tracks of all tropical cyclones which formed worldwide from 1985 to 2005. The points show the locations of the storms at six-hour intervals. The colors relate to each storm's Saffir-Simpson Hurricane Scale rating (Blue=tropical depression; teal=tropical storm; white=Category 1; yellow=Category 2; yellow-orange=Category 3; orange=Category 4; red=Category 5). Image Credit: NASA and Nilfanion [Public domain], via Wikimedia Commons.
You can probably think of some hurricanes that have struck the United States in your lifetime—Sandy in 2012, Ike in 2008, or Katrina in 2005, for instance. You may know they caused a lot of damage and that people died as a result, but what else do you know about hurricanes?
In the U.S., hurricane, or tropical cyclone, season runs June 1–November 30 in the Atlantic Ocean and May 15–November 30 in the Pacific Ocean. Nearly all hurricanes form during these periods. When a storm becomes a hurricane depends on sustained wind speeds, according to a system called the Saffir-Simpson Wind Scale. When wind speeds reach 39 mph (63 kph), a storm becomes a tropical storm and is given a name. When sustained winds reach 74 mph, the tropical storm has become a hurricane. Hurricanes fall into five categories, each designated by their sustained wind speed. While all are dangerous, hurricanes in categories 3 or higher are considered major storms, capable of inflicting catastrophic damage on anything in their path.
| Category | Sustained Wind Speed in Miles per Hour | Type of Damage Caused |
| 1 | 74–95 | Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, 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. |
| 2 | 96–110 | 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. |
| 3 | 111–129 | 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. |
| 4 | 130–156 | 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. |
| 5 | above 156 | 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. |
Credit: The National Hurricane Center
The deadliest natural disaster of all time to strike the United States hit at the turn of the 20th century. Poor forecasting and inadequate communication led the Galveston Hurricane of 1900 to strike the Texas island with barely any warning, leading to an estimated death toll of 6,000–12,000. At the time, the highest point on the island was a mere 8.7 feet above sea level, and with waves cresting more than 15 feet high, the entire island was soon underwater. So many people died that it was impossible to bury them all, and rescuers were forced to build funeral pyres and burn the bodies. As the island was rebuilt, a seawall was created to offer the island some additional protection from waves and the entire island itself was elevated by up to 17 additional feet using sand dredged from offshore. In contrast, Hurricane Katrina, in 2005, killed 1,800 people, as did the 1959 Mexico Hurricane, the deadliest Pacific hurricane of all time. The deadliest Atlantic hurricane was the Great Hurricane of 1780, which killed more than 27,500 people in the Caribbean. But none of these begin to compare to the 1970 Bhola Cyclone that hit Bangladesh and India, killing 300,000–1 million people.
The costliest tropical cyclone worldwide was Katrina, with estimated damages of more than $125 billion. The second most expensive hurricane to hit the U.S. was Hurricane Sandy, in 2012, which caused $75 billion in damages. The costliest Pacific hurricane was Hurricane Manuel in 2013, causing $4.27 billion in damages.
In a typical three-year period, two major hurricanes make landfall along the United States's Atlantic or Gulf coasts. 2005 was the year that had the most tropical cyclones in the Atlantic Ocean. Twenty-eight storms were named (making it the first time the "V" and "W" names were needed, and necessitating moving into the first six letters of the Greek alphabet), 15 of which escalated into hurricanes. The 1992 season was the most active in the Pacific, with 27 named storms, 16 of which went on to become hurricanes. (1990, 2014, and 2015 also spawned 16 hurricanes.) 1886 was the year the most hurricanes made landfall in the U.S.: seven hurricanes came ashore between June 13 and October 26.
You may notice some differences in well-known hurricanes through history. Once upon a time, major storms were named after the places most severely affected by them, dates on which they occured, or other distinguishing features. In 1887, an Australian meteorologist named Clement Wragge wanted to cut down on confusion between similarly named storms. He began by using the Greek alphabet, moved into South Seas girls names, and later resorted to naming storms after politicians he didn't like. The practice went into disuse upon his retirement, but in the 1940s, novelist George Stewart published a book in which he gave storms the names of former girlfriends. Air Force and Navy meteorologists stationed in the Pacific liked the idea, and, in 1944, named storms after their wives. The following year, the armed service adopted the practice of referring to Pacific tropical cyclones by women's names, in alphabetical order. It wasn't until 1953 that the practice became official policy for Atlantic hurricanes, as well. In 1979, naming practices switched to the current system of alternating between men's and women's names. (Atlantic hurricanes skip "Q" and "U" and stop at "W"; additional storms are named after Greek letters. Eastern Pacific hurricanes skip "Q" only. Hurricanes in the Central North Pacific area, however, are given Hawaiian names beginning with "A," "E," "H," "I," "K," "L," "M," "N," "O," "P," "U," and "W.") The regional warning centers responsible for tracking tropical storms and the World Meteorological Organization (WMO) are tasked with drawing up lists of names, but the WMO can vote to retire or withdraw any name, usually due to a storm causing excessive death or damage. While it has been suggested that hurricanes with women's names are more deadly than those with men's names, most scientists generally believe no correlation between naming and death rates has been proven.
The Americas, of course, are not the only places to be affected by hurricanes. In addition to the two areas mentioned here, there are five other "basins," areas in which tropical cyclones tend to form. As well as being called hurricanes, tropical cyclones may be known as typhoons or cyclones. Tropical cyclones are given names familiar to their regions.
Learn more about tropical cyclones with Science NetLinks' collection of hurricane resources.
This blog post originally appeared on Science NetLinks.