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The South American Monsoon System: Recent Evolution and Current Status

This report provides an update on the recent evolution and current conditions of the South American Monsoon System. It includes highlights, rainfall patterns, tropical Pacific and Atlantic SST anomalies, atmospheric circulation, NCEP/GFS model forecasts, and forecast verification. For more information, visit the provided link.

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The South American Monsoon System: Recent Evolution and Current Status

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  1. The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 7 November 2010 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons

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

  3. Highlights • During the last 7 days, above-average rainfall was observed over west-central and southeastern Brazil, while below-average rainfall prevailed over extreme southern Brazil. • The GFS predicts above-average rainfall over the core monsoon region (Amazon basin and central Brazil), and below-average rainfall to continue over southern Brazil and northeastern Argentina during the next two weeks.

  4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days above-average rainfall was observed over south-central Brazil (10-25S;40-60W), while below-average rainfall was observed to the south of this region over southern Paraguay, southern Brazil, Uruguay and northeastern Argentina. Below-average rainfall was also observed in many areas in the Amazon basin.

  5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days below-average rainfall was observed over most of the central and western Amazon basin and southeastern South America (southern Brazil, Uruguay, and northeastern Argentina). Above-average rainfall was observed over central Paraguay, northeastern Brazil and central Colombia.

  6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • In spite of the heavy rainfall during the last 7 days, 90-day rainfall totals remain below average over the core monsoon region (southern Amazon Basin and Central Brazil). • 90-day totals remain below average in southern Brazil. Deficits of about 120 mm.

  7. Tropical Pacific and Atlantic SST Anomalies During the last week, equatorial SSTs were between 0.5° - 2.5°C below average over most of the central and eastern Pacific Ocean. SSTs were 0.5°-1.5°C above average in most of the equatorial Atlantic. A La-Nina event is in progress in the tropical Pacific (for more details go to the link below). A weekly PowerPoint summarizing the ENSO Cycle: Recent Evolution, Current Status and Predictions is available at: http://www.cpc.noaa.gov/products/precip/CWlink/MJO/enso.shtml

  8. Atmospheric Circulation Recent 7 days • During 30 Oct – 5 Nov 2010, enhanced westerly winds, associated with a strong SACZ, were observed extending from southwestern Brazil eastward to the central South Atlantic. • Strong anomalous rising motion (negative omega) and above-average rainfall (see slide 4 – right panel) were observed over south-central Brazil (10-25S;40-60W). Rising motion (negative omega, yellow/red shading), usually associated with wetter- than-normal conditions. Sinking motion (positive omega, blue shading), usually associated with drier-than-normal conditions.

  9. 925-hPa Wind &Temperature Recent 30 Days Recent 7 Days • During the 7-day period (30 Oct – 5 Nov 2010) near-average temperatures were observed over most of South America south of 10S. Low-level (~600 m) wind and temperature anomalies based on the NCEP Climate Data Assimilation Systems (CDAS) analysis. The patterns of anomalous temperature and wind at 925-hPa are usually similar to surface observations. Note: Areas with surface pressure below 925-hPa are masked out.

  10. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 7 November 2010 – Days 1-7 Total Anomaly Note: Bias correction based on last 30-day forecast error.

  11. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 7 November 2010 – Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

  12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (7-13Nov), above-average rainfall is predicted over most of the Amazon basin, Colombia and Venezuela, while below-average rainfall is predicted over portions of northeastern Brazil, Bolivia, most of Paraguay, southern Brazil and northeastern Argentina. • For Days 8-14 (14-20 Nov), above-average rainfall is predicted over most of North, Northeast and central Brazil, while below-average rainfall is predicted over northwestern South America (10S-10N; 60-80W) and over southern Brazil, Uruguay and northeastern Argentina. NOTE: See forecast verification in the next slide.

  13. Forecast Verification Forecast from 24 Oct 2010 Valid 31 Oct – 6 Nov 2010 Forecast from 31 Oct 2010 Valid 31 Oct – 6 Nov 2010 Observed 31 Oct – 6 Nov 2010

  14. ClimatologyRainy Season Dates ONSET DEMISE

  15. Precipitation Climatology

  16. Precipitation Climatology Animation

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