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El Niños and anti-El Niños (La Niñas) are known to be associated with rainfall extremes in several parts of the globe. However, not all El Niños show good associations. Recently, a finer classification of El Niño events was attempted. It was noticed that Unambiguous ENSOW (El Niño–Southern Oscillation, Warm) events (years when El Niño existed, and the Tahiti minus Darwin pressure difference (T−D) minima and equatorial eastern Pacific sea surface temperature (SST) maxima occurred in the middle of the calendar year) were very well associated with droughts in India and southeast Australia (Tasmania). In addition, C (cold SST, La Niña) events showed reverse effects (excess rains) in these regions. In the present paper, rainfall in selected regions in Central and South America are examined. For the Southern Oscillation Core Region (low latitudes, 155°W–167°E) and for the Gulf–Mexico region, no finer classification was necessary. All El Niños were associated with excess rains and all La Niñas with droughts. As in India and Tasmania, Unambiguous ENSOW years were associated with droughts in some parts of northeast Brazil (Ceara, Rio grande do Norte, Paraiba, Pernambuco) and excess rains in Chile and Peru. C events did not have good associations except in Chile and Peru, where droughts occurred. The effect of El Niños showed some dependence on the month of commencement. In years when El Niños showed no effect, considerable influence of other factors (e.g. Atlantic SST on northeast Brazil rainfall) was noticed. Thus, predictions based on El Niño alone are likely to be erroneous, a fact which should be noted by the mass media. Effects of the recent El Niño of 1997–1998 are discussed. Copyright © 1999 Royal Meteorological Society
R. P. Kane (Tue,) studied this question.