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 10 September 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, the Brazilian Plateau and the extreme southern Brazil. • During the last 7 days, below-average precipitation was observed over portions of central Venezuela, western Brazil, southern Chile and Uruguay. Above-average precipitation was observed over portions of northern Brazil and eastern Colombia. • For Days 1 -7 (10 – 16 September 2018), below-average precipitation is predicted over portions of northern Colombia, Venezuela, west-central Brazil and southern Chile. Above-average precipitation is predicted for portions of central Colombia and central Argentina.

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

Rainfall Totals & Anomaly Patterns: Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over much of the far northern South America, as well as portions of southern Brazil, southern Chile and central Argentina. Aboveaverage precipitation was observed over portions of eastern Colombia, northern Peru 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 (~ 60 mm) , the Brazilian Plateau (~ 20 mm) and the extreme southern Brazil (~ 50 mm).

Tropical Pacific and Atlantic SST Anomalies SSTs are above-average across the tropical Pacific, north of the Equator. (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 02 -08 Sept 2018, anomalous anticyclonic flow (center noted by red A) was observed over southern Argentina. A • Lower panels: Anomalous sinking motion was observed over much of Brazil and northern Argentina. Anomalous rising motion was observed elsewhere. • 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 02 – 08 Sept 2018, above-average temperature was observed over northern Brazil and eastern Argentina, and below-average temperatures was observed over southern 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 10 September 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 10 September 2018– Days 8 -14 Total Note: Bias correction based on last 30 -day forecast error. Anomaly

NCEP/GFS MODEL FORECASTS • For Days 1 -7 (10 – 16 September 2018), below-average precipitation is predicted over portions of northern Colombia, Venezuela, west-central Brazil and southern Chile. Above-average precipitation is predicted for portions of central Colombia and central Argentina. • For Days 8 -14 (17 – 23 Sept 2018), below-average precipitation is predicted over portions of northern South America. Above-average precipitation is predicted for the extreme southern Brazil and southern Chile.

Climatology Rainy Season Dates ONSET DEMISE

Precipitation Climatology

Precipitation Climatology Animation