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South American Forecast Discussion
 
(Latest Discussion - Issued 1622Z Apr 08, 2020)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1222 PM EDT WED APR 08 2020

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

FORECAST DISCUSSION FROM APR 08/17UTC: CONSISTENT WITH PREVIOUS
FORECASTS...A DEEP MID/UPPER LEVEL LOW OFF THE SOUTH COAST OF
BRASIL DOMINATES THE NORTHERN STREAM FLOW OVER THE WESTERN
ATLANTIC. A RIDGE TO THE WEST AND SOUTH UNDERCUTS THE MID LEVEL
LOW/TROUGH...WITH CLOSED CIRCULATION TO STALL WHILE EXTENDING A
SHORT WAVE TROUGH TO THE SOUTHERN/SOUTHEAST STATES OF BRASIL. THIS
PATTERN HOLDS THROUGH FRIDAY/SATURDAY...THEN RAPIDLY WEAKENS LATER
DURING THE WEEKEND. AT LOW LEVELS...THE MID LEVEL TROUGH SUSTAINS
A SURFACE FRONT THAT EXTENDS ACROSS THE ATLANTIC TO ESPIRITO
SANTO/ SOUTHERN MINAS GERAIS IN BRASIL...TO SOUTHEAST BOLIVIA.
THIS IS TO REMAIN NEARLY STATIONARY DURING THE NEXT 72-84
HRS...THEN FRONTOLIZES AS IT RETROGRESSES TO PARAGUAY/MATO GROSSO
DO SUL ON SATURDAY. MOST ACTIVE CONVECTION WITH THIS FEATURE IS
EXPECTED ON THE BRAZILIAN STATES OF TOCANTINS/GOIAS-MINAS
GERAIS-BAHIA AND ESPIRITO SANTO...WHERE IT IS TO INITIALLY FAVOR
RAINFALL MAXIMA OF 20-45MM. ON THURSDAY-FRIDAY ACTIVITY
SURGES...WITH MAXIMA INCREASING TO 35-70MM...WITH MOST INTENSE
CLUSTERING OVER PORTIONS OF MINAS GERAIS-ESPIRITO SANTO. OTHER
CONVECTION IS EXPECTED ACROSS MATO GROSSO DO SUL IN BRASIL AS
ENHANCED BY THE MID/UPPER LEVEL TROUGH...WITH MAXIMA OF 05-10MM IN
POTENTIALLY SEVERE CONVECTION EARLY ON FRIDAY MORNING.

UPSTREAM OVER THE EASTERN PACIFIC...A LONG WAVE TROUGH AMPLIFIES
ALONG 90W TO 30S EARLY ON THURSDAY MORNING. AS IT PRESSES AGAINST
A RIDGE TO THE EAST...THE LONG WAVE AXIS IS TO INITIALLY FOCUS ITS
SHORT WAVE ENERGY ACROSS THE SOUTHERN REGIONS OF CHILE/TIERRA DEL
FUEGO. THROUGH FRIDAY MORNING THE RIDGE WILL WEAKEN ENOUGH TO
ALLOW THE TROUGH TO PRESS INLAND ACROSS SOUTHERN CHILE TO
PATAGONIA IN ARGENTINA. ON ITS WAKE...A SHORT WAVE TROUGH ON THE
NORTHERN STREAM IS TO THEN LIFT ACROSS THE EASTERN PACIFIC TO THE
CENTRAL REGIONS OF CHILE EARLY ON SUNDAY MORNING...TO SLOWLY SPILL
ACROSS THE CENTRAL ANDES TO CENTRAL ARGENTINA. AT 250 HPA THE
SUBTROPICAL AND POLAR JETS ARE TO ACCOMPANY THE LATTER AS IT MOVES
ACROSS THE CENTRAL ANDES TO ARGENTINA...WITH THE JETS TO COUPLE ON
THEIR DIVERGENT ENTRANCE/EXIT REGIONS. AT LOW LEVELS...A BROAD
TROUGH ON THE SOUTHERN STREAM IS TO DOMINATE THE MESO-SYNOPTIC
PATTERN OVER THE SOUTHEAST PACIFIC DURING THE NEXT 36-42
HRS...WITH AXIS PUSHING EAST ACROSS SOUTHERN CHILE TO PATAGONIA IN
ARGENTINA EARLY ON FRIDAY. THIS IS TO THEN DRIVE A SURFACE FRONT
ACROSS THE SOUTHERN CONE TO LA PAMPA/CENTRAL ARGENTINA LATER ON
SATURDAY...INTO THE BUENOS AIRES PROVINCE-MENDOZA ON SUNDAY.
ACROSS SOUTHERN CHILE EXPECTING SCATTERED CONVECTION OVER THE NEXT
TWO DAYS...TO RESULT IN MAXIMA OF 10-15MM/DAY. AS THE FRONT PUSHES
NORTH ACROSS CENTRAL ARGENTINA ON SATURDAY IT IS TO SUSTAIN LIGHT
TO MODERATE CONVECTION WITH MAXIMA OF 05-10MM. ON SUNDAY THIS
INCREASES TO 20-40MM WHILE BUILDING NORTH ACROSS THE BUENOS AIRES
PROVINCE...WHERE IT IS PROBABLE TO FAVOR SEVERE THUNDERSTORMS.

AT 250 HPA...AN ILL ORGANIZED CELL OF THE SUBTROPICAL RIDGE WILL
CONFINE TO NORTHERN SOUTH AMERICA. THE RIDGE ALOFT IS TO SUSTAIN
AN UPPER DIVERGENT PATTERN ACROSS EQUATORIAL SOUTH AMERICA...WITH
CONVECTION CLUSTERING ALONG THE NEAR EQUATORIAL TROUGH. OVER THE
AMAZON RIVER DELTA REGION-AMAPA AND PARA...CONDITIONS APPEAR
FAVORABLE FOR CONVECTION TO ECHO TRAIN...WITH MAXIMA PEAKING AT
40-80MM. ACROSS AMAZONAS-SOUTHERN COLOMBIA TO EASTERN ECUADOR ALSO
EXPECTING MODERATE TO HEAVY CONVECTION...WITH MAXIMA OF 35-70MM
EXPECTED EARLY IN THE CYCLE. ON THURSDAY-SATURDAY THIS DECREASES
TO 20-40MM/DAY. FURTHERMORE...AT LOW LEVELS...THE INTENSIFICATION
OF THE PANAMANIAN TROUGH OVER THE EASTERN PACIFIC IS TO FAVOR A
MOIST WESTERLY FLOW BETWEEN THE GALAPAGOS ISLANDS AND ECUADOR. AS
A RESULT...CONVECTION INCREASES FROM 15-20MM EARLY IN THE CYCLE TO
30-60MM EARLY ON FRIDAY MORNING. THROUGH SUNDAY THIS IS EXPECTED
TO INTENSIFY...WITH MAXIMA PEAKING AT 40-80MM.

DAVISON...WPC (USA)
GALVEZ...WPC (USA)