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 January 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 observed over Ecuador, northwestern, central, and southeastern Brazil, and portions of Colombia and Peru. Below-average rainfall was seen over northeastern, southwestern, and southern Brazil, Bolivia, Paraguay, Uruguay, and northern-northeastern Argentina. • For 9-15 Jan 2012, above-average rainfall is predicted for central and southwestern Brazil and northern Bolivia. Below-average rainfall is predicted for northern South America (north of 5S), eastern and extreme southern Brazil, Peru, Uruguay, and portions of northern Argentina. • For 16-22 Jan 2012, below-average rainfall is predicted for most of northern and central South America (north of 20S). Above-average rainfall is predicted over French Guiana and portions of northern Brazil and western Bolivia.

4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, above-average rainfall was observed over Ecuador, northwestern, central, and southeastern Brazil, and portions of Colombia and Peru. Below-average rainfall was seen over northeastern, southwestern, and southern Brazil, Bolivia, Paraguay, Uruguay, and northern-northeastern Argentina.

5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average rainfall was observed over most of eastern South America (especially northeastern and southern Brazil and northern Argentina) except portions of southeastern Brazil. Above-normal rainfall was mainly seen over northwestern South America.

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

7. Tropical Pacific and Atlantic SST Anomalies Below-average SSTs are present in the tropical Pacific Ocean and most of the tropical Atlantic. (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 from 31 December 2011 to 6 January 2012, a strong anomalous cyclonic circulation was seen over southeastern South America and the western Atlantic Ocean. • Lower panels: Anomalous rising motion (negative omega) was found over regions extending from Colombia to southeastern Brazil. Anomalous sinking motion was observed mainly over regions south of 20S. The distribution of anomalous vertical motions is consistent with the pattern of rainfall anomalies shown in slide 4. 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 from 31 December 2011 to 6 January 2012, temperatures were near normal over most of South America, except for above-normal over southeastern Argentina and below-normal over extreme southern Brazil and Uruguay. 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 Jan 2012 – 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 9 Jan 2012 – Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (9-15 Jan 2012), above-average rainfall is predicted for central and southwestern Brazil and northern Bolivia. Below-average rainfall is predicted for northern South America (north of 5S), eastern and extreme southern Brazil, Peru, Uruguay, and portions of northern Argentina. • For Days 8-14 (16-22 Jan 2012), below-average rainfall is predicted for most of northern and central South America (north of 20S). Above-average rainfall is predicted over French Guiana and portions of northern Brazil and western Bolivia.

13. Forecast Verification Forecast from 27 Dec 2011 Valid 3-9 Jan 2012 Forecast from 3 Jan 2012 Valid 3-9 Jan 2012 Observed 2-8 Jan 2012

14. ClimatologyRainy Season Dates ONSET DEMISE

15. Precipitation Climatology

16. Precipitation Climatology Animation