hurricane intensity scales
Several scales of tropical cyclone intensity have been developed, one of the first being the Saffir-Simpson hurricane wind scale, which was devised in the United States in the early 1970s. This scale—created by American engineer Herbert Saffir and American meteorologist Robert Simpson (director of the National Hurricane Center from 1968 to 1973)—is based on wind speed, and the rankings, represented by categories 1 through 5, take into account the damage and other ground-level effects produced by different wind speeds. The Saffir-Simpson scale, which is used primarily in the Atlantic Ocean and eastern Pacific Ocean, is given in the table.
| category | wind speed | damage | |
|---|---|---|---|
| mph | km/hr | ||
| *Used to rank tropical cyclones in the North Atlantic Ocean (including the Gulf of Mexico and Caribbean Sea) and the eastern North Pacific Ocean. Published by permission of Herbert Saffir, consulting engineer, Robert Simpson, meteorologist, and the National Weather Service of the National Oceanic and Atmospheric Administration. | |||
| 1 | 74–95 | 119–153 | Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days. |
| 2 | 96–110 | 154–177 | Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks. |
| 3 | 111–129 | 178–208 | Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes. |
| 4 | 130–156 | 209–251 | Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months. |
| 5 | >157 | >252 | Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months. |
Similar five-tiered scales are used to rank tropical cyclones occurring near Australia and in the northern Indian Ocean. The Australian scale of cyclone intensity and cyclone categories, used by a consortium of national weather bureaus in the southwestern Pacific, and the cyclone categories scale for the northern Indian Ocean, used by the India Meteorological Department, are given in the table and the list, respectively.
| category | wind speed | damage | |
|---|---|---|---|
| km/hr | mph | ||
| *Corresponds roughly to category 1 of the Saffir-Simpson hurricane wind scale. | |||
| Source: Commonwealth Bureau of Meteorology. | |||
| 1 | 63–90 | 39–56 | some damage to crops, trees, caravans (mobile homes); gusts to 125 km/hr (78 mph) |
| 2 | 91–125 | 57–78 | heavy damage to crops, significant damage to caravans; gusts of 125–170 km/hr (78–105 mph) |
| 3* | 126–165 | 79–102 | some caravans destroyed; some roofs and structures damaged; gusts of 170–225 km/hr (105–140 mph) |
| 4 | 166–226 | 103–140 | significant damage to roofs and structures; caravans destroyed; gusts of 225–280 km/hr (140–174 mph) |
| 5 | >226 | >140 | widespread destruction; gusts greater than 280 km/hr (174 mph) |
Cyclone categories for the northern Indian Ocean
- category 1: (120–150 km [75–93 miles] per hour)
- category 2: (150–180 km [93–112 miles] per hour)
- category 3: (180–210 [112–130 miles] per hour)
- category 4: (210–250 km [130–155 miles] per hour)
- category 5: (greater than 250 km [155 miles] per hour)
In contrast, tropical cyclones in the southwestern Indian Ocean and in the western Pacific Ocean are not ranked according to numerical scales; rather, storms that reach cyclone strength are placed into three-tiered scales of intensity. Scales of tropical cyclones forming in the southwestern Indian Ocean (tracked by Météo-France, France’s weather bureau) and of typhoons occurring in the western Pacific (monitored by the Japan Meteorological Agency, along with weather bureaus in China and the Philippines) are presented below.
Cyclone categories for the southwestern Indian Ocean
- tropical cyclone: (118–165 km [73–103 miles] per hour)
- intense tropical cyclone: (166–212 km [103–132 miles] per hour)
- very intense tropical cyclone: (greater than 212 km [132 miles] per hour)
Cyclone categories for the western Pacific Ocean
- typhoon: (64–85 knots [119–157 km {74–98 miles} per hour])
- very strong typhoon: (85–105 knots [157–194 km {98–121 miles} per hour])
- violent typhoon: (greater than 105 knots [194 km {121 miles} per hour])