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IRI Climate Digest   April 2000

April Global Climate Summary

Climatological Background In April, the sun's migration into the Northern Hemisphere has begun, bringing springtime to the northern mid-latitudes. The monsoon systems which still linger south of the equator will move northward following the solar heating of the continents in the next two months. In the southern hemisphere fall has arrived, with cooler temperatures and a strengthening of the mid latitude storm tracks.


Monthly Mean Temperature (1961-1990), data from the Climate Research Unit, University of East AngliaClick for options and more information
Monthly Mean Precipitation (1961-1990), with data from the Climate Research Unit, University of East AngliaClick for options and more information

Temperatures Over Land
North America:  In contrast to recent months, only the western United States experienced above average temperatures.  Near average conditions prevailed elsewhere except for below average temperatures in the southeastern United States.
Europe and Asia:  With the exception of southeastern Asia, temperatures continued above average over most of the entire region.  Temperatures were more than 4C above average from eastern Europe eastward to the Aral Sea.
Africa:  Temperatures were above average across most of northern and eastern Africa as well as Madagascar.  Near average conditions were observed elsewhere.
Australia: Western Australia once again experienced below average temperatures.  The remainder of the continent saw near average conditions.
South America: Temperatures were 1 to 2C above average across central and southern Brazil as well as Uruguay, Paraguay, Bolivia and northern Argentina.
 
 

Temperature Difference from the 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS.Click for options and more information

Precipitation
Africa: Unusually dry weather continued over eastern Africa from southern Ethiopia southward into Kenya, southern Somalia and northern Tanzania.
Above average rainfall was again observed in southern Africa in a band extending from northern Angola eastward across Botswana, Zimbabwe and southern Mozambique.  Rainfall in central Morocco brought limited relief to dry conditions there.
Australia: Tropical cyclone activity was primarily responsible for above average precipitation in northeastern Western Australia and much of the Northern Territory. 
Indonesia:  Above average rainfall was observed throughout the region with localized very heavy rains.
Southeast Asia:  Precipitation was well above average across Malaysia as well as much of Thailand and Burma.
China:   Below average rainfall was observed across the North China Plain.  Locally heavy rains along the central east coast resulted in above average precipitation there.
South America:  Below average rainfall occurred over western Venezuela and central Columbia as well as portions of southeastern Brazil.  Above average rainfall totals were observed in northwestern Argentina and from eastern Venezuela eastward to French Guiana.
Middle East: Rainfall continued to be below average across much of the Middle East eastward to Afghanistan and Pakistan. 
United States: Below average rainfall continued in the upper midwest. 
Europe:  Above average rainfall was observed over northern and western Europe including the Iberian peninsula which helped to ease dry conditions there.  Below average precipitation was reported across central Europe from Poland southward to the Mediterranean Sea. 

Precipitation Difference from 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS-OPI.Click for options and more information

Oceanic Conditions
 Tropics: The moderate La Niña (colder than average) conditions in the central equatorial Pacific weakened from the previous month and are expected to continue to weaken. The positive anomalies in the eastern equatorial Pacific continued to strengthen but remain a near surface phenomenon in the ocean. This evolution is unlike a typical El Niño onset but the warm ocean temperatures may enhance rainfall locally.
 Extratropics: Above average SST anomalies continued to dominate the mid latitude oceans of both Northern and Southern hemispheres, as has been the case for most of the past two years. Colder than average SSTs have been expanding in the North Pacific. 


Monthly Sea Surface Temperature Difference from the 1950-1979 mean, with data from the Environmental Modeling Center, NCEP/NOAA.Click for options and more information
Material for this Global Climate Summary has been extracted from the IRI Climate Data Library, the NOAA NCEP Climate Prediction Center, the Climate Diagnostics Center , and the NOAA ERL Pacific Marine Environmental Laboratories. Additional information has been obtained from the Bureau of Meteorology, Australia, and CPTEC, Brazil.

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