioned before, the area marked 'main cb updraught' is the main updraught of the cell. That was so solid it didn't look like an anvil, it's the calvus species (I said capillatus earlier but I was mixed up) of cb. They look more like slabs of concrete or towers instead of the classic anvil. There is no anvil but it's still a cb, I never said the grey cloud was an anvil. The main updraught flattened out at the exact same height (it is already made of ice when the image was taken) so that is the position of the tropopause. The image shows a cb very much in the same way as your nice images show. Here's another example...





These are of a thunderstorm last year, there was no anvil on this storm but instead a bunch of towers, although  glaciation was well developed. It technically becomes a CB when the cell begins to glaciate and becomes inflow and outflow balanced. The cell on the very first image (annotated one) was glaciating and producing hail from it's flanks and below. It was was both inflow and outflow balanced and hence a cb and no longer just a group of updraughts, although admitidly a very joung cb. I watched the tower eventually flatten a little further and become outflow dominant with hail before the updraught finally blew it's top. If it wasn't a cb it would be an updraught only and it clearly isn't that on the image.

Here's info on the Cb calvus species...

http://en.wikipedia.org/wiki/Cumulonimbus_calvus

Those are nice photos you took. I like the 2nd one with the billowing tops of the towers.
« Last Edit: March 10, 2009, 09:39:52 pm by martinastro » Report Spam   Logged



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