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IRI Climate Information Digest
June 1998

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El Nino/Southern Oscillation (ENSO): LA NINA CONDITIONS CONTINUE TO EVOLVE - An area of below normal sea surface temperatures continues to expand in the central equatorial Pacific marking the demise of the 1997/1998 El Nino episode and the further evolution of La Nina (Cold Episode) conditions. The rate of temperature decrease in the central Pacific has slowed somewhat reflecting a cold-episode evolution more in agreement with earlier coupled-model and statistical forecasts. If current trends continue, moderate La Nina conditions can be expected by late Northern Hemisphere summer to early fall.


Despite a dramatic shift towards La Nina (Cold Episode) conditions in sea surface temperature and the ocean substructure throughout most of the equatorial Pacific and relatively warm water has persisted along the West Coast of South America. There are no large rainfall anomalies along the immediate South American coast but satellite estimates suggest enhanced rainfall in ocean areas off the Colombia coast and south of Central America. The region of enhanced rainfall corresponds to the area of warmer sea surface temperatures. Much drier conditions were observed over the land areas to the north (Central America and southern North America). The dry areas have been linked to local atmospheric circulation features induced by the local positive sea surface temperatures.

Global Monsoon Rainfall: A mixed start

June generally marks the beginning of the monsoon summer rains in many Northern Hemisphere locations. The rains have been somewhat slow to develop in the Sahel and in southern Mexico. June rainfall over India has averaged above normal with a strong gradient from the relatively wet West Coast to relatively dry in the east.

Forecasts - for temperature and precipitation
Impacts - on fisheries, agriculture, and hazards.

Material for the IRI Climate Information Digest has been extracted from the IRI Climate Data Library, the IRI Experimental Forecast Division, the NOAA NCEP Climate Prediction Center, the Climate Diagnostic Center, and the NOAA ERL Pacific Marine Environmental Laboratories. Additional information has been obtained from the Bureau of Meteorology, Australia, and INPE, Brazil.