Lake Superior offers some interesting sights during the cold winter months, often due to the fact that the air temperature sinks below that of the water temperature.
One of the more spectacular phenomena is the waterspout, a rotating column of upward moving air over water, made visible by the water it picks up. A tornado over water is also known as a “waterspout,” however, true waterspouts are not tornadoes.
Waterspouts do not necessarily need a strong parent thunderstorm, so most of them lack the strength of tornadoes, but they can still be quite dangerous. “Non-tornadic” and “fair weather” are used to denote waterspouts not associated with the strong rotating updraft of a supercell thunderstorm (the kind that moves across the Great Plains during springtime).
A prime area for fair weather waterspouts is the Florida Keys, where hundreds occur every year. They generally remain stationary, but can move ashore, where they behave like a typical landspout.
Summer and autumn are the most common time for waterspout formation on the Great Lakes, but they can strike anytime if conditions are right.
Waterspouts have five phases: First is the “dark spot on the water” phase, a circular light-colored disk on the surface of the water surrounded by a larger dark area of water. Next comes the “spiral pattern,” light and dark water, developing from the dark spot.
This is followed by the “spray-ring” stage, in which a cascade (sea spray) forms around the dark spot like an eye. Then comes the “mature” stage, in which a funnel is visible, extending from the surface of the water all the way up to the parent cloud (like many tornadoes). Columns can be several hundred feet tall. Inflow of warm air into the funnel weakens it over time, leading to the final “dissipating” stage.
It’s always best to keep a safe distance from waterspouts. Many are harmless, but others are as dangerous as any tornado—don’t rely on your ability to discern the difference.
The National Weather Service issues a warning when waterspouts are sighted or imminent, and they may even issue a tornado warning if a waterspout moves ashore.
On December 5, 1872, the American merchant ship Mary Celeste was found adrift and deserted in the Atlantic Ocean by the Canadian Dei Gratia. Theories abound as to what may have become of the crew. One possibility is an ocean waterspout.
Marine life, such as fish, raining down from the sky is generally attributed to waterspouts. Raining fish have been reported as far as 100 miles inland.
The Szilagyi Waterspout Index, developed by Canadian meteorologist Wade Szilagyi, is designed to forecast the likelihood of waterspouts based on conditions. The index ranges from -10 to +10. Values at or above zero indicate favorable conditions for waterspouts.
A strictly cold weather phenomenon mistakenly thought to be related to the waterspout is the “steam devil,” which forms over large lakes (we’ve got one of those!) and oceans when the water is warm compared to the air. Steam devils have only been recognized since the 1970s, based on sightings over Lake Michigan.
The rotation of a steam devil is quite slow, to the point that sometimes they don’t seem to rotate at all. Like other columns of air, the core of a steam devil is typically clear (such as an “eye”). They are short-lived, and may or may not have a cloud above them (sometimes they create their own cloud).
The water needs to be unfrozen for steam devils, and very cold air and brisk winds are necessary (so bundle up if you go looking for one). The greater the difference between the air and water temperatures, the more rising air, causing instability in air flow and creating vortices.
Fog streamers can be drawn into the vortices, making visible steam devils. Fog streamers are referred to as “sea smoke,” and occur when very cold air passes over relatively warm water. The cold air mixes with moist, warmer air just above the surface, cooling the air to below the dew point, resulting in condensation.
Sea smoke doesn’t rise high enough to interfere with visibility on larger ships, but small watercraft may have trouble with it. Smoke columns can rise a hundred feet or so in some cases. Sea smoke is most common in polar climates, but sometimes it feels like a polar climate around here! Lake Superior does get sea smoke.
January kicked off a nippy 2018, but look for above average temperatures from here on out. The end of February should see flurries turning into showers as we go into March, which may very well see all of its precipitation arrive in the form of rain.