The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 19 December2016 For more information, visit:

Outline Highlights Recent Evolution and Current Conditions NCEP/GFS Model Forecasts Climatology

Long-term rainfall deficits are present over the Amazon Basin, central Brazil and the extreme southern Brazil. During the last 7 days ( Dec 2016), below-average precipitation was observed over central Colombia, much of central and southern Brazil, Bolivia, Paraguay and northern Argentina. Above-average precipitation was observed over northern Peru, northern and eastern Brazil. For Dec 2016, below-average precipitation is predicted over much of Bolivia, northern Argentina, central and southeastern Brazil, as well as western Venezuela. Above-average precipitation is predicted for portions of Colombia, Peru, northern Brazil, Uruguay and southern Chile. Highlights

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

Rainfall Totals & Anomaly Patterns: Last 30 Days During the last 30 days, below-average precipitation was observed over much of South America. Above-average precipitation was observed over north and central Colombia, central Paraguay and small portions of northern and eastern Brazil. TotalAnomaly

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

Tropical Pacific and Atlantic SST Anomalies A weekly PowerPoint summarizing the ENSO Cycle: Recent Evolution, Current Status and Predictions is available at: SSTs are below average across central and eastern tropical Pacific, and above average in the tropical Atlantic. (For details concerning El Niño – La Niña, go to the link below.)

Atmospheric Circulation Recent 7 days Upper panels: During the period of Dec 2016, anomalous anticyclonic flow (center noted by red A) was observed off the southeast coast of Brazil. Lower panels: Anomalous sinking motion was observed over southern South America. Anomalous rising motion was observed across Colombia and southeastern Brazil. 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. A

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 Dec 2016, below-average temperatures were observed over Paraguay.

NCEP/GFS Model Forecasts Bias-Corrected Precipitation Total Forecasts from 19 Dec 2016 – Days 1-7 Anomaly Note: Bias correction based on last 30-day forecast error.

NCEP/GFS Model Forecasts Bias-Corrected Precipitation Total Forecasts from 19 Dec 2016 – Days 8-14 Anomaly Note: Bias correction based on last 30-day forecast error.

For Days 1-7 (19-25 Dec 2016), below-average precipitation is predicted over much of Bolivia, northern Argentina, central and southeastern Brazil, as well as western Venezuela. Above-average precipitation is predicted for portions of Colombia, Peru, northern Brazil, Uruguay and southern Chile. For Days 8-14 (19-25 Dec 2016), below-average precipitation is predicted over much of northern part of South America as well as central and southern Brazil. Above-average precipitation is predicted over central Colombia, northwestern and southeastern Peru, the extreme southern Brazil and Uruguay. NCEP/GFS MODEL FORECASTS

Forecast Verification Forecast from 05 Dec 2016 Valid for Dec 2016 Forecast from 12 Dec 2016 Valid for Dec 2016 Observed Dec 2016

Climatology Rainy Season Dates ONSETDEMISE

Precipitation Climatology

Precipitation Climatology Animation