Monsoon arrival in Kerala likely to be delayed further

Monsoon normally arrives in Kerala around June 1 before advancing northwards and covering the entire country by July 15

The monsoon arrival in Kerala is expected to be delayed further, the India Meteorological Department (IMD) has indicated without specifying a fresh date for its likely onset. Conditions such as westerly wind patterns were making the onset conditions conducive. But the formation of a cyclonic circulation that intensified into a depression on Tuesday over the Southeast Arabian Sea has led to a reduction of cloud cover—another key condition for the onset—off the Kerala coast.

A delayed onset has little impact on monsoon rains. (PTI)

“Latest observations indicate that a depression has formed over [the] southeast Arabian Sea and about 920 km west-southwest of Goa, 1120 km south-southwest of Mumbai, 1160 km south of Porbandar... It is likely to move nearly northwards and intensify into a cyclonic storm during next 24 hours over [the] Eastcentral Arabian Sea & adjoining southeast Arabian Sea,” IMD said on Tuesday.

Monsoon normally arrives in Kerala around June 1 before advancing northwards and covering the entire country by July 15. IMD on May 16 said the monsoon was likely to arrive in Kerala on June 4 with a model error of +/-4 days.

On Monday, IMD said westerly winds continued over the south Arabian Sea. It cited the cyclonic circulation over the Southeast Arabian Sea and said the cloud mass was now more organised and concentrated over the area. “...There has been some reduction of clouds off Kerala coasts in [the] last 24 hours.”

The monsoon is critical for India’s economy as 51% of India’s farmed area accounting for 40% of production is rain-fed. As many as 47% of the country’s population is dependent on agriculture for livelihood. A bountiful monsoon is directly linked to a healthy rural economy.

HT on June 1 reported the monsoon progress was likely to be dampened after its expected arrival in Kerala around June 4 with a model error of +/-4 days due to the chances of the development of a low-pressure area over the Arabian Sea around two days later. Officials then said the model outputs remained highly variable.

READ | Rainfall to continue in northwest India for next four days: IMD

An IMD official said the monsoon onset was likely to take place in Kerala by June 8. “The system is getting organised now so it is pulling all convection towards it and clouds are around the system.”

In a tweet, former earth sciences ministry secretary M Rajeevan cited IMD forecast models and said it suggests monsoon could arrive in Kerala on 7/8 June. “All onset conditions are set to be satisfied by 8th, with deep (up to 4.5 km) strong monsoon winds, an East-West shear line at 3.1 km (black line) & good rains over Kerala,” he tweeted. “An onset vortex to be formed with a chance of its intensification & northward movement; may help monsoon progress further along the west coast.” He underlined a delayed onset has little impact on monsoon rains.

IMD has forecast a “normal” monsoon at 96% with an error margin +/-5%) of the long-period average (LPA) of 87 cm calculated from 1971 to 2020.

Private forecaster Skymet Weather has said “below normal” rainfall was expected at 94% of LPA with an error margin of +/-5%.

IMD follows a well-laid-out process of identifying onset parameters before announcing monsoon arrival.

READ | Monsoon progress likely to be dampened post-arrival in Kerala around June 4

Rajeevan said the first thing that is considered is rainfall. “Out of 14 representative weather stations in Kerala, at least 60% of stations should report more than 2.5 mm rainfall for two consecutive days. Before monsoon sets in, thunderstorms normally start,” he said.

He added when at least 60% of these stations record rainfall, it means there is largescale rainfall activity in Kerala and surrounding regions. “But if we have only rainfall as a criterion, then there is a high chance of bogus monsoon onset. This happened in 1995 and 2015. So, two other criteria are also critical: A cross-equatorial flow of winds or a westerly flow at both lower and higher levels and whether there is adequate clouding over the region which is also a sign of rainfall approaching.”

There is a nearly 100% probability of El Nino conditions during monsoon. It is expected to continue till next year, IMD said last month. El Nino is characterised by an unusual warming of waters in the eastern equatorial Pacific Ocean, which has a high correlation with warmer summers, drought, and weaker monsoon rains in India.

The 2023 El Nino is expected to develop following a triple dip La Nina event (2020-22). La Nina is the opposite of El Nino and is characterised by cooler currents in the equatorial eastern Pacific.