Climatological Background  In December, the Northern Hemisphere enters the heart of winter, with strong north-south temperature differences driving the mid-latitude jet stream and storm systems. In the Southern Hemisphere summer is under way, with monsoon systems gaining strength in South America, southern Africa, and Australia. 

Monthly Mean Temperature (1961-1990), data from the Climate Research Unit, University of East Anglia

DATA: Univ. of East Anglia

Monthly Mean Precipitation (1961-1990), with data from the Climate Research Unit, University of East Anglia

DATA: Univ. of East Anglia

Temperatures Over Land

Temperatures continued well below average over much of North America and northern Asia for the second straight month.  By contrast, continental Europe has remained unusually warm since October.

North America:  Unusually cold conditions prevailed across central Canada and most of the central and eastern United States.  In the US, the national average temperature for the November-December period was the lowest on record.  Meanwhile, Alaska was unusually mild, with temperatures as much as 8 C above average in western sections.
Asia:  Unusually cold conditions continued across the Central Siberian Uplands southward into Mongolia.  China and western Asia were unusually warm with temperatures from the Baltic states northward to Finland as much as 4 C above average.
Europe:  Unusually warm conditions have persisted across most of continental Europe since October. 
Africa:  Warmer than average conditions continued along coastal regions of West and North Africa.
Australia:  Unseasonably warm conditions continued along the southern coast while below average temperatures prevailed across much of the northern parts of the continent.
South America:  Temperatures were somewhat higher than average from Ecuador northward to Colombia and Venezuela. 
 

Temperature Difference from the 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS.

NOAA NCEP CPC CAMS anomaly temperature anomaly

Precipitation

Unusually heavy rainfall continued across western Indonesia, northern Australia and the Philippines.  Intense rains plagued the Iberian Peninsula as storminess in western Europe continues. 

Indonesia:  Following heavy rains and flooding in November, intense rainfall continued into December in Sumatra.
Europe:  Very heavy rainfall fell across Portugal and northern Spain.  Northern France and northern Italy were also unusually wet while unseasonably dry conditions prevailed across the southeast.
Africa:  Rainfall across southern Kenya,Tanzania and the Lake Victoria Basin helped ease earlier drought conditions.   Above average rainfall was observed across much of Zambia. 
Philippines:  Tropical cyclone activity brought more heavy rain.
Australia:  In regions already experiencing unusually wet conditions, heavy rainfall fell across northern sections of the Northern Territory and Queensland.  
South America:  Near-average precipitation was observed across the continent with unusually heavy rainfall confined primarily to central and eastern Brazil.
North America:  Unusually dry along the west coast and southeastern United States.
Caribbean:  Above-average rainfall across the central Caribbean.  Heavy rainfall in Jamaica and central Cuba helped ease a prolonged dry spell. 
 

Precipitation Difference from 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS-OPI.

NOAA NCEP CPC CAMS_OPI v9906 anomaly Precipitation Anomaly (mm/day). Contours 0.5, 2, 4, 6, 8,...

Oceanic Conditions

Tropics:  Surface temperatures in the eastern and central Pacific remained somewhat below average indicating continued, but weak, La  Nina conditions.    The western Pacific and central Indian oceans remained unusually warm during the month.
Midlatitudes:  Above average water temperatures persisted to the south of Australia.   Warmer than average conditions developed along coastal areas of southern Africa and persisted in the Sea of Japan and the central North Atlantic.

Monthly Sea Surface Temperature Difference from the 1950-1979 mean, with data from the Environmental Modeling Center, NCEP/NOAA.