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 14 December 2007
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Outline

• Recent Evolution and Current Conditions
• Summary
• Climatology

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Rainfall Patterns Last 90 Days
During the last 90 days rainfall has been below
normal over most of Brazil, with rainfall
deficits between 175-250 mm in portions of
central and southeastern Brazil. Deficits of up
to 100 mm are found in north-central Argentina.
Above-normal rainfall was observed over portions
of eastern Bolivia, Paraguay and southern Brazil.
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Rainfall Patterns Last 30 Days
During the last 30 days rainfall has been near
normal over most of Brazil, except for the
central and southeastern portions of the country.
Above-normal rainfall was observed over Paraguay
and eastern Bolivia, and below-normal over
Uruguay and the northern half of Argentina.
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Rainfall Patterns Last 7 Days
During the last 7 days rainfall has been slightly
above normal over northern Brazil, while
below-normal rainfall was observed over the
southern Amazon, central and southeastern Brazil,
and northern Argentina.
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Atmospheric Circulation Last 7 days

• During the last 7 days a strong 200-hPa
  anticyclonic circulation was centered over
  Brazil, just east of Bolivia.
• Stronger-than-normal low-level northwesterly flow
  extended from the western Amazon southeastward to
  the coast of Southeast Brazil.

A
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Recent Evolution Rainfall

• The SAMS wet season was delayed in many areas.
• Since October, rainfall has increased over
  western Brazil.
• Rainfall deficits continue over the Brazilian
  Plateau (BP), with deficits greater than 130 mm
  during the last 3 months.
• -

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Summary

• Rainfall has been slightly above normal in
  western Brazil and much below normal in central
  and southeastern Brazil during the last 90 days.
• The rainy season was slow to start over central
  and southeastern Brazil, where rainfall deficits
  of 100-200 mm (locally up to 250 mm) have been
  observed during the last 90 days.
• During the last 7 days rainfall has been above
  normal over the northern Amazon Basin and below
  normal over southern Amazon, central and
  southeastern Brazil.

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ClimatologyRainy Season Dates
ONSET
DEMISE
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Precipitation Climatology