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Informist, Friday, Jun. 27, 2025

LATEST DEVELOPMENTS

The southwest monsoon covered most parts of northwest India this week, while most parts of west, central, and east India received very heavy rainfall. The country's average rainfall so far in June has also improved from the deficiency seen during the first fortnight of the month as the monsoon re-entered its active phase on Jun. 16.  

During the week a low pressure area developed over northwest Bay of Bengal and adjoining north Odisha and West Bengal, which caused heavy showers over the east and central parts of India. The progress of southwest monsoon over northwest India has caused heavy showers over most parts of the region. The northern limit of the southwest monsoon is currently passing over Jaisalmer, Bikaner, Jhunjhunu, and Bharatpur in Rajasthan, over Sonipat in Haryana, and over Rampur and Anup Nagar in Uttar Pradesh, the India Meteorological Department said Friday.

The weather bureau said the monsoon is likely to cover the remaining parts of the country in the next two to three days, earlier than the usual date of Jul. 8. Private weather forecasting agency Skymet said the onset of monsoon in Delhi is expected during the weekend. Previously, the weather department and Skymet expected monsoon to arrive in Delhi earlier than the usual date of Jun. 27.

While there was humidity, and winds, clouds, and temperature in the capital city were aligning with monsoon-like conditions, it had failed to rain in the region till Friday. Skymet expects the current east-west trough from a cyclonic circulation over southwest Rajasthan to shift northward because of a western disturbance, which is likely to cause showers over Delhi from Saturday evening to Sunday. The monsoon is likely to arrive over the national capital on Sunday.

Meanwhile, rainfall over India since Jun. 1 is 10% above normal at 156.4 millimetres, an improvement from a week prior. From Jun. 1-20, rainfall over the country was 1% below normal at 92.0 millimetres. However, rainfall over east and northeast India continues to remain deficient, with 14% below normal showers at 248.9 millimetres since Jun. 1. While south India has received 1% above normal showers at 144.9 millimetres since Jun. 1, precipitation over four out of 10 sub-divisions in the region remained below normal. Rainfall over south India began improving only from Thursday—it was 5% below normal at 125.4 millimetres from Jun. 1 to Wednesday.

The weather department said a fresh upper-air cyclonic circulation is likely to develop over the north Bay of Bengal and the adjoining coastal Bangladesh and West Bengal by Sunday. During the subsequent 24 hours, this system is expected to intensify into a low-pressure area and cause heavy to very heavy rainfall over parts of east and central India till Thursday, the department said.

Following is the weekly all-India rainfall since the beginning of the southwest monsoon season (in millimetres):

Following table gives sub-division-wise rainfall during Jun 1-27 in the country (in millimetres): 

MONSOON PROGRESS

This year, the southwest monsoon hit the Kerala coast on May 24, eight days ahead of its normal date of Jun. 1, and by May 29 the monsoon current covered southern and northeast India entirely, and parts of east and central India. However, after May 29, the monsoon was in a weak phase and resumed advancing only on Jun. 16. So far, the monsoon current has covered most parts of the country, except some parts of Haryana, Delhi, Chandigarh, Rajasthan, and Uttar Pradesh. Normally, beginning Jun. 1, the southwest monsoon advances northwards and covers the entire country around Jul. 8. The withdrawal of the monsoon starts around Sept. 17, and it withdraws from the entire country around Oct. 15. 

ONSET CRITERIA

At present, the department uses criteria that was adopted in 2016 for declaring the onset of the monsoon over Kerala, which is based on the daily rainfall at 14 stations in Kerala and the neighbouring area, along with wind-field and outgoing long-wave radiation over the southeast Arabian Sea.

If, after May 10, 60% of the 14 designated stations--Minicoy and Amini in Lakshadweep, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, and Kannur in Kerala, and Kudulu and Mangalore in Karnataka--report rainfall of 2.5 millimetres or more for two consecutive days, the onset over Kerala will be declared on the second day, provided the wind-field and outgoing long-wave radiation conditions are met.

The outgoing long-wave radiation measures the amount of terrestrial radiation released into space and, by extension, the amount of cloud cover and water vapour that intercepts that radiation in the atmosphere.

The criteria emphasise the sharp increase in rainfall over Kerala along with the setting up of large-scale monsoon flow and extension of westerlies up to 600 hectopascal. 

