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What Are the Signs of a Natural Disaster of a Cyclone?

Cyclones are areas of circular wind that form over water and rotate in the same direction as the earth. For the northern hemisphere, where they are referred to as hurricanes or typhoons (these are simply regional names), they rotate clockwise and in the southern hemisphere they rotate counter clockwise. The wind speed of a cyclone can range from about 40 miles per hour to over 180 miles per hour and can cause devastating destruction when they make landfall. In addition to the damaging winds, heavy rains can lead to flooding and structural damage. Luckily, cyclones do not form quickly so people are given advanced warning when a cyclone is eminent and can prepare by gathering supplies, protecting buildings and evacuating if necessary. In addition to advanced warnings from meteorologists, there are some signs that indicate a cyclone will make landfall soon.

  1. Atmospheric Pressure

    • Atmospheric pressure is a chief indicator of changing weather conditions. Prior to a cyclone making landfall, barometric pressure will steadily drop. the drop begins about 36 hours before a cyclone makes landfall, changing only slightly at first. As the cyclone approaches a land mass, the pressure drops at a steadily increasing rate. It is only after the eye of the cyclone makes landfall and surges inland that the pressure begins to rise again.

    Winds

    • The winds also begin to pick up approximately 36 hours before the cyclone makes landfall. Like the atmospheric pressure, wind speed changes are slight at first and might not even be noticed. Over the next 12 hours, wind speeds increase to more than 30 miles per hour. As the cyclone gets closer to land, the winds steadily increase. Since cyclones range from 6 to 60 miles in diameter and travel at varying speeds, cyclone-force winds can be felt up to 12 hours before the eye of the storm actually makes landfall. Unlike pressure, the winds do not cease as soon as the eye makes landfall. Because the back part of the cyclone is more powerful than the front, wind speeds actually increase about an hour after the eye makes landfall.

    Waves

    • Ocean swells are actually the first indicator that a cyclone is on the horizon. About 3 days before the storm makes landfall, swells increase to 6 feet or more and occur in steady increments. As the storm gets closer to making landfall, the swell increases in strength and frequency. Within hours of the eye making landfall, the sea level rises, flooding coastal roads and sending waves crashing into buildings. Once the eye has moved inland, the storm surge retreats, but pounding waves persist for several more hours.

    Rain

    • Bands of heavy cloud cover and rain move in as the cyclone nears land. One of the last indicators of an impending storm, rain hits as the outer bands of the cyclone begins to move over land. The rain increases in intensity and frequency as the eye nears. While the eye is passing over land, both the winds and the rains subside, but like the wind, the rain returns in full force as the back end of the storm makes landfall.

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