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EL NINO

El Niño is a disruption of the ocean-atmosphere system in the Tropical Pacific having important consequences for weather and climate around the globe.

Over the Seychelles, El Nino, normally enhances the chance of rain during the DRY season (March to October) with two distinct months May and August having substantial increase in rainfall amount. This in effect shortens our dry season.

During the years of 1982-1983 and 1997-1999, the El Nino-Southern Oscillation (ENSO) was so severe that several regions of the world, including small island states experienced economic and human losses. In The Seychelles, the 1997-1999 ENSO resulted in several impacts which led to economic and infrastructure losses, especially in the tourism sector and the coastal areas. The main climatic events, being extreme rainfall leading to flooding and landslides, elevated sea-surface temperatures resulting in severe coral bleaching and followed by extended droughts causing acute water shortages.

Link: http://www.elnino.noaa.gov/

ENSO (El Nino Southern Oscillation)
El Nino episodes occur roughly every four to seven years. Certain changes typically occur during an El Nino period, these are wind velocity, sea surface temperature, surface air pressure, Southern Oscillation (SO) and the sea level.

Southern oscillation refers seesaw shift in surface air pressure in Darwin, Australia and south pacific island of Tahiti. During El Nino episodes it is observed that the pressure is high at Darwin and low at Tahiti. This pattern of pressure is associated with weaker than normal near surface equatorial easterly winds. These features characterise the warm phase of the southern oscillation that often referred to El Nino/Southern Oscillation (ENSO) episode.