for forecasting long range monsoon rainfall. In - , there was a wild EI-Nino event and the onset of southwest monsoon was delayed over most parts of the country ranging from five to twelve days. Figure . : Onset of Monsoon slowly, the low pressure cell attracts the southeast trades across the Equator.
These conditions help in the northward shift in the position of the ITCZ. The southwest monsoon may thus, be seen as a continuation of the southeast trades deflected towards the Indian subcontinent after crossing the Equator. These winds cross the Equator between °E and °E longitudes. Figure .
: India : Normal Dates of Onset of the Southwest Monsoon The frequency of the tropical depressions originating from the Bay of Bengal varies from year to year. Their paths over India are mainly determined by the position of ITCZ which is generally termed as the monsoon trough. As the axis of the monsoon trough oscillates, there are fluctuations in the track and direction of these depressions, and the intensity and the amount of rainfall vary from year to year. The rain which comes in spells, displays a declining trend from west to east over the west coast, and from the southeast towards the northwest over the North Indian Plain and the northern part of the Peninsula.
Break in the Monsoon During the south-west monsoon period after having rains for a few days, if rain fails to occur for one or more weeks, it is known as break in the monsoon. These dry spells are quite common during the rainy season. These breaks in the different regions are due to different reasons: In northern India rains are likely to fail if the rain-bearing storms are not very frequent along the monsoon trough or the ITCZ over this region. Over the west coast the dry spells are associated with days when winds blow parallel to the coast.
T HE R HYTHM OF S EASONS The climatic conditions of India can best be described in terms of an annual cycle of seasons. The meteorologists recognise the following four seasons :