15 Hurricane Facts: Mysteries of a Mighty Tropical Storm

Discover some basic hurricane facts, including how they form and develop, as well as when and where they occur.

Hurricanes occur only in the Atlantic basin and parts of the Pacific ocean in locations at least five degrees latitude away from the equator. The Atlantic basin includes the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. In the Pacific, hurricanes occur in the Eastern Pacific, which includes north-central and northeastern portions of the ocean. The same weather phenomenon can occur elsewhere, but the term hurricane is only used in this area. In other locations, these storms are called typhoons.

There is a designated hurricane season during which hurricanes are most likely to form. There are slightly different seasons for the Atlantic Basin and Eastern Pacific. The Atlantic hurricane season is June 1 through November 30. The Eastern Pacific hurricane season is May 1 through November 30.

Water temperature plays an important role in hurricane formation and development. In order for a hurricane to form or hold together, the water has to be at least 80 degrees Fahrenheit (27 degrees Celsius). It is very common for water temperatures in the areas where hurricanes form to be above this threshold. The heat in water functions as fuel for a hurricane. The hotter the water, the more intense the storm.

Water temperature is important for hurricanes to develop, but so is humidity. Hurricane development isn't likely when the air in the mid-levels of the atmosphere is dry. This is partly because dry air causes evaporation, which results in a cooling effect that prevents convection. Instead, moisture in the form of humidity is needed to fuel a hurricane.

Even when sufficient heat and humidity are present, hurricanes don't always develop. Wind shear also plays a role. Because intense upper-level winds can inhibit hurricane development, these storms need low vertical wind shear in order to develop. When low vertical wind shear is present, there won't be high winds in the upper levels of the atmosphere.

Discover some key facts about forecasting and monitoring hurricanes.

Storms don't start out as hurricanes but rather develop over time. They begin as a tropical wave or area of disturbed weather over water. The area of disturbed weather will dissipate or become a tropical wave. From there, it could go away or continue to develop into a tropical depression, depending on conditions. If development continues, it would then become a tropical storm before ultimately reaching hurricane status.

Once a tropical system reaches winds at least 74 miles per hour (mph), which is 64 knots, it is strong enough to be upgraded to hurricane status. The storm already has a name at this point. Names are issued for tropical storms, which are a step below hurricane status in terms of wind speed. Forecasters issue watches and warnings based on the storm location, how quickly it is moving, what direction it is traveling, how big it is, and how strong it is predicted to become.

Once a storm's winds cross the 74 miles per hour threshold, an eye starts to form in the center of the storm. This eye is the storm's center of circulation. Conditions are mostly calm inside the eye of a hurricane. The eyewall, which is the area immediately surrounding the eye, tends to have intense conditions. Rainbands extend out from the eyewall, producing intense wind, rain, thunderstorms, and sometimes tornadoes.

Forecasters monitor changes in atmospheric pressure to determine whether a hurricane is growing stronger or weaker. With hurricanes, there is an inverse relationship between atmospheric pressure and storm strength. When atmospheric pressure drops, that is a sign that the storm is intensifying, which means that it is gaining strength. Conversely, a rise in pressure indicates the storm may be losing strength.

Hurricanes can vary greatly in strength. They are categorized using the Saffir-Simpson Scale, which is based on sustained wind speed. The higher a hurricane's winds, the stronger and more destructive a hurricane can be. The Saffir-Simpson scale has five categories.

• Category 1 - winds from 74 -95 mph
• Category 2 - winds from 96 - 110 mph
• Category 3 - winds from 111 - 129 mph
• Category 4 - winds from 130 - 156 mph
• Category 5 - winds of 157 mph or higher

Storms that reach Category 3 status are classified as major hurricanes.

No two hurricanes are identical, though quite a bit is known about what to expect from this type of storm.

Not every location that a hurricane passes over feels its impact the same way. This is because the storm's strength and power are not uniformly distributed. Hurricanes are viewed in terms of quadrants, which are labeled based on the direction of the storm's movement and position relative to the eye of the storm.

• The top/front quadrant to the left of the eye is where the strongest storm surge tends to occur.
• The top/front quadrant to the right of the eye is the most intense portion of the storm overall.
• The bottom quadrant to the right of the eye is usually where the strongest wind speeds are registered.
• The bottom quadrant to the left of the eye tends to be less intense than the other quadrants (but still quite dangerous).

Hurricanes often produce tornadoes, which can spin up rapidly without advance warning. They are most common within the top/right front quadrant of a hurricane away from the eyewall, but they are not limited to that part of the storm. That portion of the storm tends to be the most unstable, so it is particularly conducive for tornadic activity. But, tornadoes can also pop up close to the eyewall and/or in other quadrants.

Storm surge occurs when the winds of a hurricane push water onto land at the coast. A lot of factors impact storm surge size, some related to the storm itself and some related to the geographic characteristics of the area being impacted. Storm surge is very dangerous, as it creates an enormous wall of water that can sweep away buildings and/or cause significant flooding. In 2005, Hurricane Katrina produced a 27.8-foot storm surge in Bay St. Louis, Mississippi. As of January of 2021, this is the highest storm surge on record.

Hurricanes begin to lose their strength as they move over land, but this doesn't occur instantly. A hurricane that continues on an inland path after landfall will gradually weaken and dissipate as it moves further and further away from water. Along the way, though, it will continue to produce high winds, significant rain, and can continue to produce tornadoes. In 2020, several inland states, including Arkansas, Tennesse, West Virginia, and Vermont, were impacted by hurricanes.

Hurricanes don't always move inland after making an initial landfall. For example, if a hurricane were to cross the Florida peninsula traveling east to west, it could go across the land and come out into the Gulf of Mexico. There, if conditions are favorable, it could gain strength and continue on until striking land again. In 2005, Hurricane Wilma made landfall three times. She impacted land twice in Mexico (Cozumel and the Yucatan Peninsula) before striking Florida's Cape Romano.

Hurricanes are very dangerous; it's important to always observe hurricane safety tips if you're in an area that could be impacted by this type of storm. Now that you know some interesting facts about hurricanes, take the time to learn more about the weather. Start by exploring facts about tsunamis. Then, learn some words to describe a tornado. From there, discover other common types of weather conditions.