Global Analysis - January 1999


Global Temp Anomalies, Jan
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Line separating section as of the report
Strong easterly winds across equatorial Pacific Ocean promoted upwelling of cold water in the eastern half of the Pacific Basin. These conditions, known as La Niña, brought dramatic changes to temperature and precipitation throughout many areas of the world in January. Many locations that received above normal precipitation in January 1998, when El Niño was dominant, were dryer than normal under current conditions. Conversely, other areas that were dry in January 1998 received abundant precipitation in January 1999.

Top of Page Temperature

Mean monthly temperature anomalies for January (using a base period 1880-1998) are show in the above figure. The combined land and sea surface temperauture anomaly for January 1999, 0.46C, shown in the top time series, remains well above the mean value, but it exhibits a considerable drop from the previous year. The ocean temperature anomaly for 1999, 0.27C , exhibits an even more pronounced drop from the 1998 value, which corresponds to the shift from warm to cold water in the east equatorial Pacific Ocean.

In contrast the land anomaly for January, 0.89C , remained well above the 1880-1998 average temperature. This was 0.02C above last years average temperature but 0.12C less than the highest January temperature recorded in 1932. This suggests that the land surface is retaining much of the warmth gained during the previous El Niño event.

GlobalTemp Diff, Jan99-Jan98
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The change in temperature between January 1998 and 1999 can be seen in the adjacent figure. Red dots indicate that temperatures were warmer in 1999 and conversely the blue dots correspond to warmer temperatures in 1998. The size of the circle indicates the magnitude of the difference between the two years.
In January 1999, temperatures were warmer throughout most of Canada where the difference reached 8.0C across the northern tier of the country. There was also a large area of warmer temperatures stretching eastward from the Mediterranean through the southern half of Russia into the Far East. The greatest difference occurred over south western Russia where values reached 7.0C.

In contrast, January 1999 brought colder temparatures across a band stretching from Finland through Siberia into Alaska. Some reporting stations near Moscow averaged more than 8.0C colder than they did in 1998. Temperatures were also colder in Eastern Europe and the western Mediterranean.

Land surface temperatures across a large portion of the world continue to be above their long-term mean. The adjacent plot shows abnormal warmth throughout most of North America, Europe and Asia. Above average temperatures also continued to occur in the southern tip of South America and the southern half of Australia.
GlobalTemp Anomalies, Jan99
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U.S. Temp Anomalies, Jan
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Preliminary data for January 1999 across the contiguous United States indicate that temperatures averaged above the long-term mean, ranking the 13th warmest January since 1895. The bars in this graph are departures from the 1895-1998 mean. The curved line is a nine-point binomial filter which shows the decadal-scale variations. This curve suggests that the last eleven Januaries have averaged much warmer than normal.

Top of Page Precipitation

Globally averaged precipitation for the month of January was higher in 1999 than at any time in the past. Precipitation averaged 20.6 millimeters above the 1900 - 1998 mean. This was 17.8 mm above the January 1998 average. Although precipitation averaged well above normal for the globe as a whole, there were many areas that were drier than normal in January.
Global Land Precip, Jan
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Global Precip Diff, Jan99-98
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The shift from El Niño to La Niña conditions corresponded to a shift in precipitation patterns throughout many areas of the world. The changes in precipitation that this shift created can best be seen in a plot of differences between January 1998 and January 1999. In the figure to the left, areas that received more precipitation in 1999 are represented by green dots; conversely, areas that were drier in 1999 are represented by brown dots.
In January 1999, the sub-tropical jet stream was much weaker than the previous year, which reduced the precipitation over the western third of the U.S. At the same time a ridge dominated southeastern China and Japan, which promoted dry conditions. Colder sea surface temperatures in the equatorial Indian Ocean corresponded with dry conditions along adjacent East Africa.

In 1999 it was wetter in the southwest Pacific as sea surface temperatures rose above normal and the easterly waves brought tropical systems to the area. Most of South America was wetter in 1999 than in 1998, as strong easterlies returned Atlantic moisture to the continent. Although there was one notable exception: north eastern Argentina was exceedingly wet last year as well. The rainy season in North Africa was stronger than normal, and higher elevations received significant snowfall.

Although some mid and high latitude areas of the Northern Hemisphere were drier than normal, on average these regions received above average rainfall. Areas in the 85N-55N latitude band averaged 4.3 mm (.17 in) above the long term mean. This was an increase of 8.3 mm over last January's average value, but well below the highest average of 17.0 mm recorded in 1949. Precipitation in the mid-latitude band (55N-30N) was 11.7 mm (0.46 in) above the long-term mean and 4.9 mm greater than last year's average. This was not far from the highest recorded average for this band; 14.4 mm recorded in 1968.
Global Precip by Lat, Jan
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Further south in the 30N to 10N latitude band, precipitation amounts were similar to last years average; 12.2 mm versus 12.7 mm recorded in January 1998. But in the equatorial band (10N - 10S) precipitation dramatically increased. Due in large part to the heavy rains in the Southwest Pacific (previously discussed), precipitation in this latitude band was 100 mm (3.9 inches) above the long term mean. This was by far the most precipitation ever recorded in this latitude band. It is 33 mm (1.3 inches) above the previous record anomaly.
US Precip Anomalies, Jan
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January 1999 was the 13th wettest such month since 1895 for the contiguous United States, based on preliminary data. The bars in this graph are departures from the 1895-1998 mean. The curved line is a nine-point binomial filter which shows the decadal-scale variations. The data indicate that the last five Januaries have been unusually wet when precipitation is areally-averaged across the country.

Top of Page Wetness

The surface was wetter than normal across northern Pakistan, Ohio River valley of the U.S., northwest Africa and the British Isles. In contrast, the surface was drier than normal in areas around the Black and Caspian Seas, eastern Australia, far eastern Mediterranean, and southeastern China.

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Top of Page Extremes

Numerous weather related natural disasters occurred in January 1999. In the U.S., a record number of tornadoes (169) occurred- that is about ten times the January climatological norm. A full report on selected global extremes is available at the Climate Watch-January 1999 WWW page

Citing This Report

NOAA National Climatic Data Center, State of the Climate: Global Analysis for January 1999, published online February 1999, retrieved on October 30, 2014 from http://www.ncdc.noaa.gov/sotc/global/1999/1.