Catastrophic
Winds: Hurricanes Catastrophic
Winds: Hurricanes Hurricanes are a type of tropical cyclone that originate in the Atlantic Ocean and usually affect the Atlantic coastal areas in northern South America, the Caribbean and Gulf Coast, and eastern North America. Hurricanes are one of the most destructive natural disturbances because of their vast size and tremendous intensity (Miller 1967), and they can cause billions of dollars of damage. Hurricane Andrew, which hit southern Florida in 1992, was one of the most intense hurricanes of the 20th century and the most destructive hurricane to hit the United States' coast. With winds gusting up to 175 mph, it was responsible for 15 deaths and $20 billion worth of damage (NOAA 1993). From the perspective of forest ecology, hurricanes are a very important for natural systems within those regions in the paths of these storms, and they can have a substantial impact on forest succession.
Image
of Hurricane Fran, a category 3 hurricane that reached Florida in Sept.
1996. Click on image to make it larger.
Hurricane Development: Click here to learn how hurricanes develope.
Storm Surge: Hurricanes, along with having very strong winds, cause a storm surge (def. below). Click here to learn more.
Hurricanes are classified according to the maximum wind speed. The Saffir/Simpson Hurricane Scale is commonly used to describe hurricane strength.
Hurricanes Hugo and Andrew are the two of the most damaging recent hurricanes. Both caused the loss of lives and extensive damage. Much of the current scientific research and federal damage assessments of hurricanes center around these two storms.
As you probably have surmised, much of the impact of hurricanes on forests is directly or indirectly linked to wind damage. Damage can range from small structural damage on individual trees to the uprooting and breakage of many large trees within a landscape. Stands regularly affected by hurricanes or any type of catastrophic events are unlikely to be in equilibrium, but instead are continually in a state of recovery from past disturbances (Merrens and Peart 1992). Thus, to understand the structure of forests found within temperate and tropical areas that regularly experience hurricanes, it is important to understand how species and stands respond to this major disturbance. Tropical and temperate forests can have different responses to a hurricane, thus both forest types will be discussed separately.
Effects of Hurricanes on Temperate Forests in New England, US
Tropical Forests in the Caribbean and Puerto Rico
Effect on Forest Organisms; e.g. migrating bird populations
Hurricanes can be very damaging to both forests and people. People can still lose their lives and suffer significant financial losses, even though recent research has increased the warning time and significantly decreased the amount of life and money lost during a hurricane (NOAA 1993). However, this type of disturbance is very important for natural systems within these regions because hurricanes can directly affect the composition and structure of forests and indirectly influence an area by changing the soil chemistry and physical properties and creating different microenviroments. Hence, hurricanes have a profound effect on forest succession.
Coriolis force: the apparent force resulting from the earth's rotation that deflects moving objects to the right in the northern hemisphere and to the left in the southern hemisphere.
Cyclone: a storm or system of winds that advances 20-30 mph and rotates around a center of low atmospheric pressure in a direction counterclockwise in the northern and clockwise in the southern hemisphere.
Hurricane: tropical cyclone with maximum sustained surface winds of at least 74 mph (64 knots).
Knot: a measurement used to measure the speed of a ship; equals one nautical mile per hour (1.15 mph or 1.85 kph).
Storm Surge: An abnormal rise of the sea along a shore caused primarily by the winds of a storm. Storm Tide: The rise in water levels as a result of both the storm surge and normal tide action.
Tropical Depression: A tropical cyclone with maximum sustained surface winds less than 38 mph (33 knots).
Tropical Disturbance/Tropical Wave: An unorganized mass of thunderstorms with very little, if any, organized wind circulation.
Tropical Storm: A tropical cyclone with maximum sustained surface winds ranging from 39-73 mph (34-63 knots).
Hurricane figure next to title and satellite image of Hurricane Fran from the National Hurricane Center, NOAA.