Driest, warmest Aug in 122 yrs, Sep may see normal rains: IMD

This August was the driest and warmest for the entire country since weather records began being kept in 1901, the India Meteorological Department (IMD) said on Thursday, adding that September rains are likely to be “normal”, which means that the four-month monsoon season is likely to end with “below normal” rainfall. September will be hotter than usual too, IMD added.

That’s not great news for a country that has seen retail inflation soar to a 15-month high of 7.44% in July, not just on account of seasonal spikes in prices of important vegetables such as tomatoes and onions, but also more obstinate inflation in cereals.

Monsoon rainfall for August was the lowest in the past 122 years since 1901 at the national level and also in Central India and the southern Peninsula.

All India rainfall was around 161.7 mm in August compared to 191.2 mm in 2005, previously the lowest. For Central India rainfall in August was around 164.5mm compared to the previous record for lowest rainfall of 172.8mm in 1905. The Peninsula recorded just 73.5mm of rain in August compared to previous record low of 89.4mm recorded in 1968.

Overall, August saw 36% rainfall deficiency and the monsoon rainfall to date (till August 31) is 10% deficient. But August wasn’t just dry, it was also hot.

The all-India average maximum temperature recorded in August was 32.09 degrees Celsius (°C) compared to normal of 31.09°C; and the all India average mean temperature was 28.40°C compared to normal of 27.55°C. Both were highest for the month since 1901. The Peninsula also saw its highest average maximum, mean and minimum temperatures since 1901.

Monsoon to end “below normal”

Poor rainfall in August, when analysed along with rainfall received in June and July, and the forecast for September suggests that monsoon season is likely to record “below normal” rainfall overall. There was 9% deficiency in rainfall in June followed by 13% excess in July and a 36% deficiency in August. Rainfall in September is likely to be “normal” , ranging between 91% to 109% of long period average (LPA), IMD forecast on Thursday. But even if it were to record the higher end of the forecast range, the average for the season is still likely to be below 96% of LPA.

If September rains are 109% of LPA, the monsoon season will end with a 6.4% deficit. If they are 91% of LPA, the season will end with a 9.9% deficit. Which means that even in the best-case scenario the monsoon will likely be “below normal” .

Weather department officials confirmed that monsoon rainfall this eason is expected to be “below normal” or the lower side of “normal” category.

Rainfall of 90 to 95% of LPA is considered to be in the “below normal” category while less than 90% is considered “deficient.” Monsoon rainfall between 96% and 104% of LPA is considered “normal.”

“We are likely to record a below normal or lower side of normal monsoon rainfall this year but we are not changing our forecast. It will not be a deficient monsoon. We had forecast that we are likely to record monsoon rain of 96% with +/-4% error margin. We will be within that error margin,” said IMD chief Mrutyunjay Mohapatra.

If this monsoon is “below normal” it will be for the first time in five years. In 2022 monsoon rainfall was 106% of LPA; it was 99% in 2021; 109% in 2020; and 110% in 2019.

IMD, the nodal body for weather forecasts in the country predicted a “normal” monsoon at 96% (with an error margin of +/-4%) of the long period average in May. LPA for monsoon season between June to September is 87 cm which is calculated for the period of 1971 to 2020. Private met forecaster, Skymet Weather forecast a “below normal” rainfall during the monsoon season.

Normal rain likely in September

IMD has forecast normal to above normal rainfall is most likely over many areas of northeast India, adjoining east India, foothills of Himalayas and some areas of east-central and south peninsular India in September. Below normal rainfall is most likely over most areas of the remaining parts of the country, it said.

Above normal maximum temperatures are likely over most parts of the country, except some areas in south peninsular India and some pockets of west central India. Minimum temperatures are also likely to be above normal over most parts of the country, except for some areas in extreme north India, the weather office said.

IMD officials said they have provided a large range from 91% to 109% for September because rainfall is normally highly variable during the month.

“Though El Nino is likely to intensify, we have entered a phase of positive Indian Ocean Dipole (IOD). The Madden Julian Oscillation is also likely to be in a more favorable position. Together these features may help counter some of the negative impacts of El Nino which is why we have forecast normal rainfall in September,” said Mohapatra.

Why was August one of the worst monsoon months in history?

There were 20 break monsoon days in August compared to 16 such days in 2005 which was the previous record for highest break days when the monsoon is extremely weak. IMD’s long term data indicates there is a gradual increase in break monsoon days in recent years. The highest previous record of rainfall deficiency in the month of August was in 2005 ( 25%); this year it was 36%.

“The predominant factor is El Nino. It impacted the monsoon,” explained Mohapatra.

Yet, IMD doesn’t expect a serious impact on agriculture. “There was very good rainfall in July when most of the sowing took place except over east India, Jharkhand, Bihar, East UP, Gangetic West Bengal which was deficient. Thankfully in August these eastern paddy growing states received rainfall and their deficiency reduced to an extent. Sowing of paddy also took place,” said Mohapatra.

El Nino has a strong influence on the southwest monsoon in India. El Nino years are characterised by an unusual warming of waters in the eastern equatorial Pacific, which has a high correlation with warmer summers and weaker monsoon rains in India. Positive IOD is good for southwest monsoon over India. IOD refers to the temperature differential between the western and eastern Indian Oceans. A positive IOD has a direct correlation with a good monsoon.

States with the most and least rains

Among states, Kerala has had 48% deficient rains this season, followed by Manipur and Jharkhand with 46% and 37% deficiency. On the positive side, Ladakh has seen the highest surplus (169%), followed by Chandigarh and Himachal Pradesh with 61% and 31%.