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IRI Climate Information Digest - October 1999

Issued 13 November 1999


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Temperature in Percentiles (NOAA CPC CAMS)
1961-1990 Base Period 

Historically  in October, the primary global rain belts retreat southward following the sun and ocean temperatures. The peak of the tropical storm season in the northern hemisphere has passed, and on average draws to a close in November.
 Rainfall observations  indicated a late end to the monsoon seasons in Mexico,  central Africa and India as rains continued well into October. Wetter than average conditions in Mexico and India were exacerbated by tropical storm activity.
Tropical Storm activity has been above average in the Atlantic, with 11 named storms compared with an average of 9.8  for the period 1944-1996. In contrast the eastern Pacific has seen only  9 named storms through October where on average 16 have been observed for the period 1966-1996.

Ocean Temperatures

  • Tropical Pacific: A moderate La Niña (colder than average sea surface temperatures) is continuing in the tropical Pacific Ocean. The La Niña is expected to persist through the next season.
  • Extratropics: Warmer than average temperatures continue to evolve in the northwestern Pacific basin.


  • Africa: Seasonal rains continued into late October across much of central Africa and into Ethiopia.
  • South Asia: The western region of India and Pakistan received much-needed late season rainfall, while excessive rains from two consecutive cyclones inundated the east coast of the subcontinent and Bangladesh.
  • Mexico: Above average rainfall in southern Mexico was associated with the remnants of a tropical depression.
  • South America: Northeastern Argentina, Uruguay, Paraguay and Southern Brasil have experienced drier than average conditions since late August.
  • Western Europe: Spain, France and England received above average rainfall.


  • Northern Hemisphere: Above average temperatures prevailed over central Asia the Middle East and North Africa.
  • South America: The north coast, central Brazil and the Southern Cone experienced persistent above average temperatures.
  • Australia: The eastern half of Australia was warmer than average for most of October.
Forecasts - Seasonal Temperature and Precipitation

Impacts - On Fisheries, Agriculture, Health and Hazards.

Material for the IRI Climate Information Digest has been extracted from the IRI Climate Data Library, the IRI Experimental Forecasts, the NOAA NCEP Climate Prediction Center, the Climate Diagnostic Center, and the NOAA ERL Pacific Marine Environmental Laboratories. Additional information has been obtained from the Bureau of Meteorology, Australia, and INPE, Brazil.