The Saffir-Simpson Hurricane Wind Scale (SSHWS) is the primary tool used by forecasters to classify tropical cyclones that reach hurricane status in the Atlantic Ocean and the Northeast Pacific basin. This standardized system is essential for public safety and preparedness in vulnerable coastal regions. The scale provides a simple, five-category rating that correlates wind speed directly with the expected property damage upon landfall.
Defining the Saffir-Simpson Scale
The Saffir-Simpson Hurricane Wind Scale (SSHWS) uses a 1-to-5 rating to classify the intensity of a storm once it surpasses the tropical storm threshold. It is focused exclusively on measuring the maximum sustained wind speed of a hurricane to estimate the potential for wind-related damage to property and infrastructure. The scale measures the highest average wind speed sustained over a one-minute interval at a height of about 33 feet (10 meters) above the surface, which is the standard used by the U.S. National Hurricane Center. This singular focus on wind speed serves as a streamlined public communication tool for preparedness.
The History of Its Creation
The scale originated in 1969 when civil engineer Herbert Saffir was tasked by the United Nations to study low-cost housing in hurricane-prone areas. Saffir developed a five-point grading system to correlate wind speed with the potential for structural damage to buildings. He shared this system with Robert Simpson, then director of the U.S. National Hurricane Center.
Simpson revised the system, changing “grade” to “category” and initially adding estimates for storm surge and central barometric pressure. The Saffir-Simpson Scale was first introduced to the public in 1973 and saw widespread use starting in 1974. The system continued to evolve, undergoing a significant revision in 2009 (operational in 2010). This revision removed the storm surge and pressure components, officially transforming it into the Saffir-Simpson Hurricane Wind Scale.
Decoding the Five Categories
The Saffir-Simpson Hurricane Wind Scale begins classifying tropical cyclones once their maximum sustained winds reach 74 miles per hour (mph), which is the threshold for a Category 1 hurricane. A storm with winds between 39 and 73 mph is classified as a tropical storm and does not appear on the hurricane wind scale. Hurricanes rated Category 3 or higher are considered “major hurricanes” due to their potential for significant loss of life and property damage.
A Category 1 storm (74 to 95 mph) produces dangerous winds that cause some damage, including damage to roof shingles, gutters, and vinyl siding. Shallowly rooted trees may topple, leading to extensive power outages lasting a few days. Category 2 storms (96 to 110 mph) cause extensive damage, including major roof and siding damage on well-constructed frame homes. Near-total power loss is expected, with outages lasting from several days to weeks.
Category 3 storms (111 to 129 mph) feature devastating damage. Well-built framed homes may incur major damage, including the removal of roof decking, and numerous trees will be snapped or uprooted, isolating areas. Category 4 storms (130 to 156 mph) bring catastrophic damage. Even well-built framed homes can sustain severe damage, losing most of the roof structure and some exterior walls. Power outages can last weeks or months, rendering the region uninhabitable for extended periods.
The most intense classification is the Category 5 hurricane, consisting of sustained winds of 157 mph or higher. At this level, a high percentage of framed homes will be destroyed, with total roof failure and wall collapse being common. Fallen trees and power poles isolate residential areas, and power outages can last for months.
Limitations of the Scale
While the Saffir-Simpson Hurricane Wind Scale is a reliable measure of wind intensity, its singular focus means it excludes other potentially deadly hazards. Foremost among these is storm surge, often the most dangerous element of a tropical cyclone. Storm surge is the abnormal rise of water generated by the storm, and its height depends on factors like the storm’s size, angle of approach, and coastal topography, not just the maximum wind speed.
The scale also does not account for rainfall totals, which can lead to catastrophic inland flooding far from the coast. Furthermore, the category number does not convey the storm’s overall size or its radius of damaging winds. A lower-category storm that is large and slow-moving can produce greater storm surge and more widespread rain-induced flooding than a smaller, faster-moving, higher-category storm. Because these factors are not included in the SSHWS rating, separate forecasts and warnings are issued for storm surge, rainfall, and potential tornadoes. The category number should not be interpreted as an all-encompassing indicator of the storm’s overall danger level.