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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1746Z Nov 14, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 PM EST FRI NOV 14 2014

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

MODEL DISCUSSION (VALID FROM NOVEMBER 14 AT 00UTC): CONFIDENCE IN
THE FORECAST REMAINS HIGH AS THE GFS...EUROPEAN AND GLOBAL
ENSEMBLE MODELS FOLLOW A SIMILAR EVOLUTION INTO THE MEDIUM RANGE
PERIOD. MOST ACTIVE CONVECTION IS TO AFFECT NORTHERN SOUTH AMERICA
AS THE SACZ IS TO REMAIN ACTIVE OVER THE NEXT FEW DAYS.

MID LEVEL TROUGH ON THE NORTHERN STREAM IS TO MEANDER NORTH ALONG
THE SOUTHEAST COAST OF BRASIL...WHERE IT IS TO REMAIN THROUGH
96-108 HRS. AS IT LIFTS NORTH...THIS IS TO FOCUS SHORT WAVE
ENERGY/CYCLONIC VORTICITY ACROSS RIO DE JANEIRO/MINAS
GERAIS-ESPIRITO SANTO. FURTHERMORE...A SUBTROPICAL JET MAXIMA IS
TO ROUND THE BASE OF THE TROUGH OVER THE NEXT COUPLE OF
DAYS...WITH DIVERGENCE ON ITS LEFT ENTRANCE REGION TO VENT
ORGANIZED DEEP CONVECTION. AT 200 HPA...A BROAD CELL OF THE
SUBTROPICAL RIDGE IS TO DOMINATE CONTINENTAL AREA TO THE NORTH OF
24S. RIDGE IS TO ANCHOR ON A CLOSED HIGH THAT MEANDERS BETWEEN
SOUTHERN PARA AND MATO GROSSO IN BRASIL. AS UPPER RIDGE PATTERN
ALOFT HOLDS...THIS IS TO ALSO VENT DEEP CONVECTION ACROSS TROPICAL
SOUTH AMERICA. AT LOW LEVELS...THE SACZ IS TO EXTEND TO THE
WEST-NORTHWEST FROM ESPIRITO SANTO/MINAS GERAIS TO NORTHERN
BOLIVIA/SOUTHERN PERU EARLY IN THE CYCLE. THROUGH 84-96 HRS THIS
IS TO WEAKEN TO A TROUGH...THAT IS TO NEARLY DISSIPATE LATER IN
THE CYCLE. A SOUTHERLY LOW LEVEL JET ACROSS BOLIVIA TO CENTRAL
PERU IS TO INITIALLY FAVOR A SURGE IN CONVECTION ACROSS
AMAZONAS-ACRE IN BRASIL TO CENTRAL/NORTHERN PERU...WITH MAXIMA OF
100-150MM. THROUGH 36-48 HRS THIS DECREASES TO 25-50MM...AND BY
60-84 HRS WANES TO 15-20MM. ALTHOUGH ACTIVITY TO THE WEST IS TO
WEAKEN...CONVECTION OVER SOUTHEAST BRASIL IS FORECAST TO GRADUALLY
INTENSIFY/BECOME BETTER ORGANIZED. CONVECTION ACROSS MINAS
GERAIS-BAHIA AND ESPIRITO SANTO IS TO PEAK AT 30-60MM LATER THIS
EVENING. BY 36-84 HRS...UNDER FAVORABLE JET DYNAMICS...THIS
INCREASES TO 50-100MM...WITH LOCALLY HIGHER AMOUNTS HIGHLY LIKELY
ACROSS PORTIONS OF BAHIA-MINAS GERAIS. BUT AS UPPER TROUGH STARTS
TO PULL AWAY...AND INFLOW OF MID LEVEL VORTICITY WEAKENS...THIS IS
TO GRADUALLY DECREASE TO 20-40MM THROUGH DAY 05.

IN A TIGHT BELT OF MID LATITUDE WESTERLIES...PROGRESSIVE MID LEVEL
PERTURBATIONS ARE TO STREAM ACROSS THE SOUTH PACIFIC TO SOUTHERN
PORTIONS OF CHILE AND PATAGONIA IN ARGENTINA. SHORT WAVE
PERTURBATIONS ARE TO GENERALLY DOMINATE OVER THE NEXT TWO DAYS...
WITH MODELS THEN TRENDING IN FAVOR OF A MORE AMPLIFIED/LONG WAVE
PATTERN LATER ON DAYS 03-04. AT LOW LEVELS THIS IS TO SUSTAIN AN
ELONGATED FRONT ACROSS SOUTHERN CHILE-PATAGONIA IN ARGENTINA...
WITH SUCCESSIVE FRONTAL WAVES TO STREAM ACROSS THIS AREA OVER THE
NEXT FEW DAYS. THESE ARE TO SUSTAIN A MOIST ADVECTIVE PATTERN
WHILE FAVORING MOISTURE CONVERGENCE INTO SOUTHERN PORTIONS OF
CHILE... WHERE WE EXPECT SCATTERED CONVECTION WITH ACCUMULATION OF
10-15MM. ON DAY 03 THIS INCREASES TO 15-30MM AS SUBTROPICAL
MOISTURE SURGES ACROSS THE EASTERN PACIFIC TO THE SOUTHERN CONE.

LATER ON DAY 05 MID/UPPER LEVEL TROUGH IS TO THEN ENVELOP THE
SOUTHERN CONE OF SOUTH AMERICA...WHILE FOCUSING SHORT WAVE ENERGY
ACROSS CENTRAL CHILE/ARGENTINA. AS THE TROUGH DEEPENS TO THE SOUTH
IT IS TO ABSORB A SHORT WAVE TROUGH TO THE NORTH...FORCING THE
LATTER TO STREAM ACROSS NORTHERN CHILE TO NORTHERN ARGENTINA/RIO
DE LA PLATA BASIN. AT LOW LEVELS...THIS IS TO SUSTAIN THE
NORTHWARD PROGRESSION OF THE SURFACE FRONT ACROSS PATAGONIA TO THE
CENTRAL PROVINCES IN ARGENTINA LATER ON DAY 05.
THIS...IN-TURN...WILL LIKELY TRIGGER SCATTERED DEEP CONVECTION ON
CENTRAL-NORTHERN PORTIONS OF ARGENTINA. NOTE THAT INFLOW OF SHORT
WAVE ENERGY ALOFT AND FAVORABLE JET DYNAMICS COULD RESULT IN
SEVERE CONVECTION DEVELOPING OVER CENTRAL ARGENTINA.

CAROCA...DMC (CHILE)
DURAN...SENAHMI (PERU)
DAVISON...WPC (USA)