Monsoon may be normal as El Nino recedes

The EL Nino, a geographical phenomenon in the Pacific Ocean, whose occurrence is generally correlated with a poor monsoon may not occur this year.

Instead, conditions are now turning favourable for the emergence of the La Nina, which normally has a positive influence over the monsoon.

The sea surface temperature in the equatorial Pacific ocean had begun rising in May and June indicating the likely development of the El Nino. This had generated the fear that the monsoon rainfall could be lower than that assessed earlier.

The India Meteorological Department (IMD) had projected this year's monsoon to be 95 per cent of the normal in its long-range forecast issued in April. The forecast was later revised downwards in June to 93 per cent of the normal.

However, the latest El Nino bulletin issued by the World Meteorological Organisation (WMO) categorically states that the development of the El Nino in the later part of 2007 is "very unlikely".

On the other hand, it maintains that it is possible that the La Nina (reflected in cooling of equatorial Pacific Ocean waters) may develop in the next one to three months. However, the timing and magnitude of this event has eluded accurate prediction.

El Nino, the Spanish word meaning Baby Christ, occurs when the sea surface temperature in the central and eastern tropical Pacific Ocean rises higher than normal. It has been found to have a substantial bearing on the climate patterns around the world, including the south-west monsoon that causes rains in India during this season year every.

The La Nina is the opposite of the El Nino and is marked by the sea surface temperatures in the Pacific Ocean being lower than the normal. The most recent strong phase of La Nina was experienced between 1998 and 2001. The monsoon was normal in all these years.

According to meteorologist, there has rarely been a poor monsoon in the La Nina years.

The El Nino generally has a negative influence on the monsoon rains, but there have been instances of normal rainfall during the El Nino years as well.

In all, in the past 107 years from 1901 onwards, there have been 20 years of strong La Nina events. Of these, only one year (1920) experienced a drought in India. In all the other years, the monsoon rainfall was either excess or normal.

On the other hand, there have been 24 El Nino years during this period. Of these, 9 years witnessed drought conditions.

This year, the conditions had begun turning favourable for the emergence of the La Nina from February onwards. But, this trend remained unsteady leading to its complete reversal in May and early June.

"A strong break in the pathway towards the La Nina occurred during May and early June, increasing the uncertainty over whether a La Nina would develop in 2007 or not", the WMO bulletin points out.

Significantly, the ocean temperatures have again begun falling from July onwards, emanating positive signals for the onset of the El Nina.

The WMO's current assessment points to a substantial likelihood of either the development of the the La Nina or a continuation of neutral conditions over the remainder of 2007. According to the WMO, the development the El Nino during this period is considered very unlikely.