With heavy rains in the north-east and now the west coast, it has been a tumultuous monsoon season so far, and so has been the forecast of the India Meteorological Department (IMD) which has frequently come under criticism for its prediction of local weather. Despite the forecast of monsoon being in full swing, the rains have been widely uneven over the plains and continue to elude certain parts.
“We have tried to make things transparent. When people said it did not rain in Delhi, we showed data that it did. Since the onset of monsoon on June 30, there have been widespread rains on July 1, 2, 4 and 12, and isolated or scattered rains on other days. Urban areas show lot of variations in local weather due to interaction with land surface and other factors,” said director general of meteorology (DGM) M Mohapatra in an exclusive interview to News18.
The weather department maintains that its forecast accuracy has improved significantly over the years. Until five years ago, it forecasted 24 hours’ weather with an accuracy of 60%, and now it is predicting the weather for the next five days with the same accuracy. The lead time has increased, and the accuracy of one-day forecast has improved to nearly 77%.
“We do not claim to be free of errors, but that error is being minimised and it is evident in the minimised loss of lives during severe weather events. Unlike countries like the UK or Japan, forecasting tropical weather is way more challenging worldwide,” he said. “But people’s expectations have also increased, and so has their demand for very localised, specific forecast. So, our next target is to improve this accuracy by 10-15%.”
Right from announcing the onset of the monsoon over Kerala three days in advance to its sluggish progress over the country and the subsequent rains, the weather agency has found itself constantly fielding questions over its capabilities. The over 140-year-old organisation is now focusing on stepping up to meet its latest challenges.
Gaps in Forecasting
Admitting the gaps in predicting small-scale events like thunderstorms, Mohapatra said: “Weather forecast is non-linear, dynamic and influenced by continuous interaction with land, surface, ocean, biosphere, cryosphere and other weather systems. We try and parameterize it and feed the data into our models. But as we go for very location-specific forecast for small-scale events, there are gaps. Worldwide, the accuracy is less, because such events require meso-scale observations and models, which need high computing power. So that is our next objective.”
The Ministry of Earth Sciences is now working to upgrade the computing power from 10 petaflops to 30 petaflops in the next two years to run the forecasting models. The enhanced processing power will be supported by increase in data observations, both from automatic weather stations as well as radars.
The IMD has set a target of expanding its radar density from 34 to 65 in the next three years, including eight X-band radars in north-east, three in Uttarakhand, and 11 C-band radars in the plains. With special focus on improving city forecast, four new radars will be installed in Mumbai, one each in five other cities, including Hyderabad, Bengaluru, and Kolkata.
“Once the initial observations improve, it will naturally improve the model output and provide better forecast,” said Mohapatra. “We will need additional manpower too, and we are in the process of recruiting that as well.”
The department has also recently added two new models for predicting thunderstorms – one of which is specifically run for north-west, north-east and south peninsular regions, and another model that assimilates lightning data. “Lightning is a killer, and India is among the only five countries in the world that provides lightning forecast and warnings,” he added.
Rise of Extreme Weather Events
The rise of extreme weather events has further accelerated the efforts to improve its forecasting abilities. While the early arrival of monsoon spread cheer, it has so far wreaked havoc over the northeastern states, leading to deadly floods and landslides. The disasters have now shifted to the west coast, engulfing Gujarat and Maharashtra.
According to IMD, the ongoing spell of extremely heavy rainfall in Gujarat is “this monsoon season’s most extremely heavy rainfall spell”, considering all spells so far in the plains this season.
Elaborating on the situation, the senior scientist said: “Flash foods are natural in case of any extreme rainfall event in north-east and even Gujarat region. What is significant is that climatologically, these are the places that often get heavy rainfall events. All this is part of vagaries of weather. But there has definitely been a tendency of increase in the number of heavy rainfall days.”
Progress of Monsoon
With overall monsoon rainfall 13 per cent excess over the country as a whole, IMD remains optimistic about the performance of the southwest monsoon, extremely critical for India’s agrarian economy.
“Till June 15, the rains remained deficient. Normal to excess rains were only limited to south peninsular India and northeast states, leading to very high intensity floods, especially in Assam and Meghalaya. But the monsoon picked up intensity after mid-June and it continues. For July alone, the rainfall has been excess to the tune of 35% so far,” said Mohapatra.
As of July 14, nearly 29 out of 36 sub-divisions have recorded normal to excess rains, though the monsoon has been deficient in Uttar Pradesh, Bihar, Jharkhand, West Bengal as well as Kerala. According to the IMD chief, the seasonal rains will maintain momentum and now shift towards the Indo-Gangetic plains post July 15. Rainfall is likely to be above normal for northwest India over the next two weeks, as per latest forecast.
“The La Nina conditions (cooler surface temperatures of equatorial Pacific Ocean) continue to prevail, and there are favourable low pressure systems forming in the month of July. Overall, large scale circulation suggests good rains will continue and we will have normal rains for the season as predicted. Monsoon still has a lot of time,” said the IMD chief, exuding confidence.
The latest assessment shows that the preceding week that ended on July 13 was the rainiest week of the monsoon season so far with rains in excess of 50% for the country as a whole.
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