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National Oceanic and Atmospheric Administration

Climate of 1999 - July
Global Regional Analyses

National Climatic Data Center, 13 August 1999

Global Wetness Product
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The summer monsoon rains over Mexico and the southwest U.S. were stronger than normal in July, which caused above average surface wetness. It was also wetter than average across the Plains near the U.S.-Canadian border. The snow in northern Canada was slow to melt this summer, which promoted above average surface wetness in July. This was also true for north central Russia. Heavy rains fell across eastern portions of the Indian subcontinent and brought major flooding across portions of eastern India and Bangladesh. Heavy rains also caused flooding in the Yangtze river basin in China. In contrast, rainfall was below average across the remainder of western and the southern portions of Asia. Much of southeastern Australia was drier than usual, while the adjoining area to the southwest had above average rainfall. Rainfall in the Sahel region of Africa was above average, but some sectors experienced unusually dry conditions.

General July 1999 mean upper air circulation patterns anomalies are available for the Northern Hemisphere and Southern Hemisphere. An animation depicting the Northern Hemisphere flow is also available.


Top of Page Africa and Mideast Temperature

The warmest anomalies this month occurred over portions of southern and southwestern Africa. Warm anomalies were also noted over northwest Africa and across portions of the Middle East. Deficit rainfall and warm temperatures have stressed crops over portions of these areas. Negative temperature anomalies covered a broad portion of the Sahel. Much of this region experienced a good deal of cloudiness and above average precipitation. The center of the Sahara desert and portions of Mozambique were cooler than average. Africa and Mideast Temperature
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Top of Page Wetness Anomalies in Africa and the Middle East

Liquid Water in Africa
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The wetness values over much of the Sahel were above average. This is normally their growing season, and the water is greatly needed for agriculture in this area. Sudan and Chad are exceptions in the Sahel, since regions in these two countries had large negative wetness anomalies and it appears that a drought is developing in those regions. There were also drier than average conditions in the equatorial area of the Great Rift Valley and Zaire.

Top of Page European Temperature

The warm anomalies across portions of eastern Europe and western Asia persisted for the second month in a row. These anomalies are associated with an upper level ridge of high pressure north of the Black Sea. Fires have been reported across this region this summer and have burned nearly 1.5 million acres in the Former Soviet Union (FSU). Cool anomalies associated with a trough of low pressure to the south and east of the upper ridge were observed east of the Caspian Sea. European Temperature
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Top of Page Wetness Anomalies in Europe

Large positive wetness anomalies associated with a low pressure trough were observed over portions of southeastern Europe. Flooding was reported over the middle and northern regions of Slovakia. Also, parts of Hungary again were affected by flooding with damages to crops and structures reported at 400 million U.S. dollars. Over 200,000 acres of agricultural land and 108 miles of public road were also affected. Two additional upper level troughs were in evidence across this region. One trough led to positive wetness anomalies over northern and central Siberia. The other trough was centered over Greenland and sent areas of associated low pressure and moisture across portions of northwestern Europe.
Liquid Water in Europe
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In contrast, large negative wetness anomalies were associated with a strong ridge of high pressure which extended from the Black Sea area north and eastward toward the Ural mountains and the Caspian Sea. Negative anomalies were also observed across portions of Spain and eastern Scandinavia.

Top of Page Asia Temperature

Asia Temperature
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A strong upper air ridge of high pressure centered over Mongolia kept that area very warm during the month. These warm conditions extended both east and west from that region to cover a large portion of eastern Asia. In contrast, negative temperature anomalies were observed east of the Caspian Sea and across portions of south China. These areas experienced cloudiness and precipitation with major flooding reported along portions of the Yangtze river in China. This was the second year in a row that the Yanzgtze River basin reported major flooding. See Flooding in China- Summer 1998 . Elsewhere across the region, portions of eastern India and Bangladesh were cooler than average while it was warmer than average across portions of Pakistan and western India.

Top of Page Wetness Anomalies in Asia

Large positive wetness anomalies were observed across eastern India and Bangladesh where heavy rains brought flooding. According to government reports, the flooding in Bangladesh left more than 100,000 people homeless. Flooding in eastern India caused over 200 deaths, 3,212 villages affected, and 15,058 houses damaged. The heavy rains were restricted to a small portion of the subcontinent, while the rest of India and Pakistan observed negative wetness anomalies and below average rainfall. July is one of the most important months in this region's growing season, and these drier conditions have stressed many crops.
Liquid Water in Asia
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It was also drier than usual in eastern Thailand and in Vietnam along the Mekong River Delta. The rice growing areas in central Cambodia and Thailand were wetter than usual with some flooding reported. Spotty areas of both anomalous wet and dry conditions covered sections of China; the lower Yangtze was wet, while to the north there were large areas that had drier than average conditions. Flooding along portions of the Yangtze river resulted in 291 deaths and flooding across the provinces of Anhui and Zhejiang have caused an estimated $2.87 billion U.S. dollars worth of damage and displaced 1.5 million people.

Top of Page North American Temperature

The upper-level flow across North America this month showed a fairly persistent upper-level ridge of high pressure over the Great Lakes and a trough across the western portion of the continent. This pattern generally allowed for cooler than average temperatures across the southern Rockies and far west while the dominant ridge in the east provided much warmer than average temperatures from the central Plains eastward. Occasionally, during the first half of the month, several mid-latitudinal troughs moved from west to east across the region. The cold bulls-eye in the Gulf of the St. Lawrence is erroneous, and efforts are under to correct the analysis. North American Temperature
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Top of Page South America Temperature

The South American continent as a whole continued to be cooler than average, which is associated with the La Niņa conditions in the east equatorial Pacific. This pattern has been quite consistent for the last several months. The coolest anomalies for the third month in a row were centered near the Argentina-Paraguay-Bolivia border. There were also significant cold anomalies along the Ecuador coast again this month which directly aligns with the cold pool of Pacific water. The only warm anomaly over South America occurred over east central Brazil. South America Temperature
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Top of Page South America Wetness Anomalies

South America Wetness
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A large section of northern Argentina had above average wetness, which is advantageous to the winter wheat crop. While the area around Buenos Aires had been drier than average this month, the area did get some beneficial rain toward the end of the month. A large area of extremely dry conditions prevailed over western Venezuela which is normally extremely wet at this time of year. The snow cover over southern Argentina was above average which corresponded to below average wetness. There were also unusually dry conditions in the usually wet, low-lying area near the Bolivia-Paraguay-Brazilian border.

References:

Basist, A., N.C. Grody, T.C. Peterson and C.N. Williams, 1998: Using the Special Sensor Microwave/Imager to Monitor Land Surface Temperatures, Wetness, and Snow Cover. Journal of Applied Meteorology, 37, 888-911.


For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:

Climate Services Division
NOAA/National Climatic Data Center
151 Patton Avenue, Room 120
Asheville, NC 28801-5001
fax: 828-271-4876
phone: 828-271-4800
email: ncdc.orders@noaa.gov

For more information, refer also to ...
SSMI Derived Products
Global Historical Climatology Network (GHCN)
The Blended GHCN - SSM/I Product
The Global Temperature Anomalies

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For further information on the historical climate perspective presented in this report, contact:

Alan Basist
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: alan.basist@noaa.gov
-or-
Tom Ross
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: tom.ross@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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