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 07 May 2018 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, the Brazilian Plateau and the extreme southern Brazil. • During the last 7 days, below-average precipitation was observed over portions of northern and southern Brazil, southern Chile, northern Peru and northern Colombia. Above-average precipitation was observed over portions of northeastern Argentina, northern Peru and eastern Colombia. • For Days 1-7 (07 - 13 May 2018), below-average precipitation is predicted over much of Brazil, southern and northeastern Peru and southern Chile. Above-average precipitation is predicted for portions of northern Brazil, northern Argentina, Ecuador and central Colombia.

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

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

6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall deficits are present over the Amazon Basin (~ 100 mm) , the Brazilian Plateau (> 80 mm) and the extreme southern Brazil (~ 100 mm).

7. Tropical Pacific and Atlantic SST Anomalies SSTs are below-average across 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 29 April – 05 May 2018, anomalous anticyclonic flow (center noted by red A) was observed over northern Argentina. • Lower panels: Anomalous sinking motion was observed over southern and central Brazil and southern Argentina. Anomalous rising motion was observed elsewhere. 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 29 April – 05 May 2018, above-average temperature was observed southern Brazil, Paraguay and northeastern 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 07 May 2018–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 07 May 2018– Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (07 - 13 May 2018), below-average precipitation is predicted over much of Brazil, southern and northeastern Peru and southern Chile. Above-average precipitation is predicted for portions of northern Brazil, northern Argentina, Ecuador and central Colombia. • For Days 8-14 (14 - 20 May 2018), below-average precipitation is predicted over much of northern South America and southern Chile. Above-average precipitation is predicted for small portions of central and southern Brazil, western Ecuador and central Colombia.

13. ClimatologyRainy Season Dates ONSET DEMISE

14. Precipitation Climatology

15. Precipitation Climatology Animation