PUNE: After forecasting widespread monsoon activity over the next fortnight, India Meteorological Department has indicated that rainfall could weaken in the second half of July, with most parts of the country likely to receive below-normal rainfall if the current extended-range forecasts hold.According to the India Meteorological Department (IMD)’s Extended Range Prediction System (ERPS), the first two weeks of July are expected to bring good rainfall over the west coast and parts of central India, aided by a favourable monsoon circulation. Projections for the third and fourth weeks of the month, however, indicate below-normal rainfall over much of the country, though officials stressed that this does not imply a complete break in rainfall.
“The coming two weeks, till around July 14, are showing good rainfall over the west coast and parts of central India. Thereafter, the current extended-range guidance suggests below-normal rainfall over most parts of the country,” IMD scientist SD Sanap told TOI.IMD said during July 9-15, rainfall is likely to be near normal over the country as a whole. It is also likely to be above normal over northwest and central India and below normal over the northeast and south peninsular India during the period.Sanap, however, cautioned that confidence in the week-three and week-four forecasts “is lower than for the first two weeks”. He said, “Forecast skill reduces in weeks three and four, so this outlook is subject to change. However, both the IMD’s Extended Range Prediction System and the European Centre for Medium Range Weather Forecasts (ECMWF)’s extended-range model are indicating a similar possibility at present.“The latest IMD extended-range rainfall anomaly maps also reflect this trend. During July 2-16, positive rainfall anomalies are forecast over the west coast and adjoining parts of central India. Thereafter, rainfall anomalies turn largely neutral to negative across much of the country, suggesting a comparatively drier second half of the month.Sanap attributed the expected weakening partly to the anticipated evolution of the Madden-Julian Oscillation (MJO), a major tropical weather system that influences monsoon activity.“At present, the MJO is in phases five to six, which favour the northward movement of the Inter-Tropical Convergence Zone (ITCZ) and support the Indian summer monsoon. Most models indicate that it is likely to move into phases seven, eight and then one in the coming days, which are generally unfavourable for the Indian monsoon,” Sanap said.“From around July 10 or during the second half of the month, the MJO is not expected to remain unfavourable for the next 15-20 days or even longer. That is one of the reasons why extended-range models are indicating below-normal rainfall,” he said.Even so, Sanap emphasised that rainfall activity would not disappear altogether. “Below-normal rainfall does not mean there will be no rain. Rainfall activity will continue. But the overall amounts are expected to be lower than normal,” he said.He added that rainfall distribution is also expected to shift during the second week of July, with Gujarat, the west coast and parts of northwest India likely to receive enhanced rainfall.Another IMD official said the outlook was based on the department’s ERF, which currently suggests a stronger monsoon during the first half of July before activity weakens later.Akshay Deoras, senior research scientist at the University of Reading, UK, said the broader outlook also pointed towards a relatively drier second half of July.“The monsoon is likely to weaken during the second half of July, so this period is expected to be drier than the first half of July for Maharashtra,” Deoras said.
