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#11833 - 04/01/2003 15:53 Green clouds and hail
Robbie Offline
Weather Freak

Registered: 25/12/2002
Posts: 241
Loc: Marcoola, Sunshine Coast
I heard once that if a storm cloud is green, it means there is hail in that cloud - is that true or should I choose my sources more carefully? :p

You guys will probably be getting real sick of me soon, but hey I'm only 17 and learning as much as I can about meteorology to hopefully have a career in it!

Rob

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#11834 - 04/01/2003 16:03 Re: Green clouds and hail
Cloudmaster_dup1 Offline
Weather Nerd

Registered: 15/10/2001
Posts: 5100
Loc: Eastern Suburbs of Sydney, NSW...
Likewise Robert!

I am trying to learn heaps, and then hopefully have a career in Meteorology!

The answer to your question is YES. When you see the green tinge, this is a sign of hail present in a Cumulonimbus (Cb) cloud.

I'm sure Craig or Matt can give us the reason why !

Cloudmaster :wave:

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#11835 - 04/01/2003 16:04 Re: Green clouds and hail
Ben Offline
Meteorological Motor Mouth

Registered: 11/10/2002
Posts: 5308
Loc: Tweed Coast
everyones already sick of me since im only learning too wink i heard that theory too. LAst hail i got here was september 1st laugh this storm season has been cruddy and worse. Otherwise Dec 3rd 2001. The cloud was pretty much dark as anything. It brough hail with it i say no green cloud. I think its just the reflection of the sun on the cloud?

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#11836 - 04/01/2003 16:21 Re: Green clouds and hail
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
I have issues with the assumption that seening the green tinge means you will get hail. Numerous times I have seen the green tinge reported, closely followed by a comment along the lines of 'but no hail where I was'. It makes me think that hail is possible, but not a definite outcome when one sees this green tinge. More likely, there is the chance of heavy precipitation when the green tinge is seen - whether it is heavy rain, hail or even snow.

As for what causes it, I think it is related to the way in which light travels through the water (whether it is liquid or ice doesn't matter) in the cloud. Rather like one needs the sun in a certain position in the sky to see a rainbow, the cloud needs to be between the observer and the sun to see the green tinge.

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#11837 - 04/01/2003 16:39 Re: Green clouds and hail
Dave Ellem Offline
Member

Registered: 01/09/2001
Posts: 1408
Loc: Wollongbar, NSW Northern River...
This is something I find really interesting. I certainly thought that green clouds were a sure sign of hail until recently. The last two severe storms that have come through our area have had definite green tinges to them, particularly the 24th of Decemeber:



The green tinge is quite obvious, and I had never seen such a green storm before!! Michael Bath and I were expecting to get hammered by hail, but we only heard about 3 small 'pings' from tiny hail, and there were no reports of hail elsewhere. As with the storm on the 10th of December (the squall line) it's menacing green appearance didn't produce any hail.

(not the best example, but the green tinge can be made out behind the red dirt).

On the other hand, the Casino HP Supercell produced a fair amount giant hail and the green tinge was no where near as obvious as the storm on the 24th of December:



It's my belief that scientists are still not 100% sure about the reasons behind the green tinge phenomenon, but there is still certainly a strong link between green clouds and hail. But these last few severe storms in my area just go to show that green clouds do not necessarily mean hail and vice versa!

Some further discussion from the experts would be great here!!!

Dave

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#11838 - 04/01/2003 16:41 Re: Green clouds and hail
Cloudmaster_dup1 Offline
Weather Nerd

Registered: 15/10/2001
Posts: 5100
Loc: Eastern Suburbs of Sydney, NSW...
Craig,

Would this green tinge phenomenon be linked to the aurora phenomenon? smile

Cloudmaster :cheers:

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#11839 - 04/01/2003 16:57 Re: Green clouds and hail
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
No. Aurorae are caused by high energy particles entering the upper atmosphere, colliding with molecules and creating the sheets of light high in the atmosphere. The 'green tinge' is related to the refractive/reflective properties of water in liquid and solid form.

