|
Scale |
Maximum Sustained Winds |
Central Pressure |
Surge |
Damage |
Description |
|
1 |
119-153 [gust |
>980 |
~1.5 |
Minimal |
Damage primarily to shrubbery, trees, foliage and unanchored mobile homes. No real damage to other structures. Some damage to poorly constructed signs. Low-lying coastal roads inundated, minor pier damage, some small craft torn from moorings in exposed anchorage |
|
2 |
154-178 [gust |
965-979 |
~2-2.5 |
Moderate |
Considerable damage to shrubbery and tree foliage; some trees blown down. Major damage to exposed mobile homes. Extensive damage to poorly constructed signs. Some damage to roofing materials of buildings; some window and door damage. No major damage to buildings. Coastal roads and low-lying escape routes inland cut by rising water 2 to 4 hours before arrival of hurricane centre. Considerable damage to piers; marinas flooded. Small craft torn from moorings in unprotected anchorages. Evacuation of some shoreline residences and low-lying island areas required. |
|
3 |
179-209 [gust |
945-964 |
~2.6-3.9 |
Extensive |
Foliage torn from trees; large trees blown down. Practically all poorly constructed signs blown down. Some damage to roofing materials of buildings; some window and door damage. Some structural damage to small buildings. Mobile homes destroyed. Serious flooding at coast; many smaller structures near coast destroyed; larger structures near coast damaged by battering waves and floating debris.. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane centre arrives. Flat terrain 1.5 m or less asl flooded inland ~13 km or more. Evacuation of low-lying residences within several blocks of shoreline possibly required. |
|
4 |
211-249 [gust |
920-944 |
~4-5.5 |
Extreme |
Shrubs and trees blown down; all signs down. Extensive damage to roofing materials, windows and doors. Complete failure of roofs on many small residences. Complete destruction of mobile homes. Flat terrain ~3 m or less asl flooded inland as far as ~10 km. Major damage to lower floors of structures near shore due to flooding and battering by waves and floating debris. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane centre arrives. Major erosion of beaches. Massive evacuation of all residences within ~455 m of shore possibly required, and evacuation of single-story residences on low ground within ~3 km of shore required. |
|
5 |
>249 [gust |
<920 |
>5.5 |
Catastrophic |
Shrubs and trees blown down; considerable damage to roofs of buildings; all signs down. Very severe and extensive damage to windows and doors. Complete failure of roofs on many residences and industrial buildings; extensive shattering of glass in windows and doors. Some complete building failures. Small buildings overturned or blown away. Complete destruction of mobile homes. Major damage to lower floors of all structures less than ~4.5 m asl within ~455 m of shore. Low-lying escape routes inland cut by rising water 3 to 5 hours before hurricane centre arrives. Massive evacuation of residential areas on low ground within ~8 to 16 km of shore possibly required. |
Gust speeds = sustained wind x 1.25 [Lander and Guard, 1991]
Saffir [1974] indicates that SS scale was intended as a scale allowing global comparison. Saffir [a consulting engineer] established the categories, scale of velocities and scale of wind damage in July 1971 in a report he prepared for the UN on construction in hurricane prone areas. Simpson at the National Hurricane Center later added descriptions of possible storm surge effects in coastal areas.
According to Saffir [1974] wind velocities are based on gust velocities at a 30 ft elevation above ground. However, Simpson and Riehl [1981, p366] indicate that maximum sustained wind speeds are used. The wind speeds given in all 3 versions are identical except that Saffir [1974] puts the boundary between SS 4 and 5 at 150 mph [155 mph in other versions].
Simpson and Riehl [1981, p366] provide some clues as to how the scale was constructed. Indicates SS 1 begins with maximum sustained winds of at least 119 km/h or which will produce a storm surge 1.4 m above normal water level. SS 5 applies to those in which the maximum sustained winds are 249 km/h or more, or which have the potential of producing a storm surge of more than 5.5 m above normal. Atmospheric-pressure ranges have been adapted to this scale. [This key piece of information is missing from the 1974 paper – Weatherwise, vol 27[4], 169, 186.]
The scale numbers represent an estimate of what the storm would do to a coastal area if it were to strike without change in size or strength. It is clear from the 1981 text that SS number can be defined in terms of either the wind speed, the storm surge height or both.
Total emphasis here is on wind damage and storm surge damage. No consideration of flooding other than that produced by storm surge.
Guam, Miami and Honolulu use 1-minute average wind speed for highest sustained wind speeds in tropical cyclone warnings [Lander and Guard, 1991]
If
2-second gust = 100%
3-second gust ~ 98%
1 minute sustained average ~80%
10 minute wind speed over open water at 10 m ~68%
10 minute wind: 1 minute wind over area of trees and houses ~75%2-second gusts over areas of water and land not much different [Lander and Guard, 1991].
References
Lander, M. A. & Guard C. P., 1991, "Towards a consensus and public understanding of the definitions of maximum sustained winds in tropical cyclones, Proceedings of the Second Workshop for Natural Disaster Reduction, Japan-U.S. Science & Technology Agreement, Karuizawa, Nagono, Japan, 23-27 September, 1991, 420-422.
Simpson, R. H. & Riehl, H., 1981, The Hurricane and its impact. Louisiana State University Press, Baton Rouge, La.
Saffir, H.S., 1974, Saffir-Simpson Scale for Hurricanes, p21-23 in unknown volume issued by Herbert S. Saffir, Consulting Engineers, Coral Gables, Florida, 23 August 1974.
