THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


SOUTH AMERICAN MODEL DISCUSSION




SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 PM EDT FRI OCT 19 2018

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

MODEL DISCUSSION FROM OCTOBER 19/00 UTC: GLOBAL MODELS AND
ENSEMBLE MEMBERS HAVE DECREASED THEIR CONFIDENCE ON THE EVOLUTION
OF THE FORECAST. NOW DISCREPANCIES START ARISING AROUND 72-84 HRS
AND INCREASE GRADUALLY. THE MAIN PROBLEMS ARE ON RESOLVING THE
SOUTHEASTERN PACIFIC TO THE SOUTH OF 30S.

RECURRENT SPLIT FLOW PATTERN OVER THE SOUTHEASTERN PACIFIC IS
FORECAST TO RESTRUCTURE BUT CONTINUE PERSISTING INTO MID-NEXT
WEEK. PRECIPITABLE WATER IN THE PACIFIC BASIN IS LIMITED...WHICH
WILL SUSTAIN GENERALLY LIGHT PRECIPITATION IN CHILE THROUGH THE
CYCLE. HOWEVER...A WEAKENING UPPER TROUGH CROSSES INTO THE
ATLANTIC ON SATURDAY THROUGH MONDAY...INSTABILITY WILL BE
SUFFICIENT TO TRIGGER ISOLATED THUNDERSTORMS IN SOUTHERN CHILE.
MORE SIGNIFICANT ACCUMULATIONS ARE EXPECTED EAST OF THE ANDES AS
NORTHEASTERLY FLOW CONTINUES ENHANCING MOISTURE CONVERGENCE IN
INTERIOR PORTIONS OF PATAGONIA. THIS WILL SUSTAIN MAXIMA OF
10-15MM/DAY ON BOTH FRIDAY AND SATURDAY.

AS UPPER TROUGH CROSSES INTO THE ATLANTIC...SURFACE FRONT WILL
ORGANIZE ON SUNDAY AND START MEANDERING NORTHWARD. BY SUNDAY
EVENING IT WILL EXTEND ACROSS THE CENTRAL BUENOS AIRES PROVINCE
INTO LA RIOJA. BY MONDAY EVENING IT WILL EXTEND INTO SANTIAGO DEL
ESTERO...TUCUMAN BY MONDAY EVENING... TO BECOME STATIONARY AFTER
ACROSS CORRIENTES...CHACO AND SOUTHERN SALTA. AS DEEP-LAYER
MOISTURE REMAINS BLOCKED TO THE NORTH OF 25N...THE FRONT WILL
INITIALLY SUSTAIN ISOLATED MAXIMA OF 15-20MM/DAY ON SUNDAY-MONDAY.
ENHANCED MOISTURE CONVERGENCE IN THE CHACO/ANDEAN FOOTHILLS WILL
HOWEVER SUSTAIN MAXIMA OF 25-50MM/DAY. BY
MONDAY-TUESDAY...EXPECTING MAXIMA OF 50-100MM/DAY IN INTERIOR
PORTIONS OF NORTHERN ARGENTINA WITH THE RISK OF MCS...WHILE IN
CORRIENTES/SOUTHERN PARAGUAY EXPECTING MAXIMA OF 20-35MM. UNDER
THE INFLUENCE OF A SHORT WAVE TROUGH EXITING FROM THE
ALTIPLANO...PRECIPITABLE WATER EXCEEDING 60MM AND VENTILATION IN
THE SOUTHERN PERIPHERY OF THE BOLIVIAN HIGH...EXPECTING  ONCE
AGAIN MAXIMA OF 50-100MM/DAY WITH THE RISK OF MCS IN THE NORTHERN
CHACO...ACROSS NORTHWESTERN PARAGUAY INTO PARTS OF MATO GROSSO DO
SUL.

NORTH ACROSS THE CONTINENT AND AT UPPER LEVELS...THE SUBTROPICAL
RIDGE/BOLIVIAN HIGH WILL CONTINUE DISPLACED TO THE SOUTH OF ITS
CLIMATOLOGICAL POSITION AND UNSEASONABLY STRONG. THIS WILL
VENTILATE CONVECTION THROUGH THE CYCLE TO SUSTAIN MODERATE
PRECIPITATION. LARGEST ACCUMULATIONS WILL ORGANIZE IN SOUTHEASTERN
BRASIL AIDED BY A SURFACE FRONT ARRIVING ON FRIDAY-SATURDAY. THIS
WILL INCREASE MAXIMA TO 25-50MM/DAY ACROSS ESPIRITO SANTO AND
MINAS GERAIS. AMOUNTS WILL PEAK ON SATURDAY-SUNDAY BETWEEN
SOUTHERN BAHIA AND MATO GROSSO...WHEN EXPECTING MAXIMA OF
30-60MM/DAY...DECREASING AFTER. COASTAL CONVECTION WILL CONTINUE
INTO EARLY NEXT WEEK AS THE FRONT MEANDERS NORTHWARD. THIS WILL
SUSTAIN MAXIMA OF 20-30MM ACROSS CENTRAL BAHIA ON SUNDAY-TUESDAY.

SALAZAR...SENAMHI (BOLIVIA)
IZA...INAMHI (ECUADOR)
GALVEZ...WPC (USA)





Last Updated: 130 PM EDT FRI OCT 19 2018