Hurricane Irma: What's the difference between a typhoon and a hurricane?

What are hurricanes and how are they formed?

In this geocolor image GOES-16 satellite image taken Friday, Sept. 8, 2017, at 11:45 UTC, sunlight, from the right, illuminates Hurricane Irma as the storm approaches Cuba and Florida. Cuba evacuated tourists from beachside resorts and Floridians emptied stores of plywood and bottled water after Hurricane Irma left at least 20 people dead and thousands homeless on a devastated string of Caribbean islands and spun toward Florida for what could be a catastrophic blow this weekend.  (NOAA via AP)
Beta V.1.0 - Powered by automated translation

Hurricane season is causing devastation across the Atlantic with two tropical storms leaving a wake of death and destruction in the United States and the Caribbean.

Hurricane Harvey made landfall in Texas at the end of August causing over 71 deaths and thousands of residents displaced. Now Hurricane Irma has ripped through the Caribbean leaving the island of Barbuda with 95% of its buildings destroyed.


Read more: Death toll rises as Florida prepares for Irma's landfall


What is a hurricane?

Hurricanes are large swirling storms that produce winds of 74 miles per hour (119 kilometres per hour) or higher.

How are they formed?

A hurricane begins as a tropical disturbance in an area of warm ocean waters where rain clouds are building. A tropical disturbance can become a tropical depression, which is an area of rotating thunderstorms with winds of 38 mph.

If winds increase to 39 mph, the depression becomes a tropical storm and if it increases to 74 miles per hour or higher, it becomes a hurricane.

Experts still do not know why a hurricane forms but two key components are essential- warm ocean waters and winds that don’t change much in speed or direction as they go up into the sky.

A view of the Baie Nettle beach in Marigot on September 5, 2017 with the wind blowing ahead of the arrival of Hurricane Irma. A hurricane is a swirling storm with wind speeds of 74 mph or higher. Lionel Chamoiseau/ AFP Photo

How are hurricanes categorised?

Hurricanes are categorised by wind speed, with category 1 the slowest type of hurricane and category 5 the fastest.

Category 1: Winds 74-95 mph (119-153 km/h)

Category 2: Winds 96-110 mph (154-177 km/h)

Category 3: Winds 111-129 mph (178-208 km/h)

Category 4: Winds 130-156 mph (209-251 km/h)

Category 5: Winds more than 157 mph (252 km/h)

What is the difference between a typhoon and a hurricane?

Hurricanes, cyclones, and typhoons are different names given to the same weather phenomenon. A hurricane is the name given to a disturbance in the Atlantic and Northeast Pacific, a typhoon is the term used in the Northwest Pacific and a hurricane or typhoon in the South Pacific and Indian Ocean is called a cyclone.

Why are hurricanes named?

A tropical storm is named and then that name passes onto the hurricane. Tropical storms and hurricanes are named in alphabetical order each year, taken from a list of names. There are six lists of hurricane names, which are reused every six years. If a hurricane causes a lot of destruction then its name will be removed from the list and replaced with another name.

A reason for naming hurricanes is to keep track of them as there can be more than one hurricane at a time.