The Saffir-Simpson Tropical Cyclone Scale (SSTCS) has two purposes. First, it is developed to give decision- makers and the general public an idea of the level of damage to expect from an advertised numerical tropical cyclone intensity value. This should alleviate much of the confusion that exists when lay people are confronted with numerical intensity values. Second, it can be used in analysis and post-analysis by a trained observer to assess the intensity of a tropical cyclone when wind-measuring instruments are not available or have malfunctioned.

The following paragraphs describe the two tropical storm categories and the five typhoon/hurricane categories of the Saffir-Simpson Tropical Cyclone Scale, and the ranges of wind that pertain to each. The categories herein are based on a 1-minute average maximum sustained wind (MSW) and a 1-3 second peak gust. These values are given in miles per hour (mph) and knots (kt). Conversions of the SSTCS for 10-minute average winds in miles per hour, knots, meters per second, and kilometers per hour are given in Appendix A. The common names of the vegetation types described in the SSTCS are for Guam, the Commonwealth of the Northern Mariana Islands, and much of Micronesia. The scientific names (Genus species) are shown in the text. If there are multiple species, the species name is replaced with spp. While the species names are useful, it is the Genus that most closely delineates the plant’s response to the wind. In adapting the SSTCS for a specific locale, the vegetation types should be converted to the more common plant names that pertain to the given Genus and local species, since plant species often vary from region to region. Corresponding scientific family names are also given in Appendix B. Structures and infrastructure described herein are those commonly found in tropical and subtropical regions. Common building techniques used in tropical regions are also factored into the Scale. The structure types span the spectrum from poorly constructed lean-to structures to steel reinforced concrete structures. The weakening effects of termites, wood rot, and salt water corrosion are addressed where appropriate. Coastal wave action/coastal inundation refer to effects in open bays fed by rivers, harbors, and at coastlines surrounded by fringing reefs. These values are given in feet (ft) and meters (m), and are independent of tidal variation. Tidal variation should be factored in to determine actual water levels. Values inside barrier reefs will be somewhat higher, depending on the distance from the reef front to the dry land and the depth of water inside the reef. Waves affecting sheer cliff lines are not specifically addressed in the Scale. However, as the waves hit the base of the cliff, they are similar in height to the wave heights in the open ocean. When the waves crash against the cliff, large volumes of water will be forced up the face of the cliff and may reach heights more than twice the height of the incoming waves. Sheets of sea spray can reach heights more than four times the height of the incoming waves. Minimum sea level pressures are not used in the Scale due to the large variability observed in the relationship between maximum sustained wind and minimum sea level pressure in Pacific tropical cyclones. This Scale has not been tested in other tropical basins; however, in constructing the Scale, a large volume of wind and damage information from other tropical basins was assessed, and the wind-damage relationships were found to be very consistent with those observed in the Pacific. In fact, data from other tropical basins were ultimately incorporated into the development of the final Scale. A User’s Manual for the Scale is currently being completed.

THE SAFFIR-SIMPSON TROPICAL CYCLONE SCALE (SSTCS)

Potential Damage - Damage done to only the flimsiest lean-to type structures. Unsecured light signs blown down. Minor damage to banana trees [Musa spp.] and near-coastal agriculture, primarily from salt spray. Some small dead limbs, ripe coconuts, and dead palm fronds blown from trees. Some fragile and tender green leaves blown from trees such as papaya [Carica papaya] and fleshy broad leaf plants.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of less than 2 ft (0.7 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can reach 2-3 ft (0.7-1.0 m); less than 1 ft (0.3 m) over reefs. Rough surf at reef margin with moderately strong along-shore currents (rip tides) inside reefs.

Potential Damage - Minor damage to buildings of light material; major damage to huts made of thatch or loosely attached corrugated sheet metal or plywood. Unattached corrugated sheet metal and plywood may become airborne. Wooden signs not supported with guy wires are blown down. Moderate damage to banana trees [Musa spp.], papaya trees [Carica papaya], and most fleshy crops. Large dead limbs, ripe coconuts, many dead palm fronds, some green leaves, and small branches are blown from trees.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of 2-4 ft (0.7-1.2 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can reach 4-6 ft (1.2-1.8 m); 1-2 ft (0.3-0.7 m) over reefs. Very rough surf at reef margin with strong along-shore currents (rip tides) inside reefs.

