The India Meteorological Department (IMD) on Monday announced the arrival of the southwest monsoon in Kerala. It, however, expressed caution over the further progress of the monsoon in view of a low pressure area over the central Arabian Sea.

In a press release, the IMD said the system could advance over coastal and south interior Karnataka and Goa over the next two days. But its later movement would depend on how the low pressure area developed.

Headed for Gujarat?

According to senior IMD officials, current indications are that the low pressure area may gradually intensify into a cyclonic storm and move initially in a north-westerly direction for the next 48 hours and then re-curve north-eastwards towards Gujarat and the adjoining Pakistan coast.

Speaking to The Hindu, India Meteorological Department Director-General Ajit Tyagi confirmed that the rainfall in the coming days was expected to remain confined to the west coast along the windward side of the Western Ghats, as the winds may not be able to reach up to the top of the mountains and flow over to the leeward side.

Next spell

Consequently, the interior areas of the southern peninsula may not get much rain now. They may have to wait for the next spell, which is expected around June 10, when the positive phase of the phenomenon called Madden-Julian Oscillation (MJO) is expected to reach the Indian Ocean.

The MJO, which refers to an inter-annual fluctuation of atmosphere pressure over the Indian and western Pacific oceans, comes in the form of alternating cyclonic and anti-cyclonic regions that enhance and suppress rainfall, respectively, and that flows eastward along the Equator.

The MJO influences monsoonal circulation and rainfall by adding moisture during its cyclonic or wet phase. The cyclonic phase is now in the offing for the Indian Ocean region. The phenomenon is named after American atmospheric scientists Roland Madden and Paul Julian.

In line with prediction

The arrival of monsoon over Kerala is almost in line with the prediction made by IMD two weeks ago. On May 14, the Department forecast that the system would set in over the State on May 30 with a model error of plus or minus four days.

(Kerala is the entry point for monsoon into the Indian mainland. The normal date for the onset over the State is June 1)

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