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#11840 - 04/01/2003 17:02 Re: Green clouds and hail
Cloudmaster_dup1 Offline
Weather Nerd

Registered: 15/10/2001
Posts: 5100
Loc: Eastern Suburbs of Sydney, NSW...
OK, cheers Craig! laugh

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#11841 - 04/01/2003 17:25 Re: Green clouds and hail
astrogen Offline
Weatherzone Addict

Registered: 19/10/2002
Posts: 1987
Loc: Brisbane
this is a picture of the gin gin (qld) cell that hit boxing day. (and a tornado was reported too, not far away)
this cell produced some nice pea sized hail.
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#11842 - 05/01/2003 00:05 Re: Green clouds and hail
Oxymoron Offline
Member

Registered: 07/11/2002
Posts: 429
Loc: Marrickville, 10kms SW of Sydn...
From my observations, I have noticed that although an approaching cloud may appear to be green, does not necessarily imply hail. I have witnessed a MAG guster (mean and green) approach and it was very green! I thought I was in for it, but alas, not a single hailstone, nor was there anywhere at all. My theory is that what I saw to be a deep green thundercloud may have been grey or blue to someone standing somewhere else, at a different angle to the oncoming storm. It all depends on the angle that the sunlight refracts through the water in the cloud.

Therefore a green cloud does not mean hail at all. In fact, at sunset you can get red clouds, or blue clouds. Even a low level Sc cloud at sunset (or really at the right angle) can seem green or any other colour. Hailstorms can appear green, black, blue, grey, white, etc...

I think rather than looking at the colour of the cloud to determine hailstones within, observe the rain itself. Flat, thick rain 'blobs' indicate hail. That is the only thing that remains constant in the hailstorms I have witnessed. Just prior to the falling of the hail, the rain becomes sparse and fat, big blobs of it come down. Sometimes it will stop altogether then BANG down comes the hail. Other times it will be mixed in.

I hope this helps.

:cheers: Ben.

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#11843 - 05/01/2003 00:42 Re: Green clouds and hail
Beachy Offline
Member

Registered: 31/05/2002
Posts: 511
Loc: Peninsula
Now I'm curious. Is this similar to the yellow reflection that can occur sometimes before a storm? I've seen this often and it has a very surreal appearance...From memory it's always rather extreme changes that produce this.

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#11844 - 05/01/2003 04:58 Re: Green clouds and hail
Cloudmaster_dup1 Offline
Weather Nerd

Registered: 15/10/2001
Posts: 5100
Loc: Eastern Suburbs of Sydney, NSW...
Good explanation Oxymoron! smile

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#11845 - 05/01/2003 15:33 Re: Green clouds and hail
Jeff Offline
Junior Member

Registered: 01/12/2001
Posts: 259
Loc: Sydney, The Storm Chasing Capi...
I got hammered by a pure hailstorm at Blacktown in the mid 90's where there was nothing but torrential hail and the front of that storm was pure black with a massive dark grey roll cloud.

No green at all.

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#11846 - 05/01/2003 20:25 Re: Green clouds and hail
Oxymoron Offline
Member

Registered: 07/11/2002
Posts: 429
Loc: Marrickville, 10kms SW of Sydn...
I cannot remember a single hailstorm that has been indicated by green clouds. Hailstorms I've seen have been really black or dark blue or occur at night.

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#11847 - 06/01/2003 00:06 Re: Green clouds and hail
bigwilly Offline
Weatherzone Mod and Photog

Registered: 25/09/2002
Posts: 6543
Loc: Junee - just north of the 'Bid...
I think (here we go wink ) that while green may indicate hail, the lack of green does not rule out hail. The clour of the cloud depends on the amount of light that gets through, so if u have the sun trying to penertrate a couple of km's (or more) of heavy moisture laden clouds then all u may see is a lack of light, ie black clouds.

I think as with any cloud, the colour means its there but whether it falls or not is another question, afterall the strength of the updraft does not effect the colour. I'm sure we've all had clouds come over us that are black and i mean BLACK but there was no rain, thats not to say that there was no moisture, its just that it did not fall.

:cheers: BW
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#11848 - 06/01/2003 08:32 Re: Green clouds and hail
Redsky@nite Offline
Weatherzone Addict

Registered: 21/01/2002
Posts: 1457
Loc: Lismore by day /Alstonville by...
The storm that hit us a couple of weeks back that caused $6000+ hail damage to my car was definitely not green but very very black. Even when the sun was no longer on the cloud. Another storm I have seen here in Port was definitely green but bought no hail. I agree that the angle of the sun and the reflection off the water in the clouds causes the colour.
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