India characterized by Seasons
India is a characterized by strong temperature variations in different seasons ranging from mean temperature of about 10°C in winter to about 32°C in summer season. Details of weather along with associated systems during different seasons are presented as under, classified into four types.
This Season starts by late November representing clear skies, fine weather, light Northerly winds, low humidity and temperatures and large any time variations of temperature. The cold air mass extending from the Siberian region has profound influence on the Indian Sub-continent (at least all of the North and most of Central India) during these methods.
The mean air temperatures usually increase from North to South. The mean temperatures vary from 14°C to 27°C during January. The mean daily minimum temperatures range from 22°C n the extreme South, to 10°C in the Northern plains and 6°C in Punjab. The rains during this season generally occur over the Western Himalaya, the extreme North-Eastern parts of Tamil Nadu and Kerala. Western disturbances and associated through in westerlies are main rain bearing system in Northern and Eastern parts of the country.
The Temperatures start to increase all over the country in March and by April, the interior parts of the Peninsula record mean daily temperatures of 30-35°C. Central Indian land mass becomes hot with day time maximum temperatures reaching about 40°C at many locations. Many Places in Gujarat, North Maharashtra, Rajasthan and North Madhya Pradesh exhibit high day time and low night time temperatures during this season.
The range of the day time maximum and night time minimum temperatures is found more than 15°C at many places in these states. Maximum temperatures rise sharply exceeding 45°C by the end of May and early June resulting in harsh summers in the North and North-West regions of the country. However, weather remains mild in coastal areas of the country owing to the influence of and sea breezes.
The season is characterized by cyclonic storms, which have intense low pressure systems over hundreds to thousands of km associated with surface winds more than 33 knots over the Indian sea viz Bay of Bengal and the Arabian sea.
These system generally, move towards a North-Westerly direction and some of them recurve to Northerly or North-Easterly path. Storms forming over the Bay of Bengal are more frequent than the ones originating over the Arabia Sea. On an average, frequency of these storms is about 7.4 per year. Weather over land areas is influenced by thunderstorms associated with rain and sometimes with hail in this season.
South West Monsoon season
Monsoons are a complex meteorological phenomenon. The onset of the South-West Monsoon normally starts over the Kerala coast, the Southern tip of the country by 1st june, advance along the Konkan coast in early June and covers the whole country by middle of July. However, onset occurs about a week earlier over islands in the Bay of Bengal. The Monsoon is a special phenomenon exhibiting regularity in onset and distribution within the country, but inter-annual and intra-annual variations are observed.
Retreating/North-East Monsoon Season
This monsoon or post-monsoon season is transition season associated with the establishment of the North-Easterly wind regime over the Indian sub-continent. Meteorological sub-divisions namely coastal Andhra Pradesh, Rayalaseema, Tamil Nadu, Kerala and south interior of Karnataka, receive good amount of rainfall accounting for about 35% of their annual total in these months.
Monsoons retreat from North to South in India following southward shifting of low pressure led by southward movement of Sun. This wind crosses through Bay of Bengal and collects moisture to pour over Tamil Nadu and adjoining area.