From the Field

Hurricane facts: How they form and how to prepare

At its peak, Hurricane Maria was a devastating Category 5 with 175 mph winds.

Hurricanes are one of nature’s most terrifying and destructive forces. What begins as small disturbances can become fierce mega storms as they gather strength and size over the ocean. The ones that make landfall over populated areas can cause tremendous destruction.

Here are the hurricane facts you need to know to better understand how they work, how you can prepare if you’re in a hurricane’s path, and how you can help people affected.

How does a hurricane form?

Here’s how a hurricane that ends up hitting the United States or the Caribbean can form: Something as simple as a child kicking up sand in Africa can cause a small disturbance in the air that turns into a dust devil. Carried by westerly winds off the desert, that harmless mini-tornado gathers mass and momentum and morphs into a turbulent eddy, a circular current of water. It then develops into a system of thunderstorms as it moves toward Africa’s west coast. As the cloud system heads off the continent and onto the eastern Atlantic Ocean, it mixes with the warm, moist tropical air. Winds increase and a tropical depression forms as it continues west. If warm ocean temperatures continue to feed the storm, it grows into a tropical storm, then a hurricane. A couple of times per year, on average, all the right factors — warm ocean, time at sea, a combination of high and low pressure driving the storm system — converge to create a major hurricane.

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What are the main parts of a hurricane?

A hurricane consists of five main parts: outflow, feeder bands, eyewall, eye, and the storm surge. Outflow is the high-level clouds moving outward from the hurricane. Feeder bands are the areas of heavy rain and gusty winds fed by the warm ocean. They get more pronounced as the storm intensifies. The eyewall is the band of clouds and intense wind and rain surrounding the eye of the hurricane. Here, the air moves violently toward the eye and upward into the cloud. The eye is the relatively calm center of the storm. The storm surge is the flood of ocean water pushed inland as the hurricane approaches land.

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Hurricane facts_Harvey makes landfalls over Rockport, Texas, Aug. 26, 2017.
Trees bend and waves crash on the shoreline as Hurricane Harvey makes landfall over Rockport, Texas, on Aug. 26, 2017. (©2017 Genesis Photo Agency)

When is hurricane season?

Globally, September is the most active month for hurricanes.

The Atlantic hurricane season is June 1 to November 30, but it sharply peaks from late August through September. This time of year accounts for more than 97 percent of tropical activity.

The Northeast Pacific basin experiences a broader peak with activity often beginning in late May and running until early November. There is a peak in storminess in late August and early September.

The Northwest Pacific basin has tropical cyclones occurring throughout the year, although the main season is from July to November with peaks in late August and early September.

The North Indian basin has peaks of activity in May and November, although tropical cyclones are seen from April to December.

The Southwest Indian and Australian/Southeast Indian basins have similar cycles, with tropical cyclones beginning in late October and early November, reaching peak activity in mid-January and mid-February to early March and then ending in May.

Storm season in the Australian/Southwest Pacific basin begins with tropical cyclone activity in late October and early November. It peaks in late February to early March and then fades out early May.

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How many hurricanes occur each year?

Between 1968 and 2017, the U.S. Atlantic and Gulf coasts have had an average of about six hurricanes per year, according to the National Oceanic and Atmospheric Administration. Two of the six typically turn into major hurricanes (category 3 or higher). In 2017, the region weathered six major hurricanes.

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Hurricane Matthew_Haiti_People pick through a jumble of broken houses, trees, and roads in Dupuy on the coast of Haiti’s southwest peninsula. Families are struggling to get by and restore their livelihoods. (©2016 Guy Vital-Herne/World Vision)
After Hurricane Matthew in 2016, people pick through a jumble of broken houses, trees, and roads in Dupuy on the coast of Haiti’s southwest peninsula. Families struggled to get by and restore their livelihoods. (©2016 World Vision/photo by Guy Vital-Herne)

Why are hurricanes dangerous?

A hurricane is dangerous in many ways. First, fierce winds can lift you off your feet or damage or destroy buildings, homes, trees, and other property and knock out power. If you’re not careful, you can be injured by flying debris. The winds and heavy storm clouds bring a storm surge to coastal areas and torrential rains, which can cause flooding and over-saturate the ground, leading to landslides. Rural communities are often cut off after landslides wash away roads and power infrastructure. This leaves children and people who depend on medical treatment or supplies especially vulnerable. Even after the storm passes, if your home flooded, you have to act quickly to remove damaged materials. Otherwise, dangerous mold can threaten your family’s health.

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How do I prepare for a hurricane?

Here are the key steps to take and things to be aware of if a hurricane is forecast in your area.

  1. Stay informed: Sign up for emergency notifications.
  2. Plan for evacuation: Check evacuation routes and emergency shelter information, stock up on gas, choose and notify an out-of-state contact, know where you will meet loved ones if separated, and pack a “go bag” with items you’ll need if you evacuate.
  3. Pack emergency supplies: Make sure you have food, water, flashlight, clothes, medicine, protective gear, radio, hygiene items, critical documents, sentimental items, and pet necessities ready to go if necessary.
  4. Prepare your home: Protect your property from wind and flooding by covering windows and elevating your furnace, furniture, or items on the floor.
  5. Decide to stay or go: If authorities order an evacuation, go. If you are not in an area that receives an evacuation notice, consider moving to higher ground and/or staying indoors and keeping up with weather status reports.
  6. Learn more: Find out more by visiting the Federal Emergency Management Agency (FEMA) or ready.gov.

