Shift in monsoon rain pattern, west coast build-up forecast

The south-west monsoon season usually begins from June and forecasts by global agencies show that in the first half of the season, heavy rains would occur on the west coast, parts of south India, western Uttar Pradesh and northeastern Madhya Pradesh. In the last two months, the southern peninsula, western and central India would receive heavy rains.

The US-based International Research Institute for Climate and Society (IRI), while making the forecast, did not specifically identify the regions of drought or deficient rainfall in India.

Temperatures would remain high in several parts of the country. The shift in the rainfall pattern is a matter of concern. Since the last two years, there has been heavy rainfall in drought-prone areas while the flood-prone areas were left dry. Meteorologists are studying this shift in the rainfall pattern and are trying to correlate with climate change.

El Nino’s opposite La Nina (cooling of Pacific waters above the normal range) causes heavy rainfall at places. Global forecasts suggest while EL Nino will remain subdued in all four regions of the Pacific (Nino 1+2, 3, 3.4 and 4), there may be a possible emergence of a weak La Nina. The forecasts, however, are not sure when the La Nina phenomena would emerge and to what extent it can impact.

The IRI, while making its projection for El Nino, has taken into consideration the forecasts made by 14 dynamical and 9 statistical models. Monsoon rainfall forecast depends upon several factors like land and ocean temperature, snow cover, wind pressure gradient.

The IRI has considered some relevant factors and said “temperature anomalies in the Indian Ocean would very slowly weaken” in the monsoon period. Temperature in the tropical Atlantic, north of the equator, would also weaken mildly below normal in the south of the equator in the eastern region.