On Saturday, December 14, an incredibly mysterious cloud bubbled out of the atmosphere along British Columbia's west coast, just hours after a departing windstorm.
Its UFO-like shape captivated those who saw it. But, as strange as it looked, the science behind this mesmerizing formation reveals how it came to be.
1. Varying winds with height
Atmospheric winds rapidly increase with height, changing directions as you move upward. This wind shear helped sculpt the cloud into its elongated shape, stretching it vertically into a striking, towering structure.
2. Moisture and lift
The low levels of the atmosphere surrounding the Comox Valley area were rich in moisture. Upper-air soundings from the time revealed strong upward motion (negative omega) in the mid-levels. This organized lift, combined with ample moisture and possible terrain forcing from eastern Vancouver Island, provided the energy needed for the cloud to grow and form its sculpted shape.
3. Turbulent features
Look closely at the cloud's edges, and you'll see sharp curls and undulations, a key signal of atmospheric turbulence. These features are often associated with mountain wave clouds or rotor clouds caused by air interacting with terrain.
High above the surface, a drier layer in the atmosphere set the stage for something extraordinary. As rising air mixed with the dry air aloft, evaporative cooling likely sharpened the cloud's edges and enhanced instability.
Conditional Instability
The atmosphere was conditionally unstable, meaning cooler air aloft fostered vertical cloud growth -- especially when lift was available from the weakening low pressure.
Lighting magic
While science explains the cloud's formation, evening light played a crucial role in its visual appeal and helped it go viral on social media. The low-angle sunlight cast dramatic contrasts, highlighting the cloud's intricate features and giving it an "out-of-this-world" glow.
The deep low that was moving inland added an extra boost. This frontal ascent -- lift caused by the frontal system's motion -- helped the cloud blossom even more dramatically.
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This cloud appears to be a hybrid formation, blending some characteristics of towering cumulus clouds with laminar, wave-like features typically seen in mountain wave clouds.
This convergence of factors -- a mix of orographic lift, wind shear, and lingering ascent from the windstorm -- created a truly one-of-a-kind cloud structure. It's a stunning reminder that even the weirdest, most photogenic clouds can be explained by atmospheric science -- though they'll always retain a bit of magic when captured in the perfect light.