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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1730Z Nov 13, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1230 PM EST THU NOV 13 2014

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

NOTE: ENVIRONMENTAL AND MJO CONDITIONS CONTINUE FAVORABLE FOR THE
DEVELOPMENT OF THE SOUTH ATLANTIC CONVERGENCE ZONE (SACZ) ACROSS
CENTRAL BRASIL-PERU EARLY IN THE CYCLE. THIS WILL FAVOR HEAVY
RAINFALL AMOUNTS...WITH MCS TO CLUSTER ACROSS NORTHERN
BOLIVIA-ACRE/RONDONIA IN BRASIL TO CENTRAL/SOUTHERN PERU OVER THE
NEXT TWO-THREE DAYS...AND ACROSS MATO GROSSO-GOIAS-MINAS
GERAIS/BAHIA IN BRASIL DURING THE MEDIUM RANGE PERIOD...WITH WET
PATTERN THEN EVOLVING INTO THE NORDESTE.

MODEL DISCUSSION (VALID FROM NOVEMBER 13 AT 00UTC): GLOBAL MODELS
ARE IN EXCELLENT AGREEMENT THROUGH DAY 05-96. SOME DISCREPANCIES
APPEAR REGARDING THE APPROACH OF A BROAD UPPER TROUGH INTO THE
SOUTHERN CONE BY DAYS 05-06. CONFIDENCE IS OTHERWISE HIGH THROUGH
THE FORECAST PERIOD.

A LARGE NORTHERN STREAM TROUGH IS MEANDERING NORTHEASTWARD WHILE
EXTENDING ACROSS URUGUAY-NORTHWESTERN ARGENTINA. THIS TROUGH IS
FORECAST TO BE A SLOW-MOVER WHILE IS PRESSES AGAINST THE
SUBTROPICAL RIDGE TO THE NORTH. BY FRIDAY EVENING IT WILL EXTEND
INTO PARAGUAY-NORTHERN ARGENTINA...BY SATURDAY EVENING INTO
PARANA-MATO GROSSO DO SUL...BY SUNDAY EVENING INTO RIO DO
JANEIRO-MINAS GERAIS AND BY MONDAY EVENING INTO ESPIRITO
SANTO/SOUTHWESTERN BAHIA. MODELS ARE THEN SHOWING TROUGH
AMPLIFYING OVER THE EASTERN COAST OF BRASIL...TO SUSTAIN A WET
PATTERN IN THE NORDESTE. AT LOW-LEVELS...BUILDING RIDGE EARLY IN
THE CYCLE ACROSS NORTHERN ARGENTINA WILL CONTINUE ENHANCING A
SOUTHERLY JET THAT IS TO EXTEND INTO CENTRAL/NORTHERN BOLIVIA
DURING THURSDAY. THIS WILL BE AN IMPORTANT FOCUS FOR LOW-LEVEL
MOISTURE CONVERGENCE...AND IN AN ENVIRONMENT WITH PRECIPITABLE
WATER EXCEEDING 60MM...HIGH CONVECTIVE INSTABILITY AND UPPER
VENTILATION...EXPECTING THE DEVELOPMENT OF STRONG THUNDERSTORMS
WITH THE RISK OF MCS FORMATION TO CONTINUE OVER THE NEXT TWO-THREE
DAYS. SIMULTANEOUSLY...SURFACE TROUGH DEVELOPING ALONG THE
NORTHERN AND EASTERN TIER OF THIS SOUTHERLY SURGE WILL INTENSIFY
AND MOVE VERY LITTLE. AS THIS TROUGH CONTINUES UNDER THE DYNAMIC
SUPPORT OF UPPER TROUGH PUSHING FROM THE SOUTH...EXPECTING THE
DEVELOPMENT OF THE SOUTH ATLANTIC CONVERGENCE ZONE (SACZ) AS EARLY
AS TODAY. BY THURSDAY EVENING...THE ESTABLISHING SACZ WILL EXTEND
FROM SOUTHWESTERN MINAS GERAIS INTO NORTHEASTERN BOLIVIA-MADRE DE
DIOS IN PERU. BY FRIDAY EVENING IT WILL EXTEND ACROSS SOUTHERN
MINAS GERAIS-SOUTHERN RONDONIA-UCAYALI IN PERU. BY SATURDAY
EVENING...THE SACZ WILL EXTEND ACROSS CENTRAL MINAS
GERAIS-SOUTHERN RONDONIA-SOUTHERN LORETO IN PERU. BY SUNDAY
EVENING...THE SACZ WILL MOVE VERY LITTLE.

IN TERMS OF ACCUMULATIONS...LARGEST AMOUNTS ARE EXPECTED THROUGH
FRIDAY MORNING WITH MAXIMA OF 100-200MM/DAY ACROSS EASTERN PERU
INTO ACRE AND NORTHERN/CENTRAL BOLIVIA. TO THE EAST...EXPECTING
MAXIMA OF 30-60MM/DAY ACROSS CENTRAL BRASIL EXTENDING NORTH INTO
SOUTHERN PIAUI/MARANHAO AND NORTHERN BAHIA. BY FRIDAY INTO EARLY
SATURDAY...EXPECTING ACCUMULATIONS OF 100-150MM/DAY ACROSS THE
WESTERN AMAZON INTO CENTRAL PERU. ACROSS CENTRAL AND SOUTHEASTERN
BRASIL EXPECTING MAXIMA OF 30-60MM/DAY. BY SATURDAY INTO EARLY
SUNDAY...EXPECTING LARGEST ACCUMULATIONS ACROSS CENTRAL AND
SOUTHEASTERN BRASIL...TO REACH MAXIMA OF 50-100MM/DAY. BY SUNDAY
INTO EARLY MONDAY EXPECTING MAXIMA OF 40-80MM/DAY ACROSS CENTRAL
AND EASTERN BRASIL. AFTERWARDS...FOCUS OF STRONGEST CONVECTION
WILL MOVE TO THE NORDESTE TO SUSTAIN SCATTERED MAXIMA OF
30-60MM/DAY. HIGHER AMOUNTS ARE POSSIBLE...DEPENDING ON THE
EVOLUTION OF UPPER TROUGH ACROSS THE EASTERN COAST OF BRASIL.

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