Types of Hurricanes: Understanding Categories
What is a Hurricane?
Hurricanes are massive tropical cyclonic storms located in the western North Atlantic. When these same cyclonic storms are in the northern Indian Ocean and the Bay of Bengal, they are referred to as cyclones, whereas if they are in the western Pacific Ocean, they are referred to as typhoons. So why the different names, if they are all the same thing?
The short answer is that the differences in word choice is the same reason why some people in America call a carbonated beverage soda and others call it pop. The origins of each word came from the influences of that area. In the North Atlantic, there was a heavy Spanish influence; therefore, the word hurricane comes from the Spanish word huracán, which was an indigenous word for evil spirits or weather gods. Typhoon was used due to the Arabic, Persian, and Hindi influence in the southwest and southern Asia area. It comes from the word tufan, which means a big cyclonic storm. Cyclone is a more generic term for all three, although it can be confused with tornadoes since they also are called cyclones as well. A more precise word choice would be a tropical cyclone.
Hurricanes are named to better keep track of the individual storm, since multiple hurricanes may occur at once. They first get their names when they officially become a tropical storm at 38 mph. The names are chosen dependent on when they occur. The first one of the year begins with A, the second B, and so on. There are six lists created each year, and the lists repeat every six years. If a storm does significant damage, the name may be taken off the list and replaced with a new name that starts with the same letter.
Despite their destructive nature, they do serve a necessary purpose. These bursts of storms are nature's way of smoothing out the extremes and balancing the weather out by transferring tropical areas near the equator to regions near the poles. Unfortunately, the aftermath can be devastating.
Types and Categories
There are five types or categories of tropical cyclones measured by their speed. Before a storm becomes a hurricane, it begins as a tropical disturbance that looks like rain clouds that form over warm ocean waters. They then build up to a tropical depression once the thunderstorms start to rotate. Once they reach 39 mph or 63 km/hr, they are to as a tropical storm. At 74 mph or 119 km/hr, they are hurricanes, typhoons, or cyclones dependent on area.
Once they become a hurricane, they are rated on the Saffir-Simpson Hurricane Scale based on their wind speed. In the chart below, you can see the breakdown of speeds for each. A category 1, the slowest hurricane, is faster than a cheetah, the fastest land animal. A category 2 becomes faster than a pro-baseball pitcher's fastball, whereas a category 3 is equivalent to the speed of a professional tennis player's serve. A category 4 is faster than the top speed of a roller-coaster. A category 5 is the most destructive hurricane with incredible wind speeds.
As a cyclone reaches land, it begins to weaken, because it gets its energy from the warm ocean waters, which does not mean that they do not do significant damage to the land. They can get far inland, causing flooding and wind damage before the storm fully subsides. Once they hit the ground, they are called a Storm Surge.
Tropical Depression (not a hurricane)
38 mph or less (62 km/hr o r less)
Tropical Storm (not a hurricane)
38-73 mph (63-118 km/hr)
74-95 mph (119-153 km/hr)
Hurricane Agnes (1972) category 1 at landfall
96-110 mph (154-177 km/hr)
Hurricane Ike (2008) category 2 at landfall
111-129 mph (178-208 km/hr)
Hurricane Katrina (2005) category 3 at landfall
130-156 mph (209-251 km/hr)
Hurricane Charley (2004) category 4 at landfall
more than 157 mph (252 km/hr)
Hurricane Andrew (1992) category 5 at landfal
How They Form
Tropical cyclones can have deadly force due to their high spiraling speeds. They use warm, moist air as fuel and begin to spin like a giant engine. As the warm moist air rises, it causes an area of lower air pressure. The air from surrounding areas that have higher air pressure then presses its way to the low-pressure area. In a cyclical fashion, the air warms, causing it to rise as well, which then causes the air to begin to swirl and form clouds. These are cumulonimbus clouds, and they increase in number surrounding the storm.
The increase continues to happen, only causing wind speeds to pick up. Because warm water is needed (at least 26 degrees Celsius or 79 degrees Fahrenheit or warmer), they only form near the equator where the sun has warmed the ocean. Hurricanes that form above the equator spin counterclockwise, while those south of the equator spin clockwise. The rotation of the Earth on its axis makes up for the difference.
As the storm rotates faster, the center of it begins to calm. They call this area the eye of the storm since all around it is fast speeds, but the center appears to be clear. Once the winds around the eye reach 74 mph or 119 km/hr, they call that a hurricane. At these spreads, they can release 2.4 trillion gallons or 9 trillion liters of rain in a single day, causing massive flooding or landslides and reach 100 miles or 161 km inland and 20 feet or 6 meters high. Fortunately, as a storm hits land, it does begin to quiet, but not soon enough to prevent damage. It is when they hit the ground that they cause the most destruction, killing many lives and destroying coastal areas.
