Everyone has probably heard of the term “waterspout”, but do you know or understand how it forms? In general terms, a waterspout is simply a tornado over an open body of water. If a tornado forms over an ocean, lake, or even a river, it is considered to be a waterspout. Waterspouts are typically weaker than most tornadoes, and usually are short lived. In this post, we will look at various images and videos of waterspouts and learn about how they form and the types that can occur.
There are two types of waterspouts we commonly see: A fair weather waterspout and a tornadic waterspout.
Fair weather waterspouts form during “fair” and relatively calm weather. These waterspouts typically occur in the early to mid morning hours, and sometimes in the early afternoon. Fair weather waterspouts typically form along dark flat bases of a line of developing cumulus clouds. Everyone associates tornadoes and waterspouts with thunderstorms, but in a fair weather waterspout, thunderstorms are nonexistent. When fair weather waterspouts form, they typically occur during light wind conditions. Because of this, these waterspouts typically move very little. When these form under fair conditions, circulations typically form at the surface of the water and develops upward.
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.
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.
Tornadic waterspouts are simply tornadoes that form over water or move from land to water. They typically occur with afternoon and evening thunderstorms. The two main ingredients for waterspout development is warm, moist air that provides an unstable atmosphere. Trade winds from boundaries can also influence the formation of a 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 NWS, 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 layer. We typically think of supercell thunderstorms as the one that produce the large, violent tornadoes. In non-supercell thunderstorms, 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 this amazing video of a waterspout pushing ashore on Grand Isle, Louisiana last week (May 8, 2012). This video went viral on the internet this past weekend. Just spectacular footage of multiple waterspouts and a tornado hitting the coast around 4 minutes into the video. Scary stuff! FYI: Do not do this at home! If you know a tornado is about to strike near you, go inside and take shelter. It is not the tornado itself that will hurt or kill you. Instead, it is the flying debris in the air that is dangerous!
When and where do they 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. It is important that this phenomenon is common throughout the world, and other countries can easily see these develop. The most common place that typically sees the most waterspouts than anyone else is along the Florida Keys. They typically form during the late spring and summer months, with tornadic waterspouts forming after 2pm in the afternoon. Florida is considered to be most prone area to see tornadoes in the United States. However, many of them end up being waterspouts. The best place in Florida to see and experience a waterspout is in the Florida Keys. According to an article from USA Today, waterspouts in the Florida Keys are generally from around to 18,000 to 22,000 feet high. It is not unusual to see 400 to 500 waterspouts a year in this area, and sometimes, there are many that go unreported. In rare instances, more than one waterspout can form from a storm off shore. The more that develops, the rarer the situation becomes.
Here is a video of two waterspouts forming off Honolulu, Hawaii back in May of 2011:
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 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 coast line 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 across the Florida Keys and across the Gulf of Mexico.
Matt Daniel is weekend Meteorologist for 13WMAZ (CBS) in Macon, Georgia, and founder of the blog Athens GA Weather. He's a self-described "big weather and music geek" and has produced weather content for CNN, MSN Weather and EarthSky. He has a passion for helping to keep people safe when severe weather strikes and says if you don't have a NOAA Weather Radio ... you should get one.