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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1601Z Jul 15, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1201 PM EDT TUE JUL 15 2014

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

MODEL DISCUSSION (VALID FROM 15 JULY 00UTC): THE GLOBAL MODELS
REMAIN IN EXCELLENT AGREEMENT THROUGH DAY 07. THE EVOLVING PATTERN
IS WELL SUPPORTED BY THE MEAN OF THE GLOBAL ENSEMBLES. AS A
RESULT...OUR CONFIDENCE IN THE FORECAST IS HIGH.

AT 500 HPA...A PROGRESSIVE TROUGH IS MOVING ACROSS THE SOUTHERN
CONE. THROUGH 24-30 HRS THE TROUGH IS TO MOVE OFF THE COAST OF
PATAGONIA TO THE WESTERN ATLANTIC. AS IT EXITS THE CONTINENT...A
BUILDING RIDGE TO THE WEST IS TO THEN INDUCE THE NORTHWARD
AMPLIFICATION OF THIS TROUGH ALONG 50W TO 30S. A SHORT WAVE TROUGH
CLOSELY FOLLOWS...ENTERING CENTRAL CHILE BY 24 HRS. THIS WILL
QUICKLY SPILL ACROSS THE ANDES INTO NORTHERN ARGENTINA BY 36-42
HRS...PULLING ACROSS URUGUAY/MESOPOTAMIA VALLEY BY 60 HRS. AS IT
MOVES OFF THE COAST OF URUGUAY/RIO GRANDE DO SUL THIS IS TO THEN
MERGE WITH THE AMPLIFYING TROUGH OVER THE WESTERN ATLANTIC. AS
THEY COMBINE...A BROAD TROUGH IS TO THEN DOMINATE THE NORTHERN
STREAM FLOW OVER THE WESTERN SOUTH ATLANTIC DURING THE LATTER PART
OF THE FORECAST. AT LOW LEVELS THIS SUSTAINS A POLAR FRONT ACROSS
BUENOS AIRES PROVINCE-CORDOBA IN ARGENTINA. THROUGH 24 HRS THE
FRONT MOVES ACROSS URUGUAY-RIO GRANDE DO SUL TO JUJUY/SALTA IN
NORTHWEST ARGENTINA. BOUNDARY IS TO REMAIN NEARLY STATIONARY
THROUGH 60-66 HRS. UNDER INFLUENCE OF THE MID LEVEL SHORT WAVE
TROUGH A FRONTAL LOW FORMS ALONG THIS BOUNDARY...MOVING OFF THE
SOUTHERN COAST OF BRASIL BY 66-72 HRS. THE LOW IS TO THEN DEEPEN
AT A NEARLY EXPLOSIVE PACE...WITH GLOBAL MODELS SHOWING A POSSIBLE
METEOROLOGICAL BOMB BETWEEN 90-114 HRS. THE DEEPENING LOW IS TO
THEN INDUCE THE NORTHWARD MIGRATION OF THE SURFACE FRONT ACROSS
SOUTHERN BRASIL-PARAGUAY TO BOLIVIA. EARLY IN THE CYCLE THIS IS TO
TRIGGER HEAVY CONVECTION ACROSS URUGUAY-RIO GRANDE DO SUL AND THE
MESOPOTAMIA VALLEY...WITH MAXIMA OF 30-60MM. THIS IS TO PERSIST
THROUGH 42-48 HRS. BY 72-96 HRS MOST INTENSE IS EXPECTED ACROSS
PARAGUAY-MATO GROSSO DO SUL TO CENTRAL BOLIVIA...WITH MAXIMA OF
20-40MM. CONVECTION IS TO THEN SPREAD WEST AND NORTH INTO SOUTHERN
JUNGLE OF PERU.

THE NEXT MID LEVEL PERTURBATION ON THE NORTHERN STREAM PULLS
ACROSS THE SOUTH PACIFIC TO THE SOUTHERN CONE OF SOUTH AMERICA BY
84-108 HRS. THE DEEP POLAR PERTURBATION IS LIKELY TO SUSTAIN A
SUBTROPICAL CONNECTION AS IT CROSSES THE EASTERN
PACIFIC...FOCUSING MOISTURE AND SHORT WAVE ENERGY ACROSS SOUTHERN
REGIONS OF CHILE. AT LOW LEVELS THE ASSOCIATED FRONT PULLS ACROSS
SOUTHERN CHILE/PATAGONIA IN ARGENTINA BY 72-84 HRS...TO STRETCH
ACROSS THE SOUTHERN CONE THROUGH 120-132 HRS. THE INFLOW OF
SUBTROPICAL MOISTURE WILL COMBINE WITH STRONG BOUNDARY LAYER WINDS
TO SUSTAIN MODERATE TO HEAVY CONVECTION ACROSS SOUTHERN CHILE. IN
THIS AREA EXPECTING MAXIMA OF 20-40MM BY 72-84 HRS...AND 15-30MM
AT 84-120 HRS.

NORTH OVER THE CONTINENT...AT 200 HPA...AN ILL ORGANIZED CELL OF
THE SUBTROPICAL RIDGE IS TO CONFINE TO NORTHERN PORTIONS OF BRASIL
AND 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/PERNAMBUCO. THIS IS TO ENHANCE LOW LEVEL
CONVERGENCE TO RESULT IN SCATTERED CONVECTION WITH ACCUMULATION OF
20-35MM. THROUGH 48-72 HRS THIS INCREASES TO 20-45MM/DAY AS
ENHANCED BY A TRADE WINDS SURGE...DECREASING TO 20-35MM/DAY
THEREAFTER.

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