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Informist, Friday, Jul. 18, 2025

LATEST DEVELOPMENTS

Rainfall continued to be confined largely over northwest, central, and some parts of east India this week. Some parts of west India saw occasional bouts of heavy rainfall, while most parts of northeast and south India were left just as dry as in the previous week.

Two low-pressure-area weather systems formed during the week, one over northwest India and the other over Gangetic West Bengal. Both systems intensified into depressions, bringing heavy to very heavy rainfall over the regions. The monsoon trough was near its normal position during most days of the week, while a western disturbance emerged mid-week.
 

Under the influence of several weather systems which were concentrated over the northern half of the country, many states such as Rajasthan, Jharkhand, and Madhya Pradesh recorded very heavy to extremely heavy rainfall during the week. Heavy to very heavy rainfall was seen over most of the subdivisions in northwest and east and central India during the week. Multiple cyclonic circulations are also lying across various parts of the country, and a low-pressure area is likely to form over north Bay of Bengal Thursday, the India Meteorological Department said.

In west India, parts of Konkan, Goa, the ghat areas of central Maharashtra, and Marathwada recorded heavy to very heavy showers. In south India, rainfall was limited to the western coast, with the coasts of Karnataka and Kerala receiving heavy to very heavy showers during the week. In northeast India, many subdivisions only recorded short spells of heavy rainfall, while light showers continued over the region for most of the week.

In the week ended Wednesday, India received an average rainfall of 58.1 millimetres, 11% below the normal of 65.1 millimetres for the week, data from the weather department showed. Rainfall was 31% above normal at 67.1 millimetres in northwest India due to continuous heavy showers over the region during the week. In central India, rainfall was 13% below average at 62.6 millimetres during the week. Rainfall was 30% below the long-period average in east and northeast India at 70.4 millimetres. Rainfall over south India was 44% below the long-period average at 26.2 millimetres.

In the coming week, heavy to very heavy showers may bring some relief to the interior regions of south peninsular India, while intense rainfall is likely to continue over the coasts of the region. The spread and intensity of rainfall is expected to remain the same over northwest, east, and central 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. 18 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 India entirely 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 key reservoirs across the country was up a whopping 96% at 94.513 billion cubic metres as of Jul. 10 due to very heavy rainfall across the country, according to data from the Central Water Commission. The water levels rose over 20% from the previous week's level of 78.381 billion cubic metres, the data showed.

The water level in the 161 key reservoirs was nearly 83% above the 10-year average for this period. The current water level is 51.8% of the total live storage capacity of 182.461 billion cubic metres.

Reservoirs in the central region held 22.328 billion cubic metres or 45.95% of the total live storage capacity of 28 reservoirs in the region, up from 26.96% a year ago. In the northern region, the water level in reservoirs was 8.187 billion cubic metres, which is 41.24% of the total live storage capacity. This was higher than 30.62% held by the reservoirs in the same period a year ago.

The water level in reservoirs in the eastern region stood at 9.844 billion cubic metres, or 45.31% of the total live storage capacity, higher than 23.19% last year. In the western region, water level stood at 20.363 billion cubic metres as of Jul. 10. The water level was 54.51% of the total live storage capacity compared with 25.44% a year ago.

The water level in the southern region was 33.792 billion cubic metres. As of Jul. 10, the water level in 45 reservoirs of the region was 61.51% of the total live storage capacity. At this time last year, the water level was just 26.41% of the total live storage capacity, much lower than the current level. 

SOWING

Above-normal rainfall has aided the progression of kharif sowing across the country. Farmers across the country have sown kharif crops over 59.8 million hectares as of Jul. 11, which is up nearly 7% from 56.1 million hectares during the same period last year, according to data released by the Ministry of Agriculture and Farmers Welfare.

The area sown under paddy was up nearly 11% at 12.4 million hectares as of Jul. 11. Maize, the second-largest cereal crop during the kharif season, was at 6.2 million hectares, up nearly 4% on year. The area under coarse cereals, promoted as "Shri Anna" by the government, rose to 11.6 million hectares, nearly 17% on year.

The area under pulses rose to 6.7 million hectares as of Jul. 11 from 5.3 million hectares during the same period a year ago. Although there was a 26% rise in total pulses acreage, the area under tur, the largest kharif legume, fell to 2.5 million hectares from 2.7 million hectares a year ago, the data showed. There was a sharp increase in moong acreage by 90% at 2.3 million hectares.

Oilseeds acreage has seen a 2% fall on year so far during the season due to a significant decline in soybean acreage. The area under soybean fell more than 8% on year to 9.9 million hectares, the data showed. The area under cotton also fell by nearly 3% on year to 9.3 million hectares.

Meanwhile, the area under groundnut rose nearly 18% on year to 3.3 million hectares as of Jul. 11. Sugarcane acreage also rose slightly to 5.52 million hectares so far from 5.49 million hectares during the same period last year, according to the data. 

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 Rajeev Pai

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