Everyone knows that hurricanes can be devastating and they are characterized by their destructive winds, storm surges and exceptional levels of rainfall which may cause flooding.

CHARACTERISTICS

Destructive Winds

Tropical cyclones can generate some exceptionally strong winds. These circulate clockwise in the Southern Hemisphere and counter clockwise in the Northern Hemisphere. Wind speeds progressively increase towards the core. As the eye arrives, winds dwindle to become almost calm but rise again just as quickly as the eye passes and are replaced by hurricane force winds from a direction nearly the reverse of those previously blowing. In general, the strongest winds are found on the right side of the hurricane. The damage caused by the wind increases exponentially instead of linearly. Therefore a category 4 hurricane will not cause 4 times as much damage as a category 1, but it may cause up to 250 times the damage!

Hurricane-force winds can easily destroy poorly constructed buildings and mobile homes. Debris such as signs, roofing material and small items left outside become flying missiles in hurricanes. Extensive damage to trees, towers, water and underground utility lines (from uprooted trees), and fallen poles cause considerable disruption.

High-rise buildings are also vulnerable to hurricane-force winds, particularly at the higher levels since wind speed tends to increase with height. Recent research suggests you should stay below the tenth floor, but still above any floors at risk for flooding. It is not uncommon for high-rise buildings to suffer a great deal of damage due to windows being blown out. Consequently, the areas around these buildings can be very dangerous. Source: http://www.nhc.noaa.gov/HAW2/english/high_winds.shtml

Storm Surges

These cause a rise in sea level above the normal tide. A storm surge is simply water that is pushed towards the shore by the force of the winds swirling around the storm. As the cyclone approaches the coast, the friction of strong on-shore winds on the sea surface, plus the "suction effect" of reduced atmospheric pressure, can pile up sea water along a coastline well above the predicted tide level. The rise of water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tide.

Excessive Rainfall and Flooding

This is caused when high humidity condenses into rain. The presence of giant cumulus clouds also results in high precipitation rates when the hurricane reaches land. The rain rapidly saturates the ground and rapid run off will result in severe flooding. Although storm surge and high winds do cause severe damage, inland flooding caused by heavy rainfall has resulted in a significant loss of life over the years.

Tropical cyclones frequently produce huge amounts of rain, and flooding can be a significant problem, particularly for inland communities. A typical hurricane brings at least 6 to 12 inches of rainfall to the area it crosses. The resulting floods cause considerable damage and loss of life, especially in mountainous areas where heavy rains mean flash floods and can also result in devastating mudslides. (http://hurricanes.noaa.gov/pdf/hurricanebook.pdf)

EFFECTS

Physical Damage

Structures will be damaged or destroyed by wind force, storm surges, landslides and flooding.  Public utilities such as overhead power lines, water and gas distribution lines, bridges, culverts and drainage systems are also subject to severe damage.  Fallen trees, wind driven rain and flying debris can also cause considerable damage.

Crops and Food Supplies

The combination of high winds and heavy rain and flooding can ruin crops and trees. Food stocks may be lost or contaminated and it is possible that food shortages will occur.

Casualties and Public Health

There are relatively few deaths associated with the impact of high winds. However, storm surges may cause many deaths but usually few injuries among survivors. The threat to public health emerges in the aftermath of events when conditions such as water contamination or shortages, flooding and damage to sanitation facilities may cause the spread of diseases.

Lack of Communication

Communication may be severely disrupted as telephone lines, radio and television antennas and satellite disks are blown down. Roads and railway lines may be blocked by fallen trees or debris and aircraft movements are curtailed for hours after a hurricane.