WEATHER | HURRICANES

When is hurricane season? How do hurricanes form?

Hurricanes forming in the Atlantic Ocean or Gulf of Mexico can potentially make landfall in the US every year from spring to fall. What are they?

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When is hurricane season? How do hurricanes form?
David Dee Delgado AFP

The official start of the Atlantic hurricane season begins 1 June lasting until 30 November; however, they are not bound by those dates. Similar storms, or tropical cyclones, are found the world over forming around the equator in tropical and subtropical waters. They are called hurricanes in the Atlantic and Eastern Pacific, typhoons in the North Pacific and cyclones in the South Pacific and Indian Ocean.

The massive storms are a collection of clouds and clusters of thunderstorms that form a cyclone shape that typically spans 300 miles, but can span 1,000 miles and rise 10 miles high with destructive winds. Depending on the strength of the storm they can cause widespread destruction if they make landfall.

How do hurricanes form?

Hurricanes get their name from the Taino, an indigenous people of the Caribbean. They called them “hurucane” which means evil wind.

Hurricanes require three main ingredients; warm water (at least 80 degrees), moist air and wind. Tropical cyclones, or hurricanes, don’t form withing 300 miles of the equator, either north or south, due to the lack of Coriolis force which causes the storm to spin.

In the Atlantic, winds coming from Africa evaporate the warm waters of the Atlantic putting more moisture in the air which then condenses to form the storm clouds. As the storm clouds cluster together around a tropical depression, they form a concentrated system which can result in a hurricane.

How many hurricanes are there on average?

On average the Atlantic hurricane season can produce 12 named storms. Storms are named when the tropical storm reaches sustained wind speeds of 39 mph. When the wind speed reaches 79 mph, the storm becomes a hurricane. There are five categories of hurricanes on the Saffir-Simpson Hurricane Wind Scale. A typical season in the Atlantic will produce six hurricanes, three of those major hurricanes.

The Atlantic hurricane season officially starts 1 June and lasts until 30 November. However, hurricanes have formed before the beginning of the season and after. The peak of the Atlantic hurricane season falls around 10 September.

How are storms named?

Names are given to the potentially deadly storms in order to make them easily recognizable to the public so that people can be informed of impending danger. The National Hurricane Center began naming Atlantic tropical storms in 1953 but the process is now maintained by an international committee of the World Meteorological Organization (WMO).

The WMO creates a list of 21 names for the six different regions where tropical cyclones form. Until 1979 only women’s names were used, but now men’s names alternate with women’s names. The lists of names are rotated every six years, but the names of especially destructive and deadly storms can be removed from the list. Examples for the US include Katrina (2005) and Sandy (2012).

The 2020 hurricane season was record-breaking with 30 named storms which necessitated using the Greek alphabet to name nine of the storms. This was the second time this has occurred, the previous time was in 2005 when there were 28 named storms. Now the WMO has created a supplemental list of 21 names for tropical storms in each of the six regions.

It is predicted that the 2021 Atlantic hurricane season will produce between 13 and 20 named storms, with six to ten becoming hurricanes. Of those, three to five could become major hurricanes.

The 2021 Atlantic hurricane season names are: Ana, Bill, Claudette, Danny, Elsa, Fred, Grace, Henri, Ida, Julian, Kate, Larry, Mindy, Nicholas, Odette, Peter, Rose, Sam, Teresa, Victor and Wanda.