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. 

Temperatures Over Land

Above average conditions were again the main feature of global temperature patterns in April.

Europe:  After an unusually warm winter across central and southern areas, temperatures returned to near average in April.
Asia:  Temperatures were well above average from western Russia southward to Iran and Pakistan.  Cooler than average conditions again prevailed across the Central Siberian Uplands.
Africa:  From the equator northward, most of northern Africa was unusually warm in April.
Australia:  Lower than average temperatures continued across central areas of Western Australia.
North America:  Much of northern Canada and Alaska were unusually warm as were central sections of the United States.

Temperature Difference from the 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS.

Precipitation

Below average rainfall failed to bring relief to drought-stricken areas in western Asia, Brazil, southwestern Western Australia and New Zealand.  Unusually heavy rainfall developed across southwestern Africa and continued across areas in the equatorial west Pacific.

Africa:  Rainfall was well above average in southwest Africa from the Gulf of Guinea southward to Angola , Namibia, and central South Africa.
South America:  Below average rainfall continued across central Brazil and from Colombia to French Guiana to the north.  By contrast, central Argentina was unusually wet as were sections of northern Peru, primarily due to raingfall early in the month.
North America:  Much of the eastern United States was unusually dry while heavy rainfall across the US Midwest contributed to flooding along the Missippi River.
Central America and Caribbean:  Below average rainfall was observed across much of the region.  Drought conditions began to emerge across parts of eastern Cuba.
Europe:  Unusually heavy rainfall from central Poland northward to Scandenavia.
Asia:  Precipitation continued below average across Afghanistan and much of Iran.  Unusually dry conditions were also observed across Burma, northern Thailand and the Korean Peninsula.
Australia:  Rainfall deficits continued across southern sections of Western Australia as well as and coastal Queensland and New South Wales.

Precipitation Difference from 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS-OPI.

Oceanic Conditions

Tropics:  The weakening of modest La Niña conditions continued in April with sea surface temperatures (SSTs) returning to near-average in the central equatorial Pacific.  The above average SSTs which developed over the past few months in the eastern Pacific weakened substantially during April and were only slightly warmer than average by the end of the month.  Currently, most statistical and computer models predict SSTs in the eastern equatorial Pacific to be near to slightly above average for the next six months.
Conditions in other tropical basins have not changed significantly from the previous month.

Midlatitudes:  Above average SSTs continued across much of the Indian Ocean. Above average SSTs were located along much of coastal South America and Africa in the Southern Hemisphere, with above average SSTs also persisting along coastal sections of the western North Pacific.

Monthly Sea Surface Temperature Difference from the 1950-1979 mean, with data from the Environmental Modeling Center, NCEP/NOAA.

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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