After devastating Cuba and Florida, Hurricane Ian is moving toward North and South Carolina. In addition to strong winds and rainfall, tropical storms cause another phenomenon with great potential for destruction on the coast: storm surges.
Hurricanes in general, and hurricanes in particular, generate strong winds, the greater the pressure difference between their interior and exterior. To understand this better we can give an example: when we blow hard with a tube we increase the air pressure at that end, so if we blow it with a straw the liquid comes out and hence the blowgun work.
A cyclonic storm is an area of low pressure. The apparent Coriolis force (Earth’s rotation on its axis) forces the air to rotate around the center of the storm. In the Northern Hemisphere, it does so in a counterclockwise direction as air moves from a high pressure area to a low pressure area.
When a storm is located over the ocean, the winds act on the surface of the water and pull it slightly in the opposite direction in which they are blowing. This drag stores water as the storm progresses.
When a storm makes landfall, the frozen water hits the coast. If it has a gentle continental slope, that is, if the coastline continues without a sudden drop of water, the storm-drawn water slide turns into a storm or the cyclone penetrates several meters into the coast. On the contrary, if the continental slope suddenly drops, the water collides and comes back. The extreme case is a rock that prevents water from entering the ground.
destruction on the coast
In the United States, the coasts of the Gulf of Mexico, Georgia, and the Carolinas are very shallow, and hurricanes produce very large storms that cause extensive damage. If these swellings occur at high tide, the effect is magnified. Hurricane Katrina, which hit the outskirts of New Orleans in 2005, caused approximately 1,500 deaths and approximately $75 billion in damage, essentially due to the hurricane. During Katrina the sea level rose about 8.5 meters like a 3-storey building.
In South Carolina, which has a gentle continental slope, Ian can produce strong storm surges.
Sometimes these waves get combined with bigger waves. Waves are generated by oscillations in air pressure as it passes over the initially undulating surface, thanks to some small fluctuations that increase as the wind blows. The highest waves ever recorded in the open ocean, without obstacles at the bottom, reach 20 m, and are repeated because they are a periodic phenomenon.
Hurricanes combine heavy rain, high waves and storm surges. They are highly destructive to coastal life in their prone areas. These areas are concentrated in warm water areas near the lines of the tropics.
How do hurricanes and cyclones form?
During the late summer and autumn of the Northern Hemisphere, tropical waters remain very warm. Storms originating in the equatorial Atlantic and Pacific Ocean move north and fall and rise on top of each other. Convection is generated by warm water on the surface of the ocean, and as the water rises up into the atmosphere as steam, it cools and condenses and generates enormous amounts of heat that sustain the storm, which slowly Gradually increasing until it becomes a hurricane (as they are called in the Americas) or a tropical cyclone (as in Asia).
The bottom of tropical storms requires very warm surface waters. This is why they form mainly in the Caribbean and the China Sea, affecting the Caribbean islands, Mesoamerica, Mexico and the US as hurricanes, and cyclones affecting the Philippines, China and the coasts of Taiwan and Japan. We do.
Hurricanes can begin to affect the Canary Islands, but it is difficult for them to affect continental European coasts as hurricanes because the ocean is cooler. Within the Mediterranean Sea, with waters as warm as the Caribbean, there is a lack of space for the necessary amplification. There will be more strong storms in this sea, but they will not reach the rank of hurricanes.
Climate change does not affect the number of storms and cyclones that occur annually at this time, but it does affect their intensity, increasing with an increase in water temperatures. It also affects the mean sea level. An increase of only 10 cm assumes a swelling of the water entrance of the waves and at least one kilometer inland if it is flat, such as in the Bay of Cádiz or in Plana de Valencia, and causes considerable damage to the foundation of the habitat and coastal infrastructure.
Increasing the destruction caused by tropical storms is one of the damages we are inflicting on ourselves with the warming of the planet.