Storm/Cloud Features

Oct 10, 2004
Madison, WI
These are some images from my "backyard chase" on May 23, 2004. I have seen the "storm spotter's guide" images and all, but I have little experience identifying supercell features in the field. Could a more experienced chaser help me identify what I was looking at here?

Note: If the links don't work (they might take you to the AngelTowns homepage, as it is finiky about remote linking), just copy and paste the URL into your browser's address line and hit "go".

Here I am looking roughly southwest as the storm approaches me. I am mainly interested in the feature at left. Is it a flanking line or some kind of inflow band?

This ragged, roughly cone-shaped lowering made my heart skip a few beats, but it did not appear to be rotating, altough it did persist for quite some time. A spotter had reported a funnel cloud with the storm earlier, although it still only had a severe thunderstorm warning on it.

This is looking east at the backside of the storm after it passed.

This is before the storm developed, again looking roughly southwest as towering cumlus punches up through the cap. I am curious about the sort of pileus-cloud feature on top of the cumulus congestus cloud and what its presence might mean.

As this storm moved overhead I recieved 3/4" diameter hail. It would later produce 1.5" diameter hail and a brief (1 minute) F0 tornado touchdown.
Looks like a flanking line to me, but you really can't see much of it. I make this presumption based on your information, as far as angle and direction.

BTW, the link you provided just goes to the angeltowns base website, I had manually type in the URL in my browser window to get to your image.

EDIT: I only viewed the top image
Shane-yes, as I said, AngelTowns is finiky about remote linking, and you might have to copy and paste (or manually type) the URL to get to the image. Sometimes the links work, sometimes they don't.

Chris-The lowering in image "D" is located roughly in the center of the updraft base. In image letter "C", you can see a silo in the distance. That is roughly where the lowering developed. It persisted for at least 10 minutes, changing shape several times, getting smaller and larger, but never really dissipating. It never appeared to rotate while I was watching it. Shortly after shooting the video from which those stills were grabbed, I went inside my house as the storm's precip was getting too close for comfort.

At around the time image "G" (of the back of the storm) was taken, the storm had just a tornado warning put on it. I recall that it had a very pronounced hook on radar plus a >50 dbz core and was clearly supercellular. A tornado may actually have been on the ground around this time, as according to NWS-MKX Storm Data for May 2004, a tornado tracked from 3.3 miles ESE of Stoughton, WI (or about 1 1/2 miles southeast of my house) to near Albion, WI. It was on the ground for 1 minute and hit nothing so was rated F0. I was looking in this direction, but never saw any rotation. Too many hills and trees.

In image"A" (the last one I posted, but the earliest chronologically), the pileus cloud I am interested in is at the top of the central cumulus congestus cloud, it looks kind of like a "cap" on top of what appears to be an updraft.

Thank you both for your help
Yes, I suppose I was wrong in calling it a "pileus cloud". I guess the term just seemed approprate because it looks like a cap on top of the expanding cloud, and pileus means "cap cloud".

I'll review my video from that day and see if I can find any other useful images to grab.
Ok, I grabbed some more images of that storm from my video:

These were looking southwest as the storm approached me.

These are some of the changes in shape that lowering went through.

These are looking southeast after the storm passed. I could see no rotation, but this would have been looking in the right general direction +/- 10 minutes either side of the occurence of the confirmed tornado.
The captures with the scud underneath the base... that appears to be an updraft region... typically, scud will rise up into the base because of the updrafts. Some of the others look like a flanking line or some outflow region. Not really a whole lot going on from what I can tell in the captures.
Originally posted by Chris Rozoff
Just curious, what are you referring to, as not a lot going on?Chris

The flanking lines, scud rising. It's kinda hard to tell from the pictures though, as I was not there in person. But rising scud is kinda cool LOL.
It could have been a developing wall cloud, it almost looks like it had that opportunity. But I've been on storms were scud would rise up like nuts and no wall cloud ever came of it.

Speaking of rising scud, I saw on one of my chases something really crazy... we pulled off the road onto the side, seeing this crazy rising scud, thinking it might have been a possible tornado, but it wasn't. What was weird was it was rising off from the trees near us! This storm seemed to be sucking off moisture from the trees, I've never seen anything like that before. It must have been one powerful updraft. I have coined it "tree scud" :)

Andy, that pileus cloud you are asking about is just a cap cloud. It doesn't really represent anything significant, just think of a high mountain and those "ufo" clouds form on top of it. Same idea applies to pileus clouds. In your picture though, it doesn't show a pileus cloud... I am not sure if there is a name for it, but it does look like that tower is overshooting it's top and starting to glaciate/anvil out.