IRI Climate Information Digest - March 1999
Highlights The La Niña (cold episode) continues to evolve as expected. Colder than average water continues to characterize the equatorial Pacific. A patch of warmer water in the eastern Pacific that briefly caused some concern along the west coast of South America during February had all but disappeared by the end of March. The magnitude of the La Niña has been slowly decreasing but the equatorial sea surface temperatures remain 1 to 2 degrees Celsius below average from 160 East through approximately 150 West longitude. Numerical computer models and statistical forecast tools are in general agreement for the continued slow demise of this La Niña over the next four to five months.
Precipitation Patterns Rainfall in the tropical Pacific continues to be strongly influenced by the current La Niña. Typical of the La Niña phenomena, there is a sharp dividing line between the areas of heavier than average rainfall in the far west Pacific and the areas of drier conditions further to the east. During January to March this dividing line was near 140 E longitude, with satellite estimates showing most of the area from Papua New Guinea eastward to be dry and much of Indonesia to be wet. Much of the southern tier of the United states and Northern Mexico were also dry, a typical La Niña pattern. Not typical of La Niña was the above average rainfall along most of the South America's West Coast and also in northern Argentina. Dry conditions in eastern Brazil were likely associated with Atlantic sea surface temperatures. In eastern Africa wetter than average rainfall was observed from Ethiopia southward through Tanzania, also not a typical La Niña pattern.
Temperature Above average temperatures characterized most of
the land areas of the world for the January through March period 1999.
Virtually all of Africa experienced above average temperatures.
Small pockets of below average temperatures included far eastern Siberia
through Alaska, central Brazil and the coastal sections of north Western