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What are Hurricanes and Typhoons? Where do hurricanes occur/form? What is a Tropical Depression? How are Tropical Storms created? What makes Hurricanes dangerous? What are the 5 deadliest hurricanes? What is the eye of a Hurricane? What is the Hurricane Surge? |
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What are Hurricanes and Typhoons? Hurricane or storm surge is an oceanographic phenomenon of water level fluctuations caused by the atmospheric pressure field and wind stress on the water surface, accompanying the moving hurricane or storm systems. Hurricanes and typhoons are both types of storms with great power and strength that cause extensive damage. They can tear apart entire cities with their powerful wind and strong storm surges. In order for a tropical storm to be classified as a typhoon, the storm must reach wind speeds of 65 knots (70 mph). Typhoons are measured on the RSMC (Regional Specialized Meteorological Centre) Cyclone Intensity Scale. Hurricanes are measured on the Saffir-Simpson scale, which was invented in 1971 by Herbert Saffir and Bob Simpson. This scale divides hurricanes into five categories. The classifications are categories 1, 2, 3, 4, and 5. In order to be classified as a hurricane or typhoon, the storm must have a minimum wind speeds of 74 mph. Any storm with winds less than 74 mph can be categorized under tropical storm or tropical depression. The following are the five categories: * Category 1 hurricanes have wind speeds of 74 - 95 mph. * Category 2 hurricanes have wind speeds of 96 - 110 mph. * Category 3 hurricanes have wind speeds of 111 - 130 mph. * Category 4 hurricanes have wind speeds of 131 - 155 mph. * Category 5 hurricanes have wind speeds greater than 156 mph. Hurricanes and typhoons form in warm ocean waters. The warm water is the source of the storm's energy. Therefore, the warmer the water, the more energy and power the storm obtains. As soon as the storm makes landfall, it begins to lose strength. All hurricanes and typhoons have a center point around which it circulates, hurricane destuction called the "eye". If the storm has enough power and strength, it can develop a large eye in the center. Weather in the eye is usually very calm. Hurricanes and typhoons can produce a number of problems. The effects could include treacherous rain, huge waves, storm surges, strong wind, and much more. Hurricanes and typhoons are known to flood streets, destroy homes, blow down trees, and kill people. Much of this could be prevented if people were more aware of how to be prepared to survive the effects of a hurricane or typhoon. If one lives where hurricanes or typhoons could make landfall, especially on the coast, one should have an emergency evacuation kit. Pre-conditions for typhoons Several atmospheric ingredients must come together for a typhoon to form. Since a typhoon is just another term for hurricane, the same conditions apply for both. There are perhaps seven atmospheric conditions which, if met, could cause a typhoon to form. A pre-existing disturbance, warm ocean water, low atmospheric stability, sufficient Coriolis force, moist mid-atmosphere, and upper atmosphere divergence are all important factors for typhoon formation. Where do hurricanes occur/form? These factors are important in that tremendous amounts of heat energy is transported from the tropics northward to the higher latitudes. The typhoon is a large heat engine, where great amounts of heat are being produced from the process of latent heat of condensation. This occurs as water vapor is being evaporated from the ocean surface and condensed into cloud droplets. Mechanisms to cause typhoon Formation If all of the pre-conditions are met, typhoon formation then becomes possible. There are several types of atmospheric disturbances that can cause a typhoon to develop. The most common mechanism to cause a typhoon to develop is the monsoon trough. This is an extension of the Inter-Tropical Convergence Zone where cyclonic spin has developed. The ITCZ is a trough of low pressure created by the convergence of the northeast and southeast trade winds. This "trade wind" trough does not contain the spin to initiate typhoon development. Typhoon ( hurricanes ) are caused mostly by the monsoon trough in six of the seven hurricane / typhoon formation basins of the world. What is a Tropical Depression? Tropical cyclone is the general term that descrives a low pressure system that originates over the tropical oceans. By international agreement, tropical cyclones are classified according to their intensity. Tropical Depression is an area of developing counterclockwise (in the northern hemisphere, clockwise in the southern hemisphere) wind circulation that may include localized rain and thunderstorms. Maximum sustained winds up to 38 MPH (33 Knots). Tropical Storm: A well defined area of counterclockwise rotating wind of 39-73 MPH (34-63 Knots). Usually includes rain and thunderstorms. It is assigned a name. How are Tropical Storms created? The great storms are driven by the heat released by condesing water vapor, and by external mechanical forces. Once cut off from the warm ocean, the storm begins to die, starved for water and heat energy, and dragged apart by friction as it moves over the land. What makes Hurricanes dangerous? What makes hurricanes the dangerous storms they are is that they combine the triple hazard of violent winds, torrential rains, and abnormally high waves and storm tides. Each of these by itself can pose a serious threat to life and property. Taken together they are capable of causing widespread destruction. For example, the hurricane that hit Galveston in 1900 resulted in 6,000 deaths and the alsmost complete destruction of the city. Hurricane Camille, which struck the Mississippi coast in 1969, killed 262 persons and caused damages of nearly $1 billion. Recent hurricanes have caused similar damages, but fortunately with a reduced toll on lives, as Warning systems have been implemented. What are the 5 deadliest hurricanes? These are the five deadliest hurricanes in American history: •The Great Galveston Storm (1900) The deadliest storm in American history, the Galveston hurricane killed 8,000 to 12,000 people. •Hurricane Maria (2017) •The Okeechobee Hurricane (1928) •Hurricane Katrina (2005) •The Chenière Caminada Hurricane (1893) What is the eye of a Hurricane? The eye, like the spiral structure of the storm, is unique to hurricanes. Here, winds are light and skies are clear or partly cloudy. But this calm is deceptive, bordered as it is by maximum force winds and torrential rains. Many persons have been killed or injured when the calm eye lured them out of shelter, only to be caught in the maximum winds at the far side of the eye, where the winds blow from a direction opposite to that in the leading half of the storm. What is the Hurricane Surge? Hurricane or storm surge is an oceanographic phenomenon of water level fluctuations caused by the atmospheric pressure field and wind stress on the water surface, accompanying the moving hurricane or storm systems. Specific factors which can combine to produce extreme water fluctuations at a coast during the passage of a storm or a hurricane include: storm intensity, size, path, and duration over water; atmospheric pressure variation; speed of translation; winds and rainfall; bathymetry of the offshore region; astronomical tides; initial water level rise; surface waves and associated wave setup and runup. Hurricane Surge constitutes a greater hazard to lives and coastal property than hurricane winds. Hurricane surges have been estimated to account for 75 to 90 percent of all deaths resulting from a hurricane. Surge inundation is also responsible for extensive damage to coastal property. Since 1900, hurricane damages to coastal property have averaged more than $50 million per year. The per year average has been far greater for the last twenty years. |