July 14 Chase Report: Close lightning, shelf cloud
Was blessed with a pretty nice storm day here on Friday. Didn't have to drive far, and I saw some good stuff. The Charleston, WV metro area saw three rounds of storms between 4PM and midnight.
For the first intercept, I drove north on I-77 about 15 miles to Pocatalico to meet a potent new cell moving up from the southeast. I wanted to just get inside the core and see some close strikes. I got what I came for. I lost count on how many blasts of thunder less than one second after strikes. One strike's thunder arrived before the return strokes were finished discharging! I even lowered the video cameras to include a lot of the ground and trees because I wanted to be sure I got the whole bolt if something hit less than 100 feet away (chances were very good). The problem with close lightning is that even with 2 cameras, the lightning is happening literally 360 degrees around you, so it is harder to catch them. I did get three very close hits in the frame, though only one of them had multiple return strokes that looked good on video. The other two were 'one-hit wonders' , one with just a ghost channel visible on one frame and the other a ghost/'real' channel hybrid.
Here is the video. I included the strikes that hit out of frame just so you could hear the thunder! I included some still frames later on in this report (scroll down to the end if my verboseness is too annoying).
I have to say, even after seeing tornadoes on the Plains, that right there is what I love the most about storms! I was under a highway overpass here, which limited my sky coverage but kept me dry and safe. I almost got the third video camera out, but the first two pretty much had the whole view covered anyway.
The second line of storms came through at dusk, right on the heels of the first. The most impressive show from this one was the massive, mountain-scraping, stacked-plate shelf cloud that swept over Charleston. I shot a timelapse of this from the overlook at Fort Hill. With temps at 82F and dewpoints at 75F, it didn't take much cool outflow to saturate the hilltop air. As a result, the shelf cloud's base was very low, and it dragged across the tops of the ridges as it turned the evening twilight to near darkness over the city. What a sight!
Here is the timelapse:
The lightning from round 2 was not as impressive, though I did get some more 'lightning bugs with lightning' video after the shelf cloud moved over:
The third and final line of storms rolled in just after midnight. Lightning was not too impressive, but the storm did give me a couple of anvil crawler/CG discharges over the downtown skyline:
As you can hear in the video, I was shooting these by 'reaction' on 35mm with 8 second exposures following. Can't really tell by the shutter clicks if I got enough of the lightning to get the channel exposure right. I was close though - I'll find out when I get the slides back.
Here are some frame grabs from the video cameras:
This first one is a ghost channel from one of the close strikes. This ghost channel was the only frame of video that showed a lightning channel. In Adobe Premiere, I counted exactly two-thirds of a second between flash and thunder, which would be about 700 feet. While the bolt did hit a tree in front of the treeline, it is not quite as close as the ghosting makes it look.
Since a video 'ghost' lightning channel is merely an image of the lightning shifted downward on the screen, the 'real' position of the 'ghost' channel can usually be obtained by shifting it up so that the top of the ghost channel is at the top of the video frame. Here is a quick cut-and-paste of this that better represents where this strike actually hit. Not as close as it initially looked, but still very close:
As you can see, the ghost lightning channel is longer than the portion of the sky in view directly above it, meaning that this bolt did hit on the camera-facing side of the hill. Here is a frame I found from camera #2 showing the true (non-ghost) bolt:
This second frame grab shows a channel that is partly a ghost and partly real. If you look closely at the top of the image, you can see the vertical displacement between the main channel and the matching channel from the stepped leader. The displacement is noticeable, but not extreme as ghost channels go (most ghosts have vertical displacements halfway down the frame or more). Therefore you can see that this bolt struck in front of the treeline in the background, but behind the treeline in the foreground (not in front of the first treeline as the ghosting would suggest).
Here are a few more frames from the first storm:
Some frame grabs from storm #3:
Finally, a few frames from the shelf cloud timelapse from storm #2: