Global Analysis - June 1999
The above figure shows June 1999 temperature anomalies calculated from available in-situ stations using an 1880 - 1998 base period. Temperature anomalies are absent from several areas of the globe due to a lack of reporting stations. To improve spatial coverage of global temperature anomalies, satellite data has been combined with in-situ station records in the spatial temperature plot below.
|Preliminary mean monthly temperature anomalies (using a base period 1880-1998) for June are shown in the figure to the left. June 1999 land and ocean temperatures were much lower than the record values recorded in 1998, but temperatures remained above the long term mean for the 23rd year in a row. This continues a trend to lower monthly anomalies that began with the end of El Niño in 1998. The average temperature over land and ocean was 0.33 C above the mean, the fourth coolest June this decade. Although both land and sea surfaces were much cooler in June 1999, when compared to June 1998 temperatures, the trend toward cooler temperatures continued to occur at a faster rate over ocean surfaces. The sea surface temperature anomaly fell from 0.51 C in June 1998 to 0.22 C in 1999. Global land temperatures averaged 0.58 C above the long term mean in June 1999, 0.32 C cooler than in June 1998.|
The extremely warm temperatures in Scandinavia and Eastern Europe were the dominant feature in June. These anomalies were associated with a persistent upper level ridge that covered the region for almost the entire month. Also noteworthy were the cold sea surface temperature anomalies that have persisted in the east equatorial Pacific for almost a year. These anomalies are associated with La Niña conditions that continue to prevail over the tropics. Another feature in June was the warm anomalies in north eastern North America, where temperatures averaged much above normal and which was associated with an upper level ridge.
Warmer than average temperatures also covered much of northern Africa, central Asia and southeastern Brazil. A trough over a portion of central Russia kept that area cooler than average. It was also colder than usual in northern Mexico and the central plains of the United States in association with above average cloud cover and above average precipitation. Some cold air outbreaks influenced eastern Australia during this winter month in the Southern Hemisphere.
As shown in the adjacent figure, global precipitation (land only) averaged below the long term mean (1900-1998), indicating global reporting stations were generally drier than average in June. The average anomaly was 2.8 mm (0.11 in) below the long term mean, 4.2 mm (0.16 in) less than in June 1998.
larger image Above average precipitation was widespread in only a few areas of the world in June. Conditions were wetter than average in a band from the central plains to the southeastern United States. A persistent low pressure trough also brought above average precipitation in an area that stretched from Great Britain through much of Scandinavia. Above average rainfall also stretched from the Baltics to the western two-thirds of Turkey. The majority of Korea and Japan was also wetter than average in June. The largest positive anomalies (greater than 250 mm (10 in)) were recorded in parts of western India.
A large band of drier than average conditions stretched from Portugal across the Mediterranean to the Middle East. Parts of the Middle East continued to endure a drought that has damaged crops and forced the implementation of water use restrictions. Drought conditions also prevailed across much of the Sudan region of Africa as precipitation was again below average in June. Much of western Russia was also drier than average in June, as a dominant upper level ridge suppressed precipitation. Large areas of below average precipitation are also shown in much of eastern China, the eastern third and western border of Brazil, and the northeastern part of the United States.
In contrast, the below average June wetness in north central Russia corresponded with unusally warm May temperatures and a premature melting of the snow pack. The plains states of the central U.S. were in an active storm track, keeping the area wetter than usual. The region north of the Black Sea and much of eastern Argentina were drier than average. There were spotty areas of positive wet anomalies over northern Mexico, India, and central China. Spotty areas of dry anomalies were evident over part of India, eastern U. S., northern China and the Sahel in Africa.
The snow cover in extreme northeastern Canada normally melts in June. However due to unusually cold weather it persisted later into the summer, leaving below average wetness values on the surface. Further southward, the snow, which normally melts in May, lingered until June, resulting in above average wetness values this month.