Title text: The rarest of all clouds is the altocumulenticulostratonimbulocirruslenticulomammanoctilucent cloud, caused by an interaction between warm moist air, cool dry air, cold slippery air, cursed air, and a cloud of nanobots.
This comic follows the naming of clouds. As with other lists (like in 2022: Sports Champions), it starts off as normal but then gets more unusual until it is unrealistic.
- The first panel shows a cumulus cloud, from the Latin for "heap". These are common clouds and are relatively small. Cumulus clouds form when warm (and thus rising) moist air condenses when it hits the dew point, the temperature at which relative humidity hits 100%. Cumulus clouds with sharp, defined borders are still growing. When they stop growing (because the rising moist air is exhausted), they get fuzzy and fluffy, and eventually dissolve.
- The second panel shows a cumulonimbus cloud, from the Latin for "heaping raincloud", with the upper part about the same size as the lower part. Though somewhat like the cumulus cloud, it is more prone to causing rain and lightning. Cumulonimbus clouds, like cumulus clouds, grow vertically because of their moist warm air, but they have enough energy to reach the top of the troposphere, giving them the distinctive anvil shape shown in the comic and their tendency to produce nasty weather.
- The third panel shows an even bigger cloud and names it cumulonimbulonimbus (Latin for "heaping rainy raincloud"). Here the scientific fact ends and the humor begins. The cloud has the upper part about twice as large as the lower part. The humor here comes from building up an even bigger name by adding another "nimbus" element for the cloud as its size increases, suggesting that its growth as compared to the second cloud shown has made it even more "rainy".
nimbulo nimbulo cumulo nimbus
- The fourth panel shows an absurdly large cloud with three major layers and gives it the name cumulonimbulonimbulocumulonimbus (Latin for "heaping rainy rainy heaping raincloud"). This is a combination of the third and second cloud names in this comic, and indeed the fourth cloud looks a lot like the second one emerging out of the top of the third. This cloud may look like a super soaker, ready to spray water on everyone, or perhaps a faucet ready to open and pour water down.
cumu lenticulo strato nimbulo cirrus lenticulo mamma noctilucent
- The title text takes this comic to its logical extreme by naming a new cloud that has the longest name of them all and is also supposedly the rarest. Its name can be translated as "mid-altitude, heaped, lense-shaped, layered, grey, rainy, wispy, breast-like and lit at night". It mentions a common joke in weather communities, making fun of the common trope that thunderstorms form when "warm moist air" meets "cold dry air," an extreme oversimplification. A complicated cloud needs complicated processes, so Randall adds in "cold slippery air," then cursed air and nanobots, which makes the cloud impossible since neither of those exist.
- The name of this cloud is a compound of the following cloud names:
- altocumulus: "heap up high"; these clouds are mid-altitude white patches.
- lenticular cloud, often shaped like a flying saucer.
- stratus: a layered cloud, effectively above-ground fog.
- nimbus: a grey cloud producing continuous rain.
- cirrus: a cloud that looks like thin, wispy strands.
- mammatus: a breast-like cloud (some thunderstorm clouds form breast-like extrusions, which signify sinking air)
- noctilucent: a cloud-like structure formed from ice crystals, often formed after volcano eruptions and other cataclysmic events and illuminated by a just-set sun.
The International Cloud Atlas defines the cloud types that are recognized by the WMO, the World Meteorological Organization. It was first published in 1896. Similarly, IUPAC publishes a manual that allows chemists to name chemical compounds in a consistent manner. The Altocumulenticulostratonimbulocirruslenticulomammanoctilucent may thus be a pun on IUPAC, which (theoretically) offers a unique name for each possible strand of DNA and other complex molecules. Therefore, Randall might have seen a unique cloud that has never been observed before, but yet, thanks to IUPAC-like cloud naming rules, he came up with a "valid" name for his observation.
- [Drawing of a small cloud with with a label beneath:]
- [Drawing of a medium sized tall hourglass shaped cloud with a label beneath:]
- [Drawing of a large cloud, larger at the top than at the bottom, with a label beneath:]
- [Drawing of a huge and very complicated cloud in three layers, with a label beneath:]
- On xkcd, this comic replaced a preceding "disappearing comic", which temporarily was assigned the sequence number 2185, as it followed the Friday comic 2184: Unpopular Opinions already on Sunday. But that was just to prevent the trouble a not numbered comic was having on the xkcd site. It was designed to disappear completely and leave no trace in xkcd's history or archives when this comic was released. The original comic does also no longer appear in explain xkcd's comic navigation either, and is hence linked here: Disappearing Sunday Update.
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