The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 7 March 2010 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 • Above-average rainfall during the past week helped to ease the long-term dry conditions over portions of central/southeastern Brazil. • The GFS predicts below-average rainfall for most of northeastern Brazil to continue during the next two weeks, which is consistent with the ongoing El-Nino. The GFS also predicts below-average rainfall over southeastern South America during the next 7 days.
Rainfall Total & Anomaly Patterns:Last 7 Days Total Anomaly During the last 7 days below-average rainfall was observed over a large area of Northern South America (from Peru to Northeast Brazil), while above-average rainfall was observed over central/southeastern Brazil (left panel, blue box).
Rainfall Totals & Anomaly Patterns:Last 30 Days Total Anomaly During the last 30 days above-average rainfall was observed over an area from eastern Bolivia to northeastern Argentina (left panel, blue oval), while much below-average rainfall was observed over North Brazil (red oval).
BP Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau CB NB BAHIA SEB • 90-day rainfall totals are below-average over central Brazil (CB), Northeast Brazil (NB and BAHIA) and over Southeast Brazil (SEB). Deficits of about 150-250 mm. • Above average rainfall during the past week helped to ease the long-term dry conditions over CB, BAHIA and SEB.
Tropical Pacific and Atlantic SST Anomalies During the last week, equatorial SSTs were at least 1°C above-average across the central and extreme eastern equatorial Pacific Ocean. SSTs were 0.5°-1°C above-average in most of the equatorial Atlantic. 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 • During 27 Feb – 5 Mar 2010, anomalous 200-hPa anticyclonic circulation (red A) was observed over central South America, and an enhanced trough (dashed black line) was present over the western South Atlantic. • Anomalous rising motion (negative omega) and above-average rainfall (see slide 4) were observed over central/southeastern Brazil (red rectangle in bottom right panel), near the trough axis. 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 (27 Feb – 5 Mar 2010) above-average temperatures were observed over Northern Brazil and southern Argentina, while below-average temperatures were observed over southeastern Brazil. Stronger than normal southeasterly winds were observed over southeastern Brazil (black arrow, left panel), just to the south of the mean frontal position (dashed blue line). Low-level (~600 m) 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 7 March 2010 – Days 1-7 Total Anomaly Note: Bias correction based on last 30-day forecast error.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 7 March 2010 – Days 8-14 Total Anomaly Note: Bias correction based on last 30-day forecast error.
NCEP/GFS MODEL FORECASTS • For Days 1-7 (7-13 Mar),near- toabove-average rainfall is predicted over portions of southeastern Brazil, the western Amazon basin and Uruguay, while below-average rainfall is predicted for the rest of Brazil, portions of Peru, Bolivia, Paraguay and northern Argentina. • For Days 8-14 (14-20 Mar), above-average rainfall is predicted over portions of the northern Amazon basin and Uruguay, while below-average rainfall is predicted to continue over northeastern Brazil. NOTE: See forecast verification in the next slide.
Forecast Verification Forecast from 21 Feb 2010 Valid 28 Feb – 6 mar 2010 Forecast from 28 Feb 2010 Valid 28 Feb – 6 Mar 2010 Observed 28 Feb – 6 Mar 2010
ClimatologyRainy Season Dates ONSET DEMISE