Tropical Storms
  • called HURRICANES in the Atlantic Ocean
  • called TYPHOONS in the Pacific Ocean
  • called CYCLONES in the Indian Ocean

Hurricanes are storms that have winds reaching at least 119 km/ 74 miles per hour (strongest hurricanes can reach up to 155 mi per hour).
  • A hurricane-like storm below this speed can be considered a "tropical storm"
Hurricanes are most common in the summer and autumn months when global temperatures are warmest.

Hurricanes form when
  • strong winds pick up moisture over warm surface waters (the warmer the water, the more moisture they'll pick up)
  • the cloud of water particles begins to spin because of wind currents and the Earth's rotation
  • the spinning causes an upward spiral of massive clouds as air is pulled upward

Predicting Hurricanes- Stormwatch centers monitor surface water temperature, wind speed, and use satellites to visualize the storm as it travels toward land. No preventative measures can be taken against hurricanes.
Hurricanes are ranked on a scale from 1-5 based on wind velocity, although some hurricanes have been rated as "above 5" due to their record wind velocities.

We have seen an increase in hurricane number and intensity since 1970, as global ocean surface temperatures rise (due to global warming). 2005 had the most hurricanes on record in the Atlantic (28 Hurricanes).

Responding To Hurricanes- cities employ the following measures when severe hurricanes threaten an area
  • sandbags to prevent the potential storm surge from making too much landfall (lessen the impact of the storm waves)
  • generally suggest citizens evacuate the area
  • Turn off public works sewer and water treatment facilities. These facilities cannot handle to volume of normal household waste AND the resulting excess water from the surge/flooding.
  • Provide higher ground evacuation sites for those unable to leave the city

Environmental and Economic Effects

Environmental Effects Include
  • Destruction of habitat due to high wind speeds
  • Storm Surges with high waves
    • Hurricane Katrina is an example of a famous storm surge, where the waves reached 25 feet above ocean height.

Economic Effects include
  • Destruction of property and infrastructure
  • Loss of life, health effects requiring medical attention
  • Potential depression of are economically as citizens may never return or companies may relocate elsewhere after a sever storm (see Katrina)

Historic Hurricanes
  1. Hurricane Mitch (1998)- caused 10,000 deaths in Central America and extensive infrastructure damage. The deadliest hurricane in the Western Hemisphere in the last 200 years.
  2. Hurricane Katrina (2005)- flooded 80% of New Orleans- read page 88
    • Part of the extensive damage was due to the established system of canals and levees. New Orleans rests at or below sea level, but a system of engineered dams have been constructed to control moderate flooding. These dams also prevent the deposit of silt from floodwaters after they recede (and this silt also acts as a guard against flooding and replenishes nutrients). Now, the silt is deposited in the Gulf of Mexico. Therefore, the attempts to keep water out of New Orleans also led to a less fertile soil structure.
    • The wetlands surrounding the Mississippi delta were developed for housing and infrastructure. This created areas of high runoff where natural grassland existed before. Roads, roofs, and cement structures can only absorb a tiny tiny fraction of the water that hits them, as opposed to the grasslands that could absorb close to 100%. This led to increased flooding during severe storms
    • Finally, as natural resources are drilled out of the Gulf of Mexico and New Orleans' surrounding area, the ground will sink. As heavier buildings, more cars, and more people populate the area, the weight pressing downward on the less stable bedrock pushes the city downward. New Orleans is subsiding (sinking) because of this instability and increased weight. This means that ocean water is more likely to wash over the city as it lowers in elevation.