Parts of a Hurricane
Hurricanes have three parts: the eye, the eyewall, and rain bands.
Eye - Because hurricanes rotate circularly, the center is relatively calm in comparison, which is called the eye of the storm and may be as large as 20-30 miles wide or 32-48 km wide. In the center of the eye, the skies may appear relatively clear.
Eye Wall - Surrounding the eye is the eyewall where the bulk of the activity occurs. It is this area that determines what category the tropical cyclone is rated. It has the strongest winds and rain of all the regions, and they circle the eye. It is a ring of thunderstorms.
Rain Bands - Rain bands are much further out from the eye, and can even be hundreds of miles away. They also contain thunderstorms and sometimes tornadoes. These consist of many clouds.
Most Catastrophic Hurricanes According to Smithsonian
1900 Galveston Hurricane
1915 Galveston Hurricane
The Great Miami Hurricane
Lake Okeechobee Hurricane
The Great New England Hurricane
Southern New England
Mississippi Gulf Coast
Mississippi Gulf Coast
As stated earlier, a tropical cyclone goes by three different names. If it is heading towards the United States or the Caribbean, it is a hurricane. If it is heading towards Asia, it is a typhoon. Everywhere else is called a cyclone.
Of these areas, tropical cyclones are by far the most common in the western Pacific Ocean. So much so, that the Philippines may get struck by up to 20 tropical storms or more a year. In the Eastern and Western Pacific hurricanes, both peak late August and early September, although in the Eastern, they begin in the middle of May, while the Western Pacific hurricanes do not usually start until July. In both areas, hurricanes typically subside by the end of November.
The South Pacific, on the other hand, peak in late February and early March, although the season begins mid-October and goes until mid-May.
The Atlantic Ocean gets far less a year, averaging anywhere between 5 and 6 hurricanes. Their peak time of year to get a tropical cyclone is August to late October, although they may occur anywhere between June 1st and November 30th. In the South Atlantic area, they are so rare, only one has occurred. It was Hurricane "Catarina" in 2004.
The Indian Ocean also has hurricanes. In the northern area, they tend to occur between April and the end of December, while in the southern region, they occur from mid-October until the end of May.
How Do We Learn About Hurricanes?
Our best defense against hurricanes is accurate forecasting. No building could withstand a category five hurricane. The only help is for the people to get out of their way. The Hurricane Center in given areas issues watches and warnings for storms that will hit land in the 24 hours. They can let people know where it is headed and how severe the wind is.
The National Hurricane Center, located in Miami, Florida, notify those that are affected by hurricanes in the North Atlantic area, which includes the area from the equator to the Arctic, the Gulf of Mexico, and the Caribbean, as well as eastern Pacific.
The Central Pacific Hurricane Center, located in Honolulu, covers the central Pacific Ocean, which consists of the area between the International Date Line (180°W) and 140°W.
These centers get their information from satellites that set 22,300 miles above the Earth. NASA built these satellites by NASA and operate the NOAA (National Oceanic and Atmospheric Administration). They have several functions, including:
- To take pictures of the storms.
- To measure cloud and ocean temperatures.
- To gauge the height of clouds.
- To see how fast the rain is falling.
- To measure the speed and direction of winds.
Satellites are not the only instruments NASA uses to measure a hurricane. They also use airplanes that are operated without people inside and fly them overtop the storms.
Hurricanes are deadly forces of nature that can kill lives and decimate buildings. It is essential to know as much about tropical cyclones as possible so that we can better warn those on their destructive path.
Difference Between Tornado and Hurricane
- Dunbar, Brian. "What Are Hurricanes?" NASA. May 13, 2015. Accessed February 15, 2018. https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-are-hurricanes-k4.html.
- "How Hurricanes Form and What Makes Them So Destructive." What Is a Hurricane? November 20, 2017. Accessed February 15, 2018. https://www.nationalgeographic.com/environment/natural-disasters/hurricanes/.
- Mersereau, Dennis. "A Typhoon and a Hurricane Are the Same, So Why Do We Call Them Different Names?" Gawker. Accessed February 19, 2018. http://thevane.gawker.com/a-typhoon-and-a-hurricane-are-the-same-so-why-do-we-ca-1728057794.
- NASA. Accessed February 15, 2018. https://spaceplace.nasa.gov/hurricanes/en/.
- Nuwer, Rachel. "Top Ten Most Damaging U.S. Hurricanes." Smithsonian.com. October 29, 2012. Accessed February 21, 2018. https://www.smithsonianmag.com/smart-news/top-ten-most-damaging-us-hurricanes-98657141/.
- "When and Where Do Hurricanes Occur?" Local Weather from AccuWeather.com - Superior Accuracy™. Accessed February 15, 2018. https://www.accuweather.com/en/weather-blogs/hurricanefacts/when-and-where-do-hurricanes-o/31028.
Questions & Answers
© 2018 Angela Michelle Schultz