Explainer: What Are Hurricanes?

In May, the World Meteorological Organization (WMO) warned about a highly active hurricane season. The U.S. National Oceanic and Atmosphere Administration (NOAA) has forecast 17 to 25 named storms, eight to 13 of which are predicted to become hurricanes. Just one hurricane making landfall can impede years of socio-economic development. But what makes them so devastating, and where does it come from?

Hurricanes are the most powerful storms on the planet. They require specific weather conditions to form over an ocean. Based on their wind speed, hurricanes are classified into different categories. Their general scientific term is a tropical cyclone, but they are known by various names.

Hurricanes, Cyclones, or Typhoons?

All these names are correct, depending on which side of the world they originate from. A report in National Geographic states that hundreds of years ago, European explorers were enlightened by the indigenous term "Arakan." It was used to define evil spirits, weather gods, and the storms that battered their ships in the Caribbean. Today, "hurricane" is one of three names for giant, spiraling tropical storms.

However, these storms are named differently based on their regions of origin. For example, storms that form over the North Atlantic, central North Pacific, and eastern North Pacific are called hurricanes. Storms that form over the South Pacific and Indian Oceans are called cyclones. When they develop in the Northwest Pacific, they are called typhoons.

The Origin:

The origin of any of these storms begins at the ocean's surface. Ocean water becomes warm as the Earth's temperature increases and sun rays hit the sea. When the temperature reaches at least 26.5°C (80°F), this heated ocean water provides the energy needed for the storm to develop.

The warm ocean water heats the air above it, causing it to rise and creating an area of low pressure beneath. As we know, our Earth is constantly rotating. Rising warm, moist air begins to spiral due to the Coriolis effect, which is crucial for forming cyclones.

For a storm to maintain its structure, the wind speed should be consistent at different altitudes. If the wind speed varies significantly, it can disrupt the storm's development. Low wind shear creates conditions that allow the storm to grow vertically and maintain its structure.

Lastly, an initial weather disturbance, such as a tropical wave, initiates the formation of a hurricane. This disturbance catalyzes the hurricane from beginning to developing.

The Structure:

Eye: These storms are spiral-shaped. The center of the hurricane is called the eye, and it is typically 20-40 miles in diameter.

Eye Wall: Encircling the eye is the eye wall, a ring of towering thunderstorms with the most intense weather and highest winds.

Rainbands: Rainbands are spiral bands of clouds, rain, and thunderstorms that extend outward from the eye wall. The bands have the potential to produce heavy rain and tornadoes.

The Stages:

Meteorologists have identified four stages of these storms as they become hurricanes: tropical disturbance, tropical depression, tropical storm, and full-fledged tropical cyclone.

Tropical Disturbance: Tropical disturbance occurs when warm ocean water vapor condenses, releasing heat into the air. This causes the warm air to rise and form cloud columns, which expand as evaporation and condensation continue—wind circulation forms around a center, creating a tropical disturbance like water swirling down a drain.

Tropical Depression: The disturbance becomes a tropical depression when winds reach 25-38 mph. Low air pressure, caused by warm air rising, leads to thunderstorm formation. As the winds gain speed, they rotate in a circular motion.

Tropical Storm: Wind speeds increase to at least 39 mph, upgrading the depression to a tropical storm. The wind circulation around a calm center (eye) strengthens. Due to the Coriolis effect, winds circulate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

Hurricane: When wind speeds hit 74 mph, a storm becomes a hurricane. It grows significantly, reaching 50,000 feet and spanning about 125 miles across. The winds push hurricanes towards the west, affecting the Caribbean, Gulf of Mexico, or the southeastern U.S. Low air pressure and strong winds cause ocean water to mound up, potentially leading to dangerous storm surges upon landfall.

Hurricanes lose strength once they land because they no longer receive energy from warm ocean waters. However, they often travel significantly inland, resulting in heavy rainfall and wind damage before dissipating entirely.

Hurricane Categories:

Hurricanes are categorized based on their wind speeds using the Saffir-Simpson Hurricane Wind Scale, which rates them from 1 to 5. The higher the category, the greater the potential for damage. Here are its types, respective wind speeds, and the typical damage they may cause at landfall.

Category 1: Wind speeds between 74 and 95 mph are considered category 1. They cause minimal damage, mainly to unanchored mobile homes, trees, and shrubs. Some seaside flooding and minor pier damage are likely.

