# Presentation: 164068

## The South American Monsoon System: Recent Evolution and Current Status

**Update prepared by**
**Climate Prediction Center / NCEP**
**   ****30 November 2007**

## Outline

** ****Recent Evolution and Current Conditions**
** ****Summary**
** ****Climatology**

## Rainfall Patterns: Last 90 Days

**Rainfall Patterns: Last 90 Days**

**During the last 90 days rainfall has been below normal over most of Brazil, with rainfall deficits of more than 175 mm in portions of central Brazil.  Slightly above-normal rainfall was observed over eastern Bolivia, Paraguay and extreme southern Brazil.**

## Rainfall Patterns: Last 30 Days

**During the last 30 days rainfall has been below normal over most of Brazil, except for the western Amazon Basin and the southern portion of the country. Below-normal rainfall was also observed over Uruguay and northern Argentina.**

## Rainfall Patterns: Last 7 Days

**During the last 7 days rainfall has been above normal over the southern Amazon Basin and eastern Brazil, while below-normal rainfall was observed over portions of southeastern Brazil and northeastern Argentina.**

## Recent Evolution: Rainfall

**The SAMS wet season was delayed in many areas. **
**Recently, rainfall has increased to above normal in western Brazil, but rainfall deficits continue over the Brazilian Plateau (BP), with deficits between 120 and 160 mm during the last 3 months.**

## During 28 October-6 November (top panel) enhanced precipitation (negative OLR anomalies) was observed over portions of southeastern and southern Brazil. Positive OLR anomalies (drier-than-average conditions) covered most of the Amazon Basin, Northeast Brazil, and central Argentina.
During 7-16 November, wetter-than normal conditions strengthened over southeastern Brazil, while drier-than-normal conditions continued over Northeast Brazil.
During 17-26 November drier-than-normal conditions dominated most of South America.

**During 28 October-6 November (top panel) enhanced precipitation (negative OLR anomalies) was observed over portions of southeastern and southern Brazil. Positive OLR anomalies (drier-than-average conditions) covered most of the Amazon Basin, Northeast Brazil, and central Argentina.**
**During 7-16 November, wetter-than normal conditions strengthened over southeastern Brazil, while drier-than-normal conditions continued over Northeast Brazil.**
**During 17-26 November drier-than-normal conditions dominated most of South America.**

## Atmospheric Circulation & OLR Last 5 days

**Atmospheric Circulation & OLR Last 5 days**

**During the last 5 days low OLR (left panel) was observed from the western Amazon eastward across Brazil and then southeastward over the western South Atlantic Ocean.**
**Precipitation was above normal (negative OLR anomalies, right panel) over portions of Northeast Brazil and eastern Bolivia.**
**During this period an amplified 200-hPa ridge was located over northern Argentina and southern Brazil and an amplified trough was located over the South Atlantic Ocean.**

## Summary

**Rainfall has been slightly above normal in western Brazil and much below normal in central and southeastern Brazil during the last 90 days.**
**The rainy season was slow to start over central and southeastern Brazil, where rainfall deficits of 120-160 mm have been observed during the last 90  days.**
**During the last 7 days rainfall has been above normal over the southern Amazon Basin and portions of eastern Brazil.**

## ClimatologyRainy Season Dates

**ONSET**

**DEMISE**

## Precipitation Climatology