Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center
 
South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1742Z Apr 06, 2020)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product


SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
142 PM EDT MON APR 06 2020

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

FORECAST DISCUSSION FROM APR 06/17UTC: DEEPENING MID/UPPER LEVEL
LOW SOUTH OF THE BUENOS AIRES PROVINCE IS QUICKLY BECOMING THE
DOMINANT MESO SCALE FEATURE OVER THE WESTERN ATLANTIC...WITH THE
MID LEVEL LOW REACHING MAXIMUM INTENSITY EARLY ON TUESDAY MORNING.
ON WEDNESDAY...AS A RIDGE TO THE WEST UNDERCUTS THE MID LEVEL
TROUGH...IT IS TO THEN STALL AS IT NEARS 40S 30W...WITH LOW
EXTENDING A SHORT WAVE TROUGH TO THE SOUTHEAST STATES OF BRASIL.
AS IT MEANDERS ACROSS SOUTHEAST BRASIL...AT 250 HPA...A
SUBTROPICAL JET IS TO BOUND THE BASE OF THE UPPER LEVEL TROUGH.
THIS IS TO FAVOR AN UPPER DIVERGENT PATTERN ACROSS SOUTHEAST
BRASIL. AT LOW LEVELS...THE MID LEVEL AXIS SUSTAINS INTENSE
CYCLOGENESIS OFF THE COAST OF ARGENTINA...WITH SURFACE LOW
DEEPENING FROM A 1002 HPA LOW EARLY IN THE CYCLE TO A 986 HPA LOW
EARLY ON TUESDAY MORNING. ACROSS ARGENTINA...THE DEEPENING LOW
WILL SUSTAIN A SOUTHERLY JET...THAT QUICKLY SPREADS ACROSS MID
SECTIONS OF SOUTH AMERICA. THIS WILL DRIVE THE ASSOCIATED FRONT
NORTH TO SOUTHERN BRASIL-NORTHERN ARGENTINA LATER THIS EVENING. ON
TUESDAY THE FRONT REACHES SAO PAULO-MATO GROSSO DO SUL/CENTRAL
PARAGUAY...WHERE IT IS TO STALL. EARLY IN THE CYCLE...AS THE FRONT
SURGES ACROSS NORTHERN ARGENTINA...IT WILL SUSTAIN A PREFRONTAL
SQUALL LINE OVER PARAGUAY-MATO GROSSO DO SUL...TO TRIGGER HEAVY
CONVECTION WITH MAXIMA OF 50-100MM. EARLY ON TUESDAY MORNING FOCUS
OF THE HEAVY CONVECTION SHIFTS TO CENTRAL BOLIVIA...WHERE IT IS TO
ALSO FAVOR HEAVY CONVECTION. UNDER INFLUENCE OF THE SOUTHERLY LOW
LEVEL JET...ACTIVITY IS TO THEN SPREAD ACROSS ACRE IN BRASIL TO
THE CENTRAL JUNGLE OF PERU...WHERE IT WILL SUSTAIN MAXIMA OF
30-60MM ON TUESDAY-WEDNESDAY...WITH ACTIVITY TO QUICKLY WANE LATER
IN THE DAY. OVER MATO GROSSO-MINAS GERAIS/ESPIRITO SANTO...THE
MEANDERING UPPER LEVEL TROUGH AND ASSOCIATED JET MAXIMA ARE TO
ENHANCE DIURNAL CONVECTION...WITH DAILY MAXIMA OF 35-70MM.

ON THE SOUTHERN STREAM FLOW...A MID LEVEL RIDGE MEANDERS OVER THE
EASTERN PACIFIC/SOUTHERN CONE OF SOUTH AMERICA. POLAR
PERTURBATIONS LIFTING ACROSS THE SOUTHEAST PACIFIC/BELLINGSHAUSEN
SEA ARE TO PRESS AGAINST THIS AXIS. OVER THE NEXT THREE DAYS THIS
WILL BLOCK MID LEVEL TROUGHS ON THE SOUTHERN STREAM TO EXTREME
SOUTHERN REGIONS OF CHILE AND THE ANTARCTIC PENINSULA. ON THURSDAY
THE RIDGE WEAKENS ENOUGH TO ALLOW A DEEPER TROUGH TO MAKE LANDFALL
OVER THE SOUTHERN REGIONS OF CHILE INTO PATAGONIA IN ARGENTINA. AT
LOW LEVELS...LOW LEVEL RIDGE IS TO ALSO BLOCK THE POLAR TROUGH TO
TIERRA DEL FUEGO/EXTREME SOUTHERN REGIONS OF CHILE...WHERE IT IS
TO SUSTAIN MODERATE CONVECTION WITH ACCUMULATION OF 15-20MM/DAY
OVER THE COURSE OF THE NEXT TWO TO THREE DAYS. LATER ON
THURSDAY...AS THE RIDGE RECEDES INTO THE WESTERN SOUTH ATLANTIC
AND A TROUGH AMPLIFIES ACROSS SOUTHERN CHILE...THE FRONT WILL PUSH
FARTHER NORTH ACROSS THE SOUTHERN CONE. THIS IS TO THEN SUSTAIN
MODERATE CONVECTION BETWEEN TEMUCO-ISLA DE CHILOE IN SOUTHERN
CHILE...WITH MAXIMA OF 10-15MM/DAY.

AT 250 HPA...AN ILL ORGANIZED CELL OF THE SUBTROPICAL RIDGE WILL
CONFINE TO NORTHWEST SOUTH AMERICA DURING THE NEXT FIVE DAYS. AS
THE RIDGE HOLDS OVER THE CONTINENT...IT IS TO STEER A SHORT WAVE
TROUGH NORTH ACROSS SOUTHEAST TO NORTHEAST BRASIL EARLY IN THE
CYCLE. THROUGH WEDNESDAY THIS IS TO LIFT ACROSS PARAIBA/CEARA IN
NORTHEAST BRASIL. MEANWHILE...THIS IS TO INTERACT WITH THE ITCZ TO
SUSTAIN A SURGE IN ACTIVITY ACROSS THE AMAZON RIVER DELTA REGION
TO PARA IN CENTRAL BRASIL. EARLY IN THE CYCLE EXPECTING
ACCUMULATION OF 20-40MM...INCREASING TO 35-70MM ON
WEDNESDAY-THURSDAY. OVER RORAIMA- NORTHERN AMAZONAS IN BRASIL TO
SOUTHERN AMAZONIA IN COLOMBIA...THE RIDGE ALOFT WILL INITIALLY
FAVOR HEAVY CONVECTION ALONG THE NEAR EQUATORIAL TROUGH...WITH
RAINFALL MAXIMA OF 35-70MM. THROUGH THURSDAY ACTIVITY IN THIS AREA
IS TO EBB...WITH MAXIMA DECREASING TO 20-40MM/DAY...WHILE LATERN
IN THE WEEK...MAXIMA IN THIS AREA PEAKS AT 20-35MM.


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