State of the Climate
Global Analysis
January 1999
National Oceanic and Atmospheric Administration
National Climatic Data Center
Use the form below to access monthly reports.
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.
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 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.
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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.
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| 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. |
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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. |
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. |
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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.
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| 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. |
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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.
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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. |
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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Snow Cover
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Snowcover anomalies
were below normal in the region around the Black and Caspian Seas,
as well as the souther Rocky mountains of the U.S. Across both
these areas temperatures were much above normal and precipitation
was below normal. Snowcover associated with the “Blizzard of
1999" produced much above normal values over the northeastern U.S.
In general, the global circulation promoted above normal snowcover
in portions of southern Europe. |
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
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