How are hurricanes rated? The Saffir-Simpson Hurricane Wind Scale explained

Hurricanes are rated by five categories

Hurricanes in the Atlantic Basin are assigned a Category 1-to-5 rating based on their maximum sustained winds. This classification method is called the Saffir-Simpson Hurricane Wind Scale, and it has been used by the National Hurricane Center to evaluate the strength of hurricanes since the early 1970s.

Herbert Saffir, a civil engineer from Florida, and Dr. Robert Simpson, director of the NHC from 1967-74, created this scale to categorize hurricanes by the types of damage that typically occur at various sustained wind speeds. Saffir initially developed the scale in 1969, and it would later be expanded by Simpson and published under the Saffir-Simpson name in 1973.

The most important thing to note with the Saffir-Simpson Hurricane Wind Scale is that it only accounts for wind, not other potentially deadly hazards from hurricanes such as storm-surge flooding, rainfall flooding and tornadoes.

WHAT IS THE ‘CONE OF UNCERTAINTY’ IN HURRICANE FORECASTS?

Water is the No. 1 killer during a hurricane or tropical storm that strikes the U.S. – comprising nearly 90% of all tropical cyclone deaths – mostly by drowning in either storm surge, rainfall flooding or high surf, according to a 2014 study by Dr. Edward Rappaport, deputy director of the NHC.

During Rappaport’s 1963-2012 period of study, storm-surge flooding claimed nearly half of the fatalities (49%), rainfall-induced freshwater floods and mudslides accounted for about one-quarter of the deaths (27%), high surf was responsible for some 6% of all hurricane deaths and another 6% occurred offshore in marine incidents within 50 nautical miles of the coast.



Rappaport found that only 8% of hurricane- or tropical-storm-related fatalities were from wind, so the Saffir-Simpson Hurricane Wind Scale might not be the best way to classify a hurricane in terms of its impacts on humans. Regardless, the scale does provide guidance on potential property damage from hurricanes of varying wind speeds in the United States.

WATER FROM HURRICANES, TROPICAL STORMS KILLS MORE IN U.S. THAN WIND

Generally, the amount of damage increases by a factor of four with every increase in category on the Saffir-Simpson Hurricane Wind Scale, the National Weather Service says. More than 85% of all damage from hurricanes comes from Category 3, 4 and 5 storms, referred to as "major" hurricanes, even though they make up only 24% of all landfalling U.S. tropical cyclones.

Below is a more in-depth breakdown of the Saffir-Simpson Hurricane Wind Scale from the NHC, which also provides a video demonstrating the types of damage that will likely occur in each category.



Category 1 (74-95 mph): Very dangerous winds will produce some damage

Well-constructed frame homes could have damage to roofs, 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.

Category 2 (96-110 mph): 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.

Category 3 (111-129 mph): 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.

Category 4 (130-156 mph): 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.

Category 5 (157 mph or higher): 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.

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