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Informist, Thursday, Aug. 14, 2025

 

LATEST DEVELOPMENTS

After a brief pause of rainfall activity over the country, monsoon has revived on Tuesday over most parts of the country with the formation of a low-pressure area over northwest Bay of Bengal Wednesday. The low pressure area is currently over the northwest Bay of Bengal and south Odisha-north Andhra Pradesh coasts because of which parts of east and central India have received extremely heavy rainfall so far during the week. 

 

With active monsoon conditions for more than a week over southern India, rainfall deficiency has narrowed in states like Andhra Pradesh and Telangana. Skymet, a private weather forecaster, said the low pressure area over Bay of Bengal is expected to evolve into a depression. 

 

In southern India, rainfall during the week ended Wednesday was 41?ove normal at 66 millimetres, according to the India Meteorological Department. Of the 10 sub-divisions in the homogeneous region, five recorded "large excess" showers during the period. Rainfall so far during the southwest monsoon period was also 1?ove normal at 458.9 millimetres. 

 

Monsoon was also active over northeast India during the week, with Arunachal Pradesh, Assam, sub-Himalayan West Bengal, Sikkim, and Meghalaya recording above normal showers. This has boosted the overall rainfall in east and northeast India to the normal level of 75.7 millimetres during the week ended Wednesday.

 

As the monsoon has been active only since Tuesday over east, central, and west India, parts of these regions recorded below normal showers during the week ended Wednesday. In central India, rainfall was 58% below normal at 31.7 millimetres during the week, data from the weather bureau showed. 

 

Torrential rainfall persisted over northwest India during the week. Rainfall was 31?low normal in northwest India at 34.2 millimetres. India received average rainfall of 46.2 millimetres, 25?low the normal of 61.7 millimetres during the week ended Wednesday for the week, according to the weather department. 

 

The weather bureau expects heavy to very heavy rainfall to continue over parts of south, east, and central during the next four-five days. It also added that the spell of intense showers would reduce over northwest India from Friday. 

 

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

 

Period	Actual	Normal	Variation (%)
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-Aug. 14 in the country (in millimetres): 

 

States	Actual	Normal	Variation(%)
East & Northeast India	758.5	904.3	(-)16
Northwest India	443.7	387.4	15
Central India	661.3	645.8	2
South Peninsula	472.7	458.2	3
All India	572.8	570.7	0

 

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:

 

Region	Date	Period	Forecast (% of LPA)	Forecast (in mm)	Normal (mm)	Model error
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 135.277 billion cubic metres as of Thursday, which is 74.13% of the total live storage capacity, according to data from the Central Water Commission. The total live storage capacity of 182.496 billion cubic metres.

 

Of the 161 reservoirs, eight were at full capacity, up from seven a week ago, data from the Central Water Commission showed. However, the number of reservoirs with water level of 40% or less fell to 19 from 21 from a week ago.

 

In the eastern region, the water level in reservoirs was 11.860 billion cubic metres, which is 54.51% of the total live storage capacity, compared with 54.14% a year ago. Reservoirs in the northern region held 15.047 billion cubic metres of water, 75.79% of total live storage capacity of the region. It is higher than 49.72% during the same period a year ago. 

 

The water level in reservoirs in the western region was at 28.397 billion cubic metres, which is 76.02% of the total live storage capacity. During the corresponding period last year, the water level was 72.53%. Reservoirs in the central region held 36.015 billion cubic metres or 74.12% of the total live storage capacity, up from 71.01% a year ago. 

 

The water level in the southern region was 43.958 billion cubic metres. As of Thursday, the water level was 80.01% of the total live storage capacity of the 45 reservoirs in the region. At this time last year, the water level was 78.16% 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 99.6 million hectares as of Friday, 4% higher than 95.7 million hectares a year ago, according to data released by the Ministry of Agriculture and Farmers Welfare.

 

Paddy acreage rose 12% on year to 36.5 million hectares. However, oilseed acreage slipped 4% on year to 17.6 million hectares from 18.2 million hectares a year ago. Except for castor seed, acreage of all major oilseeds registered a decline as of Friday. Soybean sowing dipped to 12 million hectares from 12.4 million hectares. Groundnut acreage fell to 4.3 million hectares from 4.5 million hectares.

 

The area under pulses was largely unchanged at 10.7 million hectares as of Friday compared to a year ago. While tur or arhar sowing dipped nearly 5% on year to 4.1 million hectares, moong area rose nearly 3% on year to 3.3 million hectares. 

 

The acreage of coarse cereals, promoted as 'Shri Anna' by the government, was up 5% on year at 17.9 million hectares, mainly supported by a rise in the area under maize. The area under maize rose to 9.2 million hectares from 8.3 million hectares a year ago.

 

The area under cotton fell over 3% on year to 10.7 million hectares, while sugarcane acreage 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 J. Navya Sruthi

Edited by Avishek Dutta

 

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