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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1651Z Feb 19, 2015)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1151 AM EST THU FEB 19 2015

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

MODEL DISCUSSION (VALID FROM FEBRUARY 19 AT 00UTC): MINOR
CORRECTIONS TO PREVIOUS FORECAST PACKAGE...AS THE MODELS CONTINUE
TO AGREE ON PATTERN EVOLUTION THROUGH DAY 05.

AT MID/UPPER LEVELS...A HIGH AMPLITUDE/LONG WAVE TROUGH DOMINATES
THE SOUTHERN CONE-MID SECTIONS OF SOUTH AMERICA. THROUGH 24 HRS
THE MID LEVEL TROUGH IS TO MEANDER EAST INTO THE WESTERN ATLANTIC
WHILE TRAILING TO NORTHERN ARGENTINA. THE TROUGH IS TO THEN
GRADUALLY ACCELERATE...WITH AXIS EXPECTED TO MOVE ACROSS 00W BY 72
HRS. THE ASSOCIATED SURFACE FRONT EXTENDS ACROSS URUGUAY/RIO
GRANDE DO SUL IN BRASIL TO THE NORTHERN PROVINCES IN ARGENTINA.
BOUNDARY IS TO REMAIN NEARLY STATIONARY OVER THE NEXT 96-120 HRS.
ALOFT...A SUBTROPICAL JET MAXIMA WILL HELP SUSTAIN THE LOW LEVEL
BAROCLINIC BOUNDARY... WHILE FAVORING AREAS OF DIVERGENCE ALOFT.
MOISTURE IS TO CLUSTER NORTH OF THE MEANDERING FRONT...TO FAVOR
SCATTERED CONVECTION ACROSS THE SOUTHERN STATES OF BRASIL AND
PORTIONS OF PARAGUAY. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF
15-30MM/DAY.

ON THE SOUTHERN STREAM...MEANWHILE...SUCCESSIVE MID LEVEL
PERTURBATIONS ARE EXPECTED TO MOVE ACROSS THE SOUTH PACIFIC TO THE
DRAKE PASSAGE OVER THE NEXT FEW DAYS. IN THIS
PATTERN...PROGRESSIVE MID LEVEL TROUGH IS TO REACH THE
BELLINGSHAUSEN SEA-ANTARCTIC PENINSULA BY 30-36 HRS...WITH ANOTHER
SHORT WAVE PERTURBATION TO ENTER THE DRAKE PASSAGE/SOUTHERN CHILE
BY 84 HRS. A THIRD WAVE IS NOW FORECAST TO STREAM ACROSS THE
SOUTHERN CONE BY 108-120 HRS.  ASSOCIATED SURFACE FRONTS ARE TO
CONFINE TO CHILE/ARGENTINA TO THE SOUTH OF 50S. LACKING
MOISTURE...THEY ARE TO ONLY FAVOR LIGHT CONVECTION WITH
ACCUMULATION TO PEAK AT 05-10MM. STRONG BOUNDARY LAYER WINDS OF
35-45KT ARE TO ACCOMPANY THESE PERTURBATIONS.

NORTH OVER THE CONTINENT...AT 200 HPA...WEAK CELL OF THE
SUBTROPICAL RIDGE EXTENDS TO THE NORTH OF 20S AND WEST OF 50W. A
TUTT LOW TO THE EAST LIES OFF THE COAST OF BRASIL. THE TROUGH/LOW
IS FORECAST TO RETROGRESS TO EASTERN BAHIA LATER ON DAY 02. THIS
IS TO SLOWLY MOVE FARTHER INLAND ACROSS BAHIA TO TOCANTINS IN
BRASIL LATER ON DAY 05. BEST DIVERGENCE ALOFT IS EXPECTED BETWEEN
THIS TROUGH AND THE RIDGE TO THE WEST. EARLY IN THE CYCLE THIS IS
TO ENHANCE CONVECTIVE DEVELOPMENT ACROSS NORTHEAST BRASIL. BUT AS
THE TROUGH MOVES FARTHER TO THE WEST THIS IS TO GRADUALLY SHIFT TO
THE CENTRAL-NORTHWEST STATES OF BRASIL. ACROSS NORTHEAST BRASIL
INITIALLY EXPECTING RAINFALL AMOUNTS OF 25-50MM IN SCATTERED DEEP
CONVECTION. AS THE LOW MOVES WEST THIS DECREASES TO
15-25MM...WHILE ALONG THE NEAR EQUATORIAL TROUGH TO THE NORTH THE
MAXIMA IS TO PEAK AT 20-35MM. OVER AMAZONAS-ACRE-RONDONIA IN
BRASIL TO THE PERUVIAN JUNGLE/NORTHERN BOLIVIA EXPECTING ORGANIZED
DEEP CONVECTION ON DAYS 03-05...WITH MAXIMA FORECAST TO PEAK AT
35-70MM ON DAY 3. THIS IS TO BUILD WEST INTO EASTERN
ECUADOR/SOUTHERN COLOMBIA THROUGH 96-120 HRS. HEAVY CONVECTION IS
TO ALSO CLUSTER ACROSS SOUTHERN PERU-NORTHERN BOLIVIA TO MATO
GROSSO IN BRAIL EARLY IN THE CYCLE. WITH RAINFALL AMOUNTS OF
30-60MM EXPECTED THROUGH 36 HRS...INCREASING TO 40-80MM BY 36-60
HRS.

ARREAGA...INAMHI (ECUADOR)
SCHNEIDER...INMET (BRASIL)
DAVISON...WPC (USA)