Hurricanes are infamous for their destructive history. Even today, it is almost impossible to tame them. This ScienceStruck article tell us more.
Hurricanes are the powerful forces that cause catastrophic damage to property and immeasurable sufferings to mankind and loss of lives. Since 1944, the United States Navy (USN) and the United States Air Force (USAF) have taken numerous missions to study the eye of the hurricane in order to gather vital data and warn civilians as well as military personnel.
- Hurricanes are known by different names in different parts of the world. They are termed as typhoons in Northwest Pacific Ocean and west of the International Date Line. Near Australia and in the Indian Ocean they are known as cyclones. In the Philippine Islands, they are called bagnios.
- The hurricane season in the Atlantic ocean generally peaks from mid-August to the last week of October.
- There are 6 to 8 hurricanes in an average season.
- They rotate in an anticlockwise direction in the northern hemisphere and clockwise manner in the southern hemisphere.
- They can last from 1 to 30 days. Average life of this storm is nine days and it is determined by the time and place of origin and rate of forward movement. The longest life cycle ever recorded was of Hurricane Ginger which lasted for 31 days (from September 5 to October 5 ,1971).
- The first 12 hours of any hurricane are most deadly and destructive.
- The deadliest one in US history is the Galveston Hurricane which occurred on September 8,1900 and claimed more than 6000 lives.
- Hurricane Katrina is the costliest in US history, which caused over 75 billion dollars of damage.
The main causes are tropical disturbances in warm ocean waters where the temperature of water reaches at least 80 degrees Fahrenheit (26.5 degrees Celsius). The moisture-rich air above the huge water mass becomes warm. This warm air rises, encounters with the cooler air above, and condenses. In this way storm clouds are formed. In the process of condensation, large amount of latent heat is released. This latent heat and summer sun warms the cool air which rises further, causing more warm humid air from the surface of ocean to rise. The cycle continues and more amount of warm air, laden with vapor, is drawn into the developing system. As the heat exchange continues, ultimately a wind pattern is formed. If the wind speed becomes greater than 74 mph its termed as a hurricane.
The eye of a hurricane is roughly a circular area where winds are calm. This is a low pressure area and could be 20-40 miles in diameter. The cross section of the eye is cylindrical and it is surrounded by the eyewall where the most severe weather of the hurricane occurs.
Hurricane Categories and Damage
Based on the Saffir-Simpson Scale, hurricanes are categorized into 5 types. The category determines the necessary precautions needed when it is active. Different categories, wind speed and effects are given in the table below.
|Category||Wind Speed||Damaging Effect|
|1. Weak||74-95mph||Little damage to vegetation|
|2. Moderate||96-110mph||Reasonable damage to house, farms, etc.|
|3. Strong||111-130mph||Extensive damage to small buildings|
|4. Very Strong||131-155mph||Most windows will be blown out from the high rise buildings|
|5. Devastating||>155mph||Catastrophic damage|
Naming of Hurricanes
Earlier, lack of a uniform system of naming created many difficulties in communication, forecasts, and warnings. The United States National Hurricane Center started a systematic naming (with predominantly female names) in 1953. At present, the names are maintained and updated by the World Meteorological Organization or WMO. Generally, the hurricanes once named are not renamed. Distinctive names given to hurricanes can reduce confusion when two or more hurricanes occur at the same time. To decide what names to be used every year, WMO uses six lists in rotation. The same list is used every six years. A new name is assigned only when it is extremely destructive.
Hurricanes occur in the tropical convergence zones, which are the warm regions of the earth. The main regions of hurricanes are Atlantic basins, northeast Pacific basin, northwest Pacific basin, north Indian basin, and southeast Indian basin.