SEVERE STORMS: HURRICANES The Most Powerful Storms on Earth

Hurricanes: Get the Facts  The term Hurricane comes from Huracan, a god of evil recognized by the Tainos, an ancient aboriginal tribe from Central America  In other areas hurricanes are known by other names including typhoons, cyclones and baguios  Sustained winds of 155 mph or higher  Intense rainfall  Storm surges  They can expend as much energy as 10,000 nuclear bombs in their lifetime

The Right Conditions for Formation Warm ocean water (>80°F) Converging winds force air up When they reach the top of the storm, winds flow out Warm moist air rises to make the clouds in the storm Outside wind steer the hurricane and allow it to grow

Tropical Disturbance Hurricanes begin as clusters of clouds and thunderstorms called tropical disturbances Tropical Disturbances have: low-pressure areas and little or no rotation. Most of these disturbances die out, but a few persevere down the path to hurricane status: Latent heat released which warms the disturbance The air density then drops Wind speed increases as cooler air rushes in under he less dense warm air The Coriolis Effect causes the disturbance to rotate The incoming winds bring more moisture with them, producing cloud activity which releases latent heat (feeds the storm)

The Tropical Disturbance requires wind and warm moist air to continue growing, this is like it’s “food”. As a Tropical storm builds and develops it goes through three distinct stages: Tropical depression: wind speeds of less than 38 mph Tropical storm: wind speeds of 39 to 73 mph Hurricane: wind speeds greater than 74 mph

Anatomy of a Hurricane:  Eye: A hurricane's low-pressure center of relative calm  Eye Wall: The area surrounding the eye where the storm's most violent winds occur   Rainbands: The bands of thunderstorms that circulate outward from the eye. These storms play a key role in the evaporation/condensation cycle that feeds the hurricane

Anatomy of a Hurricane

Death of a Hurricane A hurricane dies when the storm encounters conditions that deny it the warm, moist air it requires When it moves to cooler waters at a higher latitude, gradient pressure decreases, winds slow, and the entire storm is tamed, and it peters out in days. When a hurricane hits land the important supply of warm, moist air also vanishes. Condensation and the release of latent heat diminishes, and the friction of an uneven landscape decreases wind speeds.

Hurricane Categories

Where They Happen  Most Hurricanes form between 5 and 20 degrees N and S latitude  The North Pacific gets the most hurricanes each year with an average of 20 per year  The U.S. gets an average of 5 Hurricanes per year ? ?