Lack of cross-equatorial flow hinders progress of monsoon

Unfavourable cross-equatorial flow over the Arabian Sea that aids in the progress of the monsoon is one of the reasons for its delay, the national weather agency said on Sunday.

Monsoon reached the Andaman and Nicobar Islands on May 18. But it is yet to cover the entire region, the India Metrological Department said.

Conditions are likely to become favourable for the movement of the southwest monsoon into some more parts of south Bay of Bengal, Andaman Islands and north Andaman Sea during Wednesday-Thursday, the IMD said.

It is also expected to make an onset over Kerala on June 6, five days after its normal onset date, it had said.

The weather department said the monsoon was yet to get traction from the Arabian Sea.

"The slow pace is because of the lack of cross-equatorial flow in the Arabian Sea," Mritunjay Mohapatra, the additional director general of the IMD, said.

Mohapatra attributed the sluggish pace to the unfavourable MaddenJulian oscillation (MJO) and anti-cyclonic circulation over the south Indian Ocean that aids the progress on monsoon.

The MJO can be defined as an eastward moving 'pulse' of clouds, rainfall, winds and pressure near the equator that typically recurs every 30-60 days. It is a traversing phenomenon and is most prominent over the Indian and Pacific Oceans.

In its bulletin, the IMD said 'fairly widespread to widespread rainfall' activity with isolated heavy fall were very likely to occur over Assam and Meghalaya and sub-Himalayan West Bengal, Sikkim on Wednesday and Thursday.

Scattered to fairly-widespread rainfall activity with isolated heavy falls are very likely to occur over south-interior Karnataka from May 26-28 and over Tamil Nadu and Puducherry on Tuesday-Wednesday, it said.

On the other hand, heatwave conditions continue in central Indian and parts of Andhra Pradesh and Telangana.

The heatwave is expected in some parts are very likely to continue over Vidarbha and at isolated pockets over central Maharashtra, Telangana, east Madhya Pradesh, Chhattisgarh, east Uttar Pradesh, Jharkhand and Odisha during the next four-five days, it added.