How do waterspouts form?

Long sinuous funnel from twilight clouds to splashing ocean surface.
View at EarthSky Community Photos. | Mark Rutkowski said on July 3, 2020, that he caught this sunrise waterspout in the Atlantic Ocean, near Miami. Thank you, Mark!

You’ve likely heard the term waterspout. In general terms, a waterspout is just a tornado that forms over an open body of water. A tornado over an ocean, lake – or even a river – is considered to be a waterspout. Waterspouts are typically weaker than most tornadoes. They’re usually short-lived. But they can be destructive. In this post, we’ll look at some images and videos of waterspouts and learn more about how they form.

When and where do waterspouts form?

Waterspouts typically occur in tropical regions, but they can form almost anywhere. They can occur in the Gulf of Mexico, the Great Lakes, western coast of Europe, Mediterranean Sea, and the Baltic Sea. They’re common throughout the world. In the U.S., the most common place to see waterspouts is along the Florida Keys and in the Gulf of Mexico. They typically form during the late spring and summer months, with tornadic waterspouts generally forming after 2 p.m. in the afternoon. Florida is considered to be the most prone area to see tornadoes in the United States. However, many of them end up being waterspouts. It’s not unusual to see 400 to 500 waterspouts a year in this area, and many that go unreported. In rare instances, more than one waterspout can form from a storm offshore.

Narrow sinuous funnel from billowing dark clouds to surface, viewed past buildings.
Waterspout off Miami, Florida. Image via Neal Dorst/ OAR/ AOML.

Are waterspouts destructive?

Waterspouts are typically weaker than tornadoes, but as seen in the videos below, they can still cause a decent amount of damage. If you’re boating in the ocean, you’ll want to monitor the weather to avoid waterspouts. For instance, you might avoid being in the ocean around the Florida Keys in the afternoon or evening, when there’s a chance for thunderstorms at the coast. If you’re on a boat or ship and a waterspout develops, try to navigate around the area by going at right angles to its path. The National Oceanic and Atmospheric Administration (NOAA) recommends that those on boats or ships monitor special marine warnings issued by the National Weather Service.

And of course it’s highly recommended that you avoid navigating through a waterspout. They can cause decent damage, and could hurt or kill you.

Here is a video of two waterspouts forming off Honolulu, Hawaii back in May of 2011:

How do waterspouts form?

There are two types of waterspouts we commonly see: A fair weather waterspout and a tornadic waterspout.

Fair-weather waterspouts form during relatively calm weather. They typically form along the dark, flat bases of a line of developing cumulus clouds. Air begins to circulate at the surface of the water and develops upward. Unlike tornadic waterspouts, which tend to happen in the afternoon, fair-weather waterspouts typically occur in the early to mid-morning hours, and sometimes in the early afternoon. Everyone associates tornadoes and waterspouts with thunderstorms, but in a fair-weather waterspout, there are no thunderstorms in the area. When fair-weather waterspouts form, they typically occur during light wind conditions. Because of this, these waterspouts typically don’t move much.

Long thin funnel from purple clouds to sea surface.
Waterspout in the Gulf of Mexico in 2012. Image via NWS Collection.

There are five stages that occur for fair weather waterspouts:

Stage 1 is the formation of a disk on the surface of the water, known as a dark spot.
Stage 2 is a spiral pattern on the water surface.
Stage 3 is a formation of a spray ring.
Stage 4 is where the waterspout becomes a visible funnel: the waterspout!
Stage 5 is the last and final stage of the life cycle where the waterspout decays. When the waterspout decays, it likely does so because a cool rain falls near the spout. This cool air typically disrupts the supply of warm, humid air that allows to keep the waterspout going.

Very long thin arcing funnel from clouds to ocean.
Waterspout over the Gulf of Mexico in 2018. Image via National Weather Service/ Greg O’Neal of Hiram, Georgia.

Tornadic waterspouts are simply tornadoes that form over water or move from land to water. They typically occur with afternoon and evening thunderstorms. You need two main ingredients for tornadic waterspouts: warm, moist air and an unstable atmosphere. Trade winds from boundaries can also influence the formation of this kind of waterspout.

Unlike fair weather waterspouts, tornadic waterspouts typically develop downward in a thunderstorm, and begin to appear initially as funnel clouds. The storms that develop these waterspouts are typically non-supercell thunderstorms. According to NOAA, a supercell thunderstorm is defined as:

… a large severe storm occurring in a significant vertically-sheared environment; contains quasi-steady, strongly rotating updraft (mesocyclone); usually moves to the right (perhaps left) of the mean wind; can evolve from a non-supercell storm; and contain moderate-to-strong vertical speed and directional wind shear in the 0-6 km [0-3.7 miles] layer.

Supercell thunderstorms are what produce large, violent tornadoes. In non-supercell thunderstorms – like those that produce waterspouts – tornadoes that typically form are due to a boundary layer. Spin ups that do occur in the storm are typically short and do not last long. Obviously, every waterspout is different and some could last longer than others.

Check out the amazing photo and video below of a waterspout pushing ashore on Grand Isle, Louisiana, on May 8, 2012. There’s spectacular footage of multiple waterspouts and a tornado hitting the coast around four minutes into the video. Scary stuff! FYI: Do not try this at home! If you know a tornado is about to strike near you, go inside and take shelter. It’s not the tornado itself that will hurt or kill you. Instead, it’s the flying debris in the air that’s dangerous.

Two tall narrow funnels some distance apart striking the sea surface.
Grand Isle, Louisiana, pair of waterspouts taken on May 8, 2012. See these same waterspouts in the video below. Image via WVUE-TV.

Bottom line: Waterspouts can be harmless as long as you understand and avoid them. If you live along the coast, you should treat all waterspouts as you would tornadoes on land, and assume they might come ashore. Waterspouts form off non-supercell thunderstorms, and typically are short-lived. Some waterspouts can reach the coastline and become tornadoes, so it is important for everyone to monitor the weather as it evolves. Waterspouts can occur anywhere in the world, and the most common place they form in the United States is along the Florida Keys and in the Gulf of Mexico.

July 7, 2020

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