The%20South%20American%20Monsoon%20System:%20Recent%20Evolution%20and%20Current%20Status

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The South American Monsoon System Recent
Evolution and Current Status
Update prepared by Climate Prediction Center /
NCEP 17 October 2007
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Outline

• Recent Evolution and Current Conditions
• Summary
• Climatology

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Recent Evolution Rainfall

• The SAMS wet season has been slow to start over
  Central Brazil.
• Rainfall deficits over the Brazilian Plateau
  (BP), during the last 90 days, are between 60 mm
  and 80 mm.

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Recent Evolution Atmospheric Circulation OLR

• Persistent positive OLR anomalies have dominated
  Central and Southeast Brazil during the last 30
  days.
• An anomalous upper-level (200-hPa) trough has
  been a persistent feature over the eastern South
  Pacific.
• This has restricted surface cold fronts to the
  region of southern Brazil and eastern Argentina,
  thus keeping southeastern Brazil warm and dry.

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Summary

• The rainy season has been slow to start over
  central and southeastern Brazil.
• Rainfall deficits of 60 to 80 mm have been
  observed near the Brazilian Plateau.
• These features have been associated with a
  persistent trough over the eastern South Pacific,
  which has not allowed cold fronts to advance
  northward over Brazil.

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ClimatologyRainy Season Dates