The South American Monsoon System: Recent Evolution and Current Status

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The South American Monsoon System Recent
Evolution and Current Status
Update prepared by Climate Prediction Center /
NCEP 16 November 2007
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Outline

• Recent Evolution and Current Conditions
• Summary
• Climatology

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Recent Evolution Rainfall

• The SAMS wet season was delayed in many areas.
• Recently, seasonal-to-date rainfall has
  increased to near normal in western Brazil, but
  rainfall deficits continue over the Brazilian
  Plateau (BP), with deficits of 120 mm during the
  last 3 months.

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Recent Evolution OLR

• During 13-22 October (top panel) enhanced
  precipitation (negative OLR anomalies) was
  observed over the western Amazon Basin, Bolivia,
  Paraguay, northeastern Argentina and southern
  Brazil. Drier-than-normal conditions were
  observed over northeastern Brazil.
• During 23 October 1 November (middle panel)
  negative OLR anomalies (enhanced precipitation)
  were observed over southeastern Brazil and the
  western Atlantic. Positive anomalies
  (below-average precipitation) were observed over
  northeastern Brazil, Bolivia and the western
  Amazon Basin.
• During 2-11 November, wetter-than normal
  conditions continued over portions of
  southeastern Brazil, while drier-than-normal
  conditions strengthened over Northeast Brazil and
  the northern Amazon Basin.

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Atmospheric Circulation OLR Last 5 days

• During the last 5 days low OLR (left panel) was
  observed from the western Amazon southeastward
  across southeastern Brazil and over the western
  South Atlantic Ocean.
• Precipitation was above normal (negative OLR
  anomalies, right panel) over southeastern Brazil,
  and below normal (positive OLR anomalies, right
  panel) over most of the Amazon Basin, Northeast
  Brazil, and Bolivia.
• During this period an amplified 200-hPa trough
  (dashed lines lower panels) was located over
  Argentina, and enhanced low-level (850-hPa)
  northwesterly flow (dashed red oval, upper right
  panel) extended from the western Amazon Basin to
  Southeast Brazil.

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Summary

• Season-to-date rainfall has been near normal in
  western Brazil.
• The rainy season was slow to start over central
  and southeastern Brazil.
• During the last 90 days, rainfall deficits of
  120 mm have been observed over portions of
  central and southeastern Brazil.

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ClimatologyRainy Season Dates
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Precipitation Climatology