How are Hurricanes Formed

By far the most destructive forces of nature, hurricanes are violent rotating windstorms which are usually accompanied by heavy rains and often characterized by widespread destruction. While most of us are aware of their destructive power, not much is known about their formation - a complex process which depends on the prevailing weather and climatic conditions.

Hurricane Formation

Favorable Conditions
The National Oceanic and Atmospheric Administration (NOAA) defines a hurricane as a violent, strong storm that is formed when several elements combine under the 'right' conditions at the 'right' time. The conditions favorable for the formation of hurricanes include

• Warm waters, preferably above 80 degrees Fahrenheit, with a depth of at least 150 ft.
• Low pressure area, with at least moderate wind disturbance.
• Coriolis force produced by the rotation of the Earth.
• Moist ocean air, especially in the lower atmosphere.

Other than these conditions, low level winds and lack of stability in the air also contribute to the formation process.

The Formation Process
As clusters of thunderstorms drift over warm ocean waters, the warm air in them combines with the warm air over the ocean surface and starts rising. What starts of as a tropical storm in the Atlantic or Pacific oceans, eventually gains strength and becomes a full-fledged hurricane. As warm air starts rising, low pressure is created at the surface of the storm formation. At this point of time, the trade winds which blow in opposite directions start propelling the formation in a circular motion. These winds blow at a tremendous speed of around 75 to 200 miles per hour. As the warm air continues rising, the pressure begins to decrease. The vacuum created by the rising air is filled as more air is drawn from the periphery. Meanwhile, the warm air continues to rise while the cold air starts settling at the base.

As the storm formation continues moving on the ocean surface, more warm air is drawn in continuously. Owing to this warm air feeding, the intensity of the storm starts increasing. It picks up speed and the low pressure area at the center continues to flourish, thus leading to the formation of a hurricane. The time required for the formation of a full-fledged hurricane may vary between a few hours to a few days, during which its intensity may either increase or decrease depending on how favorable the conditions are.

Categories and Wind Speed
The eye of a hurricane is basically a low pressure area made up of calm wind. This eye is encircled by a surrounding vortex of high intensity winds and heavy rainstorm. In the United States, the Saffir -Simpson Scale is used to measure the intensity of these hurricanes. According to this scale, hurricanes are categorized into 5 types.

Category	Wind Speed
1	74-95 mph
2	96-110 mph
3	111-130 mph
4	131-154 mph
5	155 mph

As the speed of the wind increases, the hurricane continues to become more destructive. Type 5 hurricanes are the most dangerous, and have the capacity to blow away trees as well as buildings.

Different Names by Which Hurricanes are Known
Many people tend to misinterpret the terms - typhoon, hurricane and cyclone, all of which refer to the same geographical concept, but in different parts of the world. Although the scientific name for these violent storms is tropical cyclones, they are known as:

• Hurricanes in Atlantic and Eastern Pacific Ocean
• Typhoons in Western Pacific Ocean
• Cyclones in Bay of Bengal and Indian Ocean

These devastating cyclones can form throughout the year, but their frequency is at its highest between August and October.

The destruction caused by hurricanes like Katrina and Rita are apt examples of the ferociousness of this weather phenomenon. Interestingly, their frequency has suddenly increased over the last few years, which the scientists believe is caused as a result of global warming, wherein warm ocean waters are providing favorable conditions for hurricane formation. Efforts are being taken to monitor the formation of tropical storms, which eventually develop into hurricanes, in order to minimize the damage. When it comes to our battle against the nature, our powers are restricted to a certain extent.