Humberto 2007 was a Category 1 hurricane. Before landfall, it formed and intensified faster than any other North Atlantic tropical cyclone. It caused power outages to over 100,000 homes and businesses. Structural damage to homes, minor flooding in coastal areas, and damage to piers were observed.

Category 2: Wind speeds between 96 and 110 mph are category 2. The moderate wind can sabotage mobile homes, roofs, and small craft in unprotected moorings. Flooding near the coast could also occur.

Arthur, a category 2 hurricane formed east of Florida in 2014, landed on the North Carolina coast. It caused thousands of power outages, damaged roofs and siding, uprooted trees, and caused moderate coastal flooding.

Category 3: These hurricanes have wind speeds ranging from 111 to 129 mph. They can cause extensive damage to small residences and utility buildings, knock down trees, and destroy smaller structures. Flooding near the coast can also destroy properties, and floating debris may damage larger structures.

In 2019, Hurricane Humberto, a category 3 storm, caused strong winds in Bermuda, leading to power outages, structural damage, coastal flooding, and damage to boats and piers.

Category 4: The wind speed is between 130 and 156 mph. It causes catastrophic damage to well-built homes, with complete roof failure and wall collapse. Extensive damage to windows and doors. Significant erosion of beaches. Massive evacuation of residential areas may be required.

Hurricane Harvey was a devastating Category 4 hurricane that struck the Gulf Coast of Texas in August 2017. One of the most powerful hurricanes to hit the United States in decades caused extensive damage, including flooding, infrastructure damage, prolonged power outages, and long-term impacts for affected areas.

Category 5: The wind speed ranges between 157 mph and higher. This storm can cause catastrophic damage to many homes and businesses, resulting in total roof failure and wall collapse. Fallen trees and power poles isolate residential areas. Power outages will last for weeks to possibly months, and most of the area will be uninhabitable for weeks or months.

Category 5 hurricanes are relatively rare. Only about 1 to 2 hurricanes of this magnitude occur globally each year, with some years experiencing none and others having multiple. The Atlantic basin experiences a Category 5 hurricane approximately once every three to four years.

Before Lee and Ian, Dorian and Lorenzo in 2019, Michael in 2018, Maria and Irma in 2017, and Matthew in 2016 are the most recent Category 5 Atlantic hurricanes.

Categories help understand hurricanes' potential impact and severity based on their wind speeds at landfall.

Impact of Hurricanes:

Hurricanes are highly destructive natural disasters. They can cause substantial damage through high winds, storm surges, heavy rain, and flooding.

They cause widespread damage to structures, uproot trees, and knock down power lines. The winds from hurricanes push water onshore, significantly increasing seawater levels and causing severe coastal flooding.

Additionally, hurricanes can produce extreme amounts of rainfall, leading to flash flooding and river flooding, especially in areas far from the coast. They can also spawn tornadoes, adding to the storm's destructive power. Hurricanes can take multiple lives at once, and the damages they cause can sometimes remain unresolved even after decades of effort.

Precautions:

Residents in hurricane-prone areas should prepare an evacuation plan that includes water, non-perishable food, medications, flashlights, batteries, and important documents. Follow local evacuation orders. Learn where the evacuation routes are.

Additionally, it should consist of securing windows with storm shutters, reinforcing doors, and trimming trees to reduce damage. Residents should also monitor weather updates and follow the advice of local authorities.

As we know, hurricanes are devastating natural phenomena. Studying and monitoring them during their formation, structuring, and movement can help better plan for and respond to these storms, minimizing damage and saving lives.

Global warming is aggravating hurricane impacts in the United States. Scientists are currently skeptical whether the number of hurricanes will alter. However, they are confident that the intensity and severity of hurricanes will continue to grow. This is related to an increase in our carbon emissions. The destruction and dislocation caused by hurricanes are part of the high cost of an unsustainable lifestyle.

The 2018 hurricane season was one of the most active on record, with 22 major hurricanes in the Northern Hemisphere in three months. The 2017 season also saw devastating Atlantic storms.

While multiple factors influence a hurricane's strength and impact, warmer temperatures are crucial. Warming in the Arctic could cause future hurricane paths in the Atlantic to shift farther west, increasing the likelihood of landfall in the U.S. This makes awareness and preparation essential as the threat of dislocation, damage, and destruction continues to increase.