Hurricanes are one of Mother Nature’s fiercest forms of expression. While they are not necessarily the largest storms or the most ferocious, they combine wind, rain, and flooding as no other force of nature does. Surprisingly, it actually takes several different relatively complicated phases of development going off without a hitch for a hurricane to develop – but once they develop, look out.
Read first: How Do Hurricanes Form
A hurricane is a type of tropical cyclone that typically forms over warm waters. In order for a tropical cyclone to become a hurricane, there must be a pre-existing disturbance with thunderstorms, ocean temperatures of at least 80 degrees up to about 150 feet deep and light upper level winds with low wind shear. If the wind remains low and the ocean continues to add moisture and heat to the air, the storm can grow and sustain itself until it reaches tropical depression status with winds that are under 38 mph.
When a storm is in the tropical depression status, it goes from looking like a cluster of thunderstorms, unrelated to one another, to taking on the familiar spiraling shape of a hurricane. This is a result of the direction the wind is flowing in, combined with the rotating earth. If the storm continues to gain strength and the winds reach 39 to 73 mph, it can be classified as a tropical storm. In a tropical storm, the storm begins to sustain itself as its bands of thunderstorms continue to add heat and moisture to itself.
If the conditions continue to be right and the storm continues to gain strength, the winds will reach 74 mph and the storm can officially be classified as a hurricane. An area in the center of the storm called “the eye” will form due to the air in the center sinking so quickly that the area becomes dry. Typically the eye of the storm is free of clouds and the winds are relatively calm.
Hurricanes can last for a couple of weeks while they are traveling over warm water, but there are several factors that can slow it down as well. If the storm begins to move over cooler water or hits land, the storm loses its main source of moisture – the warm water. If the wind near the upper level of the storm picks up, that can also start to wear the hurricane down. The friction of the storm’s circular motion over dry land can have the same effect. However, if the storm moves back over warm water, it can regain speed and become deadly once again.
Resources:
Hurricaneville: Stages of Development
University of Illinois. Stages of Development from Tropical Depression to Hurricane.
National Oceanic and Atmospheric Administration. Hurricane Basics. May 1999
