Prognostic Meteorological Discussion
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FXSA20 KWBC 271530
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1129 AM EDT WED JUL 27 2016

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

MODEL DISCUSSION (VALID FROM JULY 27 AT 0000 UTC): SYSTEM OF
CONCERN IS A MEANDERING MID/UPPER LEVEL TROUGH OFF THE COAST OF
CHILE. THIS SYSTEM IS TO SUSTAIN A SUBTROPICAL...FAVORING A MOIST
ADVECTIVE PATTERN INTO SOUTHERN-CENTRAL CHILE DURING THE NEXT FEW
DAYS. GLOBAL MODELS GENERALLY AGREE ON THE EVOLUTION OF THIS
SYSTEM THROUGH 96-108 HRS...THEN DIVERGE LATER IN THE CYCLE.
OVERALL FORECAST CONFIDENCE REMAINS HIGH.

OVER THE EASTERN PACIFIC...SHORT WAVE RIDGE IS TO DOMINATE THE
SOUTHERN STREAM FLOW WHILE GRADUALLY BUILDING SOUTH INTO THE
BELLINGSHAUSEN SEA. NORTH OF THIS RIDGE...IN A SPLIT FLOW
PATTERN...A TROUGH LIES OFF THE SOUTHERN/CENTRAL COAST OF
CHILE...WHERE IT IS FORECAST TO REMAIN NEARLY STATIONARY DURING
THE NEXT 72-84 HRS. AS IT MEANDERS OVER THE EASTERN PACIFIC THIS
WILL FAVOR A MOIST ADVECTIVE PATTERN...WITH DEEP SUBTROPICAL
MOISTURE CONVERGING ON THE SOUTHERN ANDES. AT LOW LEVELS THIS WILL
SUSTAIN A BROAD TROUGH...WITH POLAR FRONTS TO STREAM ACROSS
SOUTHERN CHILE INTO PATAGONIA WHILE REVOLVING AROUND THE SURFACE
TROUGH. THIS IS TO ALSO SUSTAIN A STRONG NORTHWESTERLY FLOW INTO
SOUTHERN REGIONS OF CHILE...WITH MECHANICAL/ADIABATIC LIFTING
EXPECTED DURING THE NEXT FEW DAYS. THIS WILL RESULT IN AREAS OF
MODERATE TO HEAVY CONVECTION...WITH MAXIMA OF 25-50MM EXPECTED
BETWEEN TEMUCO-ISLA DE CHILOE ON DAY 02. OVER THE NEXT THREE DAYS
STORM TOTAL AMOUNTS ARE LIKELY TO EXCEED 100MM.

BY 96-120 HRS THE MID LEVEL TROUGH WILL PUSH EAST ACROSS THE
SOUTHERN CONE WHILE SHORT WAVE RIDGE PERSISTS TO THE SOUTH. AS IT
PULLS ACROSS ARGENTINA THIS IS TO THEN SUSTAIN A BAROCLINIC
BOUNDARY THAT RACES NORTH ACROSS LA PAMPA-BUENOS AIRES PROVINCE TO
CENTRAL ARGENTINA BY 96-108 HRS...INTO URUGUAY-NORTHERN ARGENTINA
BY 120-132 HRS. ACROSS URUGUAY-ENTRE RIOS IN ARGENTINA THIS WILL
TRIGGER MODERATE CONVECTION WITH MAXIMA EXPECTED TO PEAK AT
20-30MM BY 96-108 HRS.

ANOTHER TROUGH LIES TO THE EAST...DOMINATING FLOW OVER THE WESTERN
ATLANTIC AND OFF THE SOUTH COAST OF BRASIL-URUGUAY. THROUGH 48 HRS
THE TROUGH IS TO SLOWLY PULL ACROSS 30W...NEARING 20W BY 96 HRS.
AT LOW LEVELS IT WILL SUSTAIN A RAPIDLY DEEPENING LOW...WITH
ASSOCIATED POLAR FRONT TRAILING ACROSS RIO DE JANEIRO-MATO GROSSO
DO SUL INTO SOUTHEAST BOLIVIA. THROUGH 72 HRS THE FRONT MEANDERS
NORTH INTO ESPIRITO SANTO WHILE TRAILING END WEAKENS AS IT
RETROGRESSES ACROSS PARAGUAY TO NORTHERN ARGENTINA. AS THE FRONT
PUSHES NORTH IT WILL SUPPORT A PREFRONTAL SHEAR LINE INTO
NORTHEAST BRASIL BY 48-96 HRS. THIS WILL ENHANCE MOISTURE
TRANSPORT/CONVERGENCE BETWEEN EASTERN BAHIA AND ESPIRITO
SANTO...TO TRIGGER SCATTERED COASTAL CONVECTION WITH ACCUMULATION
OF 05-10MM/DAY EXPECTED OVER THE NEXT FOUR DAYS.

NORTH OVER THE CONTINENT...AT 200 HPA...A NEAR ZONAL WESTERLY FLOW
ESTABLISHED ACROSS PERU-BRASIL. THROUGH 48-60 HRS PATTERN WILL
GROW MORE AMPLIFIED...WITH SINUSOIDAL WAVE FEATURE TO ENVELOP AREA
TO THE NORTH OF 25S. IN THIS PATTERN A SHORT WAVE RIDGE WILL BUILD
ACROSS AMAZONAS/ACRE IN BRASIL TO PERU...WHILE A SHORT WAVE TROUGH
IS TO AMPLIFY TO THE EAST. AS THE PATTERN EVOLVES...LIGHT TO
MODERATE CONVECTION WILL CLUSTER ACROSS SOUTHERN COLOMBIA-NORTHERN
PERU/EASTERN ECUADOR AND NORTHERN AMAZONAS IN BRASIL. IN THIS AREA
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY...DECREASING TO 05-10MM
BY 60 HRS. OTHER CONVECTION IS EXPECTED ACROSS THE GUIANAS...WITH
RAINFALL AMOUNTS OF 05-10MM. HIGHER AMOUNTS ARE TO CLUSTER ALONG
THE NORTH COAST OF BRASIL STARTING ON DAY 02 AND PERSIST THROUGH
DAY 04...WITH MAXIMA OF 15-25MM.

AYALA...DINAC (PARAGUAY)
OSORIO...DMC (CHILE)
DAVISON...WPC (USA)
$$





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