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 1722Z Nov 29, 2017)
 
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
1222 PM EST WED NOV 29 2017

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

MODEL DISCUSSION (VALID FROM NOV 29 AT 0000 UTC): MINOR
CORRECTIONS TO PREVIOUS FORECAST...WITH MODELS FOLLOWING A SIMILAR
EVOLUTION THROUGH DAY 06. THE DETERMINISTIC SOLUTION IS WELL
SUPPORTED BY THE MEAN OF THE GLOBAL ENSEMBLE MEMBERS...LEADING TO
A HIGH CONFIDENCE IN THE FORECAST THROUGH THE END OF THE CYCLE.

A SHORT WAVE TROUGH ON THE NORTHERN STREAM SPILLED ACROSS THE
CENTRAL ANDES OF CHILE TO CUYO IN ARGENTINA. AT LOW LEVELS THIS IS
INTERACTING WITH A SURFACE FRONT TRAILING ACROSS SOUTHERN BRASIL
TO CENTRAL ARGENTINA....TRIGGERING CYCLOGENESIS OVER CUYO. THE
FRONTAL WAVE IS TO THEN MEANDER TO THE EAST-SOUTHEAST ACROSS LA
PAMPA/BUENOS AIRES PROVINCE. MEANWHILE...THIS IS TO SUSTAIN
SCATTERED CONVECTION WITH ACCUMULATION OF 20-30MM/DAY ON WEDNESDAY
AND THURSDAY.

PROGRESSIVE MID LEVEL TROUGH ON THE SOUTHERN STREAM IS TO
FOLLOW...TO MOVE TO THE BELLINGSHAUSEN SEA-SOUTHERN CHILE LATER
TODAY. ON THURSDAY IT IS TO MOVE ACROSS THE DRAKE
PASSAGE-PATAGONIA IN ARGENTINA...TO THEN MEANDER TO THE
EAST-SOUTHEAST ACROSS THE SOUTH ATLANTIC LATER IN THE WEEK. THE
TROUGH SUSTAINS A SURFACE FRONT ACROSS TIERRA DEL FUEGO LATER
TODAY...THAT MOVES ACROSS PATAGONIA TO THE WESTERN ATLANTIC ON
THURSDAY. IT IS TO THEN MERGE WITH/REINFORCE THE AFOREMENTIONED
FRONT OVER CENTRAL ARGENTINA ON FRIDAY. AS THEY
INTERACT...EXPECTING SCATTERED CONVECTION ACROSS LA PAMPA-CUYO IN
ARGENTINA TO TRIGGER RAINFALL AMOUNTS OF 20-40MM. ON SATURDAY THIS
SPREADS ACROSS THE BUENOS AIRES PROVINCE-ENTRE RIOS TO TRIGGER
MAXIMA OF 20-30MM.

FARTHER EAST...AT 500 HPA...A TROUGH EXTENDS OVER THE WESTERN
ATLANTIC...WITH AXIS ENVELOPING AREA BETWEEN 50W-20W AND TO THE
SOUTH OF 20S. THE SHORT WAVE TROUGH IS TO MEANDER OFF THE SOUTH
COAST OF BRASIL THROUGH SATURDAY EVENING WHILE SLOWLY WEAKENING AS
IT SHEARS SHORT WAVE ENERGY TO THE EAST-SOUTHEAST. AT LOW
LEVELS... THE TROUGH SUSTAINS AN ELONGATED FRONT ACROSS THE SOUTH
ATLANTIC TO RIO DE JANEIRO/SOUTHERN MINAS GERAIS TO MATO GROSSO DO
SUL/PARAGUAY. THE BOUNDARY IS TO PERSIST DURING THE NEXT
FOUR-TO-FIVE DAYS. MEANWHILE...THIS IS TO BECOME THE FOCUS OF LOW
LEVEL MOISTURE CONVERGENCE ACROSS MID SECTIONS OF SOUTH AMERICA.
UNDER FAVORABLE JET DYNAMICS EXPECTING ENVIRONMENTAL CONDITIONS
OVER PARAGUAY-MATO GROSSO DO SUL IN BRASIL-SOUTHEAST BOLIVIA TO
BECOME FAVORABLE FOR AN MCS TO FORM EARLY ON THURSDAY MORNING. IN
THIS AREA EXPECTING MAXIMA OF 50-100MM. ON THURSDAY TO FRIDAY THIS
INCREASES TO 75-125MM WHILE SPREADING NORTH ACROSS BOLIVIA TO
RONDONIA IN BRASIL. ON FRIDAY THIS DECREASES TO 20-45MM WHILE
CLUSTERING OVER CENTRAL BOLIVIA. OVER MINAS GERAIS-MATO GROSSO IN
BRASIL...AS DEEP TROPICAL MOISTURE CONVERGES NORTH OF THIS
BOUNDARY...EXPECTING RAINFALL MAXIMA OF 20-40MM. THROUGH FRIDAY
THIS IS TO BECOME MORE ACTIVE/BETTER ORGANIZED...WITH MAXIMA OF
40-80MM TO AFFECT MINAS GERAIS-BAHIA AND ESPIRITO SANTO IN BRASIL.
ON SATURDAY-SUNDAY THE DAILY MAXIMA WILL THEN PEAK AT 30-60MM.

NORTH OVER THE CONTINENT...AT 200 HPA...MODELS CONTINUE TO
FORECAST BROAD CELL OF THE SUBTROPICAL RIDGE TO BECOME THE
DOMINANT FEATURE TO THE NORTH OF 30S...WITH AXIS TO ANCHOR ON A
CLOSED HIGH THAT MEANDERS BETWEEN NORTHERN BOLIVIA-MATO
GROSSO/RONDONIA IN BRASIL. THE RIDGE ALOFT IS TO VENT CONVECTION
ACROSS NORTHERN SOUTH AMERICA...WITH MOST ACTIVE CLUSTERING ALONG
AND NORTH OF THE AFOREMENTIONED SURFACE FRONT OVER
BRASIL-PARAGUAY/BOLIVIA. OTHER CONVECTION IS EXPECTED ACROSS PARA
IN BRASIL TO FAVOR MAXIMA OF 15-20MM/DAY. THROUGH FRIDAY THIS IS
TO INTENSIFY...WITH MAXIMA OF 20-30MM. OVER ACRE-AMAZONAS IN
WESTERN BRASIL TO THE NORTHERN JUNGLE OF PERU/EASTERN ECUADOR
EXPECTING MAXIMA OF 10-15MM/DAY. THROUGH SATURDAY THIS IS TO
INTENSIFY...WITH MAXIMA OVER AMAZONAS-SOUTHERN COLOMBIA-NORTHERN
JUNGLE OF PERU TO PEAK AT 20-40MM. ON THE HIGH JUNGLE OF
PERU...MEANWHILE...THE DAILY MAXIMA IS TO PEAK AT 20-35MM ON
SATURDAY.

OVIEDO...SHN (ARGENTINA)
VANNUCCI...SMN (ARGENTINA)
RIVAS...SENAMHI (PERU)
DAVISON...WPC (USA)