Prognostic Meteorological Discussion
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000
FXSA20 KWBC 291618
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1217 PM EDT FRI JUL 29 2016

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

MODEL DISCUSSION (VALID FROM JULY 29 AT 0000 UTC): MODELS CONTINUE
TO FORECAST A SPLIT FLOW PATTERN TO DEVELOP ACROSS THE EASTERN
PACIFIC...WITH FLOW TO DIVIDE BETWEEN A RIDGE ON THE SOUTHERN
STREAM AND A TROUGH TO THE NORTH. THE SOUTHERN STREAM RIDGE WILL
EXTENDS BETWEEN 105W-70W AND TO THE SOUTH OF 55W INTO THE
BELLINGSHAUSEN SEA/ANTARCTIC PENINSULA. THE TROUGH TO THE
NORTH...MEANWHILE...IS TO MEANDER OFF THE SOUTH COAST OF CHILE
THROUGH 54-60 HRS. BY 72-96 HRS IT IS TO THEN SHEAR ACROSS THE
SOUTHERN CONE WHILE A NEW LOW ESTABLISHES TO THE WEST.
MEANWHILE...THIS WILL SUSTAIN A MOIST ADVECTIVE PATTERN ACROSS
CHILE TO THE SOUTH OF CONCEPCION. AT LOW LEVELS THIS SUSTAINS A
BROAD TROUGH THAT MEANDERS ACROSS THE SOUTHERN CONE. POLAR FRONTS
ARE TO REVOLVE AROUND THIS AXIS... STREAMING ACROSS SOUTHERN CHILE
TO PATAGONIA IN ARGENTINA. THIS IS TO ALSO SUSTAIN A STRONG
NORTHWESTERLY FLOW INTO SOUTHERN REGIONS OF CHILE DURING THE NEXT
FEW DAYS. STRONG WINDS AND MOIST BOUNDARY LAYER WILL COMBINE IN
SUPPORT OF MODERATE CONVECTION AS ENHANCED BY TOPOGRAPHICAL
LIFTING OVER THE SOUTHERN ANDES. THROUGH 24-36 HRS THIS IS TO
RESULT IN RAINFALL AMOUNTS OF 20-30MM...WITH MOST INTENSE EXPECTED
TO THE SOUTH OF CONCEPCION. BY 36-84 HRS DAILY RAINFALL AMOUNTS
WILL PEAK AT 15-25MM/DAY.

AS THE MID LEVEL TROUGH REMAINS OVER THE EASTERN PACIFIC...IT IS
TO SHEAR SHORT WAVE ENERGY ACROSS THE CENTRAL/NORTHERN ANDES OF
CHILE INTO ARGENTINA. IN THIS PATTERN A FAIRLY STRONG VORTEX IS TO
STREAM ACROSS THE ANDES INTO MENDOZA ARGENTINA BY 48-60
HRS...CROSSING RIO DE LA PLATA BASIN BY 72 HRS. AT LOW LEVELS THIS
IS TO SUSTAIN A FRONTAL LOW OVER ENTRE RIOS IN ARGENTINA/URUGUAY
BY 48-60 HRS...TO SLOWLY PULL TO THE EAST SOUTHEAST ACROSS URUGUAY
WHILE THE ASSOCIATED FRONT MEANDERS NORTH INTO SOUTHERN
BRASIL-NORTHERN ARGENTINA. UNDER FAVORABLE JET DYNAMICS THIS WILL
TRIGGER MODERATE CONVECTION WITH ACCUMULATION OF 15-20MM BY 48-60
HRS...INCREASING TO 20-30MM BY 60-84 HRS AS THE SURFACE LOW
DEEPENS OVER URUGUAY. ON THE CENTRAL ANDES OF CHILE THIS IS TO
ALSO TRIGGER MODERATE SNOWFALL AMOUNTS...WITH ACCUMULATION OF
10-15CM.

FARTHER EAST...OVER THE SOUTH ATLANTIC...A TROUGH EXTENDS NORTH
ALONG 25W TO 20S LATER TODAY. THROUGH 72 HRS THE TROUGH WILL PULL
ACROSS 00W. AT LOW LEVELS THIS SUSTAINS A BROAD TROUGH...WITH
POLAR FRONT TRAILING ACROSS RIO DE JANEIRO/NORTHERN SAO PAULO TO
PARAGUAY/MISIONES ARGENTINA. BUILDING POLAR RIDGE TO THE SOUTH
DISPLACES THIS BOUNDARY NORTH ACROSS ESPIRITO SANTO BY 48-72 HRS.
THE BUILDING RIDGE WILL ALSO TRIGGER A TRADE WINDS SURGE ACROSS
NORTHEAST BRASIL...AND IT IS TO ALSO FAVOR GENERATION OF A
PREFRONTAL SHEAR LINE. THE SHEAR LINE IS TO SLOWLY MOVE NORTH
ACROSS ESPIRITO SANTO-BAHIA TO RIO GRANDE DO NORTE THROUGH 54-60
HRS. BRISK SOUTHEASTERLY WINDS WILL ENHANCE COASTAL CONVECTION
ACROSS NORTHEAST BRASIL...WITH RAINFALL MAXIMA FORECAST TO PEAK AT
10-15MM/DAY OVER THE NEXT COUPLE OF DAYS. SCATTERED COASTAL
CONVECTION IS TO THEN PERSIST THROUGH 72-96 HRS.

NORTH OVER THE CONTINENT...AT 200 HPA...A SHORT WAVE RIDGE EXTENDS
ACROSS COLOMBIA TO NORTHERN PERU/NORTHERN AMAZONAS IN
BRASIL...WHILE TO THE EAST A SHORT WAVE TROUGH EXTENDS NORTH ALONG
50W TO THE AMAZON RIVER DELTA. THROUGH 48 HRS THE PATTERN WILL
GROW MORE AMPLIFIED. BY 72-96 HRS IT WILL ANCHOR ON A CLOSED HIGH
OVER NORTHERN JUNGLE OF PERU...WHILE A SECONDARY HIGH CLOSES JUST
SOUTH OF THE GALAPAGOS ISLANDS. THE RIDGE ALOFT...MEANWHILE...WILL
VENT DIURNAL CONVECTION ACROSS NORTHERN AMAZONAS IN BRASIL TO
SOUTHERN COLOMBIA/NORTHERN PERU...WITH RAINFALL MAXIMA OF 10-15MM
EXPECTED OVER THE NEXT DAY OR SO...AND 05-10MM/DAY THEREAFTER.
OVER NORTHERN BRASIL-AMAZON DELTA REGION THE MAXIMA PEAKS AROUND
15-25MM OVER THE NEXT TWO DAYS. BUT THROUGH 72-96 HRS THIS WILL
DECREASE TO 05-10MM.

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




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