El Nino active over Pacific, likely to strengthen during monsoon: IMD

El Nino conditions have developed over the equatorial Pacific Ocean and are expected to strengthen during the southwest monsoon season, according to the latest climate bulletin issued by the Earth System Science Organisation (ESSO) and the India Meteorological Department (IMD).

The agencies said both oceanic and atmospheric indicators now clearly reflect El Nino conditions. Sea surface temperatures across the Pacific are above normal, while warmer-than-average waters have also been detected below the ocean surface.

What is El Nino?

El Nino is a climate phenomenon that occurs when sea surface temperatures in the central and eastern equatorial Pacific Ocean become unusually warm. The warming disrupts normal wind patterns and atmospheric circulation, influencing weather systems worldwide.

The event develops when trade winds weaken, allowing warm ocean waters that are usually concentrated in the western Pacific to spread eastward. This shift can trigger floods in some regions, droughts in others, and often contributes to higher global temperatures. El Nino is one phase of the El Nino–Southern Oscillation (ENSO) cycle, whose opposite phase is La Nina.

Pacific and Indian oceans warming

During May, sea surface temperatures remained above normal across the central and eastern equatorial Pacific. Similar warming was observed in the western Pacific, the Maritime Continent region, and across parts of both hemispheres.

The Indian Ocean also stayed warmer than average, including the Arabian Sea and the Bay of Bengal. Compared with April, warming expanded across large stretches of both the Pacific and Indian Oceans, indicating a strengthening trend.

ENSO shifts to El Nino

The ENSO cycle has undergone rapid changes over the past year. Conditions remained neutral through mid-2025 before shifting to La Nina between August 2025 and February 2026. Neutral conditions returned in March, but by June the Pacific had warmed sufficiently to reach El Nino thresholds.

According to the IMD bulletin, warm subsurface waters are particularly evident in the eastern Pacific, providing favourable conditions for further strengthening. Forecasts from the Monsoon Mission Coupled Forecast System (MMCFS) indicate El Nino is likely to intensify between June and September and persist through the monsoon season.

Indian Ocean Dipole remains neutral

The Indian Ocean Dipole (IOD), a climate pattern driven by temperature differences between the western and eastern Indian Ocean, remains in a neutral phase after stabilising in January 2026 following a brief negative phase late last year.

Current model projections suggest the IOD will stay neutral throughout the southwest monsoon. Although some subsurface warming is present in the central equatorial Indian Ocean, it is not strong enough to trigger a phase change.

Outlook

Climate models point to sustained warming in the central Pacific through the June-August period, with further expansion expected in subsequent months. El Nino could strengthen to moderate or even strong levels during the southwest monsoon, while conditions in the Indian Ocean are forecast to remain largely stable.