"India's 2026 Southwest Monsoon Ends With Sharp Regional Deficit"
Long Period Average (LPA)
the fifty-year mean seasonal rainfall (1971-2020) used as the benchmark for classifying monsoon seasons.
El Nino-Southern Oscillation (ENSO)
periodic warming (El Nino) or cooling (La Nina) of equatorial Pacific surface waters that strongly influences Indian monsoon strength.
The southwest monsoon supplies more than 70% of India's annual rainfall between June and September. It drives irrigation, drinking water, and hydropower for the rest of the year. Its onset follows the seasonal shift of the Inter-Tropical Convergence Zone (ITCZ). Rains typically reach the Kerala coast by around June 1, advance to Mumbai and Kolkata within ten to twelve days, and cover the entire subcontinent by mid-July.
Each season is measured against the Long Period Average (LPA), the mean seasonal rainfall over the fifty-year period from 1971 to 2020. A season is classified as normal when it falls between 96% and 104% of the LPA. Anything below 90% counts as a significant deficit. The monsoon's single biggest external driver is the El Nino-Southern Oscillation (ENSO), a periodic warming and cooling of surface waters in the equatorial Pacific Ocean. El Nino years generally weaken the monsoon. The cooler La Nina phase tends to strengthen it.
The India Meteorological Department (IMD) tracks ENSO through the Southern Oscillation Index, which measures the pressure difference between Tahiti in the Pacific and Port Darwin in northern Australia. The IMD combines this with about sixteen indicators, including the Indian Ocean Dipole (IOD). The IOD measures the sea-surface temperature difference between the western and eastern Indian Ocean. A positive IOD can partly offset El Nino's dampening effect. When the IOD stays weak or neutral, El Nino's suppressive effect tends to dominate. Water supply and drought relief remain primarily State List subjects under the Constitution, even though the underlying trigger for a poor monsoon is a global oceanic phenomenon no single state controls.
The southwest monsoon is not a single uniform weather system. India's physical geography ensures that a national deficit figure never spreads evenly across the country. Monsoon duration shortens as one moves from southern India toward the north. Within the northern plains, rainfall amount declines moving from east to west. This explains why the northwest and the east-northeast can show very different outcomes under one national average.
The LPA is the benchmark against which every season is judged. The IMD issues its long-range forecast each April using the LPA alongside ENSO indicators, IOD readings, ocean mean temperatures, and about a dozen other variables. A season below 90% of the LPA is a significant deficit and typically triggers drought declarations, crop damage assessments, and relief fund releases by state governments. …
Consider the following statements:
1.The duration of the monsoon decreases from southern India to northern India.
2.The amount of annual rainfall in the northern plains of India decreases from east to west.
Which of the statements given above is/are correct?
With reference to 'Indian Ocean Dipole (IOD)' sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?
1.IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
2.An IOD phenomenon can influence an El Nino's impact on the monsoon.
Select the correct answer using the code given below:
Consider the following statements:
1.The winds which blow between 30° N and 60° S latitudes throughout the year are known as westerlies.
2.The moist air masses that cause winter rains in North-Western region of India are part of westerlies.
Which of the statements given above is/are correct?
The seasonal reversal of winds is the typical characteristic of
Which of the following statements with regard to India's indigenous new high resolution weather model, the 'Bharat Forecast System,' is/are correct?
1.Its objective is to generate forecasts at the Panchayats cluster level.
2.It was developed by IIT Delhi.
Select the answer using the code given below:
Match List I (Term) with List II (Correct Description) and select the correct answer using the code given below: List I:
A.Long Period Average
B.Indian Ocean Dipole
C.El Nino
D.ITCZ; List II:
1.Belt of low pressure whose shift drives monsoon onset
2.SST difference between western and eastern Indian Ocean
3.Mean seasonal rainfall over a fixed 50-year reference period
4.Warming of central/eastern Pacific Ocean surface waters
Consider the following statements: 1. Monsoon duration shortens moving from southern India to northern India. 2. Annual rainfall amount in the northern plains decreases moving from east to west. Which of the statements given above is/are correct?
Consider the following statements: 1. El Nino refers to the warming of sea-surface temperatures in the equatorial Pacific Ocean and is generally associated with suppressed Indian monsoon rainfall. 2. The Indian Ocean Dipole measures the sea-surface temperature difference between the equatorial Pacific Ocean and the Indian Ocean. Which of the statements given above is/are correct?
As per IMD classification, a monsoon season is categorised as 'normal' if the seasonal rainfall falls within which range of the Long Period Average (LPA)?
Consider the following statements regarding the 'Bharat Forecast System': 1. It aims to generate weather forecasts at the level of panchayat clusters. 2. It was developed by the Indian Institute of Technology, Delhi. Which of the statements given above is/are correct?
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