Wall Cloud, Scud or ?

[Scott Nelson]

Hope this dark picture does my question justice: A slow moving thunderstorm rolled into my area just before sunset this past weekend. Storm had a LOT of rotation as did this lowering from it. Problem, the storm itself didn't appear to have a lot of height to it at all. Thus I'm kind of confussed by what chugged by. Doesn't a thunderstorm need to have a minimal altitude to generate a Wall from it? And a scud is seperate from a storm but doesn't rotate? What was this?

 

[Chris Hayes]

That deffinately appears as if it's a ragged wall cloud. No, a storm doesnt need to be a certain height to produce a wall cloud or tornado. Jon Davies took this picture and is a fine example of a low top supercell with an attendant tornado. http://members.cox.net/jondavies1/tornado_fcsting/tor_minisprcll.jpg

 

[Wes Carter]

I agree, it does look like a wall cloud. It might just be my monitor, but it looks like there is a slight green tint to the right which would be a sign of hail and a pretty strong updraft. I would have kept my eye on this to see how it developed.

 

[Keith Mullen]

That is

That is pretty amazing IMO to see a torn that is that well formed from a cell that is that low-topped. What a catch that is!

Your pic looks like a wall cloud to me. It's not just the monitor, there's def green tint in there. If you saw easily visible rotation with it as well... then I guess you have your answer.

Still waiting for that rogue cell to swing past my place. Pretty dry year so far here in the South Sound.

Keith

 

[Mike Hollingshead]

I don't know that I'd call it a wall cloud. I think a wall cloud should be more than just any lowered cloud under any base. Should be more of a blocky cloud under a rain free base with any extention pointing down and towards the core, not away. I always thought of wall clouds as being a sort of special deal and not terribly common. That however doesn't look like such a thing. But maybe I'm too picky.

 

[David Wolfson]

Uh, what direction is the picture taken? If before sunset then the lighting sure looks like you're facing south, more or less -- and the feature looks elongated. In that case without a higher resolution picture and more information, I'd guess you're looking at a shelf cloud with rising scud. FWIW.

 

[Rick Schmidt]

The attendant cloud base looks elevated,(or high based), to me. I would vote for something other than a wall cloud, like a small shelf, or just a ragged base.

 

[Billy Griffin]

I'm thinking it's a shelf cloud, formed by the outflow of the rainfall (rain-cooled air) apparent in the precip core behind the lowering.

 

[Skip Talbot]

Some of you have declared this a shelf cloud or a wall cloud without much explanation. What evidence do you have? Frankly, I don't think such a judgement can be made from this picture. The sliver of storm we see from this small image, does not provide enough of a grasp as to what is happening here. I don't see any clearly defined structure here. This is not the photographer's fault, but the storm itself looks very sloppy and disorganized.

If I were really reaching, I would say the brighter area on the left might be an RFD clear slot that is causing the base to bow out in a horeshoe shape. It cloud just as well be a gap between two separate, small cells with more light filtering through it.

The color is not much of an indicator either. The green hues may or may not be from the type of precip falling. It could just be the way the light is filtering through the clouds at this hour. There also looks like there is a lot of rain falling through the base and through this lowering. While, this doesn't mean its not a wall cloud, it further shows the disorganized structure of this storm.

One of the things I look for when separating wall clouds from shelf clouds, is what direction it is pointing. Wall clouds point towards the precip core. Either they flare out in that direction, or have a tail cloud or beaver tail feeding off of the core. A shelf cloud points away from the precip core. I can't out any sort of pointing in this image, and thus I don't think I could go either way. I would just call this a lowering.

 

[Jason McKittrick]

View attachment 2882

Hope this dark picture does my question justice: A slow moving thunderstorm rolled into my area just before sunset this past weekend. Storm had a LOT of rotation as did this lowering from it. Problem, the storm itself didn't appear to have a lot of height to it at all. Thus I'm kind of confused by what chugged by. Doesn't a thunderstorm need to have a minimal altitude to generate a Wall from it? And a scud is separate from a storm but doesn't rotate? What was this?

Which direction are you looking? To answer a couple of your question about all you need to get a wall cloud is a tilted updraft. A wall cloud is formed when the strongest part of the updraft of a thunderstorm ingests rain cooled air from the core. Not all wall clouds rotate, they just show depict the strongest part of the updraft. From the picture it looks like a wall cloud since it appears to be conected however it is tilted in the wrong direction since the precipitation core looks to be on the right and the cloud in question slopes to the left. If this is the case that would suggest that it maybe the early stages of a developing shelf cloud or such.

 

[Scott Nelson]

Glad this thread caught on a bit because it really baffled me. Picture was taken looking South West (Basically west.) When I see scud clouds they normally seperate and travel a bit below a cloud base. This feature appreared to be rotating with the low topped storm albeit at a FASTER speed. Moments after this image was taken we got a good soaken but no hail. Only a mile away, they received little if any precip. Not sure if this will help with the updraft issues and green tinge questions.

As you can see from my area (central MA) we have a LOT of trees. Really a tough location for chasing and long term observation. Things kind of happen on top of you with little warning unless your glued to the radar. Even then... it's hard to get a good view. This adds to my storm ignorance so I'm thankful to have your help in matters such as this.

 

[David Wolfson]

Scott you make me a little bit homesick (grew up on the South Shore) with Big Blue visible out the west windizz. Annnnyway....

As I suspected, the feature was apparently moving right-to-left tracking just south of you. It's not too unusual IMO to see some low level (below cloud to cloud-base) rotation and scud with the updraft dynamics I think was going on. Whether this feature was a wall cloud depends on how broadly you take the definition of wall cloud.

The sort of Wall Cloud I think you have in mind has some enhanced characteristics which I didn't fully appreciate until I saw enough of the Real Thing. The most notable one for me is that they are visibly the extension below cloud base of dynamics going on within the storm. And usually this will be quite visible with more severe storms that take over the surrounding environment to a greater extent.

Also, the slow-moving, rotating severe storm you can see on the Plains is pretty darn rare in New England. Low-top or high-top, square-cut or pear-shape, they move with an energy and purpose. I'd hazard that the reason is the Plains plodder benefits from a strong mesoscale storm-relative inflow, e.g. low-level jet. You don't often get that; and the severe storms perpetuate by getting most of their storm-relative inflow from their down-shear movement. In other words, "slow-moving" isn't a characteristic I would associate with a New England storm that produces a Wall Cloud. FWIW, from a non-professional enthusiast.

 

[Eian Greene]

As for the O.P.'s photo, I would have kept watch on it for a few minutes. Was it rotating on a broad scale, was it violently moving up or down? If it was, good chance of a wall-cloud in my opinion. Otherwise, it might have been some scud in the area.
I've seen some low-topped stuff out in Tennessee before, interesting to see it off on the horizon - with the tops of the storms lower than normal - with them being SVR-warned several counties away. By the time they arrived in Middle TN, these storms would have weakened to be merely just rain showers.

 

[Steven Williams]

Yes, I agree the photo doesn't tell us much about the storm other than what you see in the sky on any showery day.

 

[Martin North]

My 'take' on a Wall Cloud is the Mike H version. But that's just me.

However, I've seen plenty other udraft related anomalies in my time which I would have to loosely tag as such.