For a storm to be classified as a hurricane, the following conditions need to be present:
Thunderstorms: The formation of a hurricane often starts with thunderstorms.
Warm Ocean Water: The water needs to be at least 26.5 degrees Celsius over a depth of 50 meters. This warm water powers the storm and provides the energy it needs to grow1.
Light Winds: Light winds are necessary for the formation of a hurricane1.
Low Wind Shear: A large difference in wind speed and direction around or near the storm can weaken it.
Moist, Humid Air: When humid air is flowing upward at a zone of low pressure over warm ocean water, the water is released from the air, creating the clouds of the storm.
Low Atmospheric Pressure: The storm begins to rotate around an area of low atmospheric pressure, forming a tropical depression.
Wind Speed: If the storm grows larger and the winds swirl faster than 74 miles per hour (119 km/h), it is classified as a hurricane.
It’s important to note that even when all these conditions are met, a hurricane doesn’t always develop. Hurricanes also weaken when they move over areas with cooler ocean water or over land.
What conditions classify a hurricane 1 through 5?
Hurricanes are classified into categories based on their sustained wind speed according to the Saffir-Simpson Hurricane Wind Scale. Here’s how they are classified:
Category 1: Winds range from 74 to 95 mph. Some damage can occur to well-constructed frame homes, large branches of trees may snap, and power outages could last a few to several days.
Category 2: Winds range from 96 to 110 mph. Extensive damage can occur, including major roof and siding damage to well-constructed frame homes. Near-total power loss is expected with outages that could last from several days to weeks.
Category 3 (Major): Winds range from 111 to 129 mph. Devastating damage will occur. Well-built framed homes may incur major damage or removal of roof decking and gable ends. Electricity and water will be unavailable for several days to weeks after the storm passes.
Category 4 (Major): Winds range from 130 to 156 mph. Catastrophic damage will occur. Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Power outages will last weeks to possibly months.
Category 5 (Major): Winds are 157 mph or higher. Catastrophic damage will occur. A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Power outages will last for weeks to possibly months.
There is no official Category 6 for hurricanes. The scale currently only goes up to Category 5. The categories give an indication of the potential damage a hurricane could cause based on its sustained wind speed. However, they do not take into account other potentially deadly hazards such as storm surge, rainfall flooding, and tornadoes.
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