The South American Monsoon System: Recent Evolution and

Current Status

Update prepared byClimate Prediction Center / NCEP

31 October 2011

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

• During the last 7 days, below-average rainfall was observed over much of South America especially the central portion of the continent. Above-average rainfall was observed over Guyana, Suriname, Paraguay, and extreme southern Brazil.

For 31 October – 6 November, above-average rainfall is predicted for northern and northeastern Brazil and portions of Peru, Colombia, and northwestern Venezuela. Below-average rainfall is predicted over southern and southwestern Brazil, Bolivia, Paraguay, Uruguay, and northeastern Argentina. For 7-14 November, above-average rainfall is predicted for portions of Colombia, northern and extreme southern Brazil, southern Peru, southern Paraguay, Uruguay, and northeastern Argentina. Below-average rainfall is predicted over western and central Brazil, northern Peru, southern Colombia, and northern Venezuela.

Highlights

Rainfall Total & Anomaly Patterns:Last 7 Days

During the last 7 days, below-average rainfall was observed over much of South America especially the central portion of the continent. Above-average rainfall was observed over Guyana, Suriname, Paraguay, and extreme southern Brazil.

Total Anomaly

Rainfall Totals & Anomaly Patterns:Last 30 Days

During the last 30 days, below-average rainfall was observed over the large domain to the west of 60W and north 25S, except for the above-average rainfall over portions of Colombia and Paraguay. Above-average rainfall was found mainly to the east 60W.

Total Anomaly

BP

Recent Evolution: RainfallLast 90 Days BP: Brazilian Plateau

• 90-day rainfall totals are clearly below average over the southern Amazon basin. Below-average rainfall has also been observed over the Brazilian Plateau.

• 90-day totals are slightly above average in southern Brazil.

Tropical Pacific and Atlantic SST Anomalies

Below-average SSTs are present in the equatorial Pacific Ocean, and above-average SSTs are found in the equatorial Atlantic. (For more details of El Niño – La Niña evolutions, 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

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.

• Upper panels: During 22-28October 2011, in the upper troposphere , anomalous easterly flow was observed over northern South America. Anomalous anticyclonic circulation (A) was observed over the eastern Pacific to the west of Chile.

• Lower panels: Anomalous rising motion (negative omega) was found over Peru and extreme southern Brazil and anomalous sinking motion was observed over northern Brazil and northwestern Argentina/northern Chile.

A

925-hPa Wind &Temperature Recent 30 Days Recent 7 Days

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.

• During the 7-day period of 22-28 October 2011, near-normal temperatures were observed over South America, except for eastern Argentine where temperatures were below-normal.

NCEP/GFS Model Forecasts Bias-Corrected Precipitation

Total

Forecasts from 31 Oct 2011 – Days 1-7

Anomaly

Note:Note: Bias correction based on last 30-day forecast error.

NCEP/GFS Model Forecasts Bias-Corrected Precipitation

Total

Forecasts from 31 October 2011– Days 8-14

Anomaly

Note:Note: Bias correction based on last 30-day forecast error.

• For Days 1-7 (31 October – 6 November), above-average rainfall is predicted for northern and northeastern Brazil and portions of Peru, Colombia, and northwestern Venezuela. Below-average rainfall is predicted over southern and southwestern Brazil, Bolivia, Paraguay, Uruguay, and northeastern Argentina.

• For Days 8-14 (7-14 November), above-average rainfall is predicted for portions of Colombia, northern and extreme southern Brazil, southern Peru, southern Paraguay, Uruguay, and northeastern Argentina. Below-average rainfall is predicted over western and central Brazil, northern Peru, southern Colombia, and northern Venezuela.

NCEP/GFS MODEL FORECASTS

Forecast Verification

Forecast from 16 Oct 2011 Valid 23-29 Oct 2011

Forecast from 25 Oct 2011 Valid 25-31 Oct 2011

Observed 24-30 Oct 2011

ClimatologyRainy Season Dates

ONSETONSET DEMISE

Precipitation Climatology

Precipitation Climatology Animation