Storm Australian Severe Weather Forum

Severe Weather Discussion => General Weather - all topics not current severe weather. => Topic started by: Mike on 22 May 2007, 09:33:33 AM

Title: Shelf clouds - do they indicate severe storms ?
Post by: Mike on 22 May 2007, 09:33:33 AM

Just a very brief quick post to ask a few questions:

The formation of shelf clouds - are they precursors or characteristics to/of severe thunderstorms? 

Are these types of storms considered to due to what type of indices or conditions?

( I should know this by now but i just want to get it confirmed!!!)

Mike

Title: RE: Shelf clouds - do they indicate severe storms ?
Post by: Robert1984 on 22 May 2007, 03:05:51 PM

According to my storm spotters book a shelf cloud/clouds are one of the characteristics and signs of a severe thunderstorm 

Title: Re: Shelf clouds - do they indicate severe storms ?
Post by: Mike on 23 May 2007, 07:30:49 AM

Thank you all for those replies.  It's something that I really should have read up on considering i've been studying everything else but!

I asked because some of the shelf clouds I have encountered contained only 'moderate' winds with little or no lightning strikes - which puzzled me somewhat considering it's size an period maturing.  Even no rain to speak of as it overran itself and lost its appearance - possibly cold pooling an answer.

Mike

Title: Re: Shelf clouds - do they indicate severe storms ?
Post by: David C on 23 May 2007, 08:33:46 AM

Shelf clouds really do not indicate storm severity at all, but rather are simply visible evidence of a storm's outflow. Indeed, up in Darwin or even south-east Queensland, shelf clouds seems to be as common as cockroaches given the very humid atmosphere.

That said, if you see a storm that has a smooth wedge-shaped shelf cloud that angles up into the storm's base, that to me suggests there is some substantial inflow happening above the outflow and, whether by 'force-feeding' or storm-scale processes, such a storm is more likely to be severe. Furthemore, if you can see a semi-circular shelf cloud or actually see evidence or a broadscale organised rotation, as well as simply outflow 'churning' and turbulence, then such a storm is quite likely a supercell and hence almost certainly severe.

Might be some examples of what I am talking about somewhere on the site here.

Title: Re: Shelf clouds - do they indicate severe storms ?
Post by: Jimmy Deguara on 23 May 2007, 05:42:23 PM

Hi David,

The best Australian examples I can think of for deep inflow and severity related to shelf clouds are:

(http://www.australiasevereweather.com/photography/photos/1989/1211mb01.jpg)

(http://www.australiasevereweather.com/photography/photos/2007/0102jd80.jpg)

Regards,

Jimmy Deguara

Title: Re: Shelf clouds - do they indicate severe storms ?
Post by: Mike on 24 May 2007, 07:01:37 AM

Here's the bugger i was photographing and perhaps you can give comments.  If they don't make it they may be too large file wise and i'll have someone else post them for me.  (thanks MB!)

mike