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Informist, Friday, Sept. 5, 2025

 

LATEST DEVELOPMENTS

The formation and combination of several weather systems over the northern half of the country led to relentless rainfall over most parts of northwest India during the week. The proximity of these weather systems also brought intense rainfall to parts of east and central India. The wet spell persisted over west and south India, though the strength of showers decreased over both regions during the week. Northeast India continued to receive deficient rainfall this week.

 

The interaction of moisture-laden southeasterly monsoonal winds with a stationary active western disturbance over north Pakistan and adjoining Punjab and Kashmir during the week led to very heavy to extremely heavy showers over northwest India for the second consecutive week. The interactions of these weather systems, coupled with a cyclonic circulation over northeast Rajasthan and adjoining Haryana, added to the spell of incessant rainfall over the region. This caused landslides and flash floods throughout the Western Himalayan states, which include Jammu and Kashmir, Himachal Pradesh, and Uttarakhand. Excessive rainfall also raised the water levels in the Yamuna river in Delhi beyond dangerous levels during the week.

 

These weather systems also caused further worsening of floods in Punjab. The state is currently facing one of its most severe flood crises in decades, with the loss of several lives, damage to infrastructure, and loss of crop. All 23 districts of the state are in the grip of floods, making this the worst disaster since 1988, private weather forecasting agency Skymet said.

 

In the first five days of September, northwest India recorded 82.3 millimetres of rainfall, a whopping 317?ove the normal of 26.0 millimetres, data from the India Meteorological Department showed.

 

A low pressure area formed over the Bay of Bengal on Monday, which intensified into a well-marked low pressure and caused heavy to very heavy rainfall over parts of east India. The wet spell over central India continued due to the combination of several cyclonic circulations, a trough running from Kashmir to Madhya Pradesh, and the other weather systems over northwest India.

 

Though no weather systems formed over west and south India this week, the remnants of the well-marked low pressure from last week brought a few spells of very heavy rainfall to states such as Telangana, Andhra Pradesh, and the interior parts of Karnataka. The interior regions of Maharashtra and Gujarat also recorded a few instances of very heavy showers due to the formation and intensification of the new low pressure area over the Bay of Bengal during the week.

 

The dry spell over northeast India continued, with only one cyclonic circulation bringing the occasional spell of heavy rainfall over parts of the region.

 

In the coming week, the spread and intensity of rainfall is likely to fall over northwest, east, central, and south India. The pattern and strength of showers is likely to be the same over west India next week. Only a few spells of heavy rainfall are seen over northeast India next week, which is likely to keep the region in a state of deficit.

 

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

 

Period	Actual	Normal	Variation (%)
Aug. 28-Sept. 3	72.5	49.0	48
Aug. 21-27	71.6	52.3	37
Aug. 14-20	70.8	57.9	22
Aug. 7-13	46.2	61.7	(-)25
Jul. 31-Aug. 6	48.0	63.0	(-)24
Jul. 24-30	78.8	66.3	19
Jul. 17-23	57.3	66.7	(-)14
Jul. 10-16	58.1	65.1	(-)11
Jul. 3-9	73.7	58.3	26
Jun. 26-Jul. 2	64.3	53.9	19
Jun. 19-25	63.9	46.3	38
Jun. 12-18	45.1	40.5	11
Jun. 5-11	12.1	28.6	(-)58
Jun. 1-4	14.3	11.5	25

 

The following table gives homogeneous region-wise rainfall during Jun. 1-Sept. 5 in the country (in millimetres): 

 

States	Actual	Normal	Variation(%)
East & Northeast India	919.0	1,133.5	(-)19
Northwest India	696.5	510.9	36
Central India	933.2	839.8	11
South Peninsula	632.6	581.8	9
All India	799.1	734.8	9

 

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 in September is likely to be above normal at 109% of the long-period average over most parts of the country, the India Meteorological Department said in its monthly outlook for rainfall and temperature. "Some parts of northeast and east India, many parts of extreme south peninsular India, and some parts of northern-most India, are likely to receive below-normal rainfall in September," it said.

 

Neutral Indian Ocean Dipole conditions are likely for the rest of the southwest monsoon season and weak negative Indian Ocean Dipole conditions are seen between the end of September and the beginning of October, the weather department said. Forecasts from the Monsoon Mission Climate Forecast System, along with other climate models, suggest that weak negative Indian Dipole conditions are likely to persist for a brief period at the end of the southwest monsoon, the 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.

 

Neutral El Nino-Southern Oscillation conditions are expected to continue for the rest of the southwest monsoon, the weather bureau said. Weak La Nina conditions are likely to develop in the last quarter of the calendar year 2025, though neutral conditions are expected to return post December, the bureau said.

 

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:

 

Region	Date	Period	Forecast (% of LPA)	Forecast (in mm)	Normal (mm)	Model error
All India	Aug. 31	Sept	109	183	167.9
All India	Jul. 31	Aug	94-106	240-270	254.9
All India	Jun. 30	Jul	106	297.22	280.4
All India	May 27	Jun	108	178.52	165.3
All India	May 27	Jun-Sept	106	922.2	870.0	4%
All India	Apr. 15	Jun-Sept	105	913.5	870.0	5%

 

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?ove the normal for the period. Last year, it received 108.7 millimetres of rainfall during Mar-May, 8.1?low 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 158.393 billion cubic metres as of Thursday, up nearly 7% on year, according to data from the Central Water Commission. The current level is 86.8% of the total live storage capacity of 182.479 billion cubic metres. The water level is over 21% higher than the 10-year average for this period.

 

Reservoirs in the northern region held 18.717 billion cubic metres, which is 94.36% of the total live storage capacity, higher than 63% during the same period a year ago. In the eastern region, the water level in reservoirs was 15.552 billion cubic metres, which is 71.47% of the total live storage capacity, compared with nearly 68% a year ago.

 

The water level in the southern region was 48.750 billion cubic metres, which is nearly 88.74% of the region's total live storage capacity across 45 reservoirs. At this time last year, the water level in the southern region was over 86% of the total live storage capacity.

 

The water level in reservoirs in the western region rose to 33.111 billion cubic metres from 32.571 billion cubic metres a week ago. It is now 88.63% of the total live storage capacity, compared with 85.9% a year ago. Reservoirs in the central region held 42.262 billion cubic metres or nearly 87% of the total live storage capacity, up from nearly 76% a year ago.

 

Out of 161 reservoirs, 150 reservoirs reported more than 80% of normal storage and 11 reservoirs reported 80% or below of normal storage. Out of these 11 reservoirs two are having storage up to 50% of normal storage, the data showed.

 

SOWING

Above-normal rainfall has helped the progress of kharif sowing across the country. Farmers across the country have sown kharif crops on 109.3 million hectares as of Aug. 29, up over 3% on year, according to data released by the Ministry of Agriculture and Farmers Welfare.

 

Paddy acreage rose 6.6% on year to 43.2 million hectares and the area under pulses was slightly up on year at 11.4 million hectares as of Aug. 29. The acreage of coarse cereals, promoted as 'Shri Anna' by the government, was up over 6% on year at 19.0 million hectares, mainly supported by a rise in the area under maize.

 

However, the area under oilseeds declined nearly 3% on year to 18.5 million hectares. The area under soybean, the largest kharif oilseed, dipped to 12 million hectares from 12.6 million hectares. Similarly, the area under cotton fell by 2.4% on year to 10.9 million hectares. The area under sugarcane rose nearly 3% on year to 5.7 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>

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 Ashish Shirke

 

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