The 2017 hurricane season officially ended on November 30. Here is the summary of observed activity versus forecast—plus, hurricane facts and information from The Old Farmer’s Almanac!
The Atlantic Hurricane Season is considered June 1 through November 30. Forecasts cover the Atlantic Basin—the area encompassing the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.
Summary of Observed 2017 Activity
The 2017 Atlantic hurricane season was forecasted as above-average by the experts at Colorado State University and other sources.
However, the season way more extreme than anticipated with levels of activity that were far higher than predicted. Hurricanes Harvey, Irma and Maria were especially destructive. Harvey brought massive flooding Houson; Irma and Maria pummeled islands throughout the Caribbean and tropical Atlantic. Irma also devastated much of the Florida Keys and parts of mainland Florida.
The 2017 hurricane season set many records. For example:
- The Atlantic had a record number of 17 named storms, 91.25 named storm days and 10 hurricanes! Each of these were the most that the Atlantic had in a season since 2012.
- 51.25 hurricane days occurred in 2017 – the most in a season since 1995.
- Six major hurricanes formed in 2017 – the most in a season since 2005.
- 19.25 major hurricane days occurred in 2017 – the most in a season since 2004.
- The continental United States had three hurricane landfalls (Harvey, Irma and Nate) for the first time since 2008.
2017 Hurricane Summary
|Median Count 1981–2010|
|Named Storm Days||60||91.25||60.1|
|Major Hurricane Days||5||19.25||3.9|
|Accumulated Cyclone Energy (ACE)||100||226||92|
|Net Cyclone Activity||110%||231%||103%|
Hurricane Facts, Questions, and Information
Q. How are Hurricane Names Chosen?
A. Most storm names are taken from a permanent list that rotates every 6 years. Here are this year’s tropical storm and hurricane names for both the Atlantic Basin and Eastern North-Pacific. Is your name listed?
More than 60 names have been retired since 1950 because they resulted in significant property damage or deaths. A name can be retired at the request of a country affected by the storm. See most recent list of retired hurricane names.
It should be noted that not all hurricanes were named, including some of the most deadly or damaging storms known to man.
Q. Just what is a hurricane?
A. A hurricane is a tropical storm with winds that have reached a constant speed of at least 74 mph in the North Atlantic Ocean, Caribbean Sea, or Gulf of Mexico. A hurricane’s winds blow in a large spiral around a relatively calm center of extremely low pressure known as the eye of the storm. Around the rim of the eye, winds may gust to more than 200 mph. The eye of a storm is usually 20 to 30 miles wide and may extend over 400 miles. The entire storm can be up to 340 miles in diameter, dominating the ocean surface and lower atmosphere for thousands of square miles.
The dangers of a storm include torrential rains, high winds, and storm surges. A hurricane can last for 2 weeks or more over open water and can follow a path across the entire length of the eastern seaboard, coastal areas, and barrier islands. All Atlantic and Gulf coastal areas are subject to hurricanes or tropical storms. Although rarely struck by hurricanes, parts of the Southwest and Pacific Coast suffer heavy rains and floods each year from the remnants of hurricanes spawned off Mexico. Islands such as Hawaii, Guam, American Samoa, and Puerto Rico also are subject to hurricanes.
Q. Is a hurricane the same as a cyclone? How is tropical weather classified?
A. A hurricane is actually one of three kinds of tropical storms, or cyclones, that circulate over tropical waters. The circulation is counterclockwise in the Northern Hemisphere. Tropical cyclones are classified as follows:
Tropical depression: An organized system of clouds and thunderstorms with a defined circulation and maximum sustained winds of 38 mph (33 knots) or less.
Tropical storm: An organized system of strong thunderstorms with a defined circulation and maximum sustained winds of 39 to 73 mph (34 to 63 knots).
Hurricane: An intense tropical weather system with a well-defined circulation and maximum sustained winds of 74 mph (64 knots) or higher. In the western Pacific, hurricanes are called typhoons. Similar storms in the Indian Ocean are called cyclones. Hurricanes are further classified by rank according to how strong their winds are.
Q. How are hurricanes classified and what are hurricane categories?
A. The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane’s present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf in the landfall region. Wind speeds are measured using a 1-minute average.
|Saffir-Simpson||Wind (mph)||Hurricane Example|
|Category One||74 - 95||Allison (1995), Danny (1997)|
|Category Two||96 - 110||Bonnie (1998), George (1998), Gustav (2002)|
|Category Three||111 - 130||Roxane (1995), Fran (1996), Rita (2005)|
|Category Four||131 - 155||Opal (1995), Iniki (1992), Charley (2004), Katrina (2005)|
|Category Five||156 +||Andrew (1992)|
Q. What causes a hurricane to happen?
A. A tropical ocean and its atmosphere create the right conditions for a hurricane. Hurricanes draw their energy from the warm surface waters of the tropics (usually above 27°C, or about 81°F) and the latent heat of condensation. Powered by heat from the sea, they are steered by the easterly trade winds and the temperate westerlies, as well as by their own ferocious energy. Around their core, winds grow with great velocity, generating violent seas. Moving ashore, they sweep the ocean inward while spawning tornadoes and producing torrential rain and floods. When hurricanes move over cold water or over large landmasses, they can die out quickly because they lose the power of the heat and condensation.
Q. How do we know a hurricane is coming?
Now, thanks to satellite technology, no hurricane goes unnoticed. See our article on “Predicting Hurricanes: The Eyes Have It” to learn more.
Q. What do the hurricane warnings mean?
A. A watch means that hurricane-force winds are possible within 48 hours. A warning means that hurricane-force winds are likely within 36 hours.
Q. What caused Hurricane Katrina?
A. Hurricane Katrina (2005) was one of the five deadliest hurricanes to ever strike the country and also the single most costly hurricane. The damage and loss of life inflicted by this powerful hurricane in Louisiana and Mississippi were devastating, with effects stretching into Florida panhandle, Georgia, and Alabama.
Katrina was a complex storm, but to put it simply: Katrina started with the interaction of a tropical wave and the remnants of a weakening storm known as Tropical Depression Ten; the pressure disturbance become organized over the central Bahamas on August 23. It rapidly strengthened into a tropical storm and then a hurricane by the next day. Katrina was lifted towards Florida by upper-level steering winds and became a category 1 hurricane a few hours before landfall in southern Florida on the 25th. Katrina was on shore for about 7 hours and then moved into the Gulf of Mexico, reaching category 5 intensity on August 28. Katrina weakened to a strong category 3 or category 4 hurricane before making landfall on the northern Gulf coast.