After a hurricane goes through its stages and matures, it still can intensify to certain sizes and strengths. Much like that of humans once they're adults. This all depends on the right environmental factors and whether or not it is near land. The Saffir-Simpson Scale is a way to indicate the strength of these storms by their sustained wind speed, and central barometric pressure.
Category 1 – 74-95 mph (64-82 knots; 119-153 km/hr). Damage is limited to foliage, signage, unanchored boats and mobile homes. There is no significant damage to buildings. The main threat to life and property may be flooding from heavy rains.
Category 2 – 96-110 mph (83-95 knots; 154-177 km/hr). Roof damage to buildings. Doors and windows damaged. Mobile homes severely damaged. Piers damaged by storm surge. Some trees blown down, more extensive limb damage.
Category 3 – 111-130 mph (96-113 knots; 178-209 km/hr). This is the first step of Major Hurricane. Landfalling major hurricanes have their names retired from the list of available hurricane names. For example, after Hurricane Charley made landfall in Florida as a Category 4 hurricane, its name was retired. In the future, when someone says “Hurricane Charley”, there will be no doubt which storm is meant. Category 3 storms cause structural damage to some buildings. Mobile homes are completely destroyed. Roof damage is common. Storm surge begins to cause significant damage in beaches and harbors, with small buildings destroyed.
Category 4 – 131-155 mph (114-135 knots; 210-249 km/hr). Structural failure of some buildings. Complete roof failures on many buildings. Extreme storm surge damage and flooding. Severe coastal erosion, with permanent changes to the coastal landscape not unheard of. Hurricane force winds extend well inland.
Category 5 – Greater than 155 mph (135 knots; 249 km/hr). Complete roof failure on most buildings. Many buildings destroyed, or structurally damaged beyond repair. Catastrophic storm surge damage. All Category 5 hurricanes’ names are retired, regardless whether they ever make landfall. In the Northwest Pacific, a typhoon that reaches 150 mph (241 km/hr) is called a Super Typhoon. The damage caused by a super typhoon is equivalent to a strong Category 4 or Category 5 hurricane, depending on how strong the typhoon is. Because conditions in the Northwest Pacific favor storm formation throughout most of the year, super typhoons are much more common than Category 5 hurricanes. Every year the Northwest Pacific sees several super typhoons, while the Atlantic might see one Category 5 every few years.
WHAT CAUSES HURRICANES?
There are approximately 100 tropical waves that travel westward from the West Coast of Africa through the Atlantic every year. So, how do these waves become one of the ten or so tropical storms, and hurricanes that occur each season. There are several key factors that come together to develop tropical storms and hurricanes: warm sea surface temperatures, light winds aloft, and rotation or spin. If any one of these factors is unavailable, then the tropical storm or hurricane can weaken or decay.
- Warm sea surface temperatures--This is a key ingredient because it serves as the fuel source for hurricanes. Sea surface, or ocean temperatures need to be at least 80 degrees Fahrenheit (27 degrees Celsius) where the system is located in order for it to develop into a tropical storm or hurricane.
- Light winds aloft--Hurricanes and tropical storms travel east to west so they are supported by an easterly wind flow. They are also vertical systems in that they have thunderstorms that build vertically in the atmosphere. These two conditions make hurricanes quite different from the storms that usually bring us our weather, and make it essential to have light westerly winds aloft so that there is no shearing, or tearing apart of thunderstorms.
- Rotation, or spin--In order for the wave to be considered a depression, storm, or hurricane, it must have some rotation, or spin generated by the winds coming together to form it. Without this ingredient, the wave is just another area of low pressure.