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Informist, Friday, Aug. 8, 2025

LATEST DEVELOPMENTS

South peninsular India witnessed more spells of heavy to extremely heavy rainfall during the week, with a few weather systems forming over the region. Rainfall over northeast India continued to be intense this week, and the adjoining parts of east India also witnessed similar weather conditions. The spread and intensity of rainfall declined over central India, while it picked up over west India after a week of lull. Torrential rainfall persisted over northwest India during the week.

Multiple upper air circulations formed across the country, while a trough stretched from the Arabian Sea into the mainland, inching eastwards on a daily basis. An east-west trough also formed across the southern half of the country. A western disturbance presenting as a cyclonic circulation remained active over northwest India during the week. A low pressure area is likely to form over the Bay of Bengal around Wednesday, the India Meteorological Department said.

After a week of no activity, a handful of weather systems formed over south peninsular India, bringing heavy to extremely heavy rainfall across the region this week, particularly over Kerala, Tamil Nadu, and the interior parts of Karnataka. However, this was not enough to lift rainfall in the region out of its deficit.

Northeast India recorded torrential showers due to the presence of a few cyclonic circulations. In west India, most spells of heavy showers were limited to the interiors during the week.

Amid intense rainfall in northwest India, weather conditions intensified over Uttarakhand due to a series of cloudbursts, which led to landslides. Flash floods were recorded across the state, with the loss of lives and damage to infrastructure, according to media reports. 

With many weather systems concentrated over the Bay of Bengal, east India witnessed a higher intensity of rainfall than central India. Central India recorded only a few spells of heavy rains, as only the peripheries of weather systems hovered over the region.

In the week ended Wednesday, India received average rainfall of 48.0 millimetres, 24% below the normal of 63.0 millimetres for the week, according to the weather department. In central India, rainfall was 77% below normal at 18.3 millimetres during the week, data from the department showed. Rainfall was 19% below normal in south peninsular India at 37.5 millimetres. It was 29% above normal in northwest India at 63.9 millimetres, and in east and northeast India, it was 26% above normal at 93.3 millimetres. Since Jun. 1, the country has recieved 527.1 millimetres of rainfall, 2% above the normal for the period.

In the coming week, the intensity of rainfall is likely to remain the same over northeast, east, and west India. Northwest India could see fewer spells of very heavy to extremely heavy showers, while rainfall in central India is expected to remain subdued. The spell of intense showers over south peninsular India could break next week, possibly increasing the deficit in the region. 

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

The following table gives homogeneous region-wise rainfall during Jun. 1-Aug. 8 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. 

The monsoon covered entire India on Jun. 29, nine days before the normal date of Jul. 8. 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 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 modelling 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 for 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.

Rainfall over the country is likely to be within the normal range of 94-106% of the long-period average in August, the India Meteorological Department said. Normal to above-normal rainfall is very likely over many parts of the country except parts of central India, western parts of peninsular India, northeast India, and some parts of eastern and northwest India where it is likely to be below normal.

In August and September, above-normal rainfall is expected at 106% of the long-period average. The intensity of rainfall is likely to decrease across the country in August and pick up again in September. The bureau has forecast normal rainfall over the country in August and above-normal rainfall in September. 

Neutral Indian Ocean Dipole conditions are also being observed over the Indian Ocean at present, the weather department said. The Indian Ocean Dipole is the difference in surface temperatures between the eastern and western tropical Indian Ocean. A negative Indian Ocean Dipole leads to less rainfall in India and a positive index leads to more rainfall.

The bureau said that currently neutral El Nino-Southern Oscillation conditions are prevailing over the equatorial pacific region and similar conditions are expected for the remaining part of the monsoon. 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, 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 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 of 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 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 across India was 132.398 billion cubic metres as of Thursday, up from 126.482 billion cubic metres as of Jul. 31, according to data from the Central Water Commission. The current level is 72.55% of the total live storage capacity of 182.496 billion cubic metres.

According to data collated by Informist, the current water level in key reservoirs is at a six-year-high. The water level as of Thursday rose 14.46% from a year ago and was 33.07% above the 10-year average for this period.

Of the 161 reservoirs, seven were at full capacity, unchanged from a week ago, data from the Central Water Commission showed. However, the number of reservoirs with water level of 40% or less fell to 21 from 24 a week ago.

In the eastern region, the water level in reservoirs was 11.941 billion cubic metres, slightly higher than last week's level of 11.297 billion cubic metres. As of Thursday, the water level was 54.88% of the total live storage capacity, compared with 48.49% a year ago.

Reservoirs in the northern region held 14.290 billion cubic metres of water, up from 12.241 billion cubic metres. The water level was 71.98% of their total live storage capacity, higher than 40.44% during the same period a year ago. The northern region saw the highest on-week rise in water levels.

The water level in reservoirs in the western region rose to 28.186 billion cubic metres, or 75.45% of the total live storage capacity, compared with 63.67% a year ago. Reservoirs in the central region held 35.284 billion cubic metres or 72.62% of the total live storage capacity, up from 64.69% a year ago. 

The water level in the southern region was 42.697 billion cubic metres. As of Thursday, the water level was 77.72% of the total live storage capacity of the 45 reservoirs in the region. At this time last year, the water level was 76.22% of the total live storage capacity.  

SOWING

Above-normal rainfall has helped the progress of kharif sowing across the country. Farmers across the country have sown kharif crops over 93.29 million hectares as of Aug. 1, over 5% higher than 88.79 million hectares a year ago, according to data released by the Ministry of Agriculture and Farmers Welfare. 

Among kharif crops, paddy acreage rose the highest--16.7% on year to 31.94 million hectares. However, oilseed acreage slipped 4% to 17.1 million hectares from 17.81 million hectares a year ago. Except for castor seed, acreage of all major oilseeds registered a decline as of Aug. 1. Soybean sowing dipped the most – to 11.85 million hectares from 12.35 million hectares. Groundnut acreage fell to 4.16 million hectares from 4.35 million hectares.

The area under pulses fell marginally to 10.12 million hectares as of Aug. 1 from 10.15 million hectares a year ago. While tur or arhar sowing dipped 7% on year to 3.83 million hectares, moong area rose over 3% on year to 3.22 million hectares. 

The acreage of coarse cereals, promoted as 'Shri Anna' by the government, was up nearly 5% on year at 17.26 million hectares, mainly supported by a rise in the area under maize. The area under maize rose to 9.16 million hectares from 8.20 million hectares a year ago. The area under cotton fell over 2% on year to 10.59 million hectares, while sugarcane acreage rose nearly 3% on year to 5.73 million hectares. 

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 Shreya Shetty

Edited by Avishek Dutta

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