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 1602Z Jul 28, 2014)
 
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
1202 PM EDT MON JUL 28 2014

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

MODEL DISCUSSION (VALID FROM 28 JULY 00UTC): THE GFS AND EUROPEAN
MODELS ARE IN EXCELLENT AGREEMENT THROUGH DAY 06...WITH MID
LATITUDE TROUGH TO PERSIST ACROSS THE FAR EASTERN PACIFIC OVER THE
NEXT FEW DAYS. THIS FORECAST IS WELL SUPPORTED BY THE GLOBAL
ENSEMBLE MEMBERS...LEADING TO A HIGH CONFIDENCE FORECAST.
PERSISTENT TROUGH WILL HELP SUSTAIN A WARM/MOIST ADVECTIVE
PATTERN...RESULTING IN ORGANIZED HEAVY RAINS ACROSS
CENTRAL/SOUTHERN CHILE.

ACROSS THE EASTERN PACIFIC...MODELS FAVOR A SLOW TO EVOLVE PATTERN
OVER THE NEXT FEW DAYS...WITH BROAD TROUGH TO ANCHOR ON A LOW THAT
IS TO MEANDER IN THE VICINITY OF 57S 90W. AS THE LOW/TROUGH
HOLDS...SHORT WAVE PERTURBATIONS ON THE NORTHERN STREAM ARE TO
REVOLVE AROUND THIS AXIS. THESE ARE TO ENTER CENTRAL/SOUTHERN
CHILE AT AN INTERVAL OF 18-24 HRS...AVERAGING ONE PERTURBATION PER
DAY. THE TROUGH WILL FOCUS THE JET STREAM ACROSS CENTRAL
CHILE...WITH DIVERGENCE ON ITS RIGHT EXIT REGION TO ENVELOP AREA
SOUTH OF CONCEPCION. FURTHERMORE...BROAD TROUGH PATTERN WILL
SUSTAIN A SUBTROPICAL CONNECTION...ENHANCING MOISTURE TRANSPORT
ACROSS CENTRAL PORTIONS OF CHILE. AT LOW LEVELS THIS IS TO REFLECT
AS A BROAD TROUGH OVER THE SOUTHEAST PACIFIC...WITH POLAR FRONTS
TO REVOLVE AROUND THIS AXIS. THESE ARE TO RAPIDLY STREAM ACROSS
THE SOUTHERN CONE OVER THE NEXT FEW DAYS...ENHANCING LOW LEVEL
CONVERGENCE WHILE SUSTAINING BOUNDARY LAYER WINDS OF 25-40KT.
INFLOW OF SUBTROPICAL MOISTURE AND STRONG TOPOGRAPHICAL FORCING IS
TO THEN FAVOR ORGANIZED CONVECTION. OVER THE NEXT FEW DAYS
EXPECTING MAXIMA BETWEEN CONCEPCION-ISLA DE CHILOE TO PEAK AT
30-60MM/DAY. THROUGH 108 HRS THIS IS TO INCREASE TO 50-100MM.
OTHER ACTIVITY TO THE NORTH IS EXPECTED BETWEEN TALCA AND
VALPARAISO IN CENTRAL CHILE...WITH RAINFALL MAXIMA IN THIS AREA TO
PEAK AT 20-30MM.

FURTHERMORE...AS THE FRONTS STREAM ACROSS ARGENTINA THEY ARE TO
SUSTAIN AN AREA OF BOUNDARY LAYER CONVERGENCE ACROSS RIO GRANDE DO
SUL IN BRASIL-URUGUAY TO CORDOBA IN CENTRAL ARGENTINA. ALSO UNDER
THE INFLUENCE OF A RIDGE OVER THE WESTERN ATLANTIC...A WARM/MOIST
NORTHERLY FLOW IS TO DEVELOP ACROSS BOLIVIA/PARAGUAY TO CENTRAL
ARGENTINA. THROUGH 60-72 HRS THE INFLOW OF MOIST AIR IS FORECAST
TO INTENSIFY. THESE...IN INTERACTION WITH AFOREMENTIONED SHORT
WAVE PERTURBATIONS WILL SUSTAIN SCATTERED CONVECTION...RESULTING
IN ACCUMULATION of 15-30MM/DAY. THIS IS TO START ON DAY 02 AND
PERSIST THROUGH DAY 05.

ALSO OVER THE SOUTH ATLANTIC...AN ELONGATED FRONT IS TO EXTEND TO
THE WEST-NORTHWEST ACROSS RIO DE JANEIRO TO SOUTHEAST BRASIL EARLY
IN THE CYCLE. THROUGH 72 HRS THE FRONT IS TO MEANDER NORTH ACROSS
ESPIRITO SANTO TO BAHIA...WHERE IT IS TO REMAIN THROUGH 96-120
HRS. EARLY I THE CYCLE THIS IS TO ENHANCE COASTAL CONVECTION
BETWEEN ESPIRITO SANTO AND RIO DE JANEIRO...WITH ACCUMULATION OF
10-15MM. AS IT MOVES NORTH...AND EASTERLY TRADES INTENSIFY...THIS
WILL INCREASE TO 15-30MM/DAY.

NORTH OVER THE CONTINENT...AT 200 HPA...A HIGH SOUTH OF THE
GALAPAGOS ISLANDS IS TO ANCHOR A RIDGE OVER THE EASTERN TROPICAL
PACIFIC. THIS WILL PERSIST OVER THE NEXT 72-84 HRS. DOWNSTREAM
FROM THIS AXIS...OVER THE CONTINENT...A SHORT WAVE TROUGH IS TO
EXTEND ACROSS RONDONIA IN BRASIL TO AMAZONAS TO THE NORTH. THE
SHORT WAVE TROUGH IS TO ENHANCE CONVECTIVE INSTABILITY ACROSS
NORTHWEST BRASIL-NORTHERN JUNGLE OF PERU/EASTERN ECUADOR...WITH
DIURNAL CONVECTION IN THIS AREA TO INITIALLY PEAK AT 10-15MM.
THROUGH 72-96 HRS...HOWEVER...THIS DECREASES TO 05-10MM AS PATTERN
TO THE WEST STARTS TO EVOLVE AND SHORT WAVE TROUGH WEAKENS. OVER
NORTHEAST BRASIL...MEANWHILE...A NORTHERN HEMISPHERE TROPICAL WAVE
ENTERS PERNAMBUCO/RIO GRANDE DO NORTE EARLY IN THE CYCLE...TO
TRIGGER SCATTERED CONVECTION WITH ACCUMULATION OF 15-25MM. ALONG
THE NORTH COAST OF BRASIL/AMAZON RIVER DELTA REGION IT IS TO THEN
SUSTAIN RAINFALL AMOUNTS OF 10-15MM.

FERNANDES...INMET (BRASIL)
JALFIN...SMN (ARGENTINA)
DAVISON...WPC (USA)