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 1801Z Feb 06, 2018)
 
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
101 PM EST TUE FEB 06 2018

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

MODEL DISCUSSION (VALID FROM FEB 06 AT 0000 UTC): MINOR CHANGES TO
PREVIOUS RUN...WITH MODELS REMAINING IN CLOSE AGREEMENT ON LONG
WAVE PATTERN EVOLUTION THROUGH DAY 06. CONFIDENCE IN THE FORECAST
IS HIGH.

SHORT WAVE TROUGH ON THE NORTHERN STREAM MOVES ACROSS SOUTHERN
CHILE-PATAGONIA IN ARGENTINA EARLY IN THE CYCLE...WITH THE MID
LEVEL VORTEX MOVING TO THE WESTERN ATLANTIC LATER TODAY. ON
WEDNESDAY IT IS THEN FORECAST TO MERGE INTO A BROAD LONG WAVE
TROUGH TO THE SOUTH. AT LOW LEVELS THIS SUSTAINS A DEEP SURFACE
LOW THAT STREAMS ACROSS SOUTHERN CHILE-PATAGONIA IN ARGENTINA TO
THE WESTERN ATLANTIC LATER ON TUESDAY...DRIVING A FRONT NORTH
ACROSS LA PAMPA TO THE BUENOS AIRES PROVINCE ON TUESDAY-WEDNESDAY.
AS IT SURFACES ACROSS CENTRAL ARGENTINA THIS IS TO SUSTAIN
RAINFALL AMOUNTS OF 15-20MM. ON WEDNESDAY...AS THE TROUGH PULLS
AWAY...THIS DECREASES TO 05-10MM.

A DEEPER MID/UPPER LEVEL TROUGH LIES TO THE SOUTH...WITH AXIS
ACROSS THE SOUTHEAST PACIFIC/BELLINGSHAUSEN SEA. THE DEEP TROUGH
IS TO MEANDER OVER THE SOUTHEAST PACIFIC DURING THE NEXT 24-36
HRS. LATER ON WEDNESDAY THE TROUGH MEANDERS ACROSS THE ANTARCTIC
PENINSULA TO THE WEDDELL SEA...AND NORTH ACROSS SOUTHERN CHILE TO
PATAGONIA IN ARGENTINA. AS IT AMPLIFIES ACROSS THE SOUTHERN CONE
THE TROUGH IS TO FOCUS SHORT WAVE ENERGY ACROSS CONTINENTAL AREA
TO THE SOUTH OF 35S. ON THURSDAY...UNDER THE INFLUENCE OF A
BUILDING RIDGE TO THE WEST...THE TROUGH IS EXPECTED TO AMPLIFY
FARTHER NORTH ACROSS ARGENTINA TO MID SECTIONS OF SOUTH AMERICA.
AT LOW LEVELS THE ASSOCIATED SURFACE FRONT IS TO MEANDERS ACROSS
SOUTHERN CHILE-TIERRA DEL FUEGO DURING THE NEXT COUPLE OF DAYS. ON
THURSDAY...BUILDING RIDGE OVER THE SOUTHEAST PACIFIC WILL THEN
FAVOR A STRONG SOUTHERLY JET ACROSS PATAGONIA TO CENTRAL
ARGENTINA. THIS IS TO DRIVE THE FRONT NORTH ACROSS LA PAMPA/BUENOS
AIRES PROVINCE TO THE RIO DE LA PLATA BASIN LATER ON FRIDAY. EARLY
IN THE CYCLE...AS THE FRONT MEANDERS OVER TIERRA DEL FUEGO...IT IS
TO FAVOR LIGHT CONVECTION WITH ACCUMULATION OF 05-10MM/DAY. AS THE
FRONT SURGES ACROSS LA PAMPA TO THE BUENOS AIRES PROVINCE ON
THURSDAY EVENING...THIS INCREASES TO 20-35MM IN POTENTIALLY SEVERE
CONVECTION. ON FRIDAY THE MAXIMA ACROSS URUGUAY-ENTRE RIOS-CENTRAL
ARGENTINA IS TO PEAK AT 25-50MM...WITH RISK OF SEVERE CONVECTION
TO PERSIST.

