SAVANNAH, Ga. (WSAV) – Easily throughout the summer and early fall, we see a few waterspouts form off our coast. Did you know from 1956 to 2020 there has been 225 documented waterspout events off our coast? To put it simply, they are tornadoes that form over water. There are some differences on how they form compared to how tornadoes form.
What is a Waterspout
A waterspout is a rotating column of air and condensation. While they share similarities with their tornado cousin, there are key differences on where and how they form. The most obvious being that waterspouts form over water. I know…shocking, right!
Did you know the “waterspout” name is somewhat misleading?? It is not a column of swirling ocean water – in fact it’s not filled with ocean water at all. It is formed by condensation from the rotation as the cloud grows from the ocean to the sky.
We have a higher chance of seeing waterspouts off our shoreline through the summer into early fall as water temperatures remain warm. We see them most times in the late morning before the sea breeze picks up. As the land breeze pushes offshore, it meets up with perpendicular winds. As they collide, we can easily get small areas of rotation. As showers either push off the coast or remain just offshore, the small areas of rotation can become columns of rotating air. With a lifting motion in the atmosphere, we see the end result of all this: waterspouts.
There are two types of waterspouts: fair-weather & tornadic. Most are fair-weather waterspouts. Both require high levels of humidity and relatively warm water temperatures.
Fair-weather waterspouts are most common. These develop along a dark flat base of developing cumulus clouds in light wind/fair-weather conditions. Hence, the name. Fair-weather waterspouts usually move very little. This type doesn’t form like land based tornadoes. Instead, the funnel develops on the ocean surface and works its way up toward the cloud. Again, the funnel is visible because of the condensation of water vapor in the cloud – not ocean water.
Stages of Fair-Weather Waterspouts
1. Dark Spot appears on surface of the ocean. This is when a column of rotating winds reach the surface.
2. Spiral Pattern of light/dark bands begin to spiral from the dark spot.
3. Spray Ring begins it form as sea spray, a.k.a. cascade” forms around dark spot.
4. Mature “Vortex” Column forms. This is when it is at it’s most “intense”, visible stage. The waterspout funnel is visible from the ocean surface to the cloud.
5. Decay is when the rotation of warm air weakens and eventually collapses.
These are simply tornadoes that form over water and form just like a tornado would in a severe thunderstorm. However unlike fair-weather waterspouts, tornadic waterspouts develop from the cloud to the ocean surface. As warm air rises, air begins to spin horizontally due to the winds in a storm changing speed and direction with height. Rising air within the thunderstorm pushes the horizontal air to become vertical.
If the conditions are perfect, a wall cloud will form at the bottom of the thunderstorm and a tornadic waterspout can possibly form. These are very dangerous and can be destructive. These are associated with torrential rain, frequent lightning, and strong wind.
In most cases, waterspouts (both fair-weather and tornadic) will stay out over the ocean. However, they can move onshore. If they do move onshore, the National Weather Service will issue a tornado warning.
While they can be weaker than tornadoes, waterspouts can still cause damage and injuries in the area it moves through. They dissipate quickly overland and don’t move too far inland. If you notice a waterspout heading towards your direction, take shelter immediately.
How to Stay Safe
Waterspouts are a hazard to boaters. Make sure you are listening for special marine warnings about spotted waterspouts or possible waterspouts from the National Weather Service. Look for a dark, flat base under a cumulus cloud with light wind conditions. If you see a waterspout, the best way to avoid it is to move at a 90 degree angel compared to the spouts apparent movement. Never try to navigate through a waterspout. They can cause significant damage to you and your boat.