Hurricane Facts
According to the National Hurricane Center, an average of 11 tropical storms develop each year over the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Many of these remain over the ocean and never impact the U.S. Coastline. Six of these storms become hurricanes each year.
In an average three year period, about 5 hurricanes strike the U.S. coastline, killing approximately 50-100 people anywhere from Texas to Maine. Of these hurricanes, 2 are typically “major” (a category 3 or higher storm on the Saffir-Simpson scale).
The official Atlantic hurricane season starts June 1 and ends November 30. In the eastern North Pacific, the official hurricane season starts May 15 and ends November 30. Both seasons cover more than 99% of all tropical cyclones in any year.
Nations in East Asia like Japan and China instead of using the term “hurricane” use the name “typhoon.” Mexicans call these storms “cordonazos” and in the Philippines they are called “baguios.” Haitians call them “tainos” and in Austrailia they are commonly referred to as “willy-willy.”
How a Hurricane forms
There are several elements that, when combined at the right amount of time and under the right conditions, will create a hurricane.
The beginning of life for any hurricane is a pre-existing tropical disturbance, an area of low atmospheric pressure in the air over the tropical Atlantic Ocean near Caribbean islands such as Bermuda and the Bahamas. The warmth and moisture of the ocean during late summer and early fall months energizes the pre-storm conditions and leads to thunderstorms. If thunderstorms persist and winds pick up to 40 miles per hour, the tropical disturbance officially becomes a tropical storm. At this point the National Hurricane Center names the storm, working from a pre-determined list of names that is recycled every six years. Regardless of where they form, hurricanes always move towards the west and spin in a circular direction about the eye, or center, of the storm.
Hurricane Definitions
Tropical Disturbance: An organized area of thunderstorms that holds itself together for at least 24 hours. If the storms continue to develop, they may be upgraded to a tropical depression.
Tropical Depression: A tropical cyclone (an area of low pressure that develops over tropical or subtropical waters with a definite organized surface circulation) in which the maximum sustained wind speed is 38mph or less. If this continues to develop, it may become a tropical storm.
Tropical Storm: A tropical cyclone with maximum sustained winds of 39mph to 73mph. If this continues to develop and maximum sustained winds reach 74mph, a hurricane is created.
Hurricane Ratings
Once a storm officially becomes a hurricane, it receives an intensity rating based on its wind speed, barometric pressure, storm surge, and potential to cause damage. The rating system that is used by the Nation Weather Service is called the Saffir-Simpson scale. As a hurricane develops, its intensity rating often changes
Category 1: Winds 74-95 mph (examples: Irene-1999; Allison-1995)
Category 2: Winds 96-110 mph (examples: Dolly 2008, Gustav 2008, Ike 2008)
Category 3: Winds 111-130 mph (examples: Keith-2000; Fran-1996; Opal-1995)
Category 4: Winds 131-155 mph (examples: Hugo-1999; Donna-1960)
Category 5: Winds More than 155 mph (examples: Andrew-1992; Camille-1969, Katrina-2005)