However, the department declares the monsoon onset or progress dates for other regions operationally in a subjective manner, considering the sharp increase in rainfall and its characteristic sustenance for a few days and associated changes in the atmospheric circulation features.

LONG-RANGE FORECAST

The India Meteorological Department has projected the southwest monsoon to be above normal at over 106% of the long-period average of 870 millimetres, which is based on historical data from 1971 to 2020. The forecast assumes a modelling error of plus or minus 4%, according to the second-stage long-range forecast for the Jun-Sept southwest monsoon season. The department had earlier predicted rainfall for Jun-Sept at 105% of the long-period average with a model error of plus or minus 5%.

The agency said that on average, it expects above-normal rainfall over most parts of the country this year except northeast India, where rainfall is expected to be lower than normal. Central and south peninsular India are expected to receive above-normal rainfall at 106% of the long-period average, while rainfall over the northwestern parts of the country is likely to be normal at 92-108% of the long-period average.

According to the bureau's forecasts for the season, there is 59% chance of above-normal monsoon rains and 31% chance of normal showers. The chances of below-normal precipitation stand at 8% and those of deficient showers are just 2%. 

The weather bureau predicts rainfall in June to be above normal at 108% of the long-period average. Normal to above-normal rainfall is very likely over most parts of the country in June. However, some southern parts of peninsular India and parts of northwest and northeast India are expected to record below-normal rainfall.

The latest climate models forecast that weak negative Indian Ocean Dipole conditions are likely to persist during the southwest monsoon period. The Indian Ocean Dipole is the difference in sea surface temperatures between the western and eastern tropical Indian Ocean. Usually, a negative Indian Ocean Dipole leads to less rainfall in India, while a positive dipole results in better rainfall.

The weak negative conditions will not affect the country's southwest monsoon as much as the El Nino-Southern Oscillation, India Meteorological Department Director General Mrutyunjay Mohapatra said. The weather department sees neutral El Nino-Southern Oscillation conditions prevailing over the equatorial Pacific region during Jun-Sept. 

The El Nino-Southern Oscillation refers to the fluctuation between El Nino and La Nina conditions in the Pacific Ocean. El Nino, which means Little Boy in Spanish, is a climate pattern marked by an unusual warming of the surface waters in the Pacific Ocean leading to drier, hotter weather in India. La Nina, which means Little Girl in Spanish, is the opposite of El Nino. It is an oceanic and atmospheric phenomenon that is associated with the colder sea surface temperatures. La Nina is usually associated with good rains in India. 

The department's long-range forecasts are as follows:

Private forecaster Skymet has predicted a 'normal' southwest monsoon at 103% of the long-period average with an error margin of plus or minus 5%. The agency had predicted a weak start to the monsoon this year but expects the rainfall to increase from July. It does not see any chance of the occurrence of El Nino.

PRE-MONSOON RAINFALL

While the monsoon arrived on May 24, the weather department said rainfall during May would not be factored into the southwest monsoon. The country received above-normal rainfall during the pre-monsoon period in Mar-May. India received 185.8 millimetres of rainfall during Mar-May, 42% above the normal for the period. Last year, it received 108.7 millimetres rainfall during Mar-May, 8.1% below the normal for the period.

RECAP 2024
The country received 934.8 millimetres of rainfall in Jun-Sept last year, which was 108% of the long-period average. The monsoon had hit the Kerala coast on May 30, two days ahead of the scheduled date, and covered the entire country by Jul. 2, six days ahead of the normal date of Jul. 8. The weather bureau's forecast for the monsoon onset over Kerala last year was May 31 and predicted rainfall during Jun-Sept 920.7 millimetres, or 96% of the long-period average.     

Overall, monsoon rainfall was above normal for the season and the spatial distribution was uniform. The rainfall in June was below-normal at 89% of the long-period average. However, the country received above-normal showers during the rest of the southwest monsoon period. Rainfall was 109% of the long-period average in July, 115% in August, and 112% in September.

Rainfall during the season was 107% of the long-period average in northwest India, 119% in central India, 86% in east and northeast India, and 114% in the southern peninsula. Of the total 36 meteorological subdivisions, two subdivisions received large excess, 10 received excess, and 21 recorded normal rainfall. Three subdivisions received deficient rainfall during Jun-Sept last year – Arunachal Pradesh, Punjab, Jammu & Kashmir, and Ladakh.

