IMD predicts normal monsoon rains but says northeast could see less rain

The Indian Meteorological Department (IMD) predicted on Thursday that this year’s monsoons are likely to be “normal”. The IMD said seasonal southwest monsoon rainfall between June and September will be between 96% and 104% Long Period Average (LPA) – indicating a normal monsoon season, so that quantitatively, the precipitation should be 99% LPA.

The IMD however said that some parts of the country will receive below normal rainfall during the monsoons, especially the northeastern states of India which have experienced below normal rainfall in recent years due to the change climatic. India’s southwest monsoon rainfall contributes 74.9% to annual rainfall.

While IMD will release an updated forecast for the monsoons in mid-May, detailing rainfall distribution patterns across the country, IMD CEO Dr M Mohapatra said on Thursday that the dry spells observed in recent years are part of the “decadal variability in India”. ” monsoons.

“The new rainfall normal for all India calculated by IMD is now based on 1971-2020 data and is 87cm as opposed to the earlier normal of 88cm calculated based on 1961-2020 data. 2010,” he added.

“This decadal variability includes large dry and wet periods. But the total precipitation received remains the same. Currently, the southwest monsoon is going through a dry period which started in 1971-80. The next decade (2021-30) will approach the neutral southwest monsoon and enter the wet era in the following decade. So far, temporal variability (in rainfall patterns) has not been detected,” Dr Mohapatra said.

The new rainfall normal was calculated using rainfall data from 4,132 well-spread rainfall stations across the country representing 703 districts of India.

“During the monsoons, the number of heavy rainfall days increased, while the number of moderate and light rainfall days decreased,” he added.

The IMD also said that currently La Niña conditions prevail in the equatorial Pacific region. Climate model predictions indicated that La Niña conditions are expected to continue into the monsoon season. At present, neutral IOD conditions are present over the Indian Ocean and the latest forecast indicates that neutral IOD conditions are expected to continue until the start of the southwest monsoon season. Subsequently, an increased probability for negative IOD conditions is predicted.

As sea surface temperature (SST) conditions over the Pacific and Indian oceans are known to have a strong influence on the Indian monsoon, IMD carefully monitors the changing sea surface conditions over these ocean basins.

Mohapatra pointed out that last year, IMD implemented a new strategy to issue monthly and seasonal operational forecasts for southwest monsoon rains over the country by modifying the existing two-step forecasting strategy. The new strategy uses a novel Multi-Model Ensemble Prediction (MME) system based on Global Coupled Climate Models (CGCMs) from different global climate prediction and research centers, including the Mission’s climate prediction system. Monsoon (MMCFS) from IMD, as well as the existing statistical forecast system to generate these forecasts.

Spatial distribution suggests normal to above normal seasonal rainfall over many parts of northern peninsular India and adjacent central India, Himalayan foothills and parts of northwestern India . Below normal rainfall is likely in many parts of northeast India, parts of northwest India and southern parts of the southern peninsula.

“The below-average monsoons in northeast India and parts of northwest India and the far southern peninsula can be attributed to climate change. But the regional impact of the climate change on rainfall patterns needs further study,” Mohapatra said.

The DG added that the parameters studied by the IMD to assess the impact of climate change include an analysis of daily maximum, minimum and average temperatures, ocean and land area temperatures for the whole country, total rainfall in a month and the distribution of rainfall during the monsoon period, as well as the frequency of extreme weather events such as cyclones, heat waves and heavy rainfall.

The new system was introduced due to the demands of different users and government authorities for the forecasts of the spatial distribution of seasonal rainfall as well as the regional average rainfall forecasts for better business planning at the regional level, he said. .

Based on the new model, the forecast for the last monsoon was accurate, the DG said. “The above normal rainfall observed over many parts of the plains of northwestern India, central India and the eastern coast was well forecast. Similarly, the below normal rainfall observed over the “extreme northwest India and northeast India were also in line with forecast. However, the below normal rainfall seen in parts of central India could not be predicted,” said he declared.

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