Skyscraper-scraping shelf cloud
Few things compare to capturing a shelf cloud invading the city. The otherworldly-ness of this cloud formation’s texture, shape, and moody light makes for truly unique scenes. Especially when it dwarfs Chicago’s skyline. And their rarity makes them especially satisfying to catch. People have asked me how I catch them, so I tried to answer that question in following post.
This past Sunday (June 30th) I captured the lead-in photo from the 18th Street bridge over Ping Tom Park. Using my Nikon D800 & Nikkor 24-70 f/2.8, the image settings were; 36mm, ISO 320, f/8, 1/640. I used a tripod and a remote release for the sharpest possible photos. While shelf clouds look ominous, the structure itself is benign; though gusty winds and drenching rains usually trail closely behind.
Here’s the most basic description of what’s happening:
Rain cooled air spills out ahead of the storm, and wedges the warm air ahead up into the atmosphere. As that warm, humid air rises, it cools and condenses into droplets that shape the front edge of the cloud – not unlike when you can see your breath on a cold day.
While your camera settings will vary based on local conditions, the hard part is getting into the right position. But predicting which storms will have a photogenic shelf cloud is tricky business. There’s no single thing on radar that’ll definitively render a shelf cloud’s outline. That said, a linear, bowing storm (left), with a sharp color gradient is more likely to produce a shelf than a scattered mix of storm cells (right). An outflow boundary (pink arrows), may also hint at a shelf cloud, but not always. Sometimes the boundary is present on radar without a shelf cloud. Other times the boundary isn’t visible, though the shelf cloud is present.
My other secret? Twitter. Shelf clouds can travel long distances and photographers may be taking and sharing photos of the shelf while it’s still hundreds miles away. And I follow enough meteorologists on Twitter, that if there’s a nice shelf cloud approaching, there’s a good chance I’ll see it before it arrives in Chicago.
Basically, Twitter often times confirms my hunch, and once that happens, I venture out to wait for it. I like to pick a location where I can photograph the storm approaching from behind the skyline for maximum effect. If you’re positioned in such a way that the self cloud rolls over you from behind, you’ll most likely miss out on the cloud’s most dramatic structure. In other words, pick a composition that allows you to point your camera at the approaching system.
Shelf clouds also roll in fast! While it may take a good half hour for the sky to darken and the shelf to become visible, peak ‘shelfage’ may last a few fleeting minutes. Here’s another comparison with timestamps. The feature photo is in the center. In the first frame, the shelf still isn’t close enough to discern its texture or appreciate its size. And in the third photo, the leading edge of the storm has almost eclipsed my position. To me, the middle photo is just right – it’s in the goldilocks zone, so to speak.
While every shelf cloud is unique, and moves at different speeds, you can see just how fast things change. You’re best bet is to get out there before the storm arrives and hope Mother Nature puts on a show.
Happy storm chasing…or waiting!
P.S. Props to Andrew Pritchard // @SkyDrama for answering many of my shelf cloud related questions. And if you want another explanation of how shelf clouds form, check out the first few minutes of Andrew’s recent forecast.