This August was kind. The rain was distributed evenly over the days and across the state.
Monsoon entered Bihar on June 15 this year. At the end of the month, the rainfall was 5 per cent surplus. But July was dry and scorching and at the end of it, the monsoon deficiency had increased to a whooping 80 per cent.
But between August 1 and 31, Patna got 185mm rain, against the normal of 265mm. The deficiency was 30 per cent. The precipitation was distributed over 16 days — the highest number of rainy days in August over the past four years.
The rain gods were merciful not only to the city but also to the rest of the state. The deficiency came down from 47 per cent at July-end to 27 per cent by August-end.
Weathermen attributed the comparatively better rainfall in August to the favourable position of the monsoon trough line as well as frequent formation of cyclonic circulations. “The monsoon trough line passed through Jharkhand, Bihar and Bengal for most of August. It was complemented by four cyclonic circulations in the region, which concentrated the moisture in the area, leading to good rainfall,” said Ashish Sen, director, India Meteorological Department, Patna.
According to the records of the local Met department, the cumulative rainfall deficiency from June 1 to September 2 is 60 per cent. But for August, it stands at 30 per cent.
“Rainfall in June was five per cent surplus. The overall cumulative rainfall deficiency has soared mainly because of scanty rainfall in July,” said Sen.
Though the rainfall condition in August was better than July, it was still the second lowest in Patna over the past 10 years. (See graphic)
Another significant feature of the rainfall in August this year was the absence of a “monsoon break” in the middle of the month.
“Normally a lull in the rains is observed across India for around eight to 15 days between first and third weeks of August because of cross-equatorial flow of monsoon winds from the southern to the northern hemisphere. However, the lull was not observed this year,” said Sen, adding that his department was trying to find out why it happened.
The benevolence of August, however, has not been able to recover the rains completely. According to the records available with IMD-Patna, only two out of the 38 districts of Bihar have shown surplus monsoon rainfall till August 31.
The rainfall deficiency in eight districts was above 50 per cent. Sitamarhi has received the least rainfall in monsoon this year. The rainfall deficiency in the district is 66 per cent.
Six districts received deficient rainfall in the category of 40 to 49 per cent, and seven districts in the category of 30 to 39 per cent.
September, too, would be kind for Bihar. “In the districts of north Bihar, rainfall is expected to be normal to marginally above normal. In the south and central parts of the state, including Patna, it would be normal,” said Sen.
There could, however, be heavy rainfall in the northern districts, which are near Nepal, leading to flooding of rivers in the Kosi region.
“The north-eastern part of the monsoon trough line is over the Bihar-Nepal border. It is stretching along the foothills of the Himalayas at present. Once the easterly winds start blowing towards the trough line and it remains static at its present position for another seven to 10 days, there would be very heavy rainfall in that region. That might worsen the flood situation in the Kosi region because of rainwater coming from rivers in Nepal,” said Sen.