Monsoon 2023 to make delayed onset amid El Nino, June to battle rain deficiency, hot and humid weather

The countdown to the Southwest Monsoon 2023 has finally begun. However, Monsoon would be making a delayed onset over the Indian Mainland of Kerala against the normal date of June 1. According to the country’s nodal agency, India Meteorological Department (IMD), Monsoon is most likely to hit Kerala on June 4 with a model error of ± 4 days.

Monsoon current has already reached parts of Andaman Sea on May 19, but the Northern Limit of Monsoon (NLM) has been stationed over its current position for over 10 days now. However, weather conditions are gradually becoming favourable for its advancement towards Indian Mainland.  

Image Credit: IMD

IMD in April had predicted normal Monsoon rainfall for the country to the tune of 96% of the Long Period Average (LPA) with a model error of ± 4%. The LPA of the seasonal rainfall over the country as a whole for the period 1971-2020 is 870 mm.

Monsoon 2023 is likely to make a feeble start, under the influence of El Nino which is invariably linked with below normal Monsoon rains.  While majority El Nino years have resulted in below normal or drought like conditions for the country, but about 40% of the EL Nino years in the past (1951-2022) were years with normal or above normal monsoon rainfall.

At present, Equatorial Sea surface temperatures (SSTs) are near-to-above average across most of the Pacific Ocean. However, Niño 3.4 region, which is a principal measure for monitoring, assessing, and predicting ENSO, has already touched the El Niño threshold of 0.5°C.

El Niño is characterized by a positive Oceanic Niño Index (ONI) greater than or equal to 0.5°C. ONI is defined as the three-month running-mean SST departures in the Niño 3.4 region. A transition from ENSO-neutral is expected in the next couple of months, with a greater than 80% chance of El Niño persisting through the Monsoon months (June-September).

Image Credit: NOAA

While El Nino is one of the deadliest phenomena to impact Indian Monsoon rains, other oceanic parameter like Indian Ocean Dipole (IOD) are responsible for driving the Monsoon current across the country. IOD when in positive phase is linked with good Monsoon rains over the Indian landmass.

At present, neutral IOD conditions are prevailing over the Indian Ocean. The latest forecast from MMCFS and other global climate models indicates the development of positive IOD conditions over the Indian ocean during the monsoon season.

June to see below normal rains, hot and humid weather to mar parts of the country

As per the latest forecast by IMD, the onset month of June is likely to witness below normal monthly rainfall to the tune of <92% of LPA. The normal rainfall for country for June stands at 165.4 mm.  

Most parts of the country would see below normal barring some areas of south peninsular India, northwest India, extreme north India, and some isolated pockets of northeast India, where above normal rainfall is expected.

Image Credit: IMD

In absence of rainfall during the month, maximum as well as minimum temperatures would settle above normal over most parts of the country. However extreme north and some parts of the southern peninsular India are likely to see maximum temperatures settling below-normal and normal temperatures, respectively.

Image Credit: IMD

What is more concerning is the high humidity levels triggered by the Monsoon current, combined with higher maximum temperatures. Humidity is a crucial factor in how high temperatures affect the human body. The way for humans to cool themselves, becomes less effective at high humidity. Thus, heat is more dangerous in humid conditions.