Japanese Weather Agency Predicts Normal to Above-Normal Rainfall in July-September

The Application Laboratory of the Japanese national weather forecaster Jamstec has predicted that India will be 'wetter than normal' (above-normal rainfall) during July, August, and September, with regional variations in actual precipitation, as is typical of the ongoing South-West monsoon.

Rainfall will be heavier along the West Coast (from Coastal Karnataka to Mumbai) and adjoining interior Maharashtra (Madhya Maharashtra and Marathawada), as well as in North Interior Karnataka; normal to slightly above-normal in Central and East India (South Gujarat, Madhya Pradesh, East Chhattisgarh, Jharkhand, East Uttar Pradesh, Bihar and adjoining foothills, West Bengal and adjoining the North-Eastern States.)

According to the Japanese forecast, rainfall will be normal to below-normal over most of Odisha and the northern parts of the North-Eastern States. Its above-normal forecast for the country as a whole corresponds with the India Meteorological Department's (IMD) upgrade of the monsoon from 95% to 103% above the long-period average during this season. This is despite its slow progress thus far, with many areas in East and Central India still waiting for the first showers.

The Japanese agency forecasted that India, along with western and northern parts of Canada, Central America, Venezuela, Guyana, eastern Australia, Eritrea, Ethiopia, Nepal, some parts of China, Eurasia and Indochina, and Indonesia, would likely experience wetter-than-normal rainfall during the reference period.

However, drier-than-normal (lower-than-normal rainfall) conditions are forecast for most of North America, northern South America, La Plata, Chile, West and Central Africa, the northern Mediterranean, and parts of China, Eurasia, Indochina, and the Philippines.

The Japanese outlook comes after the country declared that a monsoon-unfavorable negative Indian Ocean Dipole (IOD) had formed. It will mature throughout the monsoon season and beyond before decaying in the winter. When the dipole index falls below -1.5 degrees Celsius, there is an increased (80%) chance of it becoming an extreme negative IOD (currently it is around -.5 degree Celsius).

The overarching extended La Nina in the Equatorial Pacific, which has traditionally been considered beneficial for a concurrent monsoon in India, is expected to last into September and December, well beyond the South-West monsoon. Given this, it is likely that the Indian Ocean and the Pacific will compete for dominance; however, if India is to have a good monsoon, La Nina must prevail.