The “second half of the monsoon” is likely to be 104% of the Long Period Average (LPA). Rains during June and July have so far been scrupulously textbook with India getting 44.7cm (until July 30) as opposed to the historical normal of 44.3.
The Long Period Average or LPA is the average rainfall recorded during the months from June to September, calculated during the 50-year period and used as a benchmark while forecasting the quantitative rainfall for the monsoon season every year.
It is typically lower than the values estimated using a period of 10 years commonly referred to as a Short Term Average (STA). However, it is important to note that variations in station location can cause significant changes in LPA values.''
IMD maintains five rainfall distribution categories on an all-India scale. These are:
This year increased rainfall is attributed to the commencement of La Nina like conditions by the second half of the monsoon season.
La Nina is a climate pattern that describes periods of below-average sea surface temperatures across the east-central Equatorial Pacific.
The phenomenon is caused by an annual cycle in the temperature of the waters of the equatorial Pacific Ocean, and its primary effect is to disrupt monsoonal rains and create shortages of water in key agricultural regions in South America, Africa, and Asia.
La Nina is considered to be the counterpart to El Nino, and its impacts tend to be opposite those of El Niño.
Together, they form the "cold" (La Nina) and "warm" (El Nino) phases of the El Nino-Southern Oscillation (ENSO).
The India Meteorological Department (IMD) is an agency of the Ministry of Earth Sciences of the Government of India.
Headquartered in Delhi, IMD was established in 1875.
It is the principal agency responsible for meteorological observations, weather forecasting and seismology.
The Director General of Meteorology is the Head of the India Meteorological Department, with headquarters at New Delhi.