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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1603Z Oct 15, 2014)
 
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Abbreviations and acronyms used in this product


SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1203 PM EDT WED OCT 15 2014

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

MODEL DISCUSSION (VALID FROM OCTOBER 15 AT 00UTC): EXCEPT FOR
SUBTLE CORRECTIONS...MODELS CONTINUE TO AGREE AND MAINTAIN GOOD
CONTINUITY WITH PREVIOUS FORECAST PACKAGE. DURING THE NEXT FEW
DAYS...MODELS FORESEE A TRAIN OF MID LEVEL PERTURBATIONS TO STREAM
ACROSS THE SOUTHERN CONE. THIS WILL COMBINE WITH FAVORABLE
MADDEN-JULIAN OSCILLATION (MJO) CONDITIONS TO SUSTAIN GENERATION
OF ORGANIZED...POTENTIALLY SEVERE...CONVECTION ACROSS
URUGUAY-MESOPOTAMIA IN ARGENTINA AND RIO GRANDE DO SUL IN BRASIL.

IN THIS PATTERN...PROGRESSIVE MID LEVEL TROUGH ENTERED THE
SOUTHERN CONE...AND THROUGH 18-24 HRS IT IS TO RAPIDLY MOVE ACROSS
ARGENTINA TO THE WESTERN ATLANTIC. THE TROUGH IS TO THEN MEANDER
TO THE EAST-SOUTHEAST AS THE CYCLE PROGRESSES. AS THE TROUGH
ENTERS THE CONTINENT IT IS TO FOCUS A SUBTROPICAL JET ACROSS
CENTRAL/NORTHERN CHILE INTO ARGENTINA. THIS...IN-TURN...FAVORS A
DIVERGENT PATTERN ALOFT ACROSS NORTHERN ARGENTINA-SOUTHERN
BRASIL/URUGUAY. THIS IS TO PERSIST OVER THE NEXT THREE DAYS. AT
LOW LEVELS...THE ASSOCIATED FRONT STREAMS ACROSS ARGENTINA EARLY
IN THE CYCLE...REACHING RIO DE LA PLATA BASIN-URUGUAY BY 42-48
HRS...WHERE IT IS TO THEN REMAIN THROUGH 84-90 HRS. AS THE FRONT
SURGES ACROSS ARGENTINA...IT IS TO TRIGGER SCATTERED CONVECTION.
MOST ACTIVE...HOWEVER...IS EXPECTED ACROSS ENTRE RIOS IN
ARGENTINA/URUGUAY-RIO GRANDE DO SUL IN BRASIL ON DAYS 01-03. IN
THIS AREA...A NORTHERLY LOW LEVEL JET ACROSS PARAGUAY IS TO
SUSTAIN A WARM/MOIST ADVECTIVE PATTERN...WITH PRECIPITABLE WATER
CONTENT FORECAST TO INCREASE TO 50MM. CONDITIONS APPEAR FAVORABLE
FOR NIGHTTIME DEVELOPMENT OF MESO SCALE CONVECTIVE SYSTEMS AND
POTENTIALLY SEVERE CONVECTION. MOST ACTIVE IS FORECAST DURING
MORNING HOURS ON THURSDAY...FRIDAY AND SATURDAY...WHEN THE DAILY
MAXIMA IS TO PEAK AT 30-60MM/DAY. NOTE THAT LOCALLY HIGHER AMOUNTS
ARE HIGHLY LIKELY DUE TO STRONG MESO-SYNOPTIC FORCING.

THE NEXT MID LEVEL PERTURBATION ENTERS CENTRAL CHILE BY 60-72 HRS.
THIS TROUGH RAPIDLY MOVES ACROSS THE ANDES INTO ARGENTINA BY 84
HRS...AND OFF THE COAST TO THE WESTERN ATLANTIC BY 96-102 HRS. AT
LOW LEVELS THIS IS TO SUSTAIN A BROAD TROUGH ON THE NORTHERN
STREAM OFF THE SOUTHERN/CENTRAL COAST OF CHILE BY 54-60 HRS...THAT
QUICKLY MOVES INLAND THROUGH 72-84 HRS. THE ASSOCIATED FRONT IS TO
THEN RACE ACROSS CENTRAL ARGENTINA TO RIO DE LA PLATA BY 96
HRS...AND ACROSS RIO GRANDE DO SUL IN BRASIL TO THE NORTHERN
PROVINCES IN ARGENTINA BY 120 HRS. AS IT ENTERS SOUTHERN CHILE
THIS IS TO SUSTAIN SCATTED CONVECTION WITH ACCUMULATION OF
15-20MM...WHILE OVER LA PAMPA IN ARGENTINA THE MAXIMA IS TO PEAK
AT 05-10MM. A SURGE IN ACTIVITY IS FORECAST BY 96 HRS-108 HRS...AS
THE FRONT IS TO TRIGGER ORGANIZED CONVECTION ACROSS URUGUAY-ENTRE
RIOS IN ARGENTINA...WITH MAXIMA OF 25-50MM IN POTENTIALLY SEVERE
CONVECTION. AS THE FRONT MEANDERS NORTH TO SOUTHERN
BRASIL...MAXIMA IS TO PEAK AT 15-20MM...WHILE OVER NORTHWEST
ARGENTINA-PARAGUAY/SOUTHERN BOLIVIA THE MAXIMA IS TO PEAK AT
20-40MM.

NORTH OVER THE CONTINENT...AT 200 HPA...A RIDGE EXTENDS
NORTH-TO-SOUTH ALONG 70W TO PATAGONIA IN ARGENTINA. A HIGH OVER
SOUTHERN ECUADOR/NORTHERN PERU IS TO ANCHOR THIS AXIS EARLY IN THE
CYCLE. THROUGH 48-72 HRS THE MODELS FORECAST THE HIGH TO MEANDER
WEST TO THE EASTERN TROPICAL PACIFIC...TO CENTER NEAR 10S 90W
LATER IN THE CYCLE. A TROUGH LIES TO THE WEST...WITH AXIS ACROSS
SAO PAULO IN BRASIL TO ACRE/SOUTHERN AMAZONAS. THROUGH 48-60 HRS
THE TROUGH IS TO MEANDER NORTH INTO ESPIRITO SANTO/MINAS GERAIS IN
BRASIL TO MATO GROSSO/RONDONIA. BUT AS THE UPPER LEVEL HIGH MOVES
WEST INTO THE EASTERN PACIFIC...THE TROUGH ALOFT IS FORECAST TO
WEAKEN/NEARLY FILL BY 120 HRS. EARLY IN THE CYCLE THE TROUGH ALOFT
IS TO ENHANCE CONVECTION ACROSS SOUTH AMERICA TO THE NORTH OF
10S...WITH MOST ACTIVE ACROSS PARA-AMAZONAS IN BRASIL TO THE
NORTHERN JUNGLE OF PERU/SOUTHERN COLOMBIA. IN THIS AREA THE DAILY
MAXIMA IS FORECAST TO PEAK AT 15-30MM. LATER IN THE CYCLE...DAILY
MAXIMA DECREASES TO 15-20MM.

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