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What’s the difference between a tropical depression, tropical storm, hurricane, and major hurricane?

The difference between a tropical depression, tropical storm, hurricane, and major hurricane has to do with wind speed:

  • Tropical depression: Wind speed less than 39 mph
  • Tropical storm: Wind speed between 39 mph and 73 mph
  • Hurricane: Wind speed between 74 mph and 110 mph
  • Major hurricane: Wind speed greater than 110 mph

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Typhoon Haiyan in the Philippines, 2013. Local resident and World Vision staff survey damage
In the Philippines, a local resident and a World Vision staff member survey the devastation of Typhoon Haiyan on November 24, 2013. (©2013 Crislyn Felisilda/World Vision)

What’s the difference between a hurricane, a typhoon, and a cyclone?

Hurricanes form in the Atlantic and Caribbean, cyclones in the Indian Ocean, and typhoons in the Asia-Pacific region. Scientifically, they are all known as tropical cyclones.

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What is a hurricane category, and what do they mean?

A hurricane category, determined by the Saffir–Simpson hurricane wind scale, lets people know how powerful the hurricane will be:

  • Category 1: Very dangerous winds between 74 and 95 mph will cause some damage and power outages for a few days are likely.
  • Category 2: Extremely dangerous winds between 96 and 110 mph will cause extensive damage and a near-total power loss that could last up to a few weeks.
  • Category 3: Devastating damage will occur from winds between 111 and 129 mph. Electricity and water will be unavailable for up to several weeks, and trees will be snapped or uprooted, blocking roads.
  • Category 4: Catastrophic damage will occur from winds between 130 and 156 mph. Even well-built framed homes will lose most of the roof structure and/or some exterior walls. Fallen trees and power poles will likely isolate residential areas, and power outages could last possibly months.
  • Category 5: Catastrophic damage will occur from winds 157 mph or higher. A high percentage of homes will be destroyed, and most areas will be uninhabitable for weeks or months.

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How do tropical storms and hurricanes get their names?

Meteorologists name tropical storms and hurricanes to avoid confusion and streamline communication. Before the 1950s, they kept track of storms by the order in which they happened in a given year. That method became confusing over time and even caused occasional miscommunication when, while multiple storms were looming, a city would receive an alert about the wrong storm. The United States has been naming tropical storms and hurricanes since 1953. Currently, the World Meteorological Organization names them, adhering to a strict system that consists of a 21-letter list of male and female names on a 6-year rotation. The letters Q, U, X, Y, and Z are left off the list. Every seventh year, the names recycle, unless the WMO decides to retire a name because it was particularly deadly or costly. Here’s the list of tropical cyclone names for the next six years.

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What have been the most intense hurricanes to strike the United States?

Of the 41 storms that have caused more than $1 billion in damage to the mainland U.S. since 1900 — with five non-mainland exceptions — three storms have made landfall as category 5 hurricanes: Hurricane Katrina in 2005, Hurricane Andrew in 1992, and Hurricane Camille in 1969. Seven tropical cyclones have hit the U.S. as category 4 storms, including Harvey, Irma, and Maria in 2017; Charley over Florida in 2004; Iniki over Kauai in 1992; Donna over Florida and the eastern U.S. in 1960; and Hugo over Puerto Rico and the U.S. Virgin Islands in 1989.

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What have been the costliest hurricanes to strike the United States?

Hurricane Katrina tops the list of costliest hurricanes to hit the U.S. mainland since 1900. Adjusted for inflation, it caused about $160 billion in damage to Louisiana and the Gulf Coast. Causing about $125 billion in damage, Hurricane Harvey ranks as the second-costliest. Hurricane Maria, which hit Puerto Rico and the U.S. Virgin Islands as a category 4 storm within a month of Harvey, is the third-costliest after inflicting about $90 billion in damage. Hurricane Sandy, in late 2012, cost the Northeastern U.S. about $70 billion and is fourth on the list. The fifth-costliest, Hurricane Irma, affected Florida and much of the South and caused $50 billion in damage. All three of the most intense storms to hit the U.S. in 2017 made landfall as Category 4 storms.

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How does World Vision respond to hurricanes?

With decades of experience and an established global network of trained emergency staff, World Vision is responding to multiple major emergencies at any given time. That includes earthquakes, conflicts and refugee crises, floods, and hurricanes. Our approach goes beyond the immediate response reported in the news.

We maintain a system of pre-positioning sites, including several field sites in the U.S., that allows us to dispatch emergency relief supplies quickly when a hurricane or other disaster strikes. We partner with more than 40,000 churches worldwide, which can streamline delivery of supplies in hard-to-reach areas.

During and after a crisis, we provide food, water, hygiene, and other basic relief items, including clean-up supplies. We also promote personal hygiene practices to guard against deadly disease outbreaks.

Our child protection programs respond to urgent cases, such as children separated from their families, abuse, exploitation, and other forms of violence. We also respond to health, nutrition, and education needs.

Our goal is to support families not only in the short-run but also as they go through the arduous process of rebuilding their lives and livelihoods. World Vision works alongside communities to help families rebuild their homes and establish permanent housing, sustainable access to clean water, food security, access to a quality education, and re-establishing livelihoods.

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How can I help hurricane survivors?

You can help World Vision continue responding to disasters around the world.

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