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The South American Monsoon System: Recent Evolution and Current Status

This report provides an update on the recent evolution and current conditions of the South American monsoon system, including rainfall deficits and anomalies in various regions. It also includes forecasts for rainfall patterns in the coming weeks.

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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 5 October 2015 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 • Rainfall deficits increased over many areas of northern South America. • During the last 7 days (28 September-4 October 2015), below-average precipitation was observed over a large portion of northern South America. Above-average precipitation was observed over Paraguay and parts of southwestern Brazil. • For 5-11 October 2015, below-average rainfall is predicted for many areas in northern South America. Above-average rainfall is predicted for southern Brazil and northern Uruguay.

  4. Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, below-average precipitation was observed over a large portion of northern South America. Above-average precipitation was observed over Paraguay and parts of southwestern Brazil.

  5. Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over most of northern South America, and northeastern Argentina. Above-average precipitation was observed over northern Paraguay and portions of Brazil (20-30S).

  6. BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall deficits are present over the southern Amazon Basin (~150 mm) and the Brazilian Plateau (~30-50mm). • 90-day rainfall is slightly below average over southern Brazil.

  7. Tropical Pacific and Atlantic SST Anomalies SSTs are above average in the equatorial Pacific, and slightly below average in the central tropical Atlantic. (For details concerning El Niño – La Niña, go to the link below.) A weekly PowerPoint summarizing the ENSO Cycle: Recent Evolution, Current Status and Predictionsis available at: http://www.cpc.noaa.gov/products/precip/CWlink/MJO/enso.shtml

  8. Atmospheric Circulation Recent 7 days • Upper panels: During the period of 27 September-3 October 2015, anomalous anticyclonic flow (center indicated by red A) dominated the subtropical South Atlantic. Anomalously strong westerlies extended from Peru southeastward across northern Argentina, and Uruguay. • Lower panels: Anomalous rising motion was observed over Bolivia, Paraguay and southern Brazil. Anomalous sinking motion occurred over northern South America, central Chile and southeastern Argentina. A • 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 27 September-3 October 2015, above-average temperatures were observed over most of Brazil. Below-average temperatures were observed most 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-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 5 October 2015 –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 5 October 2015 – Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.

  12. NCEP/GFS MODEL FORECASTS • For Days 1-7 (5-11 October 2015), below-average rainfall is predicted for many areas in northern South. Above-average rainfall is predicted for southern Brazil and northern Uruguay. • For Days 8-14 (12-18 October 2015), below-average rainfall is predicted for many areas in northern South America and northern Bolivia. Above-average rainfall is predicted for portions of Uruguay and southern Brazil.

  13. Forecast Verification Forecast from 21 Sep. 2015 Valid for 28 Sep.-4 Oct. 2015 Forecast from 28 Sep. 2015 Valid for 28 Sep.-4 Oct. 2015 Observed 28 Sep.-4 Oct. 2015

  14. ClimatologyRainy Season Dates ONSET DEMISE

  15. Precipitation Climatology

  16. Precipitation Climatology Animation

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