Potential Damage - Corrugated metal and plywood stripped from poorly constructed or termite-infested structures and may become airborne. A few wooden, non-reinforced power poles tilted, and some rotten power poles broken. Some damage to poorly constructed, loosely attached signs. Major damage to banana trees [Musa spp.], papaya trees [Carica papaya], and fleshy crops. Some young trees downed when the ground is saturated. Some palm fronds crimped and bent back through the crown of coconut palms [Cocos nucifera]; a few palm fronds torn from the crowns of most types of palm trees; many ripe coconuts blown from coconut palms. Less than 10% defoliation of shrubbery and trees; up to 10% defoliation of tangantangan [Leucaena spp.]. Some small tree limbs downed, especially from large bushy and frail trees such as mango [Mangifera spp.], African tulip [Spathodea campanulata], poinciana [Delonix regia], etc. Overall damage can be classified as minimal.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of 4-5 ft (1.2-1.5 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can reach 5-7 ft (1.5-2.1 m) above normal; 2-3 ft (0.6-1.0 m) additional water across reef. Wind-driven waves may inundate low-lying coastal roads where reefs are narrow. Minor pier damage. Some small craft in exposed anchorages break moorings.

Potential Damage - Several rotten wooden power poles snapped and many non-reinforced wooden power poles tilted. Some secondary power lines downed. Damage to wooden and tin roofs, and doors and windows of termite-infested or rotted wooden structures, but no major damage to well-constructed wooden, sheet metal, or concrete buildings. Considerable damage to structures made of light materials. Major damage to poorly constructed, attached signs. Exposed banana trees [Musa spp.] and papaya trees [Carica papaya] totally destroyed; 10-20% defoliation of trees and shrubbery; up to 30% defoliation of tangantangan [Leucaena spp.]. Light damage to sugar cane [Saccharum spp.] and bamboo [Bambusa spp.]. Many palm fronds crimped and bent through the crown of coconut palms [Cocos nucifera] and several green fronds ripped from palm trees. Some green coconuts blown from trees. Some trees blown down, especially shallow rooted ones such as small acacia [Acacia spp.], mango [Mangifera indica] and breadfruit [Artocarpus spp.] when the ground becomes saturated. Overall damage can be classified as moderate.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of 6-8 ft (1.8-2.4 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can reach 7-9 ft (2.1-2.7 m) above normal; water is about 3-5 ft (1.0-1.5 m) above normal across reef flats. Wind-driven waves will inundate low-lying coastal roads below 4 ft (1.0 m) on windward locations where reefs are narrow. Some erosion of beach areas, some moderate pier damage, and some large boats torn from moorings.

Potential damage - . A few non-reinforced hollow-spun concrete power poles broken or tilted and many non-reinforced wooden power poles broken or blown down; many secondary power lines downed. Practically all poorly constructed signs blown down and some stand-alone steel-framed signs bent over. Some roof, window, and door damage to well-built, wooden and metal residences and utility buildings. Extensive damage to wooden structures weakened by termite infestation, wet-and-dry wood rot, and corroded roof straps (hurricane clips). Non-reinforced cinderblock walls blown down. Many mobile homes and buildings made of light materials destroyed. Some glass failure due to flying debris, but only minimal glass failure due to pressure forces associated with extreme gusts. Some unsecured construction cranes blown down. Air is full of light projectiles and debris. Major damage to shrubbery and trees; up to 50% of palm fronds bent or blown off; numerous ripe and many green coconuts blown off coconut palms; crowns blown off of a few palm trees. Moderate damage to sugar cane [Saccharum spp.] and bamboo [Bambusa spp.]. Some large trees {palm trees, breadfruit [Artocarpus spp.], monkeypod [Samanea saman], mango [Mangifera indica], acacia [Acacia spp.] and Australian pines [Casuarina spp.]} blown down when the ground becomes saturated; 30-50% defoliation of most trees and shrubs; up to 70% defoliation of tangantangan [Leucaena spp.]. Some very exposed panax [Polyscias spp.], tangantangan [Leucaena spp.], and oleander [Nerium oleander] bent over. Overall damage can be classified as extensive.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of 9-12 ft (2.7-3.6 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can reach 11-14 ft (3.3-4.2 m) above normal; water is about 5-7 ft (1.5-2.1 m) above normal across reef flats. Wind-driven waves will inundate low-lying coastal roads below 7 ft (2.1 m) of elevation on windward locations where reefs are narrow. Considerable beach erosion. Many large boats and some large ships torn from moorings.

