Studying the Clouds: Keys to Predicting the Weather

Head in the clouds? You’re in the right place.

It isn’t too difficult to predict the weather if you’re in familiar territory. Near your home base, the weather today will probably be similar to what it was yesterday. But remove yourself from your familiar territory and the weather will be as foreign as if it were another planet. Studying the clouds is important – understand the movement and formation of the clouds, you’ll need clear signals. Studing the clouds can help you decide whether you’ll be riding high and dry in your Jeep… or figuring out if your snorkel and waterproofing actually work.

Having a strong knowledge of how to figure things out for yourself, like weather or navigation, is critical to being a successful overlander. All the bells and whistles and tech in the world can’t help you if they stop working. Keep your wits about you out there!

The Study of Clouds: A History

On a warm evening in 1802, upstairs from a laboratory at 2 Plough Court in London, 30-year-old Luke Howard, a chemist and amateur meteorologist, rose before the Askesian Society—a jovial group of scientists whose irreverence was only matched by their affinity to inhale laughing gas for amusement. He presented his essay called “On the Modification of Clouds,” where the Latin terms “stratus,” “cirrus,” and “cumulus” were first used. Howard became known as the father of clouds, and although the connection between clouds and the weather had been known for thousands of years, finally, there was a universal naming system and, most importantly, it was in Latin. Today, the plaque on Howard’s house reads: The Namer of Clouds lived and died here.

Modern Meteorology

For modern human beings, checking tomorrow’s weather is as easy as clicking an app on your phone or watching the evening news. But, just try spend any amount of time wheeling on the trail and out of reach of modern methods of communications that we take for granted. Then, you’ll soon discover that the weather can change dramatically in a matter of hours—if not minutes. Sunny one moment on this side of the mountain; gale-force rains just over the horizon. Being prepared for any situation is all about reading the signs that hint at what the future holds. When it comes to weather, keep your head in the clouds.

Essentially, meteorology is the study of the air’s affect on the environment and the various natural elements that affect the air—temperature, humidity, wind, pressure. These elements, since the dawn of civilized man, have exerted a profound influence on the habitability and civilization of our planet. To a professional meteorologist, studying the types of clouds and forms of precipitation are the most important readings they can observe. So it stands to good reason that even a casual observer—especially during an extended overland journey—would gain from knowing the physical process of the atmosphere.

Classification of Clouds

From the ground, clouds can be divided into four main groups based on their structure and location: cirrus, alto, stratus, and cumulus. These basic forms may be present simultaneously, evolve from one form to another, and combine into various permutations, but elevation is a predominate factor in classifying clouds. Cirrus clouds occur only in the upper part of the troposphere, while stratus occur only at the lower levels. However, the tops of cumulus clouds may thrust up to the levels of cirrus territory, while the bases are only a few hundred feet off the ground.

High-Level Clouds

Cirrus

From Latin meaning a curling lock of hair, these are the highest forming clouds in the sky. Their main characteristics are that they consist of fine ice crystals and that they have a fibrous structure and wispy streaks in appearance. Sometimes referred to as “mare’s tails,” they drift rapidly across the sky on high-altitude winds.

As these feathery clouds spread across the sky, it usually indicates that fair weather is upon you. These clouds rarely gather together, but a gradual increase of cirrus cover indicates that a warm front is moving in. Because cirrus clouds are quick moving, use them to find out from which direction. Cirrus clouds indicate a change in the weather, usually within a day.

..educating yourself on the meanings behind the changing cloud structures … will help make any trek more enjoyable.

Cirrostratus

Cirrus (meaning curled hair) and stratus (meaning layered), a cirrostratus is a very thin, high-altitude cloud that uniformly covers the sky in layers like a light gray veil. These clouds will usually give the sky a uniformly milky appearance or sometimes a slightly fibrous one, like a thin tangled web.

When these light, pale veil clouds blanket across the sky, studying these will tell you rain is on its way within a day or so.

Cirrocumulus

These clouds are named from a combination of cirrus (wisps of curled hair) and cumulus, meaning heap. These clouds are a larger collection of layered cirrus clouds forming light heaps, which have been described as resembling white flakes of lamb’s wool or the scales of a fish (specifically a mackerel, for whatever reason) across the sky.

When old folks look up, studying the clouds, and remark, “Mackerel sky, storm is nigh,” they are looking at cirrocumulus clouds. Although a rainstorm usually isn’t “nigh,” it indicates a cold front for most of the country and a hurricane in tropical regions.

Medium-Level Clouds

Altocumulus

Meaning middle-layer heaps, these differ from cirrocumulus in that the bundles of clouds are larger, more defined, and arranged in banks. It will appear as though a fleece blanket of clouds has been pulled across the sky.

Not to be confused with the “mackerel sky” appearance of the cirrocumulus, the altocumulus is at a lower altitude and has larger bundles. Warm, humid, and sticky days will produce altocumulus and thunderstorms will likely be present by the afternoons or evenings.

Altostratus

Meaning middle-altitude layers, altostratus clouds are dense sheets of gray or bluish clouds showing a fibrous structure. Though the sun can be discerned through them, they are darker than cirrostratus and can block out the sun.

