Conditions in December are often ideal for fog. Proof of that was three foggy mornings within the past week.
Recently at Lake Louisa State Park near Clermont, I was able to see a rare natural phenomenon called a “fogbow.” It’s created when bright sunlight hits drops of moisture just right as it shines against fog. It is similar to what happens when the sun shines on raindrops causing a colorful rainbow. However, these tiny fog droplets cannot refract enough light to show colors, only white, with a possible blue edge or rim. It’s a pretty amazing sight. A fogbow stretches across the sky like a huge white arch and may only last a matter of minutes.
The fogbow has other names like white rainbow, cloud bow, and ghost rainbow. It is also called rainbow’s cousin.
How do we get fog? It occurs when the air temperature is at or near the dew point. The air then becomes saturated with moisture. The result is all those little droplets hanging in the air. Sometimes it lasts for hours. You can feel the dampness. We expect more fog in the morning, our coldest time of the day. There are good conditions for it in winter. The Earth lets go of its daytime heat. Fall and winter nights are often clear, cool, and still. No wind. Just the right mix for fog to form and linger.
When does the fog disappear? It is gone when the sun warms the air enough to have the droplets evaporate. It happens when the temperature of the air and the dew point get farther and farther apart–at least by around 5 degrees or more. Sometimes it happens so quickly you wonder if the fog was even there at all. And did that fogbow really exist?
