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 / NC
EP
12 April 2009
For more information, visit http//www.cpc.ncep.
noaa.gov/products/Global_Monsoons/American_Monsoon
s

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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 northeastern
  Argentina.
  
• The GFS predicts below normal rainfall to
  continue over Paraguay, northeastern Argentina
  and southern Brazil for the next two weeks.
  

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Rainfall Total Anomaly PatternsLast 30 Days
During the last 30 days (13 Mar 11 Apr 2009),
rainfall deficits were observed over portions of
the Amazon basin, central and Northeast Brazil,
Southern Brazil, Paraguay, Uruguay and
northern/northeastern Argentina. Above-normal
rainfall was observed over portions of the Amazon
basin, southeastern Brazil and most 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 the northeastern Amazon basin and
southwestern/southern Brazil. Above-normal
rainfall was also observed over central/southern
Colombia, northern Peru and northern Bolivia.
Below-normal rainfall was observed over southern
Paraguay, northeastern Argentina and Uruguay.
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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 180 mm).

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Recent Evolution Rainfall

• During the last 90 days, rainfall has been below
  normal over southern Brazil (deficits near 150
  mm), and over southern Paraguay and northeastern
  Argentina (deficits near 180 mm).

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Atmospheric Circulation Recent 7 days

• During 4-10 April 2009 an enhanced 200-hPa trough
  was located over the western Atlantic Ocean,
  accompanied by enhanced downward motion (positive
  omega) and below-normal precipitation over
  Paraguay, southern Brazil, northeastern Argentina
  and Uruguay (west of the trough axis).
• Upward motion (negative omega) and above-normal
  rainfall was observed over central and
  southeastern Brazil.

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

• During the last 7 days (4-10 Apr 2009)
  above-normal temperatures were observed over
  Paraguay, northeastern Argentina, Southern Brazil
  (red oval) and along the coast of Northeast
  Brazil.

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NCEP/GFS Model Forecasts Bias-Corrected
Precipitation
Forecasts from 12 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 12April 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 (12-18 Apr 2009), below-normal
  rainfall is predicted for eastern Colombia and
  Venezuela, central and southern Brazil, Paraguay,
  northeastern Argentina and Uruguay.
• For week 2 (19-25 Apr 2009), Above-normal
  rainfall is predicted for Colombia, Ecuador,
  northern Peru, and Brazil over an area between
  3S-10S. Below-normal rainfall is predicted over
  the northern Amazon basin, central/southeastern/so
  uthern Brazil, Paraguay, Uruguay, northeastern
  Argentina southern Peru and western Bolivia.

NOTE See forecast verification in the next slide.
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Forecast Verification
Observed 5-11 Apr 2009
Forecast from 5 April 2009 Valid 5-11 Apr 2009
Forecast from 29 Mar 2009 Valid 5-11 Apr 2009
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ClimatologyRainy Season Dates
ONSET
DEMISE
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Precipitation Climatology