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 11 October 2009 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 • Drier-than-average conditions persisted throughout northern South America during the last 7 days. • Much above-average rainfall has been observed over portions of southern Brazil during the last 30 days. • The GFS predicts above-average rainfall over most of Brazil during the next two weeks.

4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days below-average rainfall was observed over Colombia, Venezuela, Guyana, throughout the Amazon basin, and portions of southern Brazil, and northeastern Argentina. Slightly above-average rainfall was observed over portions of central Brazil and Uruguay.

5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days much above-average rainfall was observed over portions of southern Brazil (right panel, blue oval), while much below-average rainfall was observed over most of Colombia, Venezuela, and the northern Amazon basin (right panel, red oval).

6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau NCA CB SA SB • 90-day rainfall totals are near-average for the southern Amazon basin (SA) and central Brazil (CB), above-average over southern Brazil (SB) and below-average over the north-central Amazon basin (NCA). • 90-day rainfall totals in SB are between 200 mm and 250 mm above average.

7. Tropical Pacific and Atlantic SST Anomalies During the last week, equatorial SSTs were at least 0.5°C above-average across the Pacific Ocean, with 1°C above average over central Pacific. SSTs were near average in the equatorial Atlantic, and below average along the west coast of South America.

8. Atmospheric Circulation Recent 7 days • DUE TO COMPUTER PROBLEMS THE CIRCULATION MAPS ARE NOT AVAILABLE TODAY 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 • DUE TO COMPUTER PROBLEMS THE TEMPERATURE MAPS ARE NOT AVAILABLE TODAY 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. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 11 October 2009 – Days 1-7 Total Anomaly Note: Bias correction based on last 30-day forecast error.

11. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 11 October 2009 – Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (11 – 17 Oct 2009), above-average rainfall is predicted over most of Brazil, Paraguay, northern Bolivia and Colombia, while below-average rainfall is predicted over northern Argentina, most of Peru and Venezuela . • For Days 8-14 (18-24 Oct 2009), above-average rainfall is predicted over most of Brazil, Suriname, Guyana and eastern Venezuela, while below-average rainfall is predicted over northwestern South America (Peru, Ecuador, Colombia and western Venezuela). NOTE: See forecast verification in the next slide.

13. Forecast Verification Forecast from 27 Sep 2009 Valid 4-10 Oct 2009 Forecast from 4 Oct 2009 Valid 4-10 Oct 2009 Observed 4-10 Oct 2009

14. ClimatologyRainy Season Dates ONSET DEMISE

15. Precipitation Climatology

16. Precipitation Climatology Animation