IRI Climate Information Digest - November 1999

Temperature in Percentiles (1961-1990 Base Period )

Climatological Background   In November, the transition from the Northern Hemisphere warm to cold season and the Southern Hemisphere cold to warm season is complete.  In the Northern Hemisphere, mid-latitude storms begin to acquire wintertime strength and produce accumulating snowfall, while nearer the equator the monsoonal precipitation systems continue to weaken.   In the Southern Hemisphere, the monsoonal systems in subtropical Africa, Indonesia, and South America are gaining strength, while the mid-latitude storms have greatly weakened.

Ocean Temperatures

• Tropics:   November marked a strengthening of La Niña (below average sea surface temperatures (SSTs) in the  equatorial Pacific) as the magnitude of below average SSTs intensified to the east of the dateline.  Elsewhere in the tropics SSTs remained above average in the western Pacific, Indian and Atlantic basins.
• Extratropics:  Above average SSTs persisted in a broad band extending from Japan to the west-central North Pacific.  Warmer than average SSTs strengthened to the west of Australia and to the east of southern South America during the month.

• Europe and Asia:  After a warm start November brought a dramatic shift to below average temperatures in Europe and western Russia.  In contrast, temperatures were well above average in China, Manchuria, and Japan.
• North America:  Temperatures were significantly above average across most of the US and central Canada while below average conditions continued across Alaska.
• Australia:  In a reversal from October conditions, temperatures were below average across most of the continent.
• South America:  Cooler than average conditions prevailed from northern Argentina northward into western Paraguay and Bolivia while northeastern coastal regions recorded temperatures much warmer than average.
• Africa:  Temperatures were above average across much of northern Africa from the Sahel eastward to Ethiopia.  Southern Africa also saw a warm November as temperatures were well above average from the Cape of Good Hope northward into Zambia.

• Southeast Asia:  Above average rainfall was observed across southern China, Vietnam and Cambodia primarily due to very heavy rains which occurred during the first part of November.
• North America:   Precipitation was well below average across much of the central US northward into south-central Canada.
• Australia:  Rainfall was well above average from north-central Queensland into northeastern regions of the Northern Territory.  A noticeable lack of precipitation was reported along southeast coastal sections of New South Wales.
• South America:  Below average precipitation was observed in Uruguay and Paraguay as well as extreme southern Brazil and northeast Argentina.  Opposite conditions were observed across north-central Argentina where precipitation was well above average for the month.
• Africa:  Heavy rainfall was observed in a band extending from the Congo basin southeastward to coastal Mozambique.