Fewer weather stations reported extremely heavy rains this monsoon, compared to last year. But the corresponding figure was higher than in 2017 and 2018, which is in line with the trend of an increase in extremely humid weather, the Indian Meteorological Department (IMD) said in its analysis of the monsoon season on Thursday.
Officially, the monsoon season ended on Wednesday (September 30).
The high variation in rainfall received in each of the four monsoon months since June 1 was unique this year, according to IMD.
IMD data showed that 341 weather stations reported extremely heavy rainfall, measuring more than 20 centimeters (cm) this year, compared to 554 in 2019; and 321 and 261 in 2018 and 2017, respectively.
This year, 2,253 meteorological stations registered very intense rains, between 11 and 20 cm, compared to 3,056 in 2019; and 2,181 and 1,824 in 2018 and 2017, respectively.
The total rainfall recorded this monsoon at 108.7% of the long-term average (LPA) is the third highest since 1990.
In 1994 and 2019, 112% and 110% of the LPA were registered, respectively.
This and the previous monsoon are the two consecutive years with above-normal monsoon rains since 1958 and 1959, IMD said in its analysis.
In June, IMD had forecast normal monsoon rains of 102% of the LPA with a margin of error of +/- 4% for the season. The precipitation range of 96% to 104% of LPA is considered normal and 104% to 110% is considered above normal.
India recorded above-normal rainfall of 110% of the LPA last year.
“Taking into account the variation in rainfall from month to month in India, the season occupies a very unique place in the historical record for its distinct and contrasting monthly variation. Rainfall over the country was 118%, 90%, 127% and 104% of the LPA during June, July, August and September, respectively, ”said IMD.
IMD said its LPA forecast by region was wrong.
In May, IMD had forecast 107% of the LPA for Northwest India; Central India (103%); East and Northeast India (96%); and the southern peninsula (102%).
But, the precipitation recorded in these regions was 84%, 115%, 107% and 129% of the LPA, respectively. “Therefore, the seasonal rainfall forecasts for the central, northeast and southern regions of the peninsula were an underestimate of the actual rainfall, while the forecast for northwest India was an overestimate. The forecast for the second half of the monsoon season (August-September) for the country was 104% against the actual rainfall of 118% of the LPA, ”said IMD.
“The long-term forecast for a period of four months and that also for various regions often leads to variations. It cannot be exact. The longer the period, the forecast becomes more complicated, ”said K Sathi Devi, director of the National Weather Forecast Center (NWFC), IMD.
“The average monsoon rainfall across India was normal by definition. However, that doesn’t give much information about the regional monsoon event. This year, the two cyclones during the onset, the low pressure systems in the Bay of Bengal and the occasional strong westerly winds influenced the monsoon variability. Temperatures in the Arabian Sea were high throughout the season, increasing moisture supply and triggering some of the heavy rain events that led to regional flooding, ”said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology in Pune.
Although the post-monsoon season has officially started from October 1, widespread and abundant rains are expected over Odisha, Jharkhand and the West Bengal Ganges for the next four to five days. Isolated heavy to very heavy rains are also likely to occur in these states. This is mainly due to the influence of a low pressure area over the west-central Bay of Bengal, off the north of Andhra Pradesh (AP) and the southern coasts of Odisha. It is also likely that it will rain very heavily on Assam, Meghalaya and Tripura over the next five days.
“The withdrawal of the monsoon from these regions cannot be declared until the rain stops completely. The withdrawal parameters must be met. It is difficult to say when the monsoon will completely withdraw, ”added Devi.
.
