According to the National Oceanographic and Atmospheric Administration, hurricanes form when heat from calm, warm seas rises into a cooling atmosphere, generating a tropical system. The rising moisture causes the forming clouds to begin a rotation, much like water flowing down a drain. As the storm builds, it draws more and more energy from the ocean's warmth until it reaches hurricane strength.Know More
When the air nearest the surface of the ocean is considerably warmer than the air above, it begins to rise. As that air moves upward, it creates an area of low pressure near the surface, and nearby higher-pressure air moves in to fill this void. This air movement is the engine that initiates the rotation of the tropical depression.
As the storm builds, the winds associated with it grow stronger and stronger, changing the classification of the storm. Any tropical system with winds between 25 and 38 miles per hour is a tropical depression, while winds of 39 to 73 miles per hour indicate a tropical storm. Once wind speeds top 74 miles per hour, the storm officially becomes a hurricane, with five levels of severity depending on its wind speed. Generally, the longer a storm spends over warm ocean waters, the stronger it will become.Learn more about Storms
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Hurricane Ike, a 2008 hurricane that caused widespread damage in the Caribbean and the Southeastern United States, began forming as a tropical wave off the coast of Africa, became a tropical depression as it moved westward and was then upgraded to a tropical storm. After it briefly weakened, deep convection around the center and a lack of wind shear caused it to intensify and become upgraded to hurricane status.Full Answer >
The massive storm that became known as Hurricane Katrina originated from a tropical depression that began in the Bahamas on Aug. 23, 2005. The remnants of Katrina caused storms through the central United States before it deteriorated into a frontal boundary in southeastern Canada on Aug. 31, 2005.Full Answer >
Hurricane Katrina started in the Bahamas initially as an area of thunderstorms. On August 23, 2005, this was upgraded to a tropical depression, meaning that it had become more organized as a storm.Full Answer >