PHILADELPHIA (CBS) – A large and very impressive waterspout was captured off the Malaysian island of Penang on Monday. Though the amazing phenomenon occurred half-way across the globe, the waterspout capital of the world is actually here in the United States.
In the Florida Keys, as many as 500 waterspouts form each year.
Waterspouts are also not uncommon over the Great Lakes in late summer and have been reported in our neck of the woods, including along the Jersey Shore and even over local lakes, like this waterspout that formed on Green Pond in northern New Jersey last summer.
Now, a waterspout certainly looks like a tornado, but is it a tornado? Sometimes yes, and sometimes no.
There are two types of waterspouts: tornadic and non-tornadic, or “fair weather.” Both are intense rotating columns of air based over a body of water, but their formation processes and movement differ.
A tornadic waterspout is a tornado that is produced by a severe thunderstorm that occurs over open water. Just as a tornado over land, these types of waterspouts form as a result of complex atmospheric dynamics, thus tend to be stronger than the non-tornadic variety.
Tornadic waterspouts typically rate at EF-0 to EF-1 intensity with winds of 74 to 112 mph, but rarely can produce winds of EF-2 intensity of 113 mph or greater. During a study on the life cycle and frequency of waterspouts in the Florida Keys conducted by Dr. Joe Golden in 1977, winds up to 218 mph were recorded!
Thunderstorm-generated waterspouts are more likely to move on-shore than their fair weather counterparts. When a waterspout moves onto land, the National Weather Service will issue a tornado warning.
Though non-tornadic waterspouts are typically weaker, they can still produce winds of EF-0 intensity, up to 73 mph. They form in conjunction with a line of developing cumulus clouds over a very warm body of water.
Instability induced rising air, in combination with low-level converging air flow, creates rotation near the water’s surface, where the fair weather waterspout forms and stretches upward toward the cloud. This is in contrast to its tornadic cousin which descends from the cloud base toward the lake, ocean or sea.
Another notable difference is that a non-tornadic waterspout remains fairly stagnant, hovering over location of development, and can come in two and even threes, as seen in this video in filmed on the Italian coast.
Most waterspouts have an average lifetime of just five to 10 minutes, though a significant tornadic waterspout last for up to one hour.
Rarely life-threatening, however, both tornadic and non-tornadic waterspouts pose danger to boats, people and structures on-shore and aircraft. Some have theorized that waterspouts could be attributable in the mysterious disappearance of numbers of ships and airplanes in the Bermuda Triangle in the mid 1900s.