The powerful storm system we call a hurricane often begins off the Atlantic coast of Africa, typically near the Azores. Because this area is located so close to the equator, it receives a substantial amount of heat from the sun. This causes warm air and water vapor to rise off the ocean's surface and into the atmosphere. If a strong low pressure system should happen to form over this large area of superheated water vapor, the result is called a 'tropical wave'. Trained meteorologists can detect this phenomenon and assign staff members to track the behavior of the growing tropical storm system. If the system has enough warm water beneath it to sustain itself, it may become more organized and powerful. Eventually the wind speeds within the storm will increase, which leads to a change in definition by meteorologists. Storms with sustained winds over 45 miles per hour but less than 75 miles per hour are defined as 'tropical storms' and assigned names according to an alphabetical system.
Tropical storms could encounter conditions which will tear them apart or take away their source of fuel- the warm water. Other storm systems could force them out to open water in the colder Atlantic region where they will eventually fade away. Tropical storms are essentially pushed and prodded by whatever prevailing winds are present, including the very powerful jet stream. In general, tropical storm systems prefer to find the path of least resistance, which could be through the Bahamas, the Antilles, or the Gulf of Mexico. Essentially a tropical storm system operates like a puck on an air hockey table- if it receives a strong blow, it will continue in that direction until it either stalls out from lack of momentum or is struck by another powerful current.
If a tropical storm survives and develops winds over 75 mph, then it is now considered to be an official hurricane. Storm prediction centers will then carefully observe the previous behavior of the hurricane and calculate the possibilities of a land strike. Hurricane watches will be issued for a broad area around the leading edge of a hurricane, often a day or two in advance. Residents may be asked to evacuate the area or prepare themselves for an eventual direct hit.
But some areas will most likely be hit directly within hours, so they will receive an official hurricane warning. The hurricane's most dangerous section, an area known as the eye wall, will most likely pass directly over those areas and cause tremendous damage. Those areas covered by a hurricane warning can also expect 'storm surges'- a phenomenon in which water ahead of the storm is literally pushed into low-lying coastal areas. These storm surges are often more dangerous and damaging than the winds of a hurricane. Evacuation of areas included in a hurricane warning is almost always mandatory.
Because a hurricane's eventual path is so difficult to predict, meteorologists will often issue a widespread hurricane watch without an actual warning. As the hurricane approaches and spotters have had time to measure its strength and guiding currents, meteorologists can usually narrow the location where the hurricane will make landfall. These specific areas may receive an official warning just hours before the actual storm arrives. Hurricanes, however, can make some surprising moves shortly before their predicted landfall. They may stall out over the water and dump heavy rainfall for several days, or they may curve away from the predicted landfall area and strike another section of coastline. For this reason, hurricane warnings often include areas above and below the expected point of attack.
