India records large deficiency as monsoon enters break phase: IMD
The country recorded a “large deficiency” of rain on Tuesday, which was 60% less than normal, due to the ‘break monsoon’ period that began on Monday, according to the India Meteorological Department (IMD). The shortfall was 43% between Monday and Tuesday.
The southwest monsoon has weakened in the past week, or taken a ‘break’, as weather scientists put it.
“The models indicate that a very weak or break monsoon period will continue till July 5. Such a phase is part of the monsoon’s internal dynamics. Sometimes it’s in an active phase and sometimes it moves over to a very subdued phase. We can predict these fluctuations,” said M Rajeevan, secretary, ministry of earth sciences.
Experts say the ‘break monsoon’ phase happens when the monsoon has already covered the entire country. “The monsoon trough moves to the foothills and wind flow is mostly westerly, there is little contribution from Bay of Bengal and hence little convective activity. During break monsoon phases, rains are limited to northeast India. But this time the trough is not near the Himalayan foothills, but the monsoon flow itself has weakened,” said O P Sreejith, head, climate monitoring and prediction group, IMD.
IMD thinks the monsoon will remain “extremely subdued” till at least July 5. “We do not have model outputs for dates ahead of that. There is no indication of any low-pressure area developing over the Bay of Bengal before July 10. Low-pressure systems help monsoon advance, but other factors could also help,” said R K Jenamani, senior scientist at national weather forecasting centre, IMD.
Scientists had predicted this last week. “Up to the first week of July, there are no indications of monsoon reviving. The cross-equatorial flow has weakened, and the pressure gradient is less. Normally, monsoon flow moves from high-pressure to low-pressure areas. The monsoon current itself has weakened, so its onset is unlikely over the remaining parts of the country till it revives,” Sreejith had said on June 26.
Overall, the country has recorded 13% excess rain since June 1 with 3 of 36 subdivisions recording “large excess” (60% or more), 15 recording “excess” (20% to 59%), 11 recording “normal” (-19% to 19%), and seven recording “deficient” rain (-59% to -20%).
“We expect monsoon rains to be only 10 to 12% excess for June. In July, the normal thresholds also increase because normally more rain is recorded in July, but let’s see how monsoon makes up for the gap,” Jenamani added.
The northern limit of southwest monsoon (NLM) continues to pass through Barmer, Bhilwara, Dholpur, Aligarh, Meerut, Ambala, and Amritsar. It has been at the same position for a week now.
“Prevailing meteorological conditions, large scale atmospheric features and the forecast wind pattern by dynamic models suggest that no favourable conditions are likely to develop for further advance of southwest monsoon into the remaining parts of Rajasthan, west Uttar Pradesh, Haryana, Chandigarh, Delhi and Punjab during the next five days,” IMD said in its bulletin on Tuesday.
Subdued rain is very likely to prevail over northwest, central and western parts of Peninsular India during the next five days. Isolated/scattered thunderstorms accompanied by lightning and rain are also likely over these regions during this period.
Under the influence of strong moisture-laden southwesterly winds, widespread rain is very likely over Bihar, West Bengal, Sikkim and the other northeastern states in the next five days.
Subsequently, moist easterly winds are likely to pick up in strength, causing enhanced rain all along the Himalayan foothills of north Bihar, north Uttar Pradesh and Uttarakhand from July 1 to 3, leading to increased inflow into the rivers originating or flowing through these regions. Isolated heavy to very heavy rain is very likely over Uttarakhand and the Himalayan foothills of east Uttar Pradesh during July 1 to 3.
Strong surface winds, with speeds reaching 20-30 km/hr, are likely to blow over Haryana and west Uttar Pradesh on June 30 and July 1.
Moderate to severe thunderstorms accompanied by frequent cloud-to-ground lightning are very likely over Bihar, Jharkhand and Gangetic West Bengal during the next 24 hours. IMD warned that this could cause serious harm to both people and animals staying outdoors.