NEW DELHI: Monsoon rains spread to new territories in east, central and west India, making Monday the wettest day of the season so far and pushing the season’s rain tally to 21% above normal – a jump of five percentage points in a single day.

There is more in store as two rain-bearing systems are headed to meet over northwest India and bring a wave of wet weather into the region in a couple of days. The Met department said this would hasten the monsoon’s arrival into north India, including the national capital region, during the course of this week.

But Met experts said while this week promises to be rain-packed, the monsoon is likely to weaken thereafter.

“The monsoon’s active phase is expected to last another four days or so. Our models show a subdued period after that, particularly in the first week of July,” said M Rajeevan, director of the Indian Institute of Tropical Meteorology .

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Rajeevan said the bountiful monsoon over the past 12-13 days was a result of an eastward-moving equatorial weather pulse called the Madden Julian Oscillation (MJO) appearing over the Indian Ocean and energizing rains in the region.

B P Yadav, director, India Meteorological Department , agreed. “MJO will enter the western Pacific in four-five days and its positive impact on the monsoon is likely to end around that time.”

MJO, however, has helped give the perfect start to the monsoon which is predicted to be below par this year due to adverse conditions in the Pacific called the El Nino. June is almost certain to end with surplus rainfall.

Meanwhile, monsoon activity peaked on Monday, when the average weighted rainfall over the country was recorded at 13.8mm, almost double of normal, thanks to heavy rains across central India (except Gujarat) and the south peninsula, except Telangana.

Gujarat may get rains on Wednesday and Thursday, when a depression currently over the Arabian Sea is expected to be sucked inland by a moist wind system called a western disturbance (WD) that will hit north India at the time.

“By Wednesday, a WD is expected to strike the region and would interact with the low pressure system coming from Gujarat to bring rain across northwest India. There’s a good possibility of the monsoon progressing into north India during this time,” Yadav said.

A similar interaction between a WD and a rain-bearing system from Bay of Bengal had led to the Uttarakhand deluge in June 2013, but Yadav the current systems were not expected to be as strong.

“An increase in rain activity over the western Himalayas is expected but we are not anticipating any extreme events,” the IMD director said.