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The South American Monsoon System: Recent Evolution and Current Status

This report provides highlights, recent evolution, and current conditions of the South American Monsoon System as of March 1, 2009. It includes rainfall anomaly patterns, atmospheric circulation patterns, temperature trends, and NCEP/GFS model forecasts. For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons.

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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 1 March 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 • The GFS predicts below-normal rainfall over the monsoon core region during week 1 (1-7 March), and above-normal during week 2 (8-14 March). • Above-normal rainfall is predicted over northern Northeast Brazil during the next week (1-7 March).

  4. Rainfall Total & Anomaly Patterns:Last 90 Days During the period 1 December 2008 – 28 February 2009 rainfall was below normal over most of the monsoon core region, and much above-normal over the northwestern Amazon.

  5. Rainfall Anomaly Patterns: Last 30 Days Last 7 Days During the last 30 days, rainfall deficits were observed over the southern Amazon basin, portions of central and southeastern Brazil and the northern half of Argentina. During the last 7 days above-normal rainfall occurred over portions of the Amazon, Northeast and southern Brazil.

  6. BP Recent Evolution: Rainfall • 90-day rainfall totals are about 50 mm above normal over Northeast Brazil, due to rainfall during the last 6 weeks. • Below normal rainfall over the Brazilian Planalto (BP) since January has brought the latest 90-day rainfall total to about 200 mm below normal.

  7. BP Recent Evolution: Rainfall • During the last 90 days, rainfall totals have been below normal in southern Brazil, northeastern Argentina and southern Paraguay (deficits near 100 mm).

  8. Atmospheric Circulation Recent 7 days • During 14-20 February, a 200-hPa trough (cyclonic circulation, red dashed line) was centered over Northeast Brazil, and an enhanced ridge (anticyclonic circulation, red A) was located along the coast of southern Brazil. • Anomalous rising motion (negative omega, red ovals) and above-normal rainfall (see slide 5) were observed over northern Northeast Brazil and over the western Amazon, Peru, Bolivia, Paraguay and southern Brazil. A

  9. 925-hPa Temperature Recent 90 Days Recent 30 Days Recent 7 Days • During the last 7 days (21-27 February 2008) below-normal temperatures were observed over eastern Argentina and Uruguay associated with southerly flow over those regions. Portions of central-western and southern Brazil were warmer than normal.

  10. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 1 March 2009 – Week 1 Anomaly Total Note: Bias correction based on last 30-day forecast error.

  11. NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 1 March2009 – Week 2 Anomaly Total Note: Bias correction based on last 30-day forecast error.

  12. NCEP/GFS MODEL FORECASTS • For week 1 (1-7 March 2009), above-normal rainfall is predicted for the northern Northeast Brazil, northern Peru, Ecuador, Colombia, portions of southern Brazil, Uruguay and portions of northern Argentina. Below-normal rainfall is predicted for the southern Amazon, central and southeastern Brazil. • For week 2 (8-14 Mar 2009) slightly above-normal rainfall is predicted over most of the monsoon region (from the Amazon basin to southeastern Brazil). NOTE: See forecast verification in the next slide.

  13. Forecast Verification Observed 22-28 Feb 2009 Forecast from 15 Feb 2009 Valid 22-28 Feb 2009 Forecast from 22 Feb 2009 Valid 22-28 Feb 2009

  14. ClimatologyRainy Season Dates ONSET DEMISE

  15. Precipitation Climatology

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