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This report provides an update on the recent evolution and current conditions of the South American monsoon system. It includes highlights, forecasts, climatology, rainfall totals, and anomaly patterns. The report also discusses the Brazilian Plateau, tropical Pacific, Atlantic SST anomalies, atmospheric circulation, wind and temperature patterns, and NCEP/GFS model forecasts.
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The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 30 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 precipitation deficits continue over the core monsoon region and southern Brazil. • During the last 7 days (23-29 Dec 2013), below-average precipitation was observed over southern Brazil, Paraguay, Uruguay and northern Argentina. Above-average precipitation was observed over Suriname, French Guiana, and portions of eastern Brazil. • For 30 December 2013 - 5 January 2014, below-average precipitation is predicted for most of the Amazon Basin, central Brazil, and eastern Bolivia. Above-average precipitation is predicted for Peru, southern Paraguay and southern Brazil.
Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, below-average precipitation was observed over southern Brazil, Paraguay, Uruguay and northern Argentina. Above-average precipitation was observed over Suriname, French Guiana, and portions of eastern Brazil.
Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over southern Venezuela, southeastern Colombia, portions of the Amazon Basin, southern Brazil, northeastern Argentina and Uruguay. Above-average precipitation was found over western Colombia. Bolivia, and most of Northeast Brazil.
BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall totals are below average over the southern Amazon Basin, the western Brazilian Plateau, and southern Brazil. • Recent heavy rains have helped to alleviate long term deficits over the Brazilian Plateau.
Tropical Pacific and Atlantic SST Anomalies SSTs are above average in the western equatorial Pacific and near average in most of the equatorial Pacific between 180W and the South American coast . SSTs are slightly below average in the central 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 21-27 December 2013, anomalous cyclonic circulation (red C) was observed over central South America, indicating a weaker-than-average Bolivian High. • Lower panels: Anomalous rising motion was found over eastern Brazil, and the southern Amazon Basin, and anomalous sinking motion was observed over southern Brazil and northern Argentina, consistent with the pattern of anomalous rainfall 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 21-27 December 2013, temperatures were above average in southern Brazil, Uruguay, northern and eastern Argentina, and central Chile. 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 30 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 30 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 (30 Dec 2013-5 Jan 2014), below-average precipitation is predicted for most of the Amazon Basin, central Brazil, and eastern Bolivia. Above-average precipitation is predicted for Peru, southern Paraguay and southern Brazil. • For Days 8-14 (6-12 Jan 2014), below-average precipitation is predicted for the northern and eastern Amazon Basin, and central Brazil. Above-average precipitation is predicted for Peru, northern Bolivia and Paraguay.
Forecast Verification Forecast from 16 Dec 2013 Valid for 23-29 Dec 2013 Forecast from 23 Dec 2013 Valid for 23-29 Dec 2013 Observed 23-29 Dec 2013
ClimatologyRainy Season Dates ONSET DEMISE