Thunderstorms form when rising warm air, through a process called convection, rises into cooler air alot. Conditions have to be favorable for thunderstorm development, which can be a varietey of factors, including cold fronts, low pressure systems, tropical storms/hurricanes (low pressure systems over water), and storms that form from daytime heating when conditions allow.
Thunderstorms need two basic elements to form. They need moisture and rapidly rising warm air, which is why they are more prevalent in the spring and summer months. When humid air that is saturated with water vapor is forced to rise quickly by high temperatures, it’s easy for a thunderstorm to form. These storms involve large rainfalls, thunder and lightning. The National Oceanic and Atmospheric Administration’s National Weather Service estimates that at any given time, there are 1,800 thunderstorms occurring. They also estimate that the planet generates nearly 16 million such storms a year, which typically last about half an hour and are about 15 miles wide.
The action of warm air rising and cold air sinking (convection) plays a key role in the formation of severe thunderstorms. If the warm surface air is forced to rise, it will continue to rise, because it is less dense than the surrounding air. In addition, it will transfer heat from the land surface to upper levels of the atmosphere through the process of convection.
Two of the most important ingredients for thunderstorm formation are instability (unstable air) and moisture.
There are three main types of thunderstorms; orographic, air mass, and frontal.
The Effect – Nilam ( Recently in INDIA )
The storm brought torrential rains to Sri Lanka. The Puttalam – Mannar road has come under about a meter of water near Eluwankulama due to the overflowing of the Kala Oya river. A 27-year-old woman was killed when a sand rock fell on her house during heavy rains at Habaraduwa in Galle District, according to the police. Rail services were temporarily suspended when electricity lines fell on the railway track. In Chennai, all schools and colleges were closed as 282 schools and 52 community halls have been converted into cyclone shelters. Danger signal 7 was hosted in Chennai, Ennore, Cuddalore, Nagapattinam and Puducherry ports of Tamil Nadu and danger signal 3 in Krishnapatnam, Vadarevu, Machilipatnam and Nizampatnam ports of Andhra Pradesh.
Courtesy : http://www.eo.ucar.edu, curiosity.discovery.com, answers.yahoo.com, wikipedia.org
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