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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1800Z Nov 10, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EST MON NOV 10 2014

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

NOTE: HEAVY RAINFALL EVENT WILL DEVELOP DURING NEXT SEVERAL DAYS
FROM PARAGUAY/SOUTHERN BOLIVIA INTO CENTRAL PERU/WESTERN BRASIL.
DEVELOPING SOUTHERLY WIND SURGE IN MID-SECTIONS OF THE CONTINENT
WILL ENHANCE LOW-LEVEL CONVERGENCE TO TRIGGER STRONG THUNDERSTORMS
WITH MAXIMUM ACCUMULATIONS EXCEEDING 100MM/DAY AFTER
WEDNESDAY...AND THE RISK OF MCS FORMATION.

MODEL DISCUSSION (VALID FROM NOVEMBER 10 AT 00UTC): GLOBAL MODELS
AND ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT REGARDING FORECAST
EVOLUTION. FORECAST CONFIDENCE IS HIGH.

BROAD NORTHERN STREAM TROUGH IS FORECAST TO CROSS THE ANDES LATE
ON MONDAY INTO EARLY TUESDAY...LEADING TO HEIGHT FALLS OF 15-30
GPM/DAY. ALTHOUGH THIS DOES NOT SOUND IMPRESSIVE...THE LOW-LEVEL
JET IS REESTABLISHING ACROSS CENTRAL BOLIVIA AND WILL NOT ONLY
TRANSPORT A VERY MOIST AIRMASS INTO NORTHWESTERN ARGENTINA...BUT
WILL PROVIDE ENHANCED LOW-LEVEL CONVERGENCE ACROSS THE REGION.
EXPECTING STRONG THUNDERSTORMS TO START DEVELOPING LATE ON MONDAY
ALONG AND EAST OF THE ANDEAN FOOTHILLS OF NORTHWESTERN
ARGENTINA...AND PRODUCE LOCALLY HEAVY RAINS ACROSS THE ARGENTINEAN
AND PARTS OF THE PARAGUAYAN CHACO WITH MAXIMA OF 35-70MM/DAY AND
THE RISK FOR MCS FORMATION. THE STORMS...AIDED BY THE SLOW
CROSSING OF THE UPPER TROUGH...WILL HELP TO INTENSIFY SURFACE
TROUGH ACROSS SOUTHERN BOLIVIA/PARAGUAY. THIS...TOGETHER WITH
ENHANCED LOW-LEVEL CONVERGENCE AND ENHANCED UPPER DIVERGENCE IN
THE LEFT ENTRANCE OF AN UPPER JET...WILL SUSTAIN STRONG CONVECTION
AND LEAD TO MAXIMA OF 40-80MM/DAY ACROSS THE BOLIVIAN CHACO INTO
MOST OF PARAGUAY DURING TUESDAY INTO EARLY WEDNESDAY. DURING
WEDNESDAY INTO EARLY THURSDAY...THE DEVELOPMENT OF A SOUTHERLY JET
ACROSS THE BOLIVIAN LOWLANDS WILL ENHANCE LOW-LEVEL MOISTURE
CONVERGENCE AND LEAD TO SCATTERED MAXIMA OF 50-100MM/DAY...WITH
CONTINUED RISK FOR MCS FORMATION. FURTHER EAST..EXPECTING MAXIMA
OF 30-60MM/DAY ACROSS MATO GROSSO/SOUTHEASTERN BOLIVIA. BY
THURSDAY INTO EARLY FRIDAY...EXPECTING STRONGEST CONVECTION TO
CONTINUE MEANDER NORTHWARD INTO NORTHERN BOLIVIA/SOUTHEASTERN PERU
WITH MAXIMA OF 75-125MM/DAY AND CONTINUED RISK FOR MCS FORMATION.
STRONG CONVECTION WILL THEN FOCUS ACROSS CENTRAL PERU.

NORTH ACROSS THE CONTINENT...WEAKENING COLD FRONT AND SHEAR LINE
WILL CONTINUE SUSTAINING LOCALLY HEAVY RAINS ACROSS PARTS OF BAHIA
INTO NORTHERN MINAS GERAIS/GOIAS IN BRASIL EARLY IN THE CYCLE.
AIDED BY UPPER DIVERGENCE AHEAD OF UPPER TROUGH AXIS...EXPECTING
LARGEST AMOUNTS IN COASTAL AREAS REACHING MAXIMA OF 40-80MM/DAY
THROUGH EARLY TUESDAY...AND MAXIMA OF 25-50MM/DAY INLAND. BY
TUESDAY INTO EARLY WEDNESDAY...SHEAR LINE WILL START LOSING
DEFINITION. STILL EXPECTING LOCALIZED MAXIMA OF 30-60MM/DAY IN
COASTAL AREA...WITH MAXIMA DECREASING TO 20-40MM/DAY INLAND.
AMOUNTS ARE TO DECREASE AFTERWARDS IN COASTAL LOCATIONS. FURTHER
INLAND HOWEVER...IMPROVING UPPER VENTILATION AND SURFACE
TROUGHS/ENHANCED CONVECTIVE INSTABILITY WILL LEAD TO SCATTERED
MAXIMA OF 20-35MM/DAY IN DIURNAL CONVECTION ACROSS GOIAS/TOCANTINS
INTO SOUTHEASTERN PARA. BY THURSDAY INTO FRIDAY...VENTILATION IS
TO PEAK ACROSS MOST OF SOUTHEASTERN BRASIL. THIS WILL SUSTAIN
SCATTERED STRONG THUNDERSTORMS ACROSS THE REGION WITH MAXIMA OF
20-45MM/DAY. BY FRIDAY INTO SATURDAY...STRONGEST CONVECTION IS
EXPECTED ACROSS SOUTHEASTERN MINAS/RIO DE JANEIRO...WHERE MAXIMA
OS TO REACH 30-60MM/DAY.
CAROCA...DMC (CHILE)
DURAN...SENAHMI (PERU)
GALVEZ...WPC (USA)