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The South American Monsoon System: Recent Evolution and Current Status

This report provides highlights of the recent evolution and current conditions of the South American monsoon system, including rainfall anomalies and forecasts. It also includes information on atmospheric circulation and temperature patterns. For more details, visit the provided link.

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The South American Monsoon System: Recent Evolution and Current Status

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  1. The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 14 March 2010 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 • Below-average rainfall dominated most of Brazil during the past week. Below-average rainfall was also observed extending from Bolivia to northeastern Argentina. • For the next 7days, the GFS predicts below-average rainfall to continue over most of northeastern Brazil, which is consistent with the ongoing El-Nino. The GFS also predicts below-average rainfall over southern and central Brazil.

  4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days below-average rainfall was observed over most of Brazil, Bolivia, Paraguay, Uruguay and northeastern Argentina, while near-average rainfall was observed for the rest of South America.

  5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days above-average rainfall was observed over Paraguay, Uruguay and the northern two-thirds of Argentina (left panel, blue oval), while much below-average rainfall was observed over northern South America (red oval).

  6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau CB NB BAHIA SEB • 90-day rainfall totals are below-average over central Brazil (CB), Northeast Brazil (NB and BAHIA) and over Southeast Brazil (SEB). Deficits of about 100-250 mm. • Rainfall during the past week (blue ovals) helped to ease the long-term dry conditions over CB, BAHIA and SEB.

  7. Tropical Pacific and Atlantic SST Anomalies During the last week, equatorial SSTs were at least 1°C above-average across the central and portions of extreme eastern equatorial Pacific Ocean. SSTs were 0.5°-1°C above-average in the equatorial Atlantic. 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 6-12 Mar 2010, anomalous 200-hPa cyclonic circulation (red C) was centered near the coast of southern Brazil. • Anomalous sinking motion (negative omega) and below-average rainfall (see slide 4) were observed over southern Brazil, Bolivia, Paraguay, Uruguay and northeastern Argentina (blue rectangle in bottom right panel), on the west and south flanks of the cyclonic circulation. Rising motion (positive omega) and near-average rainfall were observed over the state of Bahia, Brazil. C 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 C • During the 7-day period (6-12 Mar 2010) above-average temperatures were observed over most of South America and the adjacent Atlantic Ocean. Anomalous low-level cyclonic circulation was centered near the southern Brazil coast (red C). 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 14 March 2010 – 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 14 March 2010 – Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

  12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (14-20 Mar),below-average rainfall is predicted over most of Brazil, with the exception of slightly above-average over portions of the western Amazon basin and near the coast of Southeast Brazil. • For Days 8-14 (21-27 Mar), near-average rainfall is predicted over southern and northeastern Brazil, while below-average rainfall is predicted over western Amazon basin and southeastern Brazil. Below-average rainfall is also predicted over Bolivia. NOTE: See forecast verification in the next slide.

  13. Forecast Verification Forecast from 28 Feb 2010 Valid 7-13 Mar 2010 Forecast from 7 Mar 2010 Valid 7-13 Mar 2010 Observed 7-13 Mar 2010

  14. ClimatologyRainy Season Dates ONSET DEMISE

  15. Precipitation Climatology

  16. Precipitation Climatology Animation

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