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This report provides an overview of the recent evolution and current conditions of the South American Monsoon System. It includes information on rainfall patterns, SST anomalies, temperature trends, and model forecasts. Visit the link for more details.
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The South American Monsoon System: Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 30 August 2009 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 • The increased frequency of synoptic weather disturbances, cold fronts, over southern Brazil and southern Paraguay, in part associated with El Niño conditions, brought the July-August 2009 rainfall total to much above-average. • The GFS predicts above-normal rainfall over southern Brazil and Paraguay for the next two weeks.
Rainfall Total & Anomaly Patterns:1 July – 29 August 2009 From early July to late August (1 Jul – 29 Aug 2009), rainfall was much above-average over southern Brazil and southern Paraguay (blue box, right panel). The above-average rainfall over this region during July and August was due to the increase frequency of synoptic weather disturbances, cold fronts, which are partly associated with El-Niño conditions. Above-average rainfall was also observed over portions of Northeast Brazil and central Colombia.
Tropical Pacific and Atlantic SST Anomalies (1 Jul-29 Aug 2009) During 1 July – 29 August 2009, equatorial SSTs were at least 0.5°C above-average across the Pacific Ocean and at least 1.0°C above average over the central and eastern Pacific near the northern South American coast. SSTs were below average in the Tropical Atlantic near the South American coast extending eastward to the African coast.
Rainfall Total & Anomaly Patterns:Last 7 Days During the last 7 days below-average rainfall was observed over southern Brazil, southern Paraguay and the northern Amazon Basin. Above-average rainfall was observed over portions of coastal Northeast Brazil, and from the southern Amazon Basin extending southeastward into the state of Mato Grosso do Sul in Brazil.
BP Recent Evolution: Rainfall • 90-day rainfall totals over Northeast Brazil are above-average (surpluses of about 100 mm). • The increased frequency in wet days over Southern Brazil during July and August brought the latest 90-days total to slightly above-average over that region.
925-hPa Temperature Recent 30 Days Recent 7 Days • During the 7-day period (20-26 August 2009) below-normal temperatures were observed over portions of eastern Bolivia, Paraguay, southern and southwestern (Mato Grosso do Sul) Brazil, while above-normal temperatures were observed over portions of eastern Argentina near Buenos Aires.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 30 August 2009 – Days 1-7 Anomaly Total Note: Bias correction based on last 30-day forecast error.
NCEP/GFS Model Forecasts Bias-Corrected Precipitation Forecasts from 30 August2009 – Days 8-14 Anomaly Total Note: Bias correction based on last 30-day forecast error.
NCEP/GFS MODEL FORECASTS • For Days 1-7 (30 Aug-5 Sep 2009), above-average rainfall is predicted over southern Brazil, southern Paraguay, Uruguay, and portions of Peru and Bolivia, while below-average rainfall is expected over the extreme northern Amazon Basin, covering most of Venezuela and Guyana. • For Days 8-14 (6-12 Sep 2009), below-average rainfall is predicted throughout the western Amazon Basin, and above-average rainfall is expected to continue over portions of southern Brazil and southern Paraguay.
ClimatologyRainy Season Dates ONSET DEMISE
