Environmental: The annual Atlantic hurricane season begins in June and runs through November, although hurricanes have occurred outside of this period. Hurricanes originate in the Atlantic basin, which includes the Atlantic Ocean, Caribbean Sea, and the Gulf of Mexico, the eastern North Pacific Ocean, and, less frequently, the central North Pacific Ocean. The most impactful hurricanes are usually experienced between August and October each year.
How is a Hurricane Formed?
Hurricanes begin as tropical disturbances in warm ocean waters with surface temperatures of at least 26.5 degrees Celsius. These systems of low-pressure are fed by energy from the warm seas. If a storm reaches wind speeds of 61km/h, it becomes known as a tropical depression. A tropical depression becomes a tropical storm when its sustained wind speeds reach 63km/h and then becomes a named storm (the first of the season will be storm Alberto). When a storm possesses wind speeds reaching 119km/h, it becomes a hurricane. Hurricanes generate energy on an enormous scale, drawing energy from warm, moist ocean air and release energy through thunderstorms. Hurricanes spin around a low-energy centre or the ‘eye of the storm’. This area is usually 32 to 48km wide and is home to significantly calmer conditions. The eye of a hurricane is surrounded by an ‘eye wall’, the area with the strongest winds and rain.
Defining a hurricane -The Saffir-Simpson Hurricane Wind Scale (from the US National Hurricane Center):
|Category||Sustained Winds||Types of Damage Due to Hurricane Winds|
|Very dangerous winds will produce some damage: Well-constructed homes could have damage to roof, tiles, and gutters. Large tree branches may snap and trees with shallow roots may be toppled. Damage to power lines could lead to power outages lasting several days.|
|Extremely dangerous winds will cause extensive damage: Well-constructed homes could sustain major damage to their roofs. Many shallowly rooted trees are likely to be uprooted and block numerous roads. Near-total power loss is expected to last from several days to weeks.|
|Devastating damage will occur: Well-built homes may incur significant damage. Many trees will be uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes.|
|Catastrophic damage will occur: Well-built homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted, and power poles downed, isolating residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months.|
|137 kt or higher
252 km/h or higher
|Catastrophic damage will occur: A high percentage of homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.|
A hurricane is damaging in a series of ways. Firstly, a hurricane creates a devastating storm surge that can reach six metres high and extend 161km on making landfall. Approximately 90 per cent of all hurricane-related deaths are caused by storm surges. Tornadoes, torrential rains, flooding, and landslides may follow a hurricane.
The 2017 Hurricane Season
The 2017 Atlantic hurricane season was most the joint fifth-most active hurricane season since records began in 1851. The 2017 season was hyperactive and featured 17 named storms, 10 hurricanes, and six major hurricanes (above category 3); the highest number of hurricanes since 2005. Last year’s hurricane season in the Atlantic started earlier than usual, with the first system forming in April while the last storm dissipated in November. 2017 was only the second year after 2007 to feature two Category 5 hurricanes to make landfall at that intensity. Most of the damage reported was attributed to Hurricanes Harvey, Irma, and Maria and was the costliest season on record – around US$282 billion worth of damage in total. Thousands in the region, notably in Puerto Rico, continue to live without electricity and other basic utilities.
Predictions for 2018
The impact of a hurricane season is difficult to predict. However, scientists estimate that as sea temperatures warm due to climate change, more damaging storms are predicted to occur. A study by Colorado State University suggests that there could be 14 named storms in 2018. At least seven of these are predicted to reach hurricane intensity, three of which could reach major hurricane strength (category 3-5). This would represent an above average year (the 1950-2017 average for named storms was 11) but potentially less active than the 2017 hurricane season.