The official 2018 Hurricane season ended on November 30. How did it go? Here’s the summary of what happened versus the forecast—plus common questions and answers about Earth’s most violent storms.
About Hurricane Forecasts
The Old Farmer’s Almanac does not get into great detail about hurricanes in our annual long-range predictions, though we do predict storms.
For that, we go to Colorado State University and the Department of Atmospheric Science. These guys study hurricanes all day, ever day!
For many years, they have issued a forecast for upcoming hurricane seasons. While hurricanes aren’t completely predictable, there are many indicators related to atmospheric and oceanic conditions that indicate what to expect.
In their forecast, CSU provides an estimate of the number of total storms for the season, as well as the expected seasonal activity level as compared to prior years. Additionally, CSU releases regular updates to their forecast throughout the spring and summer, up until just before the height of hurricane season in August.
The Atlantic hurricane season lasts from June 1 through November 30. Forecasts cover the Atlantic Basin—the area encompassing the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.
While reading the hurricane forecast, keep in mind that even if it suggests that there won’t be as many storms as prior years, that doesn’t necessarily mean that the storms that do occur will be weak ones. If you live in an area regularly affected by hurricanes, always be prepared for the worst case scenario. As CSU states, “it only takes one hurricane making landfall to make it an active hurricane season.”
2018 Hurricane Season Summary
Now that the 2018 hurricane season has officially ended, let’s take a look at CSU’s hurricane season summary. In their original 2018 forecast, CSU predicted a “slightly above-average” activity level for the season (but subsequent updates downgraded that to a prediction of “below-average” by early August).
Despite initial signs of low activity, the season took an unexpected turn in September and October, with Hurricane Florence bringing devastating flooding to North and South Carolina in early September, and Hurricane Michael causing massive damage along the Florida Panhandle in October. These storms—among others—resulted in the 2018 season seeing slightly above-average activity overall.
Bottom-line, what does this mean in terms of storm numbers? Well, let’s take a look at CSU’s forecasted totals versus the actual totals and 1981–2010 median storm counts:
Initial 2018 Forecast
Final 2018 Forecast
Actual 2018 Storms
|Named Storm Days||70||53||87.25||60.1|
|Major Hurricane Days||7||2||5||3.9|
|Accumulated Cyclone Energy||130||64||129||92|
|Net Tropical Cyclone Activity||135%||78%||128%||103%|
|Activity Level||Slightly above-average||Below-average||Slightly above-average||–|
The above-average level of activity led to many records being set this year. Here are a few of the highlights from CSU’s summary:
- In the past two years, three Category 4 storms have made landfall in the US: Harvey, Irma, and Michael. This is the greatest number of Category 4 storms to hit the continental US in a two-year period on record.
- Hurricane Michael was the first Category 4 storm on record to hit the Florida Panhandle.
- Hurricane Florence broke rainfall records in North Carolina, dropping nearly 12 inches more rain (35.93”) than the previous record (24.06”), which came from Hurricane Floyd in 1999.
- On September 10, there were three hurricanes active at the same time: Florence, Helene, and Isaac. This is the 11th time on record that three storms have occurred simultaneously in the Atlantic.
For more records from this season, see CSU’s full 2018 Hurricane Season Summary.
Facts About Hurricanes
Q. 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.
Q. Where Does a Hurricane Form?
A. Hurricanes only form over warm waters in the tropics (usually above 27°C, or about 81°F). Think of a hurricane like a giant engine. It’s fuel is warm, moist air—which rises from from the oceans causing an area of lower pressure below. Then the air from surrounding areas with higher air pressure pushes in to the low pressure area. Then that “new” air becomes warm and moist and rises, too. As the warm air continues to rise, the surrounding air swirls in to take its place. As the warmed, moist air rises and cools off, the water in the air forms clouds. The whole system of clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the surface. 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.
Storms that form north of the equator spin counterclockwise. Storms south of the equator spin clockwise. This difference is because of Earth’s rotation on its axis.
Q. How do we know a hurricane is coming?
A. Now, thanks to satellite technology, no hurricane goes unnoticed. See our article on “Predicting Hurricanes: The Eyes Have It” to learn more.
It also usually takes several days to a week for a tropical storm to grow into a hurricane and there is often plenty of time to take precautionary measures unlike some extreme weather events (such as a tornado).
But if conditions are just right, a powerful major hurricane can develop in just hours. This has been called “rapid intensification” by the National Hurricane Center. When conditions are just perfect, a storm can increase its wind speed 35 mph in 24 hours or less—about two categories on the Saffir-Simpson scale, which grades hurricane strength from 1 to 5. Rapid intensification, however, is rare, with just one or two Atlantic storms per year undergoing such an acceleration.
Q. What is the cause of hurricane damage?
A. Hurricanes actually weaken when they hit land, because they are no longer being “fed” by the energy from the warm ocean waters. When hurricanes move over large landmasses, they can die out quickly because they lose the power of the heat and condensation. However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely. So it’s not just high winds that cause danger; it’s the torrential rains 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.
Q. Which areas are most susceptible to hurricanes?
A. 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.
Hurricane Felix (2007)
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. See more about the Saffir-Simpson Hurricane Scale.
|Saffir-Simpson||Wind (mph)||Hurricane Examples|
|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), Matthew (2016), Irma (2017), Maria (2017)|
Q. What do hurricane warnings mean?
A. A hurricane watch means that hurricane-force winds are possible within 48 hours. A hurricane warning means that hurricane-force winds are likely within 36 hours.
Q. What caused Hurricane Katrina?
A. We are often asked about Hurricane Katrina (2005), one of the five deadliest hurricanes to ever strike the U.S. and tied with Hurricane Andrew (2017) as one the most costly hurricanes in the Atlantic (both storms did an estimated $125 billion of damage each). 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.
Q. How are hurricane names chosen? Can the same name be used twice?
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?
Names can be used more than once, but if a storm is significant enough, its name is usually retired. 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 the most recent list of retired hurricane names.
Have you ever experienced a hurricane first hand? Tell us about it in the comments below.