The monsoon, the economy and forecasting

Detail

1. The monsoon is the axis of the farm cycle

• Monsoon and the Indian economy: India's farm year turns around the monsoon (the seasonal reversal of winds that brings south-west rain from June to September).

• The time of sowing, the choice of crop and the size of the harvest all depend on when the rain comes, how much falls and how it is spread.

• People who depend on farming:

• (NCERT: about 64 per cent of people depend on agriculture.)

• About 46 per cent of the workforce is in agriculture (PLFS 2023-24; verify current). PLFS is the Periodic Labour Force Survey of MoSPI.

• Why the climate suits farming:

• Outside the Himalaya, temperatures are high enough all year for crops to grow in every season.

• Climate differs from region to region, so many kinds of crops are grown, from rice in the wet east to millets in the dry west.

• Variability: monsoon rain is uneven over time and place. Some part of India has a drought or a flood almost every year.

• Prosperity needs rain at the right time and in the right places. This matters most where there is no irrigation.

• About half of India's net sown area is still rainfed, which means it has no irrigation and depends only on rain (verify current).

• Sudden burst of the monsoon (the very heavy first rain at onset):

• Heavy rain falls on dry, loose topsoil → the water runs off fast → soil erosion over large areas.

• Winter rain helps rabi crops:

• Western disturbances (low-pressure systems that start over the Mediterranean region and move east with the westerly jet stream) bring winter rain to north-west India (Punjab, Haryana, western Uttar Pradesh).

• This rain helps rabi (winter-sown) crops such as wheat.

• Climate shapes daily life: food, clothes and house types across India follow the local climate. Examples are rice where it is wet, sloping roofs in heavy-rain areas, and thick-walled houses in hot, dry areas.

2. How the monsoon moves the wider economy

• Kharif output: the timing and spread of rain decide kharif (monsoon-sown) crops such as rice, pulses, oilseeds and cotton. Weekly kharif sowing data is watched as an early sign of the harvest.
• Reservoir levels and hydropower: monsoon inflow fills reservoirs. This water is used for rabi irrigation, drinking water and hydroelectric power until the next monsoon.
• Rural incomes and demand: a good harvest raises farm incomes. Rural families then buy more tractors, two-wheelers and consumer goods.
• Food prices: a weak monsoon cuts supply of rice, pulses and vegetables → prices rise → food inflation. The RBI considers the monsoon when it makes its inflation projections and monetary policy.
• Monsoon core zone (MCZ): the central belt that covers most of India's rain-fed farm regions. IMD tracks its rain separately. Its LPA is 832.2 mm (1971-2020) [2].

3. Monsoon failure and its effects

• Monsoon failure: a deficient season (below 90% of LPA), or a long break in rain at sowing time, even if the seasonal total looks normal.
• Effects:
• Crop loss. Sowing is delayed or seedlings dry out.
• Water scarcity. People walk long distances for water, and it is mostly women who do this.
• Migration to cities. Farm workers move to towns to find work.

• Food inflation. Less supply leads to higher prices.

• Drought year (IMD meaning): all-India seasonal rain is more than 10 per cent below LPA, and more than 20 per cent of the country's area is hit by drought (verify current IMD definition).

• The all-India total can hide regional failure. In 2025 all-India rain was 108% of LPA, but East & Northeast India got only 80%. Its total of 1,089.9 mm was the 2nd lowest since 1901. Three subdivisions were deficient: Arunachal Pradesh, Assam & Meghalaya, and Bihar (9% of India's area) [2].

4. IMD vocabulary: LPA and rainfall categories

• IMD: the India Meteorological Department, set up in 1875. It now works under the Ministry of Earth Sciences (MoES).
• Long Period Average (LPA): the average all-India rainfall for June to September over a long base period. Every season is measured against it.
• Current LPA is 87 cm (868.6 mm), based on 1971-2020 [2][3].

