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 5 April 2009
For more information, visit http//www.cpc.ncep.
noaa.gov/products/Global_Monsoons/American_Monsoon
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Outline

• Highlights
• Recent Evolution and Current Conditions
• NCEP/GFS Model Forecasts
• Climatology

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Highlights

• Rainfall deficits continue to be observed over
  Paraguay, southern Brazil and northern Argentina.
• The GFS predicts below normal rainfall to
  continue over Paraguay, northern Argentina and
  southern Brazil for the next two weeks.

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Rainfall Total Anomaly PatternsLast 30 Days
During the last 30 days (6 Mar 4 Apr 2009),
rainfall deficits were observed over the southern
Amazon basin, portions of central/Northeast/southe
rn Brazil, Paraguay, western Uruguay and
northern and central Argentina. Above-normal
rainfall was observed over portions of the Amazon
basin, southeastern Brazil and portions of
Bolivia.
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Rainfall Total Anomaly PatternsLast 7 Days
During the last 7 days above-to-near-normal
rainfall occurred over most of Brazil, with the
exception of portions of the Amazon basin and
southern Brazil. Below-normal rainfall was also
observed over portions of Paraguay and
northeastern Argentina.
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Recent Evolution Rainfall

• 90-day rainfall totals are near-normal over
  Northeast Brazil, and below normal over the
  Brazilian Planalto (BP) (deficits near 220 mm)

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Recent Evolution Rainfall

• During the last 90 days, rainfall has been below
  normal in southern Brazil, (deficits near 150
  mm).
• 90-day rainfall totals are below normal over
  southern Paraguay and northern Argentina
  (deficits near 180 mm).

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Atmospheric Circulation Recent 7 days

• During 29 Mar-4 April 2009 an enhanced 200-hPa
  anticyclonic circulation was centered near the
  southeastern Brazil coast, accompanied by
  enhanced upward motion (negative omega) and
  above-normal precipitation.
• Enhanced sinking motion (positive omega) and
  below-normal precipitation was observed over
  southern Brazil.

A
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925-hPa Temperature
Recent 90 Days
Recent 30 Days
Recent 7 Days

• During the last 7 days (29 Mar 4 Apr 2009)
  above-normal temperatures were observed over
  Paraguay, northern Argentina, Southern Brazil
  (red circle) and along the coast of Northeast
  Brazil.

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NCEP/GFS Model Forecasts Bias-Corrected
Precipitation
Forecasts from 5 April 2009 Week 1
Anomaly
Total
Note Bias correction based on last 30-day
forecast error.
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NCEP/GFS Model Forecasts Bias-Corrected
Precipitation
Forecasts from 5 April 2009 Week 2
Anomaly
Total
Note Bias correction based on last 30-day
forecast error.
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NCEP/GFS MODEL FORECASTS

• For week 1 (5-11Apr 2009), below-normal rainfall
  is predicted for northwestern Colombia, northern
  Peru, portions of the Amazon basin, southern
  Brazil, Paraguay and northern Argentina.
  Above-normal rainfall is predicted over
  central-southeastern Brazil and northern Bolivia.
• For week 2 (12-18 Apr 2009), below-normal
  rainfall is predicted for most of Colombia and
  Venezuela, portions of Northeast Brazil, southern
  Peru, southern Bolivia, Paraguay, northern
  Argentina and southern Brazil.

NOTE See forecast verification in the next slide.
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Forecast Verification
Observed 29 Mar- 4 Apr 2009
Forecast from 29 Mar 2009 Valid 29 Mar- 4 Apr
2009
Forecast from 22 Mar 2009 Valid 29 Mar- 4 Apr
2009
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ClimatologyRainy Season Dates
ONSET
DEMISE
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Precipitation Climatology