Hurricanes start when a series of thunderstorms move over warm ocean waters. The warm air of the storm combines with the heat of the surface of the water and begins to rise. This produces a low pressure on the sea surface, and the winds that circulate in opposite directions cause the storm to start spinning. In turn, the elevation of the warm air displaces the cold and forces it to lower and occupy the void left. This process repeats itself and causes the air to rise faster and faster, attracting more warm air from the sea surface, absorbing cooler, drier air from the upper layers, pushing it down. As the storm moves over the water, it will be nourished by more humid and warm air. The wind speed increases as the air is being sucked by the low-pressure center. After a while the depression turns into a hurricane and the eye forms, which is a center of calm winds, surrounded by a band of intense winds and storms that produce great rainfall.