Hurricanes are the most powerful storms on Earth in terms of size, energy released, and the scale of damage they can produced. The wind and the rain can be unrelenting, but the storm surge often times causes more damage. And if that’s not bad enough, hurricanes can even spawn tornadoes which makes some locations sustain far greater damage than the surrounding areas.
The terms typhoon and hurricane mean the same thing, that is, they are both non-frontal synoptic scale low-pressure systems over tropical or sub-tropical waters with organized convection (i.e.; thunderstorm activity). The names correspond to their geographic location of where they formed. For example, typhoons form in the Northwest Pacific Ocean west of the dateline. Hurricanes form in the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E.
The scale was developed in 1971 by civil engineer Herbert Saffir and meteorologist Robert Simpson and became the standard for measuring hurricane strength in 1973. Saffir devised the hurricane scale as a way to estimate damage based on a hurricane’s sustained wind speed. In 2012, the the National Hurricane Center expanded the Category 4 windspeed range for 1 mph in both directions, to 130–156 mph.
Category One Hurricane
Winds 74-95 mph (64-82 kt or 119-153 km/hr): Storm surge 4-5 ft above normal. No serious damage to building structures other than cosmetic due to small debris. Some structure may suffer moderate damage due to large fallen trees, mostly as a result of supersaturated ground which weakens root stability. However, most damage is afflicted upon mobile homes and vegetation. Some damage may occur on large billboard signs. There may be some coastal road flooding. More serious damage is probably due to embedded tornadoes. Loss of life is expected to be very low.
Category Two Hurricane
Winds 96-110 mph (83-95 kt or 154-177 km/hr): Storm surge usually 6-8 feet above normal. Some roofing material, door, and window damage afflicted upon buildings due to wind and flying debris. Considerable damage to vegetation, especially larger high-profile trees. Considerable damage to mobile homes, billboard signs, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of the hurricane center due to torrential rains. Small craft in unprotected docks may be set adrift. Loss of life is expected to be very low.
Category Three Hurricane
Winds 111-129 mph (96-112 kt or 178-208 km/hr): Storm surge 9-12 ft above normal. Some structural damage to well built small residences. Utility poles downed. Considerable damage to large trees, with large limbs breaking or the tree completely uprooting. Mobile homes are heavily damaged, if not destroyed, and offer no protection. Billboards of all types are either destroyed or heavily damaged. Low-lying escape routes are cutoff by rising water due to rain and storm surge. More small craft will be set adrift as they break moorings. Some sink or will be thrown ashore in storm surge. Terrain lower than 5 ft above mean sea level may be flooded inland. Some loss of life expected.
Category Four Hurricane
Winds 131-156 mph (114-135 kt or 210-249 km/hr): Storm surge 13-18 ft above normal and causes substantial damage to low lying areas near the coast. Massive evacuations as far as 6 miles (10 km) inland may be required. Heavy damage to boats and docks. Major damage to lower floors of structures near the shore due to storm surge. Well constructed residential and large buildings start to suffer moderate damage primarily due to debris, downed trees and wind. Complete destruction of mobile homes. Terrain lower than 10 ft above sea level may be flooded depending on geography and flood control.
Category Five Hurricane
Winds greater than 157 mph (137 kt or 252 km/hr): Storm surge greater than 18 ft above normal. Complete roof failure on many inland residences and industrial buildings. Well built homes along the coastline are heavily damaged. Large airborne debris inflicts even greater damage inland. No trace of mobile homes that were not secured to a foundation. Massive evacuations of residential areas near the coastline, or in low lying regions within the path of the hurricane. Marinas, docks and boats destroyed or sunk. Loss of life is probable.
Only three Category Five Hurricanes have made landfall in the United States since records began: The “Labor Day Hurricane” of 1935, Hurricane Camille in 1969, and Hurricane Andrew in August, 1992. Although Hurricane Katrina was the most costly hurricane to hit the United States, it made landfall as a Category 3. Most of the damage was a result of New Orleans being below sea level and serious failure of the levy system which caused massive flooding.