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National Oceanic and Atmospheric Administration

December 1998-February 1999
Global Regional Analyses

National Climatic Data Center, March 12, 1999

Global Mean Temperature Anomalies
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The December 1998 - February 1999 season was dominated by the mature La Niña (cold water) conditions in the east equatorial Pacific. This corresponded to colder than normal temperatures in southern Europe, northwestern Africa and western Australia. The eastern two thirds of North America was warmer than normal, as a result of fewer than normal Arctic outbreaks. A persistent ridge over northeastern Africa and the Middle East kept that region warmer and drier than normal. It was also warmer and drier over China throughout the season. A broad ridge over Asia resulted in above normal temperatures over most of Russia except for the eastern-most portion. A persistent trough off the northwest coast of North America produce near record rain and snow cover in the area. Drought was widespread in southern Africa during the season.

Top of Page Africa Temperature

The pattern of warm and cold anomalies over Africa were quite persistent throughout the season. February's temperatures were consistent with January 1999, although the warm/cool anomaly structure amplified across the northern section of the continent.

A strong trough over the northwestern corner of the continent kept that area cooler than normal, while a ridge to the east promoted warmer than normal temperatures. These warm anomalies extended down into the equatorial region. There was a contrast of warm and cold anomalies in the southern quarter of the continent. Africa Temperature
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Top of Page Asia Temperature

Asia Temperature
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During the period from December 1998 through February 1999, southeast China and northern Indochina had some of the warmest surface anomalies for that season. These warmer than normal conditions extended across portions of northern India into Pakistan and Afghanistan. South of these areas there were cold anomalies but they were relatively weak in comparison (with the exception of a large cool anomaly over central India.).

Top of Page Australia Temperature

New Zealand continued to be quite warm from December 1998 through Febraury 1999 with some areas as high as 3 degrees C above normal. Temperatures across most of central and eastern Australia remained above normal throughout the majority of the season. In contrast, temperatures across western Australia were quite cool. These cooler conditions corresponded with a broad trough that brought rain and clouds to the area. There was a cool area in the far northeast, where tropical storms affected the area. Detailed analyses for Australia can be found at http://www.bom.gov.au/climate/current/ Australia
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Top of Page U.S. Temperature

U.S. Temperature
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The southeastern third of the United States experienced warmer than normal temperatures during its winter season. It was generally cooler than normal along the Pacific coast due to frequent storminess, and an onshore flow. This pattern agrees with a La Niña pattern, where a persistent westerly flow off the Pacific Ocean results in a reduction of Arctic outbreaks in the southeastern U.S.

Top of Page Temperature Anomalies in South America

The majority of South America had above normal temperatures during the summer season. The warmest anomalies were in eastern Brazil and central Argentina. The area of negative anomalies occurred in the northern section of the continent. South America
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Top of Page Wetness Anomalies in Africa

Wetness Anomalies in Africa
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The rainy season across portions of Namibia, Botswana, and South Africa continued to be weaker than normal during the period. The Atlas Mountains in northern Morocco were also drier than normal, due to a northerly flow of dry polar air during much of the season. The precipitation that did fall was locked in a frozen state. However, there were small positive anomalies over the coastal region of Morocco and Algeria, where the precipitation fell as rain. The largest negative anomalies were east of the Mediterranean Sea, where a ridge persisted during much of the season.

Top of Page Wetness Anomalies in Asia

Low precipitation and above normal temperatures caused a drought over southeastern China. Sections of central India were also drier than normal this season, although that region does not normally receive much precipitation this time of year. The Ganges river valley exhibited above normal wetness, although much of this moisture was left over from the flooding conditions late in 1998. Wetness Anomalies in Asia
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Top of Page Wetness Anomalies in Australia

Wetness Anomalies in Australia
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Eastern New Zealand continued to experience below normal surface wetness, while the western section was wetter than normal. A trough in the western part of Australia kept much of that portion of the continent near normal. It was also normal along the eastern and northeast coastal regions of the continent. However, further inland it was considerably drier than normal. Detailed analyses for Australia can be found at http://www.bom.gov.au/climate/current/

Top of Page Wetness Anomalies in Europe

The coastal areas of northern Europe were wetter than normal while further to the south, abnormally dry conditions prevailed during the season. In eastern Europe and western Russia, the snow pack did not undergo any significant melting; therefore liquid water was not observed, and the wetness anomalies are once again negative. A southwest flow to the east of the main trough axis brought some rain to the areas south and east of the Black Sea. Further south a ridge dominated and the region was drier than normal. Wetness Anomalies in Europe
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Top of Page Wetness Anomalies in the United States

Wetness Anomalies in the United States
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A persistent storm track produced wetter than normal conditions from northern Texas, across Oklahoma, into parts of the Ohio Valley. Further north there was less than normal snow cover since temperatures averaged above normal. It was also drier than normal around the Gulf of Mexico coast and in the southwestern U.S. where the moisture associated with the subtropical jet stream has been largely absent this year.

In contrast, the Pacific Northwest was wetter than normal, and the eastern seaboard was wet. However, the forest cover along the eastern seaboard obscures the wetness signal from the satellite sensor. Therefore the wetness analysis over that area is not reliable and depict accurate surface wetness.


Top of Page Snow Cover Anomalies in the U.S.

Snowcover anomalies were well above normal along the storm track extending from the central coast of northwestern North America into the northern Plains. In contrast, a weaker than normal sub-tropical jet stream brought fewer days with snowcover to the Four Corners area and the central Plains. The lack of snowcover in the northern Midwest is related to above normal temperatures and lack of moisture from the Gulf of Mexico. There were also fewer than normal days with snow cover in southeastern Canada after rainstorms melted the snow pack. Snow Cover Anomalies in the U.S.
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Top of Page Snow Cover in Europe

Snow Cover in Europe
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A persistent trough in western Europe brought much cold Arctic air to eastern and central Europe, reflected by the above normal snowpack. This abundant snow pack resulted in numerous avalanches late in the season. To the east, in contrast, a southwest flow brought warm temperatures and fewer than normal days with snow to parts of Russia east of the Ukraine and the countries south and east of the Black Sea.

Top of Page Snow Cover in Asia

The Tibetan Plateau had more snow than usual this season. Further east in central China, the warm dry conditions produced less snow than normal. The plains of Mongolia had less snow than usual, while the mountains to the north had more than normal. A ridge over southwestern Asia caused there to be fewer days with snow cover than normal across part of Afghanistan, Kazakhstan and extreme southwestern China. Snow Cover in Asia
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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.


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


For further information, contact:

Tom Ross
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Tom.Ross@noaa.gov

-or-

David Easterling
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: David.Easterling@noaa.gov

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