AT 200 HPA...A MEANDERING HIGH OVER NORTHERN CHILE-SOUTHERN PERU
ANCHORS A CELL OF THE SUBTROPICAL RIDGE THAT EXTENDS
NORTH-TO-SOUTH OVER THE CONTINENT TO THE WEST OF 60W. EAST OF THIS
AXIS...A TROUGH EXTENDS ACROSS SOUTHEAST BRASIL TO MATO
GROSSO/SOUTHERN PARA. THIS PATTERN IS TO GRADUALLY WEAKEN DURING
THE NEXT THREE DAYS...WITH THE RIDGE TO NEARLY COLLAPSE AND THE
TROUGH TO GRADUALLY FILL. AT LOW LEVELS...THE SOUTH ATLANTIC
CONVERGENCE ZONE (SACZ) EXTENDS TO THE NORTHWEST ACROSS MINAS
GERAIS/MATO GROSSO TO RONDONIA IN BRASIL/NORTHERN BOLIVIA. AS THE
UPPER PATTERN EVOLVES AND THE SACZ LOSES ITS UPPER LEVEL
SUPPORT...THE CONVERGENCE ZONE IS FORECAST TO GRADUALLY WEAKEN TO
AN OPEN TROUGH ON WEDNESDAY. CONVECTION OVER NORTHERN SOUTH
AMERICA IS TO THEN CLUSTER BETWEEN THE WANING SACZ AND THE NEAR
EQUATORIAL TROUGH TO THE NORTH. OVER ACRE-RONDONIA-AMAZONAS IN
BRASIL TO CENTRAL/NORTHERN PERU EXPECTING MAXIMA OF 25-50MM. ON
WEDNESDAY-THURSDAY THIS DECREASES TO 15-30MM/DAY. OVER NORTHEAST
BRASIL...MEANWHILE...EXPECTING MAXIMA OF 75-125MM THROUGH
WEDNESDAY MORNING...AND 40-80MM/DAY ON WEDNESDAY THROUGH FRIDAY.

THE RIDGE ALOFT IS TO ALSO VENT CONVECTION ALONG THE NORTHERN
ANDES OF ARGENTINA...WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM. HIGHER AMOUNTS ARE EXPECTED ACROSS THE
ALTIPLANO OF BOLIVIA-NORTHERN CHILE TO SOUTHERN PERU. IN THIS AREA
GDI CONTINUE TO SHOW HIGH RISK OF MODERATE TO HEAVY RAINFALL
AMOUNTS TO SUSTAIN ACCUMULATION OF 15-30MM/DAY ON
TUESDAY-WEDNESDAY...AND 05-10MM ON WEDNESDAY TO THURSDAY MORNING.
ON FRIDAY TO SATURDAY FOCUS OF THE HEAVY CONVECTION SHIFTS TO
SOUTHERN BOLIVIA...WHERE THE MAXIMA IS TO PEAK AT 25-50MM. LOCALLY
HIGHER AMOUNTS ARE HIGHLY PROBABLE. FATHER NORTH...THE PANAMANIAN
LOW/TROUGH WILL ENHANCE COASTAL CONVERGENCE ACROSS ECUADOR...TO
FAVOR MODERATE RAINFALL AMOUNTS WITH ACCUMULATION OF 15-25MM OVER
THE NEXT COUPLE OF DAYS. ON THURSDAY-FRIDAY THIS DECREASES TO
05-10MM AS THE MOIST INFLOW WEAKENS.

BALBINO...INMET (BRASIL)
POMIER...SENAMHI (BOLIVIA)
DAVISON...WPC (USA)