Sunday, March 22, 2015

Its Thunder storm season India - A special write-up from Tamil Nadu Weatherman

The Pre-monsoon season or Hot weather or summer season is the names you would have heared in text books. The temperatures, particularly the maximum, during this season are very high over most parts of the country especially over central and northwest India. But there are many other Names called in different parts of India. This is also one of my favorite seasons to track weather.

Kali Andhi

Convective dust-storms occur over northwest India during the premonsoon season. In Africa and Arabia this phenomenon is called as Haboob. Sometimes, the distance between the cumulonimbus cloud and the associated Andhi dust-wall on the ground can be as large as 30 Km. The dust raised by strong wind reduces horizontal visibility to less than 100 meters. It may quickly build up out of the blue, transforming the dry hot afternoon into a dark brown mush. The assault of the Andhi usually lasts only a few minutes. North India often get affected by these Kali Andi every year. They are also called as black storms - Last year (2014) Delhi got hit by one of the Kali Andhi -

Loo winds

The Loo mainly originates in the large desert regions of the northwestern Indian subcontinent: the Great Indian Desert, the Cholistan Desert and the desert areas of Southern Balochistan. The plains of North India and Pakistan are both very hot and extremely dry during this season, water evaporates quite readily.  Loo direction is from west  to  east  and  they  are  usually  experienced  in  the  afternoons and its temperature varies between 45°C to 50°C. Entire North and north west India gets affected by Loo.  It makes life miserable for the people and the heat wave takes its toll and many people die because of it.

Kalbaishakhi / Norwestor

Moisture inflow from bay of bengal coupled with the heating of air, cold advection at 500 hpa and and presence of a jet stream between the levels 300 mb and 200 mb are extremely helpful for the occurrence of nor’westers. They normally form over Jharkhand and Bihar and travel entire East India affecting Odisha, West Bengal, Bangladesh. If u track the radar u can see  derechos too. Tornados too form in this period.

Last year Bangladesh got hit by one of the norwestor and it overturned a train -

Tornado in Odisha (rare image too) in 2009 -


It is similar to Norwestor or it is a other name of Norwestor. The local severe storms of Assam and North East India during the pre-monsoon season are termed as Bordoichila, meaning the angry daughter of Assam. Advection of warm air in the lower levels and cold air in the upper levels increases the conditional instability in the atmosphere and favor the outbreak of severe thunderstorms.

The southerlies approaching the north–east India, originate from the Bay of Bengal and thus, are warm and moist  On the contrary, the westerlies originating from the Tibetan plateau and eastern Himalaya are cold and dry. At nighttime while the Garo, Khasi and Jaintia hills cool down more rapidly than the plains, the katabatic wind blows down the slope toward the valley. This, in turn, brings down the moist air to the valley and a front-like structure develops during the nighttime, having two different types of air masses on—either side and this causes severe thunderstorms to occur over the valley mostly during the nighttime. North Eastern states mostly, Assam, Meghalaya Tirupura gets affected by these storms.

News of Bordoichila in 2013

Mango Showers

Mango shower occurs along Kerala, Karnataka and also in parts of Tamil Nadu. The showers prevent the mangoes from dropping prematurely from trees and are crucial for the mango cultivation in South India.

Mango Showers -

'Cherry Blossom’ or ‘Coffee showers’

It is a local wind that blows over the interior Karnataka during the hot weather season and is extremely helpful for coffee cultivation. The Hills in the interior Karnataka gets most of these rains. -

Blossom or Coffee Showers -

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