How Do Hurricanes Form?

The Atlantic Hurricane Season begins in just a few weeks on June 1st, so let’s review just exactly how a hurricane forms.

The first ingredient for a hurricane is a complex of thunderstorms or weather system that already exists. Without already existing showers and thunderstorms, a hurricane cannot form. However, just because there is active weather doesn’t mean a hurricane will form either, so let’s look at the second ingredient; warm sea-surface temperatures.

Sea-surface temperatures of at least 26.5 degrees Celsius, or 80 degrees Fahrenheit, are usually the threshold in which a hurricane can form. Hurricanes are warm-core systems and extract heat from the warm ocean temperatures, so it’s critical for sea-surface temperatures to be at this threshold for at least 50 meters, or more than half a football field, in depth.

Low wind shear is the third ingredient for hurricanes to form. Wind shear, the change of wind direction or speed with height, can rip thunderstorms apart from a tropical disturbance and cause disorganization. However, when there’s low wind shear, thunderstorms can continuously build upon another and allow the system to strengthen.

These three ingredients can help form an area of low pressure, that after enough time, can organize into a closed circulation with wind speeds greater than 39 mph. When this occurs, a tropical storm is formed and given a name by the National Hurricane Center. If the tropical storm continues to gain wind speed to have sustained winds of at least 74 mph, a hurricane is formed.

While these ingredients support hurricanes, that doesn’t mean one will form. There are a lot more factors that go into whether a hurricane can form such as proximity to land and the amount of dry air nearby. This is just a rough overview of the building blocks hurricanes and helps to get you informed and prepared before the upcoming hurricane season.

Source: oceanservice.noaa.gov
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