Be Clear on Clouds and their Potential Hazards

Any experienced pilot will tell you that clouds can contain unique hazards, such as updrafts, downdrafts, and turbulence. Here’s an overview of the basic forms of clouds and the dangers they hide, courtesy of the March/April issue of FAA Safety Briefing.

There are three established basic forms of clouds: cirrus, cumulus, and stratus. While there are some similarities between them, each cloud type presents a different set of possible hazards. The better we understand clouds, the better informed we are to handle them.

Cirrus Clouds

Cirrus clouds are high altitude clouds made of ice crystals that are generally found above 20,000 feet above ground level (AGL). Since they form in stable air, they usually don’t pose a risk as far as turbulence or icing. Also, since they only form in instrument flight rules (IFR) airspace, small aircraft pilots and FBOs generally don’t need to be worried about cirrus-related visibility impacts.

Cumulus Clouds

Cumulus clouds, also known as “puffy” or “Florida” clouds, are white, pillowy clouds created by liquid water droplets near the surface. They can vary in height and size depending on atmospheric instability, are detached from each other and do not produce rain.

Pilots shouldn’t be fooled by their cheerful appearance; cumulus clouds can be turbulent, and can limit visibility much more than cirrus clouds. On the up side, since cumulus clouds are detached from each other, your plane should pass through them fairly quickly. Be warned though: cirrus clouds may contain supercooled water droplets that could cause icing, so you may opt to fly around them.

GA pilots should be particularly concerned about cumulonimbus clouds. The addition of the -nimbus suffix to any cloud type means the cloud creates rain. But it’s not just the rain that’s concerning with these gas giants — cumulonimbus clouds are typically very large clouds exceeding 20,000 feet AGL, and in extreme cases approaching 60,000 feet AGL. That means there’s no flying above or around them in most GA aircraft.

And then, there’s the hail. The FAA recommends avoiding them by at least 20 nautical miles because large cumulonimbus clouds can throw hail for miles beyond their physical dimensions.

Stratocumulus Clouds

Like the name suggests, stratocumulus clouds are a combination of stratus and cumulus clouds. One of the most common clouds worldwide, stratocumulus clouds are a good indicator of moisture in the lower levels of the atmosphere. Stratocumulus clouds can be both wide and deep, vertically, which means they can hide embedded thunderstorms, or even terrain such as mountains.

They usually occur between 2,000 and 6,500 feet, have a ragged appearance along their upper surface, but can have a well-defined and flattish base. They tend to form in comparatively shallow layers, sometimes several hundred miles wide.

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