Hurricane Laura, a Category 4 storm, made landfall in southwestern Louisiana on Thursday with wind speeds reaching up to 250 km (150 miles) an hour. The US National Hurricane Center (NHC) warned of “life-threatening conditions”.
What are hurricanes and how do they form?
Tropical cyclones or hurricanes use warm, moist air as fuel, and therefore form over warm ocean waters near the equator. As NASA describes it, when the warm, moist air rises upward from the surface of the ocean, it creates an area of low air pressure below. When this happens, the air from the surrounding areas rushes to fill this place, eventually rising when it becomes warm and moist too.
When the warm air rises and cools off, the moisture forms clouds. This system of clouds and winds continues to grow and spin, fuelled by the ocean’s heat and the water that evaporates from its surface.
As such storm systems rotate faster and faster, an eye forms in the centre. Storms that form towards the north of the equator rotate counterclockwise, while those that form to the south spin clockwise because of the rotation of the Earth.
What is the difference between a hurricane and a tropical storm?
There is no difference. Depending on where they occur, hurricanes may be called typhoons or cyclones. As per NASA, the scientific name for all these kinds of storms is tropical cyclones.
The tropical cyclones that form over the Atlantic Ocean or the eastern Pacific Ocean are called hurricanes and the ones that form in the Northwest Pacific are called typhoons. Tropical storms that form in the Bay of Bengal or the Arabian Sea are called cyclones.
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How severe is Hurricane Laura?
Hurricanes are categorised on the Saffir-Simpson Hurricane Wind Scale, which rates them on a scale of 1 to 5 based on wind speed. Hurricanes that reach category three or higher are classified as major hurricanes because of their potential to cause devastating damage to property and life.
Hurricane Laura is a Category 4 storm, which means well-built framed houses can suffer severe damage with loss of most of the roof structure and exterior walls. A Category 4 storm has wind speeds between 130-156 mph and can uproot trees and bring down power lines. The resulting power outages can last for weeks or months, rendering the area uninhabitable for weeks or months.
The NHC said in a tweet Wednesday, “Unsurvivable storm surge with large and destructive waves will cause catastrophic damage from Sea Rim State Park, Texas, to Intracoastal City, Louisiana, including Calcasieu and Sabine Lakes. This surge could penetrate up to 30 miles inland from the immediate coastline. #Laura”.
The last storm, Hurricane Hanna, which made landfall on the Texan coast late last month reached wind speeds of up to 90 mph, and was listed as a Category 1 storm. It was the first hurricane of the 2020 Atlantic hurricane season. As the hurricane made landfall, power outages were reported across the state, and it caused extensive damage to property.
How can you protect yourself during a hurricane?
During a hurricane, storm surge (abnormal rise of water generated by a storm) and inland flooding are the two main reasons that can cause loss of life.
NHC has advised that the “safest place” to be during a major landfalling hurricane is in a reinforced interior room away from windows. “Get under a table or other piece of sturdy furniture. Use mattresses, blankets or pillows to cover your head and body. Remain in place through the passage of these life-threatening conditions,” it said in an advisory.
Why do hurricanes hit the east coast of the US at this time every year?
In May, the National Oceanic and Atmospheric Administration (NOAA) said it expected an “above-normal” hurricane season this year. The outlook predicted a 60 per cent chance of an above-normal season, 30 per cent chance of a near-normal season and a 10 per cent chance of a below-normal season.
The Atlantic hurricane season runs from June 1 to November 30, and as per NOAA, an average hurricane season produces 12 storms, of which, six become hurricanes, including three major hurricanes. In the East Pacific, the season runs from May 15 to November 30.
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While hurricanes can occur outside of this window, the period accounts for 97 per cent of the tropical activity. Until 1965, June 15 and November 15 were the official start and end dates of the season, after which it was decided to extend it from June 1 to November 30.
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