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 16 April 2018 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 the Brazilian Plateau. • During the last 7 days, below-average precipitation was observed over portions of northern and the extreme southern Brazil, Paraguay and northeastern Argentina. Above-average precipitation was observed over portions of northeastern and central Brazil, northern Argentina, southern Chile, northern Peru and western Colombia. • For Days 1 -7 (16 - 22 April 2018), below-average precipitation is predicted over much of central and the extreme southern Brazil, northeastern Argentina, Paraguay, Uruguay, southern Bolivia, central and southern Peru, as well as western Ecuador. Above-average precipitation is predicted for portions of northern South America and southern Chile.

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

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 northern Argentina. Above-average precipitation was observed over portions of Colombia, central Peru, central and the extreme southern Brazil.

Recent Evolution: Rainfall Last 90 Days BP: Brazilian Plateau BP • 90 -day rainfall deficits are present over the Amazon Basin (> 100 mm) and the Brazilian Plateau (> 150 mm).

Tropical Pacific and Atlantic SST Anomalies SSTs are below-average across the central and far 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 • Upper panels: During the period of 08 – 14 April 2018, anomalous anticyclonic flow (center noted by red A) was observed over northern Argentina. A • Lower panels: Anomalous sinking motion was observed over the extreme southern Brazil. Anomalous rising motion was observed over much of northern South America and northern Argentina. • 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 08 – 14 April 2018, above-average temperature was observed over Paraguay and the extreme souther Brazil. 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 16 April 2018– Days 1 -7 Total Note: Bias correction based on last 30 -day forecast error. Anomaly

NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 16 April 2018– Days 8 -14 Total Note: Bias correction based on last 30 -day forecast error. Anomaly

NCEP/GFS MODEL FORECASTS • For Days 1 -7 (16 - 22 April 2018), below-average precipitation is predicted over much of central and the extreme southern Brazil, northeastern Argentina, Paraguay, Uruguay, southern Bolivia, central and southern Peru, as well as western Ecuador. Above-average precipitation is predicted for portions of northern South America and southern Chile. • For Days 8 -14 (23 - 29 Apr 2018), below-average precipitation is predicted over much of Brazil, Paraguay, Bolivia, southern Peru and southern Chile. Above-average precipitation is predicted for portions of northern Argentina and northwestern South America.

Climatology Rainy Season Dates ONSET DEMISE

Precipitation Climatology

Precipitation Climatology Animation