NOAA National Climatic Data Center 13 June 2003

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Climate of 2003 – May in Historical Perspective Including Boreal Spring

Global Highlights:

* Global average combined land and sea surface temperature was the second warmest for May 2003 and fourth warmest March-May 2003
* March-May 2003 temperatures were much above average across the western U.S. and Europe with below average temperatures in the northeastern U.S. and most of the Middle East
* Precipitation during March-May 2003 was above average in the southeastern U.S. and East Asia, with drier than average conditions over most of Australia, the lower Great Plains of the U.S. and India
* Cooler sea surface temperatures in the central and eastern equatorial Pacific continued to indicate development of La Nina conditions

Introduction

The March-May 2003 mean temperature was above the 1988-2002 average across Alaska, western Europe and most of Asia. Cooler than average temperatures occurred over southeastern Brazil and eastern Canada. The mean position of upper level ridges and troughs of low pressure (positive and negative 500 millibar height anomalies) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. May temperature anomalies calculated from the Global Historical Climatology Network data set of land surface stations (using a 1961-1990 base period) also show above average temperatures throughout much of Europe, the Middle East, East Asia and Mexico. Monthly temperatures were 2-4°C (3.6-7.2°F) above the mean. Cooler than average temperatures were present throughout the northeastern U.S. into the Great Lakes region and the eastern coast of Australia where monthly temperatures were as much as 1-3°C (1.8-5.4°F) below average.

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Temperature May

* For May 2003, the global average land and ocean surface temperature was 0.54°C (0.97°F) above the 1880-2002 average, ranking as the second warmest May in the period of record
* The warmest May occurred in 1998, when the global anomaly was
+0.66°C (+1.19°F)
* Globally averaged land temperatures were warmest on record, 0.96°C
(1.73°F) above the long-term mean
* May 2003 temperatures averaged across the Northern Hemisphere were second warmest on record, 0.61°C (1.10°F) above the long term mean
* Temperatures averaged throughout the Southern Hemisphere were fourth warmest, 0.45°C (0.81°F) above average
* Stratospheric temperatures in May 2003 were below average globally, with a departure of -0.31°C (-0.59°F)

Temperature: Spring 2003

* For March-May 2003, the global average land and ocean surface temperature was 0.55°C (0.99°F) above the long term mean, fourth warmest for boreal spring.
* Ocean surface temperatures were 0.40°C (0.72°F) above the 1880-2001 mean, third warmest for March-May 2003.
* March-May 2003 temperatures averaged across the Northern Hemisphere were sixth warmest on record, 0.58°C (1.00°F) above the long term mean
* Temperatures averaged throughout the Southern Hemisphere were third warmest, 0.48°C


(0.86°F) above average
* Globally averaged surface temperatures (land and ocean) have been warmer than the 1971-2000 average for the last 85 consecutive months
* March-May 2003 temperatures were below the 1984-1990 average in the lower stratosphere, -0.27°C (-0.49°F) cooler than the mean

Precipitation: Spring 2003 and May

* During March-May 2003, much above average precipitation fell across the southeastern U.S., northern Argentina and East Asia
* Below average precipitation was observed in southern Brazil, most of Canada and the majority of Europe and Australia
* During the month of May 2003 , unusually wet weather occurred in Scandinavia, western Europe and the East Coast of Australia while areas of Ethiopia, India and the Middle East experienced drier than average conditions.

ENSO

La Niña conditions continued to develop in May as sea surface temperatures further cooled in the central and equatorial Pacific. This trend as well as others, such as a steady deepening in the central and eastern equatorial Pacific oceanic thermocline are indicators of strengthening La Niña conditions.