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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1606Z Aug 18, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1206 PM EDT MON AUG 18 2014

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

MODEL DISCUSSION (VALID FROM AUGUST 18 AT 00UTC): GLOBAL MODELS
ARE IN EXCELLENT AGREEMENT THROUGH DAY 06...WITH BLOCKING RIDGE
PATTERN OVER THE CONTINENT TO DOMINATE FLOW THROUGH THE MEDIUM
RANGE PERIOD. THE RIDGE IS TO ENVELOP THE SOUTHERN CONE OF SOUTH
AMERICA WHILE CENTERING AT 500 HPA ON A CLOSED HIGH NEAR CORDOBA
IN ARGENTINA. THROUGH 96 HRS THE HIGH MEANDERS TO THE SOUTHERN
STATES OF BRASIL...WHILE RIDGE OVER ARGENTINA PERSISTS. LATER IN
THE CYCLE THE HIGH IS TO COLLAPSE. AS THE RIDGE HOLDS...IT WILL
SUSTAIN A SUBSIDENCE CAP. THIS IS TO FAVOR ABOVE NORMAL
TEMPERATURES ACROSS MOST OF ARGENTINA-MID SECTIONS OF SOUTH
AMERICA.

A DEEP MID/UPPER LEVEL TROUGH LIES WEST OF THIS RIDGE...WITH AXIS
AT 500 HPA TO EXTEND BETWEEN 120W-80W AND TO THE SOUTH OF 15S. AS
THE TROUGH PRESSES AGAINST THIS RIDGE...IT IS TO FOCUS SHORT WAVE
ENERGY AND SUBTROPICAL MOISTURE ACROSS THE SOUTHERN REGIONS OF
CHILE. THIS PATTERN IS TO HOLD NEARLY UNCHANGED THROUGH 72-84 HRS.
THEN LATER IN THE CYCLE...AS THE RIDGE TO THE EAST WEAKENS...THE
TROUGH WILL GRADUALLY PUSH EAST ACROSS CENTRAL CHILE TO ARGENTINA.
THIS IS TO THEN TRIGGER HEIGHT FALLS OF 80-120GPM ACROSS CENTRAL
CHILE TO THE CENTRAL PROVINCES IN ARGENTINA. AT LOW LEVELS IT IS
TO SUSTAIN A BROAD TROUGH OVER THE FAR EASTERN PACIFIC...WITH
ASSOCIATED FRONT TO STRETCH ACROSS SOUTHERN CHILE-PATAGONIA IN
ARGENTINA. THE DEEP SURFACE TROUGH IS TO CONFINE TO THE EASTERN
PACIFIC OVER THE NEXT FOUR DAYS...WHILE ASSOCIATED FRONT MEANDERS
ACROSS THE SOUTHERN CONE. MEANWHILE...THIS IS TO FAVOR SCATTERED
CONVECTION ACROSS CHILE BETWEEN TEMUCO-ISLA DE CHILOE...WITH
ACCUMULATION OF 05-10MM/DAY. THROUGH 36-72 HRS THIS IS TO INCREASE
TO 15-20MM.

LATER IN THE PERIOD...AS THE RIDGE TO THE EAST WEAKENS AND THE MID
LEVEL TROUGH SPILLS ACROSS THE ANDES...THIS IS TO SUSTAIN
CYCLOGENESIS ON THE CENTRAL PROVINCES OF ARGENTINA. THROUGH
132-144 HRS THE SURFACE LOW IS TO RAPIDLY DEEPEN WHILE MIGRATING
ACROSS THE BUENOS AIRES PROVINCE/RIO DE LA PLATA BASIN. THIS WILL
DRAW THE FRONT NORTH ACROSS CENTRAL ARGENTINA...WHILE SUSTAINING A
PAMPERO LOW LEVEL JET. ALSO AT LOW LEVELS...A NORTHERLY JET WILL
ESTABLISH ACROSS PARAGUAY. THIS WILL SUSTAIN A WARM/MOIST
ADVECTIVE PATTERN...WITH MOISTURE TO CONVERGE ACROSS MESOPOTAMIA
VALLEY IN ARGENTINA TO THE BUENOS AIRES PROVINCE/LA PAMPA. INFLOW
OF ENERGY ALOFT...FAVORABLE JET DYNAMICS AND INTENSIFYING
BAROCLINIC BOUNDARY ARE LIKELY TO FAVOR ORGANIZED DEEP CONVECTION
LATER ON DAY 05. DURING THAT PERIOD MAXIMA OVER CENTRAL ARGENTINA
IS TO PEAK AT 20-35MM...WITH LOCALLY HIGHER AMOUNTS HIGHLY LIKELY.
THERE IS ALSO A RISK OF SEVERE CONVECTION DURING THAT PERIOD.

NORTH OVER THE CONTINENT...A 200 HPA...A TROUGH EXTENDS ACROSS
BRASIL...SPLITTING THE SUBTROPICAL RIDGE IN TWO CELLS. THE
WESTERNMOST CONFINES TO PERU/EASTERN TROPICAL PACIFIC...WHILE THE
EASTERNMOST LIMITS TO THE TROPICAL ATLANTIC/NORTHEAST BRASIL. THIS
PATTER WILL REMAIN NEARLY UNCHANGED THROUGH 48-60 HRS...THEN
WEAKEN THROUGH 96-120 HRS AS THE RIDGE TO THE NORTH STRENGTHENS.
IN THIS PATTERN...TROPICAL CONVECTION WILL CONFINE TO EQUATORIAL
SOUTH AMERICA WITH RAINFALL AMOUNTS OF 05-10MM/DAY IN ISOLATED TO
SCATTERED CONVECTION.

JALFIN...SMN (ARGENTINA)
CAROCA...DMC (CHILE)
DAVISON...WPC (USA)