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The global mean circulation this month featured several distinct ridges and troughs which led to various global temperature and precipitation anomalies. There were two major troughs across the western hemisphere during October: one over southeast of James Bay in eastern Canada, the another over south central Alaska. These troughs led to cooler and wetter conditions in these regions. Additional, but weaker, troughs associated with above average precipitation were observed off the Iberian coasts of Spain/Portugal, between the Black and Caspian Seas, and over east central China. Ridges were located over the southwestern U.S, near the Barents Sea in northwestern Russia, and near the Kamchatka peninsula in eastern Russia. These areas were warmer than the (1992-1999) average.
Across the southern hemisphere, the only major anomalies noted were two fairly strong ridges, one over southern South America and another centered near New Zealand. These ridges were responsible for warmer than average conditions in those areas. Two destructive typhoons hit eastern India this month. The second storm on the 29th was a supercyclone that killed an estimated 3,400 people and had winds over 160 mph. A special report is available at Climate Watch. The general October 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.
 Europe / Asia Blended Temperatures
| The warmest anomalies were noted across portions of Kazakhstan northward into western Siberia due to a strong ridge of high pressure aloft. A weaker ridge was observed over the Mediterranean region into portions of the Middle East which kept those areas mainly dry and warm. In contrast, India was cool due to persistant cloudiness and a trough over east central China kept that region cool as well.
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Wetness Anomalies in Europe
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For the second month in a row, a trough of low pressure in the eastern Atlantic was responsible for wet weather and positive wetness anomalies across portions of the British Isles, the Iberian Peninsula and into Morocco. Another weak trough, centered between the Black and Caspian Seas, brought widespread cloudiness and precipitation to parts of that region. Dryness was noted across a good portion of eastern and central Europe and across Kazakhstan.
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Precipitation Time Series from In-Situ Stations - Spain and Portugal
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A trough of low pressure in the eastern Atlantic was responsible again this month for the wet weather and sent storms eastward across the Iberian peninsula from late August through October. This pattern led to periodic rainfall with some heavy rains. In fact, the region as a whole has experienced excessive rainfall during the last three months with precipitation 100 millimeters (mm) above average. This is the wettest August-October period since the 1972. This wet pattern is reflected in the graph to the left which shows precipitation anomalies for the three month period August-October since 1900.
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Wetness Anomalies in Asia
Two distinctive positive wetness anomalies were observed this month. One area over east central China was associated with a trough of low pressure which led to persistent cloudiness and precipitation. The second region over portions of western and central India was associated with heavy periodic monsoonal rains. The heavy rain in the eastern India/Bangladesh region during the month was associated with two typhoons that hit in October-- one around mid month, the second near the end of the month. Both typhoons hit the Orissa and West Bengal region of eastern India, with more than 3,400 deaths reported. See the Climate Watch for more information.
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In contrast, dryness was noted over portions of southeast Asia, especially in Cambodia. Also, a large area of dryness was noted over northeastern China. The apparent dry anomaly in this region maybe a consequence of an above average snow cover signal. Snow cover is not reflected in the wetness anomaly, which makes the region appear dry. So an area which reports positive snow cover anomalies will usually show up with a negative wetness anomaly. See the following for more details on the SSMI Monthly Products.
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Africa/ Middle East Temperature
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The largest anomaly across the region is the continued cool temperatures across central and southern Africa. This region was quite cool due to a persistant cloud cover and frequent episodes of precipitation. The only region with positive temperature anomalies was across portions of northern Africa and most of the Middle East. These regions were dry and warm due to a weak ridge of high pressure along the Mediterranean coast. This region climatologically remains quite hot through October but begins to cool down somewhat during November.
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Wetness Anomalies across Africa / Middle East
North central and eastern Africa, a region that usually receives very little rainfall (less than 25 millimeters or an inch or so during October), showed even less than the usual surface wetness during the month of October 1999. A trough of low pressure in the eastern Atlantic brought some needed rains to portions of Morocco.
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Positive wetness anomalies again were noted for the third month in a row across portions of the Sahel, mainly from southern Ethopia, Sudan westward across parts of Chad, then into parts of western Africa. Media reports indicate that persistant flooding across Niger left 80,000 people in need of food and shelter. Flooding in Togo has affected some 65,000 people while destroying 100 bridges, impairing 800 km of road network, and destroying several hundred houses.
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Precipitation Time Series from In Situ Stations - Sahel Region of Africa
| The Sahael region continues to be cool and wet again this month. Numerous areas from portions of southern Ethopia westward across southern Chad into the southwestern coast of Africa continue to report flooding problems this October. This October was the wettest October on record across the region since the late 1970's.
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Asia Snowcover
| Moisture transported northward from the tropics fell as snow across the mountainous regions of south central Asia. This led to a rapid increase in the snow pack during the month. Positive snow cover anomalies were also observed across the colder high latitude regions of Mongolia, east central Siberia into the northeastern corner of Manchuria. An animation of the monthly snowcover across this region is available at Eurasia Snowcover Animation
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South America Wetness
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A ridge of high pressure aloft, just off the southeastern coast of Argentina, kept much of the region fairly warm. A good deal of the region has experiencing drought. In fact, drought conditions have been reported in Paraguay since June of this year and have affected some 75,000 people in the Departments of Concepción and San Pedro, in the central part of Paraguay. Positive wetness anomalies were scattered across portions of northcentral South America. According to media reports, three days of heavy rain resulted in flooding and landslides in parts of Colombia. The worst area affected was reportedly in southern Columbia near Florencia where two rivers burst their banks and flooded a poor district.
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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
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
 NCDC / Climate Monitoring / Climate of 1999 / Help
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