The South American Monsoon System: Recent Evolution and Current Status

1. The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 31 January 2011 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons

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

3. Highlights • During the last 7 days, below-average rainfall was observed over southern Brazil, southern Bolivia, part of Paraguay, and part of northern South America. Above-average rainfall was observed over northern Brazil, part of Peru, and northern Argentina (near 30S). • Products of week-1 and week-2 predictions by the NCEP GFS are not available due to a technical problem.

4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, below-average rainfall was observed over southern Brazil, southern Bolivia, part of Paraguay, and part of northern South America. Above-average rainfall was observed over northern Brazil, part of Peru, and northern Argentina (near 30S).

5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average rainfall was observed over Peru, western and southeastern Brazil, Bolivia, and northern Argentina. Above-average rainfall was observed over portions of northern and central Brazil and part of northern Argentina.

6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • in spite of the recent heavy rains, 90-day accumulated rainfall totals remain below average over the southern Amazon Basin. Also, slightly-above-average rainfall has been observed over the western core monsoon region due to the early January rainfall (BP). • 90-day totals are near average in southern Brazil, where rainfall during December eliminated previous deficits.

7. Tropical Pacific and Atlantic SST Anomalies During the last week, equatorial SSTs were between 0.5° - 2.0°C below average over most of the central and eastern Pacific Ocean. SSTs were 0.5°-1.0°C above average in the equatorial Atlantic. A La-Nina event is in progress in the tropical Pacific (for more details go to the link below). A weekly PowerPoint summarizing the ENSO Cycle: Recent Evolution, Current Status and Predictions is available at: http://www.cpc.noaa.gov/products/precip/CWlink/MJO/enso.shtml

8. Atmospheric Circulation Recent 7 days • During 22-28 Jan 2011, anomalous easterly flow was observed over 15S-30S with an anomalous cyclonic pattern over southeastern Brazil. • Anomalous rising motion (negative omega) and wetter-than-average conditions (see slide 4, right panel) were observed over northern and western Brazil and extreme southern Brazil. Sinking motion (positive omega) and below-average rainfall were observed over 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.

9. 925-hPa Wind &Temperature Recent 30 Days Recent 7 Days • During the 7-day period (22-28 Jan 2011) near-average temperatures were observed over South America (except the above-average temperature over the southeast), with an anomalous low-level cyclonic pattern over western Brazil. Low-level (~600 m) 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.

10. ClimatologyRainy Season Dates ONSET DEMISE

11. Precipitation Climatology

12. Precipitation Climatology Animation