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 September 2013 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 • During the last 7 days (9 -15 September 2013), above-average precipitation was observed over portions of the Amazon Basin, eastern Bolivia and Uruguay. Below-average precipitation was observed over Venezuela and most of southern Brazil. • For 16 -22 September, below-average precipitation is predicted for Colombia, Venezuela, Ecuador, extreme southern Brazil, and southern Chile. Above-average precipitation is predicted for southern Peru, and most of southern Brazil.

Rainfall Total & Anomaly Patterns: Last 7 Days Total Anomaly During the last 7 days, above-average precipitation was observed over portions of the Amazon Basin, eastern Bolivia and Uruguay. Below-average precipitation was observed over Venezuela and most of southern Brazil.

Rainfall Totals & Anomaly Patterns: Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over most of Venezuela, Colombia, central Chile, and Brazil between 15 S and 30 S. Above-average precipitation was found over the north-central Amazon Basin, coastal Northeast Brazil and Uruguay.

Recent Evolution: Rainfall Last 90 Days BP: Brazilian Plateau BP • 90 -day rainfall totals are above average over the southern Amazon Basin, below average over the Brazilian Plateau, and near average over southern Brazil.

Tropical Pacific and Atlantic SST Anomalies SSTs are near average in the central equatorial Pacific, and below average in the eastern equatorial Pacific and central and eastern equatorial Atlantic. (For more 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 7 -13 September 2013, an anomalous trough extended from Bolivia east-southeastward to Southeast Brazil and the western South Atlantic (heavy dashed line in top right panel). An anomalous ridge extended from northern Chile east-southeastward across Uruguay to the western Atlantic (heavy solid line in top panel) • Lower panels: Anomalous sinking motion was found over Southeast Brazil, and anomalous rising motion was observed over eastern Argentina and Uruguay. 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 7 -13 September 2013, above-average temperatures were observed over Southern Brazil, Paraguay, Uruguay and the northern half of 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 16 Sep 2013– 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 Sep 2013– 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 September), below-average precipitation is predicted for Colombia, Venezuela, Ecuador, extreme southern Brazil, and southern Chile. Above-average precipitation is predicted for southern Peru, and most of southern Brazil. • For Days 8 -14 (23 -29 September), above-average precipitation is predicted for southern Peru, and below-average precipitation is predicted for Venezuela, Colombia, northern Peru, portions of southern Brazil, Uruguay, northeastern Argentina and southern Chile.

Forecast Verification Forecast from 2 Sep 2013 Valid for 9 -15 Sep 2013 Not Available Forecast from 9 Sep 2013 Valid for 9 -15 Sep 2013 Observed 9 -15 Sep 2013

Climatology Rainy Season Dates ONSET DEMISE

Precipitation Climatology

Precipitation Climatology Animation