What is the Saffir-Simpson scale; How it works; is there a category 6? – 102.3 KRMG


One was a structural engineer who thought about how engineers are trained – in a logical and results-oriented way.

The other was a meteorologist who, at the age of 6, had survived one of the deadliest hurricanes to ever hit the United States and was eager to warn others of the destructive potential of a system tropical weather.

Together, engineer Herbert Saffir and meteorologist Robert Simpson developed a system that gave people living in storm-prone areas clear, early warning of trouble ahead.

Hurricane Saffir-Simpson Wind Scale was developed in 1971 and unveiled to the public in 1973.

Here’s a look at the system that classifies tropical cyclones based on their potential destructive power, how it works, and the men who invented it.

What is the Hurricane Saffir-Simpson Wind Scale?

The scale rates the potential for hurricane damage based on the storm’s sustained wind speed.

Who were Saffir and Simpson?

Herbert Saffir was a structural engineer who moved to Florida to become a county engineer after graduating from Georgia Tech and serving in World War II.

After living in South Florida for a while, Saffir became interested in the effects of hurricane-force winds on coastal structures, and in 1959 opened a structural engineering business in Coral Gables, Florida.

He quickly became an expert on the forces that damage buildings during a storm and was asked to help develop building codes for the area.

His expertise has led to a appointment to lead a United Nations project looking for a low cost way to reduce damage to buildings in hurricane prone areas. The work he did on this project became the basis for Saffir’s Wind Damage Scale.

Saffir continued to work in structural engineering until four weeks before his death at age 90 in 2007.

Robert Simpson had first-hand knowledge of hurricanes from an early age. In 1919, when he was 6 years old, he and his family survived a massive hurricane that made landfall near Corpus Christi, Texas. The family had to swim through city streets to safety as waters rose 8 feet above street level.

“The family had to swim — with me on my father’s back — three blocks in near hurricane-force winds to safety in the courthouse,” Simpson said. “Much of what I saw frightened me, but also provided a fascination that left me with a lifelong interest in hurricanes.”

After graduating from Southwestern University in Georgetown, Texas, and then earning a master’s degree at Emory University in Atlanta, he worked as a music teacher at high schools in Texas because he couldn’t find work as a music teacher. than a physicist. Finally, in 1940, he was hired by the US Weather Bureau as a meteorologist. Simpson has worked all over the world for the Weather Bureau, with stints in New Orleans, Panama, Miami, Hawaii, and Washington DC.

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In the 1950s, he lobbied officials of the Weather Bureau (the forerunner of the National Weather Service) to do more research on tropical systems and their effects on coastal areas. His arguments worked, and in 1955 he was appointed to leading the National Hurricane Research Project.

He led the project for four years and then left to do a doctorate at the University of Chicago. In the 1960s, he was in charge of STORMFURY projectan experiment in which clouds were seeded with silver iodide in hopes of decreasing the intensity of hurricanes.

In 1967 Simpson became the assistant director of the National Hurricane Center. In 1968, he was appointed director of the center. He remained at the NHC until 1973.

He retired to Washington to start a weather consulting company with his wife, Joanne.

How was the Saffir-Simpson Hurricane Wind Scale developed?

The category system that has become how the National Hurricane Center conveys the force and destructive potential of a storm did not begin as an NHC project.

Saffir’s work on the United Nations project led him to create a hurricane rating system that the UN could use to try to match buildings with their potential risk of damage. At the time, hurricanes were classified as “minor” or “major” storms. In 1969, Saffir proposed a rating system that included five categories using wind speed, barometric pressure, likely flooding, and storm surge as determining factors.

Saffir entrusted his work to Simpson, who was the head of the NHC at the time. Simpson wanted to have a system that gives people common sense information about storms to help them make a decision on whether to stay put or evacuate a coastal area.

Neil Frank, who succeeded Simpson as director of the NHC, told the Washington Post that Simpson was “very responsive to being able to communicate to the public in meaningful terminology”.

Simpson and Saffir worked together. Simpson assigned a range of wind speeds and storm surges for each category, and the Saffir-Simpson Hurricane Wind Scale was born.

The NHC released the scale to the public in 1973 and began rating storms the following season.

The system remained as developed until 2009, when the NHC eliminated storm surge, pressure, and potential flooding from the factors that make up the categories. These factors, the NHC explained, did not always correlate with the damage storms can inflict.

Another change was made in 2012, when the wind speed for a Category 4 storm was changed by 1 mph at both ends of the category. This was done because wind speeds are measured in 5-knot increments by the NHC, and converting to a measurement in miles per hour incorrectly classified storms as Category 3 or Category 5.

How does the Saffir-Simpson scale work?

The scale has five categories ranging from Category 1 – with winds of 74 mph to 95 mph to a Category 5 – with sustained winds above 155 mph. The National Hurricane Center uses an average time of one minute to establish a measure of sustained winds. In other words, the highest sustained wind speed for a full minute would be the highest sustained wind speed for a storm.

Here are the categories of the scale from the National Hurricane Center:

Category 1: Maximum sustained winds are at 74-95 mph. Very dangerous winds will cause damage: Well-built frame homes could damage the roof, shingles, vinyl siding and gutters. Large tree branches break and trees with shallow roots can be knocked over. Extensive damage to power lines and poles will likely result in power outages lasting from a few days to several days.

Category 2: Maximum sustained winds are at 96-110 mph. Extremely dangerous winds will cause considerable damage: well-built frame houses could suffer significant damage to the roof and siding. Many trees with shallow roots will be broken or uprooted and block many roads. Near total loss of power is expected with outages that could last from several days to several weeks.

Category 3: Maximum sustained winds are at 111-129 mph. Devastating damage will occur: Well-constructed frame homes can suffer major damage or removal of roof decking and gables. Many trees will be snapped or uprooted, blocking many roads. Electricity and water will be unavailable for several days to several weeks after the storm has passed.

Category 4: Maximum sustained winds are at 130-156 mph. Well-constructed frame homes can sustain severe damage with the loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and utility poles knocked down. Fallen trees and utility poles will isolate residential areas. Power outages will last for weeks or even months. Most of the area will be uninhabitable for weeks or months.

Category 5: Maximum sustained winds are at 157 or more. Catastrophic damage will occur: a high percentage of frame houses will be destroyed, with total roof failure and wall collapse. Fallen trees and utility poles will isolate residential areas. Power outages will last for weeks or even months. Most of the area will be uninhabitable for weeks or months.

Can there be a category 6 hurricane?

With the stronger storms of the past decade, some have wondered if there should be another category for hurricanes, a Category 6 that would include storms with sustained winds of 158mph-180mph.

Before his death in 2014, Simpson argued there was no need for another category since what is being measured is the potential damage a hurricane’s winds can inflict on man-made structures. Simpson once told the Washington Post that “when you get into winds above 155 mph (249 km/h), you have enough damage if that extreme wind stays for six seconds on a building, it’s going to cause a breaking damage that is serious, no matter how good the engineering.

In other words, the winds from a Category 5 storm will be enough to severely damage or destroy most man-made structures.

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