How do hurricanes form?

Radar imagery shows Hurricane Dorian making landfall on Grand Bahama, the northernmost island...
Radar imagery shows Hurricane Dorian making landfall on Grand Bahama, the northernmost island in the archipelago, as a Category 5 storm. (Source: CNN)((Source: CNN))
Updated: Mar. 31, 2020 at 12:25 PM EDT
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SAVANNAH, Ga. (WTOC) - We all know that living along the coast, we need to be concerned about hurricanes. But do you know how and why they form?

Hurricane Season begins June 1 and ends Nov. 30. That means six months out of the year we need to monitor the tropics. The peak of the hurricane season is around mid-September. That's when sea surface temps are at their warmest. But warm sea surface temperatures are only one of three key ingredients for hurricanes to form.

The 3 key ingredients are:

One is sea surface temps at or above 80 degrees. The warmer the temps, the more moisture or fuel for the storm. Once a hurricane moves over land, its fuel is cut off and the storm begins to weaken. The second ingredient is a pre-existing spin or area of low pressure. The third ingredient is light vertical wind shear. This allows the thunderstorms to grow tall and not be sheared apart by strong winds.

So now it's time to talk about how hurricanes form. Hurricanes form when warm moist air over water begins to rise. The rising air is replaced by cooler air. This process continues to grow large clouds and thunderstorms. These thunderstorms continue to grow and begin to rotate thanks to earth's Coriolis Effect. The thunderstorms will rotate counterclockwise in the north hemisphere around the center which is called the eye. The eye is an area of descending air which produces light winds and dry conditions. The strongest winds will be located just outside the eye in the eye wall.

Let's talk about tropical classifications. A tropical Depression is an area of low pressure with a closed center of circulation and sustained winds less than 39mph. A Tropical Storm is when that area of low pressure continues to deepen and has winds between 39-74mph. This is when a storm gets a name! Hurricane Names come from the World Meteorological Organization and are on a 6 year rotating list which alternates between male and female names. A storm name can be retired if it causes extreme damage and/or loss of life. A hurricane is a strong area of low pressure with rotating thunderstorms close to its center of circulation. Winds are at least 74mph. The Saffir-Simpson Scale classifies hurricanes from Category 1 to Category 5.

There are many dangers associated with hurricanes including storm surge flooding, strong winds and tornadoes. Our hurricane threats come from storms in the Atlantic Basin which is made up of the Atlantic Ocean, Caribbean Sea and the Gulf of Mexico. Hurricanes will generally be steered by the upper level wind currents. That is normally the Atlantic High pressure ridge for us. This will move storms from east to west in lower latitudes and west to east in higher latitudes. A weaker high pressure will keep storms further east. A stronger high pressure will push storms further south and west. The strength and position of the Atlantic Ridge fluctuates throughout the season. That’s why we need to pay close attention to the forecast as storms can form and move quickly.

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