RESERVOIR LEVELS

The water level in 161 key reservoirs was 58.030 billion cubic metres as of Jun. 19, which was a six-year high level, according to data collated by Informist. The water level had also risen from the previous week's level of 55.519 billion cubic metres as monsoon re-entered its active phase on Jun. 16.

The current level in these reservoirs is 31.81% of the total live storage; it is also over 50% higher on year and 39% above the 10-year average for this period. In the corresponding period last year, the live storage available in these reservoirs was 38.542 billion cubic metres and normal storage was 41.778 billion cubic metres.

In the northern region, reservoirs held 5.418 billion cubic metres of water, over 27% of their total live storage capacity. The water level in reservoirs in the eastern region stood at 5.125 billion cubic metres, or nearly 24% of the total live storage capacity.

Reservoirs in the western region held 12.132 billion cubic metres of water, or 32% of the total live storage capacity. Water levels in this region's reservoirs were at a five-year-high due to extremely heavy rainfall in the region, which includes Gujarat, Goa, and Maharashtra. 

In the central region, which includes Madhya Pradesh, Uttar Pradesh, Uttarakhand, and Chhattisgarh, the water level in reservoirs was 13.883 billion cubic metres, and over 29% of the total live storage capacity. The water level in the southern region was 21.471 billion cubic metres, or 39% of the total live storage capacity of the 45 reservoirs in the region.

The current live storage capacity of these 161 reservoirs is 182.444 billion cubic metres. Water in these reservoirs, which is used for irrigation and generating electricity, is replenished during the monsoon season.

SOWING

Farmers across the country have planted kharif crops over 13.8 million hectares as of Jun. 20, up 10% from 12.5 million hectares a year ago, according to data released by the Ministry of Agriculture and Farmers Welfare. The sowing of kharif crops has begun well due to the early onset of southwest monsoon. The forecast of above-normal rainfall this season has boosted the acreage of key crops such as paddy, pulses, coarse cereals, and cotton.

The area under paddy, one of the main kharif crops, was up over 58% on year at 1.32 million hectares, as of Jun. 20. The area under pulses rose to 944,000 hectares, up from 663,000 hectares at the same time last year. Under pulses, acreage of urad and moong rose from last year, but the area under tur, the largest kharif pulses crop, was down nearly 5% on year at 248,000 hectares. 

Soybean acreage was down 2% at 307,000 hectares. The area under cotton was up 7% on year at 3.12 million hectares. The acreage of maize was up 19% on year at 1.23 million hectares as of Jun. 20.   

TERMS

LARGE EXCESS: Percentage departure of actual rainfall from normal rainfall is 60% or more 

EXCESS: Percentage departure of actual rainfall from normal rainfall is 20-59% 

NORMAL: Percentage departure of actual rainfall from normal rainfall is -19% to +19%

DEFICIENT: Percentage departure of actual rainfall from normal rainfall is (-)59-20%

LARGE DEFICIENT: Percentage departure of actual rainfall from normal rainfall is (-)99-60%

NORMAL: Percentage departure of actual rainfall is within +/-10% of the long period average

BELOW NORMAL: Percentage departure of actual rainfall is <10% of the long period average

ABOVE NORMAL: Percentage departure of actual rainfall is within >10% of the long period average

EXCEPTIONALLY HEAVY RAINFALL: Rainfall realised in a day is a value near about the highest recorded rainfall at or near the station for the month or season. However, this term will be used only when the actual rainfall amount exceeds 120 mm. 

EXTREMELY HEAVY RAIN: Amount of rainfall realised in a day is >/= 244.5 mm

VERY HEAVY RAIN: Amount of rainfall realised in a day is 124.5-244.4 mm

HEAVY RAIN: Amount of rainfall realised in a day is 64.5-124.4 mm

MODERATE RAIN: Amount of rainfall realised in a day is 7.6-35.5 mm 

RED ALERT: Very heavy rainfall of over 204.4 mm in 24 hours

ORANGE ALERT: Heavy rainfall of 115.6-204.4 mm in 24 hours 

YELLOW ALERT: Warning to be aware of worsening weather conditions that could disrupt daily life

End

Internet links:
India Meteorological Department - www.imd.gov.in
National Centre for Medium Range Weather Forecasting - www.ncmrwf.gov.in
Indian Institute of Tropical Meteorology - www.tropmet.res.in.  

Reported by J. Navya Sruthi

Edited by Tanima Banerjee

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