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This report provides an update on the recent evolution and current conditions of the South American Monsoon System, including rainfall patterns, temperature anomalies, and forecast predictions.
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The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 2 December 2013 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/American_Monsoons
Outline • Highlights • Recent Evolution and Current Conditions • NCEP/GFS Model Forecasts • Climatology
Highlights • Long-term rainfall deficits continue over the core monsoon region. • During the last 7 days (25 Nov-1 Dec 2013), below-average precipitation was observed over western and extreme southern Brazil, eastern Bolivia, and southern Venezuela. Above-average precipitation was observed over western Colombia, eastern Argentina and eastern Brazil. • For 2-8 December, below-average rainfall is predicted for most of Brazil, southern Venezuela, eastern Bolivia , eastern Argentina and Uruguay. Above-average rainfall is predicted for most of Colombia, Peru and Paraguay.
Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, below-average precipitation was observed over western and extreme southern Brazil, eastern Bolivia, and southern Venezuela. Above-average precipitation was observed over western Colombia, eastern Argentina and eastern Brazil.
Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over southern Venezuela, southern Colombia and portions of central and southeastern Brazil. Above-average precipitation was found over northeastern Argentina, Uruguay, extreme southern Brazil, portions of the western Amazon Basin, and northern Peru .
BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall totals are below average over the southern Amazon Basin, the Brazilian Plateau. And southern Brazil.
Tropical Pacific and Atlantic SST Anomalies SSTs are above average in the western equatorial Pacific and near average in most of the equatorial Pacific from 180W to the South American coast . SSTs are near or slightly below average in the equatorial 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 Predictions is available at: http://www.cpc.noaa.gov/products/precip/CWlink/MJO/enso.shtml
Atmospheric Circulation Recent 7 days • Upper panels: During the period of 23-29 November 2013, anomalous cyclonic circulation (red C) was observed over Bolivia, indicating a weaker than normal Bolivian High. • Lower panels: Anomalous rising motion was found over eastern Argentina and eastern Brazil, consistent with the anomalous precipitation pattern shown in slide 4. 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.
925-hPa Wind &Temperature Recent 30 Days Recent 7 Days • During the 7-day period 23-29 November 2013, temperatures were below average in central Argentina and Chile, and near average elsewhere in South America. 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.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 2 Dec 2013– Days 1-7 Total Anomaly Note: Bias correction based on last 30-day forecast error.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 2 Dec 2013– Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.
NCEP/GFS MODEL FORECASTS • For Days 1-7 (2-8 Dec), below-average rainfall is predicted for most of Brazil, southern Venezuela, eastern Bolivia , eastern Argentina and Uruguay. Above-average rainfall is predicted for most of Colombia, Peru and Paraguay. • For Days 8-14 (2-8 Dec), below-average rainfall is predicted for southern Venezuela, and northern and central Brazil. Above-average rainfall is predicted for western Colombia, northern and central Peru, and portions of eastern Brazil.
Forecast Verification Forecast from 18 Nov 2013 Valid for 25 Nov-1 Dec 2013 Forecast from 25 Nov 2013 Valid for 25 Nov-1 Dec 2013 Observed 25Nov-1 Dec 2013
ClimatologyRainy Season Dates ONSET DEMISE