What Does Hurricane Category 1, 2, 3, 4, 5...Mean?
If you happen to turn on the news during hurricane season and a storm is abrewin' there's a good chance that one of the anchors will mention that a tropical storm has been upgraded and is now designated a Category Two, a Category Three storm, or heaven forbid a Category 5 storm. If you live in the South there's a good chance that the mention of a Category 4 or 5 storm gives you flashbacks to Hurricane Katrina or Andrew or Charley or Irma or Florence or any of the many, many storms that have battered the coast over the years. But what exactly is the difference between a tropical storm and a Category 3 or a Category 5 storm?
All hurricanes start out as tropical cyclones, whipping up winds out in the Atlantic Ocean, usually accompanied by rain and storm surges. When a tropical storm gets big enough to attract attention, it's usually a tropical depression that is given a number by the National Hurricane Center (NHC) who is keeping tabs on them. Once its winds kick up to 39 miles per hour and sustain that speed for 10 minutes, it becomes a tropical storm and the NHC gives it a name. If the storm keeps growing and eventually sustains winds of 74 mph, it graduates to being a fully-fledged hurricane.
How Hurricane Categories Are Determined
To determine which category a storm belongs in, meteorologists use something called the Saffir-Simpson Hurricane Wind Scale, which measures a hurricane's strength based sustained wind speed. The scale was originally developed by wind engineer Herb Saffir and meteorologist Bob Simpson in the mid-70s and has been used ever since to help alert the public so they can prepare for the possible impact of impending storms. The scale lays out the speed of the wind and the type of damage and impact it can have.
According to the experts at the National Hurricane Center, the system divides storms into five categories. In general, damage rises by about a factor of four for every category increase.
Category 1: Winds 74 to 95 mph, which will usually produce minor damage, including to trees and power lines.
Category 2: Winds 96 to 110 mph, that could result in extensive damage, uprooting trees, breaking windows, and snapping power lines.
Category 3: Winds 111 to 129 mph that can lead to devastating damage to homes and trees and loss of power and water.
Category 4: Winds 130 to 156 mph lead to catastrophic damage to homes with winds strong enough to tear off roofs and walls. Can make areas uninhabitable for weeks or months.
Category 5: Winds 157 mph or higher, which can result in leveled homes, fallen trees, downed power lines potentially leading to months-long outages and devastated communities.
Hurricane Damage and Safety
While winds zipping by at 129 miles per hour can certainly be terrifying, just because a storm has high-speed wind doesn't mean it will always cause a lot of damage. Things like up-to-date building codes can dramatically lessen the impact of storms, and other factors, such as the duration of high winds and a change of wind direction can also mitigate damage.
High winds, of course, are just a part of the damage that comes with a hurricane. The Saffir-Simpson Scale only measures wind and does not address those other forms of potential damage that people who live in hurricane zones know by heart: storm surge, floods, and tornadoes.
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