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National Oceanic and Atmospheric Administration

Climate of 1999 - September
Global Regional Analyses

National Climatic Data Center, 15 October 1999

Global Blended Temperature Product North American Temperature Anomalies South American Temperature Anomalies African Temperature Anomalies European Temperature Anomalies European Temperature Anomalies Australian Temperature Anomalies
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Several distinct anomalies were observed in the global circulation this month. Ridges of high pressure aloft over portions of the St. Lawrence River Valley in eastern Canada, much of central Europe, and near Korea and Japan kept these areas warmer than (1992-1999) average. Troughs of low pressure were over the eastern Atlantic, central Russia, and northeastern Siberia. These areas were generally cooler than average. Persistent cloudiness and precipitation across portions of the central plains of the U.S. and most of central and southern Africa were responsible for the cool wet conditions. In the southern hemisphere, a strong ridge of high pressure aloft over southern Australia and New Zealand was responsible for warmer than average conditions in those areas. The general September 1999 mean upper air circulation pattern anomalies are available for the Northern Hemisphere and Southern Hemisphere. An animation depicting the Northern Hemisphere flow is also available.


Top of Page Europe / Asia Blended Temperatures

A strong ridge of high pressure was anchored over central Europe during much of the month. This high pressure area was responsible for hot late summer weather across most of the region. Daytime average high temperatures were in the 30-38 degree C (86-100 F) range across portions of central Europe eastward into the Ukraine. Warm anomalies were also noted across portions of Pakistan, western India and eastern China. In contrast, cool anomaly areas were weak and restricted to the Ural mountain region of Russia and scattered across portions of northeast Asia. Europe / Asia Blended Temperature
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Top of Page Wetness Anomalies in Europe

Liquid Water in Europe
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A ridge of high pressure aloft over central Europe was responsible for hot temperatures during the month, as well as the dry weather reflected in negative wetness anomalies. These dry conditions extended from central Europe, southeastward across southern Russia, then eastward to the area just west of the Caspian Sea. Wetness anomalies were above average across parts of the Ural mountains in central Russia. A trough of low pressure in the eastern Atlantic was responsible for wet weather and positive wetness anomalies across portions of the British Isles and the Iberian Peninsula.

Top of Page Precipitation Time Series from In-Situ Stations - Spain and Portugal

A trough of low pressure in the eastern Atlantic was responsible for sending several storms eastward across the Iberian peninsula from late August through September. This pattern led to periodic rainfall with some heavy rains. Several stations in Spain reported over 300 mm (11.8 in) since August. This wet pattern is reflected in the graph to the right which shows precipitation anomalies for September 1999. This September was one of the four wettest September's since the mid 1960's Spain / Portugal Precipitation Time Series
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Top of Page Wetness Anomalies in Asia

Negative wetness anomalies were observed again this month over portions of eastern Pakistan and western India. This region has been generally dry since the beginning of July; much of this region is dependant upon the tropical monsoon for their summer rainfall. Negative wetness anomalies were also observed over southeast Asia and across northeastern China in Manchuria. The Manchuria region in China has been generally dry since early August.
Liquid Water in Asia
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In contrast, positive wetness anomalies were noted across parts of central India, southeastern Tibet, and near the India/Bangladesh border. These areas reported some heavy rains with local flooding. Tropical cyclones caused flooding problems across parts of southeastern China, southwestern Japan, and parts of Korea.

Top of Page Africa/ Middle East Temperature

Africa Temperature
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Northern Africa and most of the Middle East observed positive temperature anomalies this month. This region is normally hot in September. High temperatures in excess of 40 C (104 F) were reported over northeastern Sudan, Saudia Arabia, Iran and Afghanistan. In contrast, persistent patterns of cloudiness and precipitation kept the southern Sahel and western and southern Africa cooler than average.

Top of Page Wetness Anomalies across Africa / Middle East

Northern and north central Africa, a region that usually receives very little summer rainfall (less than 25 millimeters or an inch or so), showed even less than the usual surface wetness during the month of September. Drought has severely affected crop production in parts of Ethiopia and northeastern Somalia.
Liquid Water in Asia
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Positive wetness anomalies again were noted across portions of the Sahel, mainly from southern Sudan westward across parts of Chad, Niger, Nigeria, Mali and then into parts of western Africa. Floods indundated 200 villages in central Nigeria, and the governments of Mauritania and Niger appealed for international assistance due to the heavy rains and flooding. Fourteen deaths were reported in western Africa due to flooding.

Top of Page North American Temperature

A ridge of high pressure aloft over the St. Lawrence River Valley in eastern Canada, was responsible for dry and very warm conditions from the northern Great Lakes eastward into New England and most of Quebec. In contrast, parts of the southeast and a large portion of the central Plains were cooler than average due to cloud cover and above average rainfall. The northeast part of the U.S. was both warmer and wetter this September. The warmth was due to a persistent ridge of high pressure; the heavy rains were due to hurricanes Dennis and Floyd. From coastal areas of southern California southward across Baja California, temperatures were below average for the second month in a row. This is due to a persistent cool on-shore flow typical of a La Nina pattern. North American Temperature
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Top of Page Australia / New Zealand Temperature

An upper-level area of high pressure centered near the southeast coast of Australia, kept most of southern Australia and New Zealand warm this month. Drought conditions were reported across parts of the area. Cooler than normal conditions were reported across portions of western and northern Australia due to cloudiness and scattered showers. For a complete report, see Australian Bureau of Meteorology Current Season Maps Australia / New Zealand Temperature
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Top of Page South America Temperature

South America Temperature
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No significant features in the upper air pattern were prevalent this month across the continent, however there were some unusual temperature extremes. Temperatures were warmer than average across portions of central and northern Argentina, northward across Paraguay, eastern Bolivia, and southwestern Brazil. In the Mato Grosso do Sul region in southwestern Brazil, temperatures soared to 40 C (104 F) late in the month. In contrast, temperatures were cooler than average across portions of southeastern Brazil, and in areas along and near the northwest and northern portions of the continent. The cool conditions along the northwest coast of South America were due to the continuation of the La Nina pattern.

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.


Peterson, Thomas C. and Russell S. Vose, 1997: An overview of the Global Historical Climatology Network temperature data base. Bulletin of the American Meteorological Society, 78, 2837-2849.

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: 828-271-4107
email: alan.basist@noaa.gov
-or-
Tom Ross
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4499
email: tom.ross@noaa.gov
-or-
Mike Changery
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4750
email: mchangry@ncdc.noaa.gov
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