cloud, one formation per page
Twenty-four lessons on what a cloud is: visible water suspended in the sky, air lifted by sun front or mountain and cooled to its dew point, condensation on salt and dust, the troposphere holding eighty percent of the air, Luke Howard's Latin names of 1803, the ten genera, the high cirrus family and its halo, the alto family, the low family of sheets and rolls, cumulus the heap and cumulonimbus the anvil-topped tower, species and varieties, rain, snow crystals, hail and downbursts, fog as a cloud at the ground, contrails, lenticular lenses, mammatus pouches, nacreous pearl light, reading the sky ahead of a front, clouds on other worlds, when the sky lies, and teaching a friend to name the sky in one sitting.
One formation, one honest page. That's a lesson.
cloud, one formation per page
Twenty-four lessons on what a cloud is: visible water suspended in the sky, air lifted by sun front or mountain and cooled to its dew point, condensation on salt and dust, the troposphere holding eighty percent of the air, Luke Howard's Latin names of 1803, the ten genera, the high cirrus family and its halo, the alto family, the low family of sheets and rolls, cumulus the heap and cumulonimbus the anvil-topped tower, species and varieties, rain, snow crystals, hail and downbursts, fog as a cloud at the ground, contrails, lenticular lenses, mammatus pouches, nacreous pearl light, reading the sky ahead of a front, clouds on other worlds, when the sky lies, and teaching a friend to name the sky in one sitting.
Set in Space Grotesk, Inter and JetBrains Mono (SIL Open Font License).
Every fact in this book is as the primary source states it, fetched and read during this build: the Wikipedia articles Cloud, Condensation, Troposphere, Luke Howard (meteorologist), Cumulus cloud, Cumulonimbus cloud, Stratus cloud, Cirrus cloud, Cirrocumulus cloud, Cirrostratus cloud, Altocumulus cloud, Altostratus cloud, Nimbostratus cloud, Stratocumulus cloud, Nimbus cloud, Precipitation, Fog, Contrail, Lenticular cloud, Mammatus cloud, Polar stratospheric cloud and International Cloud Atlas, all cached at build time and cited in each lesson's source line.
Honest redirects, disclosed: Nacreous cloud and Nimbus cloud are redirect pages, so their facts come from Polar stratospheric cloud and Nimbostratus cloud, and Luke Howard and Cirrus are disambiguation pages, read at Luke Howard (meteorologist) and Cirrus cloud. No cached article gives a forecast ritual, a sky-reading habit or a teaching order, so those rituals are this book's plan. An honest no-demo book: no sky was photographed or filmed by this machine. Not affiliated with or endorsed by Wikipedia or the Wikimedia Foundation. No facts from Reddit, forums, vendor blogs or search engines.
Your purchase is for personal use only. You do not have redistribution rights: please do not share, resell, or republish this book or its pages.
© 2026 Steve Hodgkiss. All rights reserved. Personal use only; no redistribution rights.
Edition 1.0 · stevehodgkiss.net
Contents
Per the Wikipedia article Cloud, in meteorology a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, ice crystals, or other particles, suspended in the atmosphere of a planetary body or similar space; water, primarily, comprises the droplets and crystals; on Earth clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture, usually in the form of water vapor, from an adjacent source to raise the dew point to the ambient temperature; and per the same article the origin of the term cloud is the Old English clud or clod, meaning a hill or a mass of stone, the word coming to be used as a metaphor for rain clouds around the beginning of the 13th century because of the similarity in appearance between a mass of rock and cumulus heap cloud.
What a cloud is
A cloud is a visible mass of miniature droplets, ice crystals or particles, suspended in the air. It is an aerosol, and water, primarily, comprises it.
It begins one of two ways: air cooled to its dew point, or air that gains enough moisture to lift the dew point to the temperature it already has.
The word is older than the science. Old English clud meant a hill or a mass of stone, a metaphor for rain clouds since around the 13th century, because a cumulus heap looks like rock.
Say out loud what a cloud is this week, before you look anything up: visible water, suspended.
Per the Wikipedia article Cloud, high clouds form at altitudes of 10,000 to 25,000 ft in the polar regions, 16,500 to 40,000 ft in the temperate regions, and 20,000 to 60,000 ft in the tropics; all cirriform clouds are classified as high, thus constituting a single genus cirrus, while stratocumuliform and stratiform clouds in the high altitude range carry the prefix cirro-, yielding the genus names cirrocumulus and cirrostratus; cirrus are mostly fibrous wisps of delicate white ice-crystal clouds that often form along a high altitude jetstream and at the very leading edge of a frontal or low-pressure disturbance, and this genus does not produce precipitation; cirrostratus is a thin nonconvective stratiform ice-crystal veil that typically gives rise to halos caused by refraction of the Sun's rays; and per the Wikipedia article Cirrus cloud, cirrus comes in five visually distinct species, among them uncinus, commonly called mare's tails.
