Whether you’re heading to the mountains, the beach, or just going to see your family, the weather is always a pressing concern in the winter. It’s not all snow and ice, though; there are some pretty cool weather events you might be able to see on your travels. Here are five beautiful phenomena you should keep an eye out for as you travel around our impressive little world.
1. LENTICULAR CLOUDS
Mountain vistas are often so beautiful that you don’t need clouds to make the gorgeous sights even more stunning. However, the sharp rises and drops in elevation can have a significant impact on the weather nearby, generating some interesting phenomena of their own. One of the most prominent forms of mountain-induced weather conditions is known as a lenticular cloud. See the image above.
Lenticular clouds derive their name from the lens shape these formations take as winds blow over the peak of a mountain. This air cools as it blows up the side of the mountain, eventually reaching its dew point (the temperature at which the air becomes saturated), allowing the water vapor to condense into a cloud as the wind crests the mountain peak. The shape of the cloud follows the path of the wind as the air sinks on the other side of the mountain, which warms up and dries out while it descends toward the ground.
The result is a spectacular formation that can look like a lens obscuring the top of the mountain, or even a smooth, gray cloud that resembles a UFO. Lenticular clouds, while ominous, are completely harmless, and only serve to make a pretty sight even more visually appealing. You’ll most commonly find these clouds near tall mountains like those in the Rockies or Japan’s Mount Fuji.
2. WAVE CLOUDS
A satellite image of wave clouds taken by the GOES East geostationary weather satellite on December 18, 2015. Image credit: NASA/NOAA
A close relative to the lenticular cloud is the wave cloud, which also forms as a result of wind blowing over the ridge of a mountain. When steady, moist winds blow over a mountain range, the terrain can create such a disruption in the flow that the atmospheric wave keeps going for dozens of miles downstream, much like ripples on the surface of a still pond. As the wind crests the ridge in each wave pattern, the moisture will condense to form a long row of clouds.
The resulting ripples of clouds are a sight to see from the ground, the air, and even space, as seen above. These clouds are a common occurrence in the eastern United States on the eastern side of the Appalachian Mountains, as seen above, but they can also occur near any region with jagged terrain. Wave clouds are even possible over flat areas like plains or the ocean as a result of thunderstorms.
3. KELVIN-HELMHOLTZ CLOUDS
If you follow the right pages on social media, your feeds might have recently been flooded with phenomenal pictures of strange cloud formations out over the western United States. The clouds closely resemble the peaks of breaking waves, very similar to the famous Japanese painting The Great Wave off Kanagawa.
While it seems like these should be called “wave clouds” instead, they’re known as Kelvin-Helmholtz clouds, named after two 19th-century physicists who studied the particular area of fluid dynamics that allows these formations to develop. Kelvin-Helmholtz clouds come to life when a deck of clouds develops in an area where there is strong speed shear, or close layers of winds that are going different speeds. If the winds above the clouds are going faster than the winds below, the swiftly-moving air can shear the tops of the clouds into the iconic curl that makes this formation so dramatic.
4. FALLSTREAK HOLES
These formations, common during the cool season, can develop when there’s a thin layer of clouds made up of supercooled water droplets. These droplets, which still exist in liquid form below the freezing point because they lack a nucleus around which ice can develop, can suddenly freeze into ice crystals if they’re disturbed by a foreign substance like the exhaust from a passing airplane. Once disturbed, the newly formed ice crystals will precipitate out of the surrounding cloud deck. The chain reaction that follows allows a hole to develop in the clouds, with a shallow streak of feathery ice crystals falling groundward beneath the hole. Have you ever looked up at a deck of clouds and seen a strange hole in the middle of it that seems to have formed for no apparent reason? Odds are, you’re looking at a fallstreak hole, also known as a hole punch cloud.
Fallstreak holes can be small and isolated, or one can develop so large that it causes the entire deck of clouds to dissipate in a matter of minutes.
5. SUN DOGS
If you’re lucky enough to find yourself in the right place at the right time, you can witness a dazzling atmospheric treat thanks to a thin layer of cirrus clouds and our very own star. If the sun is at the right angle in the sky relative to the clouds, a sun dog can develop, which is an optical phenomenon that reflects both the image of the sun and generates a small but often vivid rainbow in the clouds.
Decks of cirrus clouds consist of ice crystals that can refract incoming sunlight at a 22° angle on either side of the sun, causing observers to see two reflections of the sun. The phenomenon is more pronounced when the sun dips closer to the horizon, and it’s most stunning near the poles, where icy adventurers can experience sun dogs almost as bright and large as the actual sun appears in the sky. For most of us in the mid-latitudes, however, sun dogs are characterized by the distinct wedge-shape rainbow coloring appearing in the clouds on either side of the sun.