Low-Level Clouds

Stratocumulus

The study of these clouds shows they’re formed by air turbulence. This low cloud layer consists of large lumpy masses of a dull grey color. They are often in patterns (like rolls with blue sky in between) and resemble altocumulus, but they are lower.

Rain rarely occurs with these types of clouds, and if the temperature between the day/night’s high and low is only a few degrees, stratocumulus point to dry weather.

Stratus

This is a low, evenly grey layer of fog-like cloud which comes close but doesn’t touch the ground. It produces a fine mist and is greatly affected by local air currents.

Since they cover the entire sky usually in what we’d call “overcast,” the humidity level is up high enough to produce drizzle at most. Normally present in the morning and burning off by afternoon, stratus clouds can start as fog (if they touch the ground).

Large Vertical Clouds

Cumulus

Latin for “heap,” cumulus clouds are high-pile clouds with flat bases and tops in the shape of domes that can resemble tall towers. Often resembling cauliflower in shape, there are two basic types. First, Cumulus humilis (fair-weather cumulus) are flat cumulus clouds. Cumulus congestus, on the other hand, are much greater in size but are usually taller than they are wide. They often develop into cumulonimbus.

Cloud study shows most cumulus are fair-weather clouds. Generally, dry conditions of a fair summer (or hot) day produce them. They only last for a short time, but if they do generate rain, it will be light. However, enough cumulus clouds can grow into a cumulonimbus formation and produce thunderstorms.

Cumulonimbus

These are what we call thunderclouds or shower clouds, great masses of clouds rising like mountains and dominate the sky. They often have an anvil shape at the top and bring thunderstorms, heavy rain, squalls, and hail.

Make no mistake when you study these clouds. They’re enormously tall and can forecast some extreme weather, from heavy rain, snow, thunderstorms to tornadoes and hurricanes. When you see large masses of cumulonimbus on the eastern horizon (the anvil shape points in the direction of travel) prepare yourself for rain or worse.

Being prepared for any situation is all about reading the signs that hint at what the future holds.

Nimbostratus

Dense, shapeless, and ragged, nimbostratus are a low layer of dark clouds that blanket the sky. Often connected to altostratus above, nimbostratus almost always deliver rain. You can readily assure yourself that rain (or snow in cold climates) is coming—and lots of it.

Although it is very wise to check the weather for the area you are going to be driving into, studying the meanings behind the changing cloud structures and temperatures throughout the day will help make any trek more enjoyable. Afterall, the weatherman gets it wrong all the time. Even though it’s fun to get those mud tires working, a rainy weekend on the trails isn’t fun if you aren’t ready for it.

Why Does It Rain? 

It is common to see a cloud exist for a couple of days without releasing any rain, but on other occasions, a heavy downpour will seem like it came out of nowhere. Study shows that water droplets in clouds form via two processes that might lead to rain: ice crystal and capture.

Ice Crystal

When air rises, it cools by expansion and as it cools, relative humidity increases. When the air reaches saturation (of moisture), cloud droplets form.

Capture

As clouds rise high into the sky, they allow some moisture to escape, and as that moisture falls, it collides with other water droplets to create larger droplets in a cloud that is not a rain cloud.

There are a variety of methods that lead to rainfall, but the most common is coalescence, where tiny water droplets fuse with each other to form larger and larger droplets until their weight is greater than the force of air resistance that keeps them aloft.

Depending on temperature and altitude of the cloud, water droplets can be as large as 5mm in diameter when they fall. A large raindrop like this will reach a terminal velocity of around 20 mph when it hits the ground.

Killer Flash Floods

Flash flooding is a major killer; what looks like a little bit of moving water can have a serious undertow that can easily sweep you or your car away. Because most storms occur at night, flash floods are also frequently at night, which makes them more difficult to see.

Tips to follow if caught in a flash flood:

• Do not attempt to drive or walk across a flooded roadway or low water crossing. Nearly half of all flash flood deaths are vehicle related. Moving water 2-feet deep can carry away most cars.
• If your rig becomes caught in high water and stalls, leave it immediately and seek higher ground, if you can do so safely. Rapidly rising water can easily sweep away a vehicle and its occupants.
• When there is an evident threat of a flash flood (e.g., a dry season followed by the first heavy rain), be aware of your location and head to higher ground. If water looks like it has been there before (e.g. dried creek bed, collected drift logs), a flash flood will likely choose the same course again.

Basic Lightning Safety

Lightning occurs in all thunderstorms, and it is also a significant threat to life, as it kills nearly 24,000 around the world each year.

The following lightning safety rules are important:

• Lightning tends to strike the tallest object in an area…make sure it is not you. Remain in your rig or an indoor location whenever possible.
• If you are outside and in a vulnerable position (top of a hill), crouch down to make yourself a poor lightning target. Cover your head with your hands and perch on your toes. Do not lie flat on the ground since you will be more likely to be victim to a severe shock if lightning strikes close to you.

Editor’s note: A version of this story previously appeared in the Tread July/August 2022 issue.