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 20 March2017 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 • Long-term rainfall deficits are present over the Amazon Basin and central Brazil. • During the last 7 days (13 - 19 Mar 2017), below-average precipitation was observed over much of central Brazil, northeastern Peru, Uruguay, northern Argentina and southern Chile. Above-average precipitation was observed over portions of western Colombia, Ecuador, northern Peru, Paraguay, northern and the extreme southern Brazil. • For 20 – 26 Mar 2017, below-average precipitation is predicted over much of Brazil, Bolivia, Paraguay, Uruguay and southern Chile. Above-average precipitation is predicted for large portions of northwestern South America.

4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, below-average precipitation was observed over much of central Brazil, northeastern Peru, Uruguay, northern Argentina and southern Chile. Above-average precipitation was observed over portions of western Colombia, Ecuador, northern Peru, Paraguay, northern and the extreme southern Brazil.

5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over much of central South America and northern Argentina. Above-average precipitation was observed over Colombia, Ecuador, Peru, Uruguay and the extreme southern Brazil.

6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall deficits are present over Amazon Basin (~ 150 mm) and the Brazilian Plateau (> 250 mm).

7. Tropical Pacific and Atlantic SST Anomalies SSTs are slightly below average over central tropical Pacific and above average in the eastern tropical Pacific. (For details concerning El Niño – La Niña, go to the link below.) A weekly PowerPoint summarizing the ENSO Cycle: Recent Evolution, Current Status and Predictionsis 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 12-18 Mar2017, anomalous cyclonic flow (center noted by red C) was observed off the coast of Argentina. • Lower panels: Anomalous sinking motion was observed over eastern Brazil and southern South America. Anomalous rising motion was observed over northwestern South America, northern Chile and the extreme 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 12-18 Mar 2017, above-average temperatures were observed over southern Brazil and below-average temperatures were observed over eastern Argentina. 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.

10. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 20 Mar 2017–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 20 Mar 2017– Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (20 - 26 Mar 2017), below-average precipitation is predicted over much of Brazil, Bolivia, Paraguay, Uruguay and southern Chile. Above-average precipitation is predicted for large portions of northwestern South America. • For Days 8-14 (27 Mar – 02 Apr 2017), below-average precipitation is predicted over much of central South America and northern Argentina. Above-average precipitation is predicted over Venezuela and portions of northwestern and southern Brazil.

13. Forecast Verification Forecast from 06 Mar 2017 Valid for 13 – 19 Mar 2017 Forecast from 13 Mar 2017 Valid for 13 -19 Mar 2017 Observed 13 -19 Mar 2017

14. ClimatologyRainy Season Dates ONSET DEMISE

15. Precipitation Climatology

16. Precipitation Climatology Animation