Potential Damage - Some reinforced hollow-spun concrete and many reinforced wooden power poles blown down; numerous secondary and a few primary power lines downed. Extensive damage to non-concrete roofs; complete failure of many roof structures, window frames and doors, especially unprotected, non-reinforced ones; many well-built wooden and metal structures severely damaged or destroyed. Considerable glass failures due to flying debris and explosive pressure forces created by extreme wind gusts. Weakly reinforced cinderblock walls blown down. Complete disintegration of mobile homes and other structures of lighter materials. Most small and medium-sized steel-framed signs bent over or blown down. Some secured construction cranes and gantry cranes blown down. Some fuel storage tanks may rupture. Air is full of large projectiles and debris. Shrubs and trees 50-90% defoliated; up to 100% of tangantangan (Leucaena spp.) defoliated. Up to 75% of palm fronds bent, twisted, or blown off; many crowns stripped from palm trees. Numerous green and virtually all ripe coconuts blown from trees. Severe damage to sugar cane [Saccharum spp.] and bamboo [Bambusa spp.]. Many large trees blown down {palms, breadfruit [Artocarpus spp.], monkeypod [Samanea saman], mango [Mangifera indica], acacia [Acacia spp.], and Australian pine (Casuarina spp.). Considerable bark and some pulp removed from trees; most standing trees are void of all but the largest branches (severely pruned), with remaining branches stubby in appearance; numerous trunks and branches are sandblasted. Patches of panax [Polyscias spp.], tangantangan [Leucaena spp.], and oleander [Nerium oleander] bent over or flattened. Overall damage can be classified as extreme.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of 13-18 ft (3.9-5.5 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can reach 15-24 ft (4.5-7.3 m) above normal; water is about 8-12 ft (2.4-3.7 m) above normal across reef flats. Wind-driven waves will inundate coastal areas below 12 ft (3.7 m) elevation. Large boulders carried inland with waves. Severe beach erosion. Severe damage to port facilities including some loading derricks and gantry cranes. Most ships torn from moorings.

Potential Damage - Severe damage to some solid concrete power poles, to numerous reinforced hollow-spun concrete power poles, to many steel towers, and to virtually all wooden poles; all secondary power lines and most primary power lines downed. Total failure of non-concrete reinforced roofs. Extensive or total destruction to non-concrete residences and industrial buildings. Some structural damage to concrete structures, especially from large debris, such as cars, large appliances, etc. Extensive glass failure due to impact of flying debris and explosive pressure forces during extreme gusts. Many well-constructed storm shutters ripped from structures. Some fuel storage tanks rupture. Nearly all construction cranes blown down. Air full of very large and heavy projectiles and debris. Shrubs and trees up to 100% defoliated; numerous large trees blown down. Up to 100% of palm fronds bent, twisted, or blown off; numerous crowns blown from palm trees; virtually all coconuts blown from trees. Most bark and considerable pulp removed from trees. Most standing trees are void of all but the largest branches, which are very stubby in appearance and severely sandblasted. Overall damage can be classified as catastrophic.

Coastal Inundation and Wave Action - On windward coasts, sea level rise of > 25 ft (> 7.6 m) above normal in open bays and inlets due to storm surge and wind-driven waves; breaking waves inside bays can be > 30 ft (9.2 m) above normal; water is about 12-18 ft (3.7-5.5 m) above normal across reef flats. Serious inundation likely for windward coastal areas below 18 ft (5.5 m) elevation. Very large boulders carried inland with waves. Extensive beach erosion. Extensive damage to port facilities including most loading derricks and gantry cranes. Virtually all ships, regardless of size, torn from moorings.

Appendix A. Wind speed ranges for 10-minute average sustained winds and associated wind gusts for the various tropical storm and typhoon/hurricane wind-damage categories. Values are given in miles per hour (mph), knots (kt), kilometers per hour (km/hr), and meters per second (m/s).

Appendix B. Local and scientific names of trees on Guam.

Note: This article was originally written in MS Word Format by the said authors. Reformatted in HTML Coding w/ permission by David Michael V. Padua of TYPHOON '99 Website (http://www.geocities.com/capecanaveral/6825) (http://borg.ncf.edu.ph/typhoon99). A very special thanks goes to Mr. Gary Padgett (Global Tropical Cyclone Monthly Summary) & Mr. Charles ‘Chip’ Guard (University of Guam) for allowing me to publish this very useful information.

Date published: Sunday, 08 August 1999