1. The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 18 May 2015 For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons 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. Large long-term rainfall deficits remain over the southern Amazon Basin and portions of central Brazil. During the last 7 days (11-17 May 2015), below-average precipitation was observed over northern and northeastern South America, southern Brazil and Uruguay. Above-average precipitation was observed over portions of Peru, Bolivia, and southern Chile. For 18-25 May 2015, above-average rainfall is predicted for portions of Colombia, Venezuela and extreme northern Brazil. Drier-than-average conditions are predicted for most of Brazil south of the equator and most of Peru. Highlights

4. Rainfall Total & Anomaly Patterns: Last 7 Days During the last 7 days, below-average precipitation was observed over northern and northeastern South America, southern Brazil and Uruguay. Above-average precipitation was observed over portions of Peru, Bolivia, and southern Chile. TotalAnomaly

5. Rainfall Totals & Anomaly Patterns: Last 30 Days During the last 30 days, below-average precipitation was observed over the central, eastern and southern Amazon Basin, northern Northeast Brazil, northeastern Argentina, Uruguay and southern Brazil. Above-average precipitation was observed over portions of Ecuador, Peru, Bolivia and Paraguay. TotalAnomaly

6. BP Recent Evolution: Rainfall Last 90 Days BP: Brazilian Plateau 90-day rainfall deficits are present over the southern Amazon Basin (~200 mm) and the western Brazilian Plateau (50-100 mm). 90-day rainfall is below average (~150 mm) over southern Brazil.

7. Tropical Pacific and Atlantic SST Anomalies 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 SSTs are above average in the equatorial Pacific, below average in the low latitudes of the North Atlantic, and above average in the eastern tropical Atlantic. (For details concerning El Niño – La Niña, go to the link below.)

8. Atmospheric Circulation Recent 7 days Upper panels: During the period of 10-16 May 2015, anomalous cyclonic flow (center indicated by red C) was located over the western South Atlantic. Stronger-than-average westerlies were observed over Southeast Brazil. Lower panels: Anomalous rising motion occurred over Bolivia and Paraguay, and anomalous sinking motion occurred over portions of Northeast Brazil, eastern Argentina and Uruguay. 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. C

9. 925-hPa Wind &Temperature Recent 30 DaysRecent 7 Days Low-level (~600 m above sea level) 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. During the 7-day period 10-16 May 2015, above-average temperatures were observed over most of Chile and Argentina.

10. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Total Forecasts from 18 May 2015 – Days 1-7 Anomaly Note: Bias correction based on last 30-day forecast error.

11. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Total Forecasts from 18 May 2015 – Days 8-14 Anomaly Note: Bias correction based on last 30-day forecast error.

12. For Days 1-7 (18-24 May 2015), above-average rainfall is predicted for portions of Colombia, Venezuela and extreme northern Brazil. Drier-than- average conditions are predicted for most of Brazil south of the equator and most of Peru. For Days 8-14 (25-31 May 2015), above-average precipitation is indicated for portions of Venezuela, Colombia, northern Peru, southern Paraguay and southern Brazil. Below-average precipitation is predicted for southern Peru and most of Brazil between the equator and 20S. NCEP/GFS MODEL FORECASTS

13. Forecast Verification Forecast from 4 May 2015 Valid for 11-17 May 2015 Forecast from 11 May 2015 Valid for 11-17 May 2015 Observed 11-17 May 2015

14. Climatology Rainy Season Dates ONSETDEMISE

15. Precipitation Climatology

16. Precipitation Climatology Animation