A hurricane, also called a typhoon or a cyclone, depending on where they occur, is a type of storm called a tropical cyclone, which forms over tropical or subtropical waters. The scientific term for all these storms is tropical cyclone. Only tropical cyclones that form over the Atlantic Ocean or eastern Pacific Ocean are called "hurricanes."
A tropical cyclone is a rotating low-pressure weather system that has organized thunderstorms but no fronts (a boundary separating two air masses of different densities). Tropical cyclones with maximum sustained surface winds of less than 39 miles per hour are called tropical depressions. Those with maximum sustained winds of 39 mph or higher are called tropical storms.
The last tropical storm that occurred in the US eventually fizzled out into light to moderate rain that reached as far north as Lake Erie.
In 2012 when Hurricane Sandy made landfall along the New Jersey coast at 8 pm Monday with sustained 90 mile-an-hour winds, Ohio's north coast, 450 miles away, was being hammered by rain and wind gusts near hurricane strength. Northeast Ohio was battered because a cold front that traveled east over Cleveland, stalled and then merged into the western edge of Sandy. The hurricane's winds then swept south across Lake Erie with no trees or buildings to reduce the wind speed. Around the corner from my house there is a large park that was filled with oak trees, many of which were diseased and rotten inside. As a result, about half the trees in the park were toppled.
When a storm's maximum sustained winds reach 74 mph, it is called a hurricane. The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 category which is based on a hurricane's maximum sustained winds. See the chart below for their effects.
Hurricanes originate in the Atlantic basin, which includes the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico, the eastern North Pacific Ocean, and, less frequently, the central North Pacific Ocean. A six-year rotating list of names, updated and maintained by the World Meteorological Organization, is used to identify these storms.
Hurricane Season begins on June 1 and ends on November 30, although hurricanes can occurred outside of this time frame. They occur, on average, 12 times a year in the Atlantic basin.
Tropical cyclones are like giant engines that use warm, moist air as fuel which is why they form only over warm water near the equator. The warm, moist air over the ocean rises upward from near the surface and as a result, there is less air left near the surface causing an area of lower air pressure below.
Air from surrounding areas pushes in to the low pressure area which also becomes warm and moist and rises. As the warmed, moist air rises and cools off, the water in the air forms clouds and the whole system of clouds and wind spins (storms that form north of the equator spin counterclockwise. Storms south of the equator spin clockwise. This difference is because of Earth's rotation on its axis.) and grows, fed by the ocean's heat and water evaporating from the surface.
As the storm system rotates faster and faster, an eye forms in the center. The eye is very calm and clear with very low air pressure. Higher pressure air from above flows down into the eye.
Tropical cyclones usually weaken when they hit land, because they are no longer being fed by the energy from the warm ocean waters. However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.
For US residents, AccuWeather has a good Interactive Hurricane Tracker HERE.