 Global Temperature
Mean monthly temperature anomalies for the three-month period December through February (using a base period 1880-1998) are show in the above figure. The combined land and sea surface temperature anomaly for December 1998-February 1999, 0.496 degC, shown in the top time series, remained well above the mean value, but it exhibited a drop from the previous year. The ocean temperature anomaly for Dec98-Feb99, 0.328 degC, exhibited a similar drop from the '97-98 value, which corresponds to the shift from warm to cold water in the east equatorial Pacific Ocean. The land anomaly, 0.889 degC, remained well above the 1880-1998 average temperature.
| Land temperatures continued to be above their long-term mean (1880-1998) throughout many areas of the world during the December through February period. Temperatures were more than 2 C above average over most of the United States and Japan with areas in the Central US reporting temperature anomalies near 4 C. Temperatures were from 1 to 2 C above average in most areas of Europe with anomalies as large as 3 C in Norway.
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Above average temperatures were also recorded in Russia, China and India while near normal temperatures prevailed across Australia. Temperatures along the west coast of the United States and the southern two-thirds of Alaska were below average as upper level flow in the western US was dominated by a persistent low pressure trough throughout much of the Northern Hemisphere winter.
Global Precipitation
La Niña was a major factor influencing precipitation patterns during the Northern Hemisphere winter. Above normal sea surface temperatures in the western Pacific (http://psbsgi1.nesdis.noaa.gov:8080/PSB/EPS/SST/climo.html) contributed to precipitation that was 475 mm (18.7 inches) above normal across the islands of the southwest Pacific during the December through February period. Cooler sea surface temperatures in the equatorial eastern Pacific shifted the flow of moisture north along the western United States coast and resulted in drier than normal conditions in the southwest US and extremely wet conditions along the northwest coast. Precipitation was as much as 101 mm (4.0 inches) below normal in areas of the southwest US and 120 mm (4.7 inches) above average in the northwest.
| Extremely dry conditions prevailed across Japan, Korea and southeastern China as a large ridge of high pressure persisted over the region throughout the period. Dry anomalies as large as -109 mm (-4.3 inches) were recorded in parts of Japan. Southwestern areas of Africa received near normal precipitation while the Mediteranean region was slightly drier than normal. Countries across Europe were wetter than average, with precipitation as much as 155 mm (6.1 inches) above average in northern areas of the United Kingdom.
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Although some high latitude areas of the Northern Hemisphere were drier than normal, on average this region received above average rainfall during the period December 1998-February 1999. Areas in the 85N-55N latitude band averaged 18.9 mm (0.75 in) above the long term mean. This was an increase of 9.1 mm over the Dec'97-Feb'98 average value and below the highest average of 23.1 mm recorded in 1990.
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Precipitation in the mid-latitude band (55N-30N) dropped significantly as El Niño was replaced by La Niña. Precipitation was 4.0 mm (0.16 in) below the long-term mean and 25.5 mm (1.0 in) less than last year's average. Further south in the 30N to 10N latitude band, precipitation continued to be near-normal.
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Global Snow Cover
This snow cover anomaly map indicates areas which had more days with snow cover than is normal for the month (indicated as a positive anomaly with shades of green and blue) as well as areas which had fewer than normal days with snow cover (indicated as a negative anomaly by shades of yellow and red).
| The percentage of days with snow cover was greater than normal from December 1998 through February 1999 over the central west coast of North America. This positive anomaly extended into the northern plains. In contrast, further south and east there was less than normal snow cover.
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Above normal snow cover was found through most of Europe extending eastward into the Ukraine. In the Caucasus Mountains and the region around the Caspian Sea, the anomaly was less than average whereas further eastward much of northwestern China had above normal snow cover.
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
-or-
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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