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What are tsunami clouds that appear before a thunderstorm?
What are tsunami clouds that appear before a thunderstorm?
Tsunami clouds have the shape of rolling ocean waves and often appear before thunderstorms and storms.
Tsunami clouds, also known as shelf clouds, are distant storm circulation clouds that typically form along the leading edge of a thunderstorm. They appear as wedge-shaped structures, often extending in an arc across the sky, sometimes creating the illusion of a rolling tsunami.
Thunderstorm clouds in Vinh City, Nghe An, morning of September 6. Photo: Hung Le
This type of cloud is a low, horizontally formed cloud with a well-defined cloud mass. The long, prominent line in the cloud is the boundary between the updraft and downdraft of a thunderstorm.
The appearance of tsunami clouds is a sign of a strong storm. In places where it appears, it will cause heavy rain and lightning.
When cold, dense air is pushed by wind into a warmer air mass, which often occurs in the strong downdraft of a thunderstorm, shelf clouds form.
The cold air rushes down to the ground before spreading out in all directions. As the cloud passes, the wind direction changes abruptly and its speed increases. A few minutes later, heavy rain or hail and strong winds will appear.
According to the National Weather Service, shelf clouds are always associated with the base of a parent cloud or thunderstorm. This is an important identifying feature of shelf clouds. They are often associated with strong, straight-line winds and rarely produce tornadoes.