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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, rainfall 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 03 April 2017 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 are present over the Amazon Basin and central Brazil. • During the last 7 days (27 Mar – 02 Apr 2017), below-average precipitation was observed over much of northern and the extreme southern Brazil, Uruguay and eastern Argentina. Above-average precipitation was observed over Colombia, Ecuador, western Argentina and portions of central Brazil. • For 03 - 09 Apr 2017, below-average precipitation is predicted over much of northern South America. Above-average precipitation is predicted for portions of Paraguay, northeastern and the extreme southern Brazil, as well as southern Argentina.
Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days, below-average precipitation was observed over much of northern and the extreme southern Brazil, Uruguay and eastern Argentina. Above-average precipitation was observed over Colombia, Ecuador, western Argentina and portions of central Brazil.
Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days, below-average precipitation was observed over much of Brazil and eastern Argentina. Above-average precipitation was observed over much of Colombia, Ecuador, Peru, and portions of central and southern Argentina.
BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau • 90-day rainfall deficits are present over Amazon Basin (~ 200 mm) and the Brazilian Plateau (~ 250 mm).
Tropical Pacific and Atlantic SST Anomalies SSTs are slightly below average over central tropical Pacific and above average in the eastern tropical Pacific. (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
Atmospheric Circulation Recent 7 days • Upper panels: During the period of 26 Mar – 01 Apr 2017, anomalous anticyclonic flow (center noted by red A) was observed over central South America. • Lower panels: Anomalous sinking motion was observed over eastern South America. Anomalous rising motion was observed over western South America. 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.
925-hPa Wind &Temperature Recent 30 Days Recent 7 Days During the 7-day period 26 Mar – 01 Apr 2017, above-average temperatures were observed over portions of central and northern Brazil as well as eastern 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.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 03 Apr 2017–Days 1-7 Total Anomaly Note: Bias correction based on last 30-day forecast error.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 03 Apr 2017– Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.
NCEP/GFS MODEL FORECASTS • For Days 1-7 (03 - 09 Apr 2017), below-average precipitation is predicted over much of northern South America. Above-average precipitation is predicted for portions of Paraguay, northeastern and the extreme southern Brazil, as well as southern Argentina. • For Days 8-14 (10 – 16 Apr 2017), below-average precipitation is predicted over much of Brazil, Bolivia and southern Peru. Above-average precipitation is predicted over northwestern South America.
Forecast Verification Forecast from 20 Mar 2017 Valid for 27 Mar – 02 Apr 2017 Forecast from 27 Mar 2017 Valid for 27 Mar – 02 Apr 2017 Observed 27 Mar – 02 Apr 2017
ClimatologyRainy Season Dates ONSET DEMISE