• The earlier LPA was 88 cm, based on 1961-2010.

• LPA of the four homogeneous regions (regions with similar rain patterns), 1971-2020 base [2]:

Region	LPA (mm)
East & Northeast India	1,367.3
Central India	978.0
South Peninsula	716.2
Northwest India	587.6
All India	868.6

• IMD's five rainfall categories, as % of LPA. The climatological probability is how often each category has happened in the past [3]:

Category	% of LPA	Climatological probability (%)
Deficient	below 90	16
Below normal	90-95	17
Normal	96-104	33
Above normal	105-110	16
Excess	above 110	17

5. Monsoon forecasting by IMD: from 16 indicators to dynamical models

• Old method:
• (NCERT: IMD forecasts the monsoon using 16 indicators.)

• This 16-parameter power regression model was used from 1988 to 2002. A power regression model is a statistical formula that links past signals, such as ocean temperatures and snow cover, to rainfall. It was later replaced by smaller statistical ensembles, so it is now outdated.

• Two-stage long-range forecast (LRF) since 2003: a first forecast in April and an update by the end of May [3].

• New strategy since 2021 [3]:
• It uses both dynamical and statistical systems.
• A dynamical model is a computer model that solves the physical equations of the ocean and the air.

• A Multi-Model Ensemble (MME) combines many coupled global climate models (CGCMs) from climate centres around the world. One of these is IMD's own Monsoon Mission Climate Forecast System (MMCFS).

• What is issued and when [3]:

When	What IMD issues
Mid-April (first stage)	All-India seasonal forecast, given as a number and as probabilities, plus a map of likely above-normal, normal and below-normal areas
End of May (second stage)	Update of the April forecast, forecasts for the 4 homogeneous regions and the monsoon core zone, and the June forecast
End of June, July and August	Forecast for the next month
End of July	Forecast for the second half of the season (August-September)

• Main signals IMD tracks [3]:
• ENSO (El Niño-Southern Oscillation): a cycle of sea-surface warming (El Niño) and cooling (La Niña) in the equatorial Pacific. El Niño usually weakens the Indian monsoon.
• IOD (Indian Ocean Dipole): the temperature difference between the western and eastern Indian Ocean. A positive IOD (western side warmer) usually helps the monsoon.

• Northern Hemisphere and Eurasian snow cover in winter and spring has a general inverse relationship with monsoon rain. More snow usually means less monsoon rain.

• Forecast for 2026 (issued 13 April 2026) [3]:

• 92% of LPA ± 5%, which is below normal.
• Reasons: MMCFS showed El Niño developing during the season, a positive IOD was likely only towards the end of the season, and snow cover from January to March 2026 was slightly below normal.
• The final 2026 figure should be checked against IMD's end-of-season report (verify current).

6. National Monsoon Mission

• Launched by MoES in 2012 and led by IITM Pune (Indian Institute of Tropical Meteorology).
• Aim: build a coupled ocean-atmosphere model, in which the ocean and air models exchange heat and moisture, to forecast at all time scales. These run from short range (days) to extended range (weeks) to a whole season.
• Output: the MMCFS, which is now part of IMD's MME for the seasonal forecast [3].

7. Mission Mausam

• What it is: a national programme of MoES to make India "Weather-ready and Climate-smart" [4].
• Outlay of ₹2,000 crore over two years, approved by the Union Cabinet in September 2024 [4].

• Phase I runs 2024-26, and Phase II runs 2026-31 [4].

• Why it was needed [4]:

• Weather observations in India are sparse.
• NWP (Numerical Weather Prediction: computer weather models) works at 12 km resolution. This is too coarse to catch cloudbursts and local storms.
• The aim is 6 km resolution, so forecasts can be given for each Panchayat.

• Forecast accuracy up to 5 days improved by about 40-50% over the past decade compared with the decade before.

