What Was That Cloud Over Cleveland?

Towering cumulonimbus cloud over Cleveland, Ohio on a clear summer evening

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For a few minutes Wednesday evening, Cleveland stopped worrying about the Browns quarterback situation and what to make for dinner. We all just looked up.

A cauliflower-shaped cloud went up like a slow-motion explosion in an otherwise clear sky, and within about ten minutes half the city was asking the same thing: what was that cloud over Cleveland?

For a guy who has been described as having his head in the clouds, I was pretty much powerless here.

So what was that cloud over Cleveland?

Short answer: a thunderstorm being born.

Longer answer: it was almost certainly a towering cumulus cloud growing into a young cumulonimbus. Meteorologists call that in-between stage cumulus congestus. Cumulonimbus is what it graduates into once it becomes a full storm cloud with rain and lightning.

The mechanics are simpler than the vocabulary. Hot, humid air near the ground is lighter than the cooler air sitting above it, so it rises. As it climbs it cools off, the moisture in it condenses into droplets, and you get a cloud. When that air keeps rising hard, the cloud builds straight up instead of spreading out sideways.

That vertical shove is the whole story.

Why it looked like a giant head of cauliflower

Every one of those bumps is a separate column of rising air pushing through the top of the cloud.

They billow, they get sharp-edged, and then a new one bursts through the one next to it. That is why the thing looked like it was growing while you watched it, and why the edges looked crisp instead of soft and smeared. A cloud with hard, well-defined cauliflower edges is a cloud with a lot of energy in it.

Compare that to the flat gray sheet we get in February. Same water, completely different engine.

Why late summer in Northeast Ohio is prime time for this

Two things stack up here.

• Heat and humidity. Late summer air over Cleveland holds a lot of moisture, which is the fuel. More moisture, more cloud, taller tower.
• Lake Erie. The lake breeze pushes inland on hot afternoons and collides with warmer air over land. Air has nowhere to go but up, which is exactly the nudge a cloud like this needs.
• Clear surroundings. With nothing else in the sky, a single tower looks enormous. Same cloud on a cloudy day and nobody grabs their phone.

Should you have been worried? Generally, no. A cloud at this stage is doing what it does most summer evenings. It is worth paying attention when one keeps growing, flattens out at the top into an anvil shape, or starts putting out lightning, and that is when you check the radar instead of the sky.

Cleveland turned into a city of amateur meteorologists

The best part was not the cloud. It was the group chat.

For a solid stretch, everybody with a phone became a storm photographer, and the shots came in from all over Northeast Ohio:

• The Akron RubberDucks game
• Chagrin Falls
• North Ridgeville
• Downtown Cleveland

Four wildly different vantage points, one cloud. Seeing the same thing framed by a ballpark, a waterfall town, a suburban driveway, and the skyline is the kind of thing that makes a region feel small in the best way.

Photo Gallery

Cleveland cloud FAQ

What is a cumulonimbus cloud?A tall, dense cloud that produces thunderstorms. It forms from strong rising air and can reach several miles high, sometimes flattening into an anvil shape at the top.

Why do storm clouds look like cauliflower?Because rising air keeps punching new bubbles through the cloud top. Each bubble is its own updraft, and together they make that lumpy, bright white texture.

Was Wednesday's cloud dangerous?No reports suggested it was. A young cumulonimbus can bring rain, lightning, and gusty wind if it keeps developing, but plenty of them fizzle out before they get there.

How can I tell if a cloud is about to become a storm?Watch the top. If it keeps climbing and the edges stay sharp, it is still growing. If it spreads flat and hazy, it has hit its ceiling and is starting to fall apart.

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