NOAA's National Centers for Environmental Information
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Temperature
| Land and ocean temperatures continued to average well-above the 1880-1999 long-term mean in April (see figure above). The average temperature anomaly for both land and ocean surfaces was 0.51C, slightly cooler than the record warm temperatures recorded during the 1998 El Nino episode. Sea surface temperatures averaged 0.35C above the long-term mean, the sixth warmest April since 1880. As in recent months, the much warmer than average global temperatures were largely due to a continuation of the extemely warm conditions observed over Northern Hemisphere land surfaces. The global land temperature anomaly was 1.01C in April, second only to the 1.27C anomaly recorded in 1998. With no stations in Africa reporting at the time of this report, the Southern Hemisphere land anomaly (0.16C) was only the 25th warmest on record, while the average anomaly over the Northern Hemisphere was 0.93C, only 0.09C less than the record 1998 temperature (see figures below). |
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Widespread above-average temperatures over Northern Hemisphere land surfaces can be seen in the adjacent plot. A persistent high pressure ridge produced much above average temperatures throughout Eastern Europe in April with temperatures more than 3C above the 1961-1990 mean stretching from Scandinavia to the Mediterranean and Southwest Asia. |
| Warmer than normal conditions also blanketed much of Asia for the third month in a row, as temperatures from 2 to 4C above normal occurred in many areas. Warm anomalies also stretched across the Northwest Territories of Canada, Alaska and the western United States. A persistent northwesterly flow brought slightly cooler than normal temperatures to eastern areas of the United States in April. Near-normal temperatures were observed in southern Canada and the Far East. Temperatures were near normal over much of the South American continent in April, while cooler than normal conditions prevailed over much of Australia as the effects of tropical systems brought cooler and wetter than normal conditions to the continent. |
Precipitation
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Australia received heavy rainfall from two tropical cyclones in April. Cyclone Tessi crossed the northeast coast early in the month and Cyclone Rosita, a strong category 4 storm at one time, struck remote areas of the northwest coast near Broome later in the month. Some northern areas received precipitation totals in excess of 600mm (24in) above the 1961-1990 average, while areas in the south reported near normal precipitation totals. |
| Much above normal precipitation also fell throughout much of Brazil, with the greatest extremes recorded along the Amazon basin. Above normal precipitation fell across much of Western Europe as a persistent westerly flow throughout the month brought unsettled weather to the region. Eastern and western coastal areas of the United States were wetter than normal while central areas were slightly drier than normal. For additional details on precipitation and temperatures in April see the Global Regional page . |
References:
Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global
Historical Climatology Network Database. Bull. Amer. Meteorol.
Soc., 78, 2837-2849.