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Informist, Friday, Jul. 25, 2025

LATEST DEVELOPMENTS

The dry spell over the southern peninsula broke this week, with many subdivisions in the region receiving heavy to very heavy rainfall. However, rainfall continued to be deficient over northeast India, with only light to moderate rainfall with passing spells of heavy showers recorded over parts of the region. Rainfall over most parts of northwest India remained torrential, while parts of west, east, and central India also witnessed heavy to very heavy rainfall during the week.

Multiple cyclonic circulations formed during the week, which were largely concentrated over the northwest and eastern regions of the country. An east-west trough emerged over south India and another trough formed over the coasts of the southern peninsula. On Thursday, a low pressure area formed over north Bay of Bengal under the influence of the remnants of tropical cyclone Wipha, which moved northwestward and intensified into a depression on Friday, the India Meteorological Department said.

While the western coasts of south India continued to record intense rainfall, the presence of two troughs brought a much-needed rise in rainfall activity over the region, with extremely heavy rainfall recorded in most parts of Telangana for two consecutive days. As such, the rainfall deficit in Telangana, as well as Andhra Pradesh, Tamil Nadu, and Kerala narrowed during the week. 

In west India, parts of Konkan, Goa, the ghat areas of central Maharashtra and Marathwada recorded heavy to very heavy showers. Though the spread and intensity of rainfall over east and central India were lower compared with the previous week, it did not result in any shortfall in rain. Rainfall in most of northeast India remained low, with only a passing cyclonic circulation bringing heavy rain to some parts of the region during the week. 

For the week ended Wednesday, India received an average rainfall of 57.3 millimetres, 14% below the normal of 66.7 millimetres, data from the weather department showed. In south peninsula, rainfall was 47% above average at 71.8 millimetres during the week and it was 6% above the long-period average in northwest India at 53.8 millimetres. However, rainfall was 44% below the long-period average in east and northeast India at 54.0 millimetres. In central India, rainfall was 31% below the average at 53.6 millimetres.

In the coming week, extremely heavy showers are likely over some parts of east and central India, with heavy to very heavy rainfall expected over most parts of the region. The spread and intensity of rainfall are expected to remain the same over northwest and west India. Northeast India is likely to continue facing a deficit in rainfall, with only short spells of heavy rain predicted over some regions.

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-Jul. 25 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.

For July, the weather department has forecast above-normal rainfall for the country at over 106% of the long-period average. The weather bureau sees most parts of northeast and east India as well as many areas of extreme south peninsular India and some areas of northwest India receiving below-normal rainfall.

Indian Ocean Dipole conditions are neutral currently, the department said. Its model forecasts a possible transition from neutral to negative Indian Ocean Dipole conditions in the coming months. However, the shift may be brief, and the Indian Ocean Dipole could move back to neutral conditions soon after.

The current weather systems indicate a neutral El Nino-Southern Oscillation, showing that there is no probability of either El Nino or La Nina weather phenomenon, at least till the end 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 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 rose sharply by 91% on year to 104.364 billion cubic metres as of Jul. 17, according to data from the Central Water Commission. The current level is 57.20% of the total live storage capacity of 182.461 billion cubic metres.

The water levels also rose from the previous week's level of 94.513 billion cubic metres, the data showed. According to data collated by Informist, the current water level in key reservoirs is at a six-year-high. The water level as of Jul. 17 was 69.65% above the 10-year average for this period.

The water level in the southern region was 35.937 billion cubic metres, which is a six-year-high level. As of Jul. 17, the water level was 65.41% of the total live storage capacity of the 45 reservoirs in the region. At this time last year, the water level was just 33.58% of the total live storage capacity, much lower than the current level.

Reservoirs in the eastern region held 10.995 billion cubic metres of water, which is 50.61% of their total live storage capacity, marking a six-year-high level. This was higher than 23.74% held by the reservoirs in the same period a year ago. 

The water level in reservoirs in the northern region stood at 8.740 billion cubic metres, or 44.02% of the total live storage capacity, up from 29.89% a year ago. In the western region, the water level in reservoirs was 22.226 billion cubic metres. This marks a six-year-high level, according to data collated by Informist. As of Jul. 17, the water level was 59.5% of the total live storage capacity, compared with 30.63% a year ago.

Reservoirs in the central region held 26.466 billion cubic metres or 54.47% of the total live storage capacity of 28 reservoirs in the region, up from 27.96% a year ago. Water level in reservoirs in the region currently stands at a six-year-high.

SOWING

Above-normal rainfall has aided the progress of kharif sowing across the country. Farmers have sown kharif crop across 70.8 million hectares as of Jul. 18, up 4.1% from 68.0 million hectares seen during the same period last year, according to data released by the Ministry of Agriculture and Farmers Welfare. As of Jul. 18, nearly 65% of the normal kharif area of 110 million hectares has been covered across the country. Only 62% of the normal area was covered during the same period last year.

The area sown under paddy was up 12.4% at 17.7 million hectares as of Jul. 18. Paddy is the largest food grain crop, in terms of both acreage and output, sown during the kharif season. Maize area was at 7.1 million hectares, up 15.4% on year. The area under coarse cereals, promoted as "Shri Anna" by the government, was 13.4 million hectares, up 13.6% on year. 

The area under pulses rose to 8.2 million hectares as of Jul. 18 from 8.0 million hectares during the same period last year. The rise in total pulses area has narrowed to 2% from 26% in the previous week as the area under tur, the largest kharif pulse, fell by 5.1% on year to 3.0 million hectares, the data showed. 

Oilseed acreage fell 3.7% on year due to a significant decline in the soybean acreage. The area under cotton fell over 3% on year to 9.9 million hectares while sugarcane acreage rose marginally to 5.5 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 Akul Nishant Akhoury

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