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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1607Z Jul 14, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1207 PM EDT MON JUL 14 2014

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

MODEL DISCUSSION (VALID FROM 14 JULY 00UTC): GLOBAL MODELS ARE IN
GENERAL AGREEMENT ON HOW PATTERN IS GOING TO EVOLVE DURING THE
NEXT FEW DAYS. THE SYSTEM OF CONCERN IS A MID LEVEL TROUGH PULLING
ACROSS THE SOUTHERN CONE EARLY IN THE CYCLE. THIS SYSTEM IS
FORECAST TO TRIGGER SEVERE CONVECTION AS IT PULLS ACROSS THE
SOUTHERN CONE.

AT 500 HPA...A TROUGH EXTENDS OFF THE SOUTHERN COAST OF CHILE.
THROUGH 36 HRS IT IS TO SPILL ACROSS THE ANDES INTO ARGENTINA...
MEANWHILE SUSTAINING HEIGHT FALLS OF 75-150GPM. THROUGH 48-54 HRS
THE TROUGH IS TO MOVE OFF THE COAST OF PATAGONIA TO THE WESTERN
ATLANTIC. AS IT PULLS ACROSS THE CONTINENT...A POLAR/SUBTROPICAL
JET PAIR ARE TO ACCOMPANY THIS TROUGH...FAVORING A DIVERGENT
PATTERN ALOFT ACROSS CENTRAL PORTIONS OF ARGENTINA. EARLY ON
TUESDAY MORNING THE JETS ARE TO COUPLE OVER RIO DE LA PLATA
BASIN...SUSTAINING A BROAD AREA OF DIVERGENCE. TROUGH IS TO SLOWLY
MIGRATE ACROSS 30W/35W THROUGH 96 HRS. A SHORT WAVE TROUGH IS TO
FOLLOW...ENTERING CENTRAL CHILE BY 48 HRS...AND ACROSS CENTRAL
CHILE TO THE NORTHERN PROVINCES IN ARGENTINA BY 72 HRS...PULLING
ACROSS URUGUAY/RIO GRANDE DO SUL IN BRASIL BY 96 HRS.

AT LOW LEVELS THIS IS TO SUSTAIN A POLAR TROUGH OVER THE SOUTHERN
CONE EARLY IN THE CYCLE. ASSOCIATED FRONT SURGES ACROSS THE BUENOS
AIRES PROVINCE-MENDOZA IN ARGENTINA BY 24-30 HRS AS A 35KT PAMPERO
JET DEVELOPS TO THE SOUTH. AS THE FRONT SURGES ACROSS THE BUENOS
AIRES PROVINCE IT IS TO THEN SUSTAIN A PREFRONTAL SQUALL LINE...
TRIGGERING SEVERE CONVECTION AND HEAVY RAINFALL AMOUNTS. A
NORTHERLY LOW LEVEL JET ACROSS PARAGUAY/CHACO ARGENTINO WILL
SUSTAIN BOUNDARY LAYER DEW POINT TEMPERATURES OF 18-20C AHEAD OF
THE ADVANCING POLAR FRONT. THE BOUNDARY IS TO THEN STALL OVER
URUGUAY/SOUTHERN BRASIL-NORTHERN PROVINCES IN ARGENTINA BY 36-84
HRS. BY 84-96 HRS...AS MID LEVEL TROUGH INTERACTS WITH THE SURFACE
FRONT...A FRONTAL WAVE WAVE/LOW DEVELOPS ALONG THIS BOUNDARY. THE
LOW DEEPENS AS IT MOVES OFF THE COAST OF BRASIL THROUGH 96-108
HRS...DRIVING THE FRONT NORTH ACROSS PARAGUAY TO MATO GROSSO DO
SUL/BOLIVIA LATER IN THE CYCLE. OVER CHILE THIS IS TO SUSTAIN
SCATTERED CONVECTION TO THE SOUTH OF CONCEPCION...WITH MAXIMA TO
PEAK AT 15-20MM EARLY IN THE CYCLE. IT IS ALSO LIKELY TO TRIGGER
HEAVY SNOWFALL AMOUNTS ACROSS THE CENTRAL ANDES OF CHILE WITH
ACCUMULATION OF 10-15CM. OVER SOUTHERN-WESTERN PORTIONS OF THE
BUENOS AIRES PROVINCE EXPECTING MAXIMA OF 20-35MM THROUGH 36
HRS...WHILE OVER EASTERN/NORTHERN PORTIONS-ENTRE RIOS AND URUGUAY
EXPECTING MAXIMA OF 35-70MM. BY 36-60 HRS EXPECTING MODERATE
CONVECTION ACROSS URUGUAY-RIO GRANDE DO SUL-CORRIENTES/ENTRE RIOS
IN ARGENTINA TO SUSTAIN ACCUMULATION OF 20-40MM. THIS INCREASES TO
30-60MM BY 60-84 HRS. AS THE FRONT SURGES ACROSS BOLIVIA LATER IN
THE CYCLE...IT IS TO SUSTAIN RAINFALL AMOUNTS OF 20-40MM.

THE NEXT MID LEVEL PERTURBATION PULLS ACROSS THE SOUTH PACIFIC TO
THE SOUTHERN CONE OF SOUTH AMERICA BY 108-132 HRS. DEEP POLAR
PERTURBATION IS LIKELY TO SUSTAIN A SUBTROPICAL CONNECTION AS IT
PULLS TOWARDS SOUTHERN CHILE...FOCUSING MOISTURE/ENERGY ACROSS
SOUTHERN REGIONS OF CHILE. THIS IS TO FEED CONVECTIVE DEVELOPMENT
LATER IN THE CYCLE TO SUSTAIN RAINFALL AMOUNTS OF 15-30MM.

NORTH OVER THE CONTINENT...ILL ORGANIZED CELL OF THE SUBTROPICAL
RIDGE IS TO CONFINE TO NORTHERN PORTIONS OF BRASIL/EQUATORIAL
SOUTH AMERICA. THE RIDGE ALOFT IS TO VENT DIURNAL CONVECTION...TO
RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM OVER
NORTHERN PORTIONS OF PARA-AMAZONAS-RONDONIA IN BRASIL. HIGHER
AMOUNTS ARE EXPECTED ACROSS SOUTHERN COLOMBIA TO NORTHERN
PERU-ECUADOR...WHERE FORCING ON THE LEE OF THE ANDES IS TO RESULT
IN ACCUMULATION OF 15-25MM. OVER NORTHEAST BRASIL...MEANWHILE...A
SHEAR LINE IS TO EXTEND TO THE NORTHWEST ACROSS EASTERN BAHIA.
THIS IS TO ENHANCE LOW LEVEL CONVERGENCE TO RESULT IN SCATTERED
CONVECTION WITH ACCUMULATION OF 15-20MM. THROUGH 72-96 HRS THIS
INCREASES TO 25-50MM/DAY AS ENHANCED BY A TRADE WINDS SURGE.

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