National Oceanic and Atmospheric Administration

National Climatic Data Center, 17 June 1999

• Mar 1999 - May 1999: Climate Overview
• Detailed Climate Perspectives . . .
  • Global Analysis
    
  • Global Regional Analyses
    
  • U.S. National Analysis
    
  • U.S. Regional/Statewide Analyses
    
  • Extreme Events
    
• 1999 Monthly Reports

Global Temperature Mean monthly temperature anomalies for the three-month period March through May (using a base period 1880-1998) are shown in the above figure. The combined land and sea surface temperature anomaly for this period was 0.43 deg C, down 0.30 deg C from the record value recorded in 1998. The effects of the shift from El Niño to La Niña conditions are evident in both land and ocean temperatures. The ocean temperature anomaly, 0.26 deg C, was less than half the 1998 value, 0.55 deg C, while the average land temperature anomaly fell to 0.81 degC from 1.15 deg C in the year-ago period. Although global land temperatures have cooled below the record 1998 values, most land areas of the world continue to experience much above normal temperatures. The adjacent figure shows the largest positive anomalies in the March through May period occurred in the eastern half of Canada, with temperatures more than 4 deg C above the long term average in many areas. (Grid boxes contain at least 2 out of 3 months of data during the March - May period.) larger image

Temperatures were near average throughout much of the United States, with a small area of 2-3 deg C anomalies in the Northern Plains and a few isolated areas of below average temperatures in the western and southeastern United States. Above average temperatures (1-2 deg C in most areas) are widespread throughout Europe and extend into India and the Far East. The only area of widespread below average temperatures extends throughout a large part of Russia, although areas of slightly above average temperatures are interspersed among the negative anomalies. The lack of available reporting stations in Russia complicates the discernment of any clear temperature pattern.

Global Precipitation

As shown in the adjacent figure, global precipitation (land only) averaged 7.7 mm (0.30 inches) above the long term mean (1900-1998) in the March - May season. This is consistent with the trend toward above average precipitation totals that have been recorded throughout much of the past half century.

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Several areas experienced much above average precipitation in the March - May season. The most notable areas include the central United States, Argentina, much of western Europe and parts of southern China. Above average precipitation in southern China brought relief to some drought stricken areas of the country. Much of Argentina received well above normal rainfall, with many anomalies greater than 100 mm (4 inches). Precipitation in some areas of the central United States and western Europe was also more than 100 mm above the 1900-1998 mean.

While the central part of the United States received above average precipitation, much of the East Coast of the United States was much drier than average throughout the March - May season. Precipitation in the southeastern United States was as much as 100 mm (4 inches) below average in some areas. Areas along the southern coast of China were also much drier than average. A large band of near normal to below average precipitation extended from eastern Europe across Russia, Mongolia and northern China.

Global Snow Cover

A persistent trough over the northwest coast of North America kept snow covering the ground through the most of the spring, whereas further to the east, a persistent ridge forced the snow to melt much earlier than expected. Similarly the snow pack melted earlier than usual over central Europe, while unusually cold air over eastern Russia, allowed the snow season to extended later than usual into the spring season. The atmospheric wave pattern brought above average temperatures into central Russia, causing the snow to melt earlier than usual. Dry conditions over southwestern Russia and the Ukraine promoted a below average snow season. Cold air over eastern Russia and northeastern China promoted above average snow cover. As a whole the snow pack was less than expected across the Tibetan Plateau.

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For further information, contact:

David Easterling
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: david.easterling@noaa.gov

Mike Changery
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: mchangry@ncdc.noaa.gov

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