The South American Monsoon System Recent Evolution and

The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 11 December 2017 For more information, visit: http: //www. cpc. ncep. noaa. gov/products/Global_Monsoons/American_Monsoons

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

Highlights • Long-term rainfall deficits are present over the Amazon Basin and Brazilian Plateau. • During the last 7 days, below-average precipitation was observed over much of northern and southern Brazil, Uruguay and eastern Argentina. Above-average precipitation was observed over portions of central Brazil, northern Peru and northern Bolivia. • For Days 1 -7 (11 -17 Dec 2017), below-average precipitation is predicted over much of southern Brazil, Paraguay, northern Argentina, Bolivia, southern Colombia and western Venezuela. Above-average precipitation is predicted for portions of central Brazil, central Colombia and southern Chile.

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

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

Recent Evolution: Rainfall Last 90 Days BP: Brazilian Plateau BP • 90 -day rainfall deficits are present over Amazon Basin (~ 40 mm) and the Brazilian Plateau (~ 100 mm).

Tropical Pacific and Atlantic SST Anomalies SSTs are below-average across the central and eastern tropical Pacific. (For details concerning El Niño – La Niña, go to the link below. ) A weekly Power. Point summarizing the ENSO Cycle: Recent Evolution, Current Status and Predictions is available at: http: //www. cpc. noaa. gov/products/precip/CWlink/MJO/enso. shtml

Atmospheric Circulation Recent 7 days A • Upper panels: During the period of 03 -09 Dec 2017, anomalous anticyclonic flow (center noted by red A) was observed over southern Brazil. • Lower panels: Anomalous sinking motion was observed over northeastern South America. Anomalous rising motion was observed across the central South America. • Rising motion (negative omega, yellow/red shading), usually associated with wetter- thannormal conditions. • Sinking motion (positive omega, blue shading), usually associated with drier-than-normal conditions.

925 -h. Pa Wind &Temperature Recent 30 Days Recent 7 Days During the 7 -day period 03 -09 Dec 2017, slightly above-average temperatures were observed over northern Brazil. Below-average temperatures were seen over Paraguay and 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 -h. Pa are usually similar to surface observations. Note: Areas with surface pressure below 925 -h. Pa are masked out.

NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 11 December 2017– Days 1 -7 Total Note: Bias correction based on last 30 -day forecast error. Anomaly

NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 11 December 2017– Days 8 -14 Total Note: Bias correction based on last 30 -day forecast error. Anomaly

NCEP/GFS MODEL FORECASTS • For Days 1 -7 (11 -17 Dec 2017), below-average precipitation is predicted over much of southern Brazil, Paraguay, northern Argentina, Bolivia, southern Colombia and western Venezuela. Above-average precipitation is predicted for portions of central Brazil, central Colombia and southern Chile. • For Days 8 -14 (18 -24 Dec 2017), below-average precipitation is predicted over much of northern and central Brazil, northeastern Argentina, Paraguay and southern Chile. Above-average precipitation is predicted over portions of central Colombia, central and southern Peru and Uruguay.

Forecast Verification Forecast from 27 Nov 2017 Valid for 04 -10 Dec 2017 Forecast from 04 Dec 2017 Valid for 04 -10 Dec 2017 Observed 04 -10 Dec 2017

Climatology Rainy Season Dates ONSET DEMISE

Precipitation Climatology

Precipitation Climatology Animation