The Green Analysis

With the vast amounts of severe weather hitting the United States these past few weeks, it is essential to understand why and how these storms form so that the general public has a greater understanding in hopes of protecting people affected by such weather.

The Basics

Storms are large masses of unstable air that carry large amounts of moisture. This moisture is deposited in various precipitation forms, stabilizing the atmosphere. Air masses become unstable once a layer of warm moist air is underneath a layer of cold, dry air. After this, due to thermal convection, the warm air lifts over the cold air, where it cools down, causing the moisture to condense and precipitate, and the air becomes stable following the end of the precipitation. Think of unstable air as a dam holding water from its natural course, the transition between unstable and stable as the act of all the water being released at once, and stability as the water peacefully flowing along its course. Another key term is convection cells. Convection cells are the cycle of warm and cold air moving in a vertical environment. The sun’s radiation warms the ground, and the upper regions are cooler because there are fewer air molecules to be heated. This phenomenon within the troposphere is one of the main drivers of weather; as air in contact with the ground becomes warm, it rises in the atmosphere; once high enough in the atmosphere, it cools down and sinks back down to the ground, where it heats up and rises once again—creating a cycle of moving air which is termed a convection cell.

General Storm Formation

Firstly, two high-pressure systems, one with warm air and the other with cold air, converge, forming a low-pressure system with warm air below the cold air, creating thermal instability. Then, a warm and cold front forms within the low-pressure system, with the warm front forming “ahead” of the cold front. These fronts represent the leading edge of the movement of warm and cold air masses as they spiral around the center of a low-pressure system. In general, the cold front moves faster than the warm front, so it will “catch” the warm front after some time. Once this happens, since cold air is much denser than warm air, it forces the warm air up and releases all the built-up energy in the form of intense precipitation and large storms. Once the storms die out due to the energy being used up, the atmosphere will stabilize again.

Hurricane Formation

Hurricanes are very similar to regular storm systems in terms of structure. However, hurricanes are leagues more powerful than regular storm systems because hurricanes are supplied with a vast amount of thermal energy and moisture from oceans in tropical regions instead of relying on warm moisture in the air or lakes like storm systems that form on land. Hurricanes constantly grow in strength over warm water; only when a hurricane reaches land or cold ocean areas will it die down. Some unique characteristics of hurricanes are the eye and hurricane walls. The eye is the very center of the hurricane. It is very calm because hurricanes are essentially gigantic convection cells, with stormy areas where the air is going up and not stormy areas where the air is going down.

Tornado Formation

Tornadoes form at the base of storms, more specifically, supercell storms. Supercells are unique from regular thunderstorms because they have a vortex of spinning air in the storm’s center. This vortex is caused by high-altitude winds moving faster than low-altitude winds, causing the fast winds to fall, spin, and roll over the slower wind, forming a horizontally rotating air cylinder. Strong updrafts from warm air tilt the cylinder of air vertically. This vortex of air is then pushed down by downward-moving cold air inside the storm. Once the cold air has pushed the vortex to the ground, it becomes a tornado.

Bibliography

https://www.britannica.com/story/how-do-tornadoes-form

https://www.e-education.psu.edu/earth107/node/1045

All images taken from Wikimedia commons.