How Hurricanes Form

Hurricanes are huge, spiraling tropical storms that can have wind speeds that exceed 160 miles per hour and produce nine trillion liters of rain a day. The word hurricane comes from the native Spanish word huracan, a name the Spanish used for the evil spirits and weather gods they believed drowned their ships sailing in the Caribbean. This tropical storm is known as a cyclone in the northern Indian Ocean and the Bay of Bengal, and as typhoons in the western Pacific Ocean.

The Atlantic Ocean produces five to six hurricanes per year from mid-August to late October. Hurricanes are huge heat engines that generate energy on a massive scale. Hurricanes start as tropical disturbances in hot ocean waters where the temperatures reach at least 80 degrees Fahrenheit. The energy from warm oceans sustains these low-pressure systems. Hurricanes swirl around a low-pressure middle called the ‘eye’. The low-pressure air in the eye falls, which makes a strangely calm 20 to 30 mile-wide space. The storm’s strongest wind and rain are in the eye wall, which surrounds the eye.

A storm with wind speeds of 38 miles per hour or less is considered a tropical depression; a storm with wind speeds between 39 and 73 miles per hour is considered a tropical storm. When wind speeds reach 74 miles per hour, the wind turns into a hurricane. At this point, meteorologists give it a category rating of one to five. The closer the rating is to five, the worse the storm is.

Hurricanes cause havoc on land in lots of different ways. Once a hurricane makes landfall, it usually creates a devastating storm surge that can reach 20 feet high and expand about 100 miles inland. Ninety percent of all hurricane deaths are caused by storm surges. A hurricane’s high winds are devastating as well and may spawn tornadoes. Heavy rainfalls cause more harm by producing floods and landslides, which may happen many miles inland.

A good way for people to avoid hurricanes is to watch weather forecasts. These forecasts give people advance warnings of storms, which gives them time to get out of a storm’s path. National Hurricane Center (NHC) reports hurricane watches when harm to cities is possible and issues hurricane warnings for storms they predict will make landfall in less than 24 hours.

[Source: National Geographic]