Atlantic Hurricane Season

By: Colleen Anderson

How Hurricanes Develop in the Atlantic Ocean

Hurricanes form near the equator over warm ocean waters. They require warm, humid air to form. The first thing needed for a hurricane is warm ocean water, that’s why they form in places where the ocean is at least 80°F. The second thing needed for a Hurricane is wind. In hurricanes that form in the Atlantic Ocean, the wind blowing westward across the Atlantic from Africa gives the necessary wind needed.
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Air from surrounding areas with higher air pressure pushes into the low pressure area. Then that air becomes warm and moist and rises, warm air rises due to low pressure. As the warm air continues to rise, the surrounding air swirls in to take its place. The Coriolis Effect causes the warm air to rise and spiral. As the warmed, moist air rises and cools off, the water in the air forms clouds. The whole system of clouds and wind spins and grows, using the ocean's heat and water. As warm, moist air cools, it condenses and rains. Hurricanes keep strengthening as long as they are over warm water, they begin to weaken in water colder than 80°F.

Water Temperature

For hurricanes to form over an ocean, there must be warm water. When a hurricane encounters water colder than 80°F it begins to weaken in intensity and size. The warm water currents in the Atlantic Ocean make it easier for hurricanes to form.
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Facts About Hurricanes

Storms that form in the northern hemisphere north spin counterclockwise. Storms in the southern hemisphere spin clockwise. As hurricanes rotate faster and faster, an eye forms in the center. It is very calm and clear in the eye, with low air pressure.
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The Bermuda High

The Bermuda High is an area of a high pressure system that forms over the Atlantic Ocean during the summer, that brings hot weather. It’s southeast of the Mid-Atlantic Coast near Bermuda, and it is the main player for most of the eastern USA weather, and for the Atlantic hurricane season. The clockwise rotation brings hot, humid wind to the East, especially the Southeast. Other than heating up summer-time temperatures in the East, the Bermuda High affects the intensity of hurricanes. The sinking motion caused by the Bermuda High causes the air to become drier and warmer. This air can stop cloud formation off the water, and the sun is better able to heat the ocean. This can allow water temperatures to become warmer, and warmer sea surface temperatures can help with strengthening and aiding the formation of hurricanes. Depending on where the high lies each summer, the location of the Bermuda High can determine the direction hurricanes will go. The Bermuda High directs hurricanes to move up the East Coast and out to sea. The clockwise direction of flow it produces causes African waves to often be forced away from the coast of West Africa towards North America and the Caribbean. When the Bermuda High is displaced more to the south and west, it can stretch its western edges close to the East Coast. When this happens, the eastern U.S. coastline can be left extremely vulnerable to hurricanes.

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El Niño

An El Niño is a change in the climate of the Pacific ocean. In an El Niño, the winds push the water around and it gets weaker, because of that, some of the warm water piled up in the west goes back down to the east, and a little cold water gets pulled up from below. In the Atlantic Ocean, El Niño lessons the intensity and size of the hurricane. With the increase of vertical wind shear, it suppresses hurricane activity, by chopping the top of the hurricane. Also, El Niño suppresses Atlantic hurricane activity by increasing the amount of sinking motion and increasing the atmospheric stability. There's less hurricane activity in the Atlantic Ocean during an El Niño.

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