Weather is a complex dance of atmospheric forces that sometimes creates strange and fascinating phenomena but signals danger through the shape of clouds.
Tsunami clouds – rare type of cloud that appears before storms
First of all, we must mention tsunami clouds – another name for shelf clouds, a special natural phenomenon that looks scary like rolling ocean waves that often appear before storms and hurricanes.
This is a storm cloud band, also known as a shelf cloud or tsunami cloud, which is one of two types of arcus clouds, the other being a roll cloud. This type of cloud usually forms along the leading edge of a thunderstorm. This is a sign of a strong storm. The cloud band will cause heavy rain and lightning in the places where it appears.
Shelf clouds develop when cold, dense air is pushed into a warmer air mass by the wind. Such a rush often occurs in the downdraft of a thunderstorm. The cold air rushes toward the ground before spreading out in all directions. As a shelf cloud passes, the wind direction changes abruptly and speeds increase, followed within minutes by heavy rain or hail.
Virga: Ghost Rain
Virga presents a surreal sight in the sky – a phenomenon where rain or snow never reaches the ground. This fascinating phenomenon occurs when moisture falls from a cloud in the form of rain or ice but evaporates before it reaches the ground. The reason for this is atmospheric conditions where the air below the cloud is extremely dry, sucking up all the moisture before it can reach the ground.
When rain or snow falls from the base of a cloud, it encounters dry air and evaporates quickly. What remains are thin, wispy streaks that resemble the original path of the precipitation before it turned to water vapor. These streaks, which sometimes resemble fine hairs, represent a complex combination of moisture and high-altitude air currents.
Although virga may seem like a mere visual effect, it represents an important process taking place in the atmosphere. Sometimes a short, strong gust of wind can clear the clouds. Even if there are major storms brewing high above, the only evidence on the ground may be the trails of virga hovering in the sky, leaving a mysterious and intriguing atmosphere.
Fujiwhara effect – storm on storm
The Fujiwhara effect reveals the interaction that occurs when two cyclonic storms moving in the same direction approach each other. As the storms approach each other, their proximity and similar vorticity trigger a complex interaction. Depending on their relative strengths, a variety of outcomes can occur. If one storm is much more intense than the other, the smaller storm may revolve around the larger one, eventually merging or being absorbed. Conversely, storms of similar strength may gravitate toward each other, circling around a common center before separating or merging into a more powerful storm.
The Fujiwara effect often results in these storms merging into one giant storm. The most recent example was in 2017, when Hurricanes Hilary and Irwin collided in the eastern Pacific, off the coast of Mexico.
Tornado – waterspout
Tornado. Photo:Justin/Wikipedia
A tornado or waterspout is a rotating column of air extending from a thunderstorm cloud to the ground.
Tornadoes usually develop from thunderstorms, often from very strong or super strong thunderstorms, so wherever there are severe thunderstorms, there can be tornadoes. Sometimes they are born from a band of strong gusts (called a line) or from a storm. It is believed that when the cold air in the upper layer presses on the warm air below, the hot air will be forced to move up very strongly. But when tornadoes occur over water, there is usually no convection and no difference in temperature between the layers.
A tornado or waterspout is shaped like a straw, funnel, or vortex. As this straw-shaped tornado sweeps through, it can sweep away everything in its path.