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 24 April 2017 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 (17-23 Apr 2017), below-average precipitation was observed over portions of Ecuador, northern Peru, northern and the extreme southern Brazil. Above-average precipitation was observed over much of Colombia, northern Bolivia, Paraguay and west-central Brazil. • For 24 - 30 Apr 2017, below-average precipitation is predicted over portions of Peru, northern Argentina , as well as northern and central Brazil. Above-average precipitation is predicted for northern Bolivia, Paraguay, southern Chile, and southern Brazil.

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

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

6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall deficits are present over Amazon Basin (~ 100 mm) and the Brazilian Plateau (~ 200 mm).

7. Tropical Pacific and Atlantic SST Anomalies SSTs are near-average across the central and eastern tropical Pacific and above average in the far 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 16-22 Apr 2017, anomalous anticyclonic flow (center noted by red A) was observed over central Brazil. • Lower panels: Anomalous sinking motion was observed over east-central Brazil and central Argentina. Anomalous rising motion was observed over much of central and northern South America. A • 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 16-22 Apr 2017, above-average temperatures were observed over central Brazil and below-average temperatures were seen 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 24 Apr 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 24 Apr 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 (24 - 30 Apr 2017), below-average precipitation is predicted over portions of Peru, northern Argentina , northern and central Brazil. Above-average precipitation is predicted for northern Bolivia, Paraguay, southern Chile, and southern Brazil. • For Days 8-14 (01-07 May 2017), below-average precipitation is predicted over much of central South America as well as Uruguay and the extreme southern Brazil. Above-average precipitation is predicted over portions of northern Brazil, Colombia, northern Peru, central Argentina and southern Chile.

13. Forecast Verification Forecast from 10 Apr 2017 Valid for 17 - 23 Apr 2017 Forecast from 17 Apr 2017 Valid for 17 - 23 Apr 2017 Observed 17 - 23 Apr 2017

14. ClimatologyRainy Season Dates ONSET DEMISE

15. Precipitation Climatology

16. Precipitation Climatology Animation