The high family
The high floor is ice country: cirrus wisps, cirrocumulus ripples, cirrostratus veil. In the temperate zone that means 16,500 to 40,000 ft.
All three are made of ice crystals. A halo around the Sun or Moon is cirrostratus refracting light.
Cirrus often rides the jetstream, at a disturbance's leading edge, and makes no rain. Watch for uncinus, the mare's tails.
Test one high cloud this week: a halo means cirrostratus, hooks mean cirrus uncinus.
Per the Wikipedia article Cumulonimbus cloud, cumulonimbus, from cumulus heap and nimbus rain cloud, is a dense towering vertical cloud typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents, capable of producing lightning and other dangerous severe weather such as tornadoes, hazardous winds and large hailstones; normal peaks usually reach to as much as 12,000 m, with unusually high ones typically topping out around 20,000 m; well-developed cumulonimbus clouds are characterized by a flat anvil-shaped top caused by wind shear or inversion at the equilibrium level near the tropopause; cumulonimbus typically go through three stages, the developing stage, the mature stage and the dissipation stage; and per the same article the average cumulonimbus cloud weighs 500,000 kilograms.
Cumulonimbus
The tower: cumulus heap plus nimbus rain. It builds on powerful buoyant currents, normally to 12,000 m, unusually 20,000.
Near the tropopause the rise stops and the top spreads into a flat anvil. It lives in three stages: developing, mature, dissipating.
The red letters: lightning, tornadoes, large hail, hazardous winds. An average one weighs 500,000 kg. Admire it from indoors.
Spot one anvil from a safe distance this week and name its stage, from indoors, never under it.
Per the Wikipedia article Fog, fog is a visible aerosol consisting of tiny water droplets or ice crystals held in the air near the Earth's surface, and by definition fog reduces visibility to less than 1 km, whereas mist causes lesser impairment of visibility; radiation fog is formed by the cooling of Earth's surface and lower atmosphere after sunset in clear and calm conditions, when humid air underneath an inversion layer reaches the dew point; advection fog occurs when moist air passes over a cool surface by advection and is cooled, most common at sea when moist air encounters cooler waters, such as along the California coast; and per the Wikipedia article Cloud, when a very low stratus cloud subsides to surface level it is given the common name fog if the prevailing surface visibility is less than 1 km.
Fog
Fog is a cloud with its base on the ground, and the definition is a number: visibility under 1 km. More than that, and it is only mist.
The two recipes: radiation fog, ground cooling after sunset under clear calm air, and advection fog, moist sea air over cooler water, California's coast.
The family tie runs both ways: stratus sinking to the ground becomes fog. Same droplets, lower address.
Walk one fog this week and name its recipe out loud: night cooling, or sea air over cold water.
Per the Wikipedia article Mammatus cloud, mammatus, also called mama, meaning mammary cloud, is a cellular pattern of pouches hanging underneath the base of a cloud, typically a cumulonimbus raincloud; according to the World Meteorological Organization's International Cloud Atlas, mamma is a cloud supplementary feature rather than a genus, species or variety of cloud; the distinct lumpy undersides form as cold air sinks, creating pockets that contrast with the rising puffs of clouds caused by the convection of warm air; these formations were first described in 1894 by William Clement Ley; individual mammatus lobes average 1 to 3 km in diameter, a lobe can last an average of 10 minutes, and a whole cluster of mamma can range from 15 minutes to a few hours; and mammatus are most often associated with anvil clouds and also severe thunderstorms, usually appearing around, before, or even after severe weather.
Mammatus
Mammatus is a supplementary feature, not a genus: pouches hanging under a base, most often a cumulonimbus anvil.
The mechanism is a downdraft: cold air sinks in pockets against the warm updrafts. First described in 1894, by William Clement Ley.
Scale and tempo: lobes 1 to 3 km across, each lasting about 10 minutes, clusters from 15 minutes to hours. Often near severe weather.
If pouches hang overhead this week, enjoy them from shelter and time one lobe with a watch.
This book's plan for teaching a friend in one sitting, stated honestly: the teaching order on this page is this book's plan; the sourced parts it rests on are, per the Wikipedia article Cloud, that clouds form when air is cooled to its dew point and water vapor condenses on cloud condensation nuclei such as salt or dust particles, that the modern system divides clouds into five physical forms cross-classified by altitude levels to derive ten basic genera, most of which can be subdivided into species and varieties, and per the Wikipedia article Luke Howard (meteorologist), that Luke Howard named the three principal categories cumulus, stratus and cirrus in an essay published in 1803, applying Linnaean principles to phenomena as short-lived as clouds.
Teaching a friend
This book's plan, one sitting, four sentences: the recipe, the roots, the levels, the address.
Start with the recipe: air cooled to its dew point, vapor condensing on salt or dust. Then the roots: heap, layer, curl, rain, Latin since 1803.
Then the ladder: five forms, three levels, ten genera, and the address down to species and variety. One sky, one friend, one hour.
Take one friend from curious to naming three genera this week in a single sitting.