The South American Monsoon System: Recent Evolution and Current Status

1. The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 9 April 2012 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 mainly observed over portions of northern South America. Below-average rainfall was found over most of Brazil, Bolivia, Uruguay, and northeastern Argentina. • Updated forecasts are not available.

4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, above-average rainfall was mainly observed over portions of northern South America. Below-average rainfall was found over most of Brazil, Bolivia, Uruguay, and northeastern Argentina.

5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, above-average rainfall was mainly observed over Colombia, Ecuador, and northern Brazil. Below-average rainfall occurred over most of the remainder of South America.

6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall totals are below average over the southern Amazon basin. They are also clearly below average over the Brazilian Plateau, the core monsoon region. • 90-day totals are significantly below average in southern Brazil.

7. Tropical Pacific and Atlantic SST Anomalies Above-average SSTs are observed in the tropical eastern Pacific and below-average SSTs are present in the equatorial central Pacific and portions of the equatorial Atlantic Ocean. (For more details concerning El Niño – La Niña, 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 • Upper panels: During the period of 31 March-6 April 2012, anomalous upper-tropospheric cyclonic circulation occurred over southern and southeastern Brazil (center indicated by red C). • Lower panels: Anomalous rising motion (negative omega) occurred over northwestern South America and southeastern Brazil. Anomalous sinking motion was observed over northeastern and southern Brazil. C 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 of 31 March-6 April 2012, temperatures were above average between 10S and 30S. 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 9 April 2012 – Days 1-7 Total Anomaly Forecasts not available Note: Bias correction based on last 30-day forecast error.

11. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 9 April 2012 – Days 8-14 Total Anomaly Forecasts not available Note: Bias correction based on last 30-day forecast error.

12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (9-15 April 2012), forecast not available. • For Days 8-14 (16-22 April 2012), forecast not available.

13. Forecast Verification Forecast from 26 March 2012 Valid 2-8 Apr 2012 Forecast from 2 Apr 2012 Valid 2-8 Apr 2012 Observed 1-7 Apr 2012

14. ClimatologyRainy Season Dates ONSET DEMISE

15. Precipitation Climatology

16. Precipitation Climatology Animation