Monsoon ends with 94% rainfall across India; ‘normal’ in Nagaland

NEW DELHI, SEPTEMBER 30 (MExN): The four-month monsoon season (June-September) ended with rainfall over the country as a whole recorded at 94% of its long period average (LPA) and considered ‘normal,’ informed the India Meteorological Department (IMD) on Saturday.

Rainfall in Nagaland was -10% departure from the LPA but designated as normal in the IMD’s categorization.

According to the IMD’s ‘End of Season Report: Southwest Monsoon 2023’ issued on September 30, India recorded 820 mm of rainfall in the four-month period against the LPA of 868.6 mm.

Seasonal rainfalls over Northwest India, Central India, South Peninsula, and Northeast (NE) India were 101%, 100%, 92%, and 82% of their respective LPA, it said. 

The core zone, which consists of most of the rain-fed agricultural regions in the country, received 101% of the LPA and was thus considered normal (94-106% of LPA), it added.

The IMD classifies rainfall data into five categories: Large Excess (60% or more above normal), Excess (20% or more above normal), Normal (19% to -19% of normal), Deficient (-20% to -59% of normal), and Large Deficient (-60% or more below normal).

As per the national weather agency, out of the total 36 meteorological subdivisions, 3 subdivisions constituting 9% of the total area of the country received excess rainfall, 26 subdivisions received normal rainfall (73% of the total area), and 7 subdivisions (18% of the total area) received deficient season rainfall.

The 7 Meteorological subdivisions which received deficient rainfall are Nagaland, Manipur, Mizoram & Tripura (NMMT), Gangetic West Bengal, Jharkhand, Bihar, East UP, South interior Karnataka, and Kerala.

Monthly rainfall over the country as a whole was 91% of the LPA in June, 113% of the LPA in July, 64% of the LPA in August, and 113% of the LPA in September.

Providing an overall status of the Southwest Monsoon current, the IMD further informed that it advanced to the south Andaman Sea and Nicobar Islands in time (on May 19, 3 days ahead of its normal date). However, further advance thereafter was sluggish.

Accordingly, it set in over Kerala on June 8, seven days behind the normal date, and covered the entire country by July 2, six days ahead of the normal date.

Conversely, Monsoon withdrawal commenced from west Rajasthan on September 25 (with a delay of 8 days), according to the IMD.

The forecast for the monsoon onset over Kerala for this year was correct, marking the seventeenth consecutive correct forecast for this event except for the year 2015 since the commencement of this forecast in 2005, it maintained. 

It forecasted onset of monsoon over Kerala on June 4 with a model error of ± 4 days, and the monsoon set on June 8.

The forecasts for the rainfall over the country as a whole during the season could be predicted well, as the realized rainfall is 94% of LPA against the forecast of 96% ± 4%, it added.

Meanwhile, the IMD noted that historically, El Niño events have often been linked to below-average rainfall in India, while most La Niña years correlate with above-average precipitation.

The relationship is not straightforward, with some El Niño years resulting in above-normal rainfall, and conversely, some La Niña years resulting in below-normal precipitation, it said. 

The year 2023 serves as an illustrative example of this complex interplay, the IMD stated. While India experienced below-average rainfall, yet, the presence of the Indian Ocean Dipole (IOD) during the monsoon's latter phase offset this deficiency, bringing the rainfall anomaly within the standard deviation, it added.

Nagaland’s status

While Nagaland, Manipur, Mizoram & Tripura (NMMT) are categorized under one meteorological subdivision, it was classified as receiving ‘deficient’ (-27% of LPA) as a whole. Individually, there were varied results.

State-wise rainfall information on IMD’s website shows that out of the four states in NMMT, Tripura (-12%) and Nagaland (-10%) received normal rainfall, while there were deficits in Mizoram (-28%) and Manipur (-46%).

From June-September period, Nagaland received 934.9 mm of rain as against the normal LPA of 1038.8 mm.

As per the district-wise data given on the IMD website, out of the 11 districts listed, Dimapur and Kiphire recorded ‘Excess’ rainfall while Kohima, Peren, Wokha, and Zunheboto were deficient.

It was normal in the rest of the districts – Longleng, Mokokchung, Mon, Tuensang, and Phek.