• What it will build [4]:

• 50 Doppler Weather Radars (DWRs), 60 radiosonde/radiowind stations, 100 disdrometers (instruments that measure raindrop size), 10 wind profilers and 25 radiometers.
• An urban testbed, an ocean research station and 10 marine automatic weather stations.
• High-performance computing, AI/ML forecasting tools, and a nowcast system that updates every 1 hour.
• Weather management research: rain-enhancement experiments, cloud seeding using drones and ground burners, a cloud chamber (a lab for studying how clouds form), and research aircraft (with the IAF).

8. Recent monsoon seasons

Year	All-India rain (% of LPA)	Category	Note
2023	94	Below normal	El Niño year
2024	108	Above normal	—
2025	108 (937.2 mm)	Above normal	5th highest since 2001 [2]
2026	Forecast 92 ± 5	Below normal (forecast)	El Niño expected [3]; verify final

• 2025 in detail [2]:
• Regions: Northwest India 127% (747.9 mm, highest since 2001), Central India 115%, South Peninsula 110%, East & Northeast 80%. Monsoon core zone 122%.
• Months: June 109%, July 105%, August 105%, September 115%.
• Onset over Kerala on 24 May (normal date 1 June). This was the earliest onset since 2009.
• Covered the whole country by 29 June (normal 8 July).
• Withdrawal began from west Rajasthan on 14 September (normal 17 September).
• 7 monsoon depressions formed. There were 69 low-pressure-system days, against a normal of 55.

Prelims Hooks

• LPA = 87 cm (868.6 mm), base period 1971-2020. The old LPA was 88 cm (1961-2010) [2][3].
• "Normal" monsoon = 96-104% of LPA. Deficient is below 90 and excess is above 110. Trap: 105-110 is "above normal", not "excess" [3].
• Normal is the most common category: 33% climatological probability. Each of the other four is about 16-17% [3].
• 16-parameter model used 1988-2002. Dynamical MME strategy since 2021. Two-stage forecast (April and end-May) since 2003 [3].
• MMCFS comes from the National Monsoon Mission (MoES, 2012, IITM Pune).
• Snow cover vs monsoon is an inverse relationship. El Niño weakens the monsoon, and a positive IOD helps it [3].
• Mission Mausam: ₹2,000 crore, Phase I 2024-26, "Weather-ready and Climate-smart", NWP to go from 12 km to 6 km [4].
• 2025: 108% of LPA, but East & Northeast India got only 80% (2nd lowest since 1901). Kerala onset was on 24 May [2].
• IMD was founded in 1875.

Mains Points

• Monsoon dependence of the economy (GS-III):
• About half the net sown area is rainfed, and about 46% of workers are in farming (PLFS 2023-24).
• So the monsoon affects kharif output, reservoir storage, hydropower, rural demand and food inflation, and through these the RBI's policy.

• Policy responses: expand irrigation (micro-irrigation), use drought-tolerant varieties, offer crop insurance and build buffer stocks.

• Distribution matters more than the total:

• In 2025 all-India rain was 108%, yet East & Northeast India got 80% and Bihar, Assam & Meghalaya and Arunachal Pradesh were deficient [2].
• Breaks at sowing time and sudden bursts (which cause soil erosion and floods) cause "monsoon failure" even in a normal year.

• So district- and block-level forecasts and contingency crop plans are needed.

• Forecasting has improved:

• It moved from statistical regression (16 parameters) to dynamical coupled-model ensembles (MME with MMCFS) that issue monthly and regional outlooks [3].
• Mission Mausam (radars, HPC, AI/ML, 6 km models, hourly nowcasts) aims to give Panchayat-level warnings of cloudbursts and extreme rain [4].

• This is useful for disaster management and climate adaptation.

• Climate change makes forecasting harder:

• The atmosphere is becoming more chaotic, with isolated heavy rain and local drought happening in the same season [4].
• This calls for both flood and drought preparedness, plus research on rain enhancement (cloud seeding).