Prognostic Meteorological Discussion
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000
FXSA20 KWBC 291606
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1205 PM EDT MON JUN 29 2015

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

MODEL DISCUSSION (VALID FROM JUN 29 AT 0000 UTC): A SHORT WAVE
TROUGH ON THE NORTHERN STREAM MOVES ACROSS CHILE TO
CENTRAL/NORTHERN ARGENTINA EARLY IN THE CYCLE...FOCUSING SHORT
WAVE ENERGY ACROSS URUGUAY-MESOPOTAMIA VALLEY IN
ARGENTINA-SOUTHERN STATES OF BRASIL. THROUGH 48 HRS THE TROUGH
MOVES INTO SOUTHEAST BRASIL...CLEARING THE COAST BY 60-66 HRS. A
SUBTROPICAL JET MAXIMA IS TO ACCOMPANY THIS PERTURBATION AS IT
MIGRATES ACROSS CHILE/ARGENTINA...FAVORING AN UPPER DIVERGENT
PATTERN ON ITS RIGHT EXIT REGION. THIS IS TO VENT ORGANIZED DEEP
CONVECTION ACROSS SOUTHEAST PARAGUAY-MESOPOTAMIA
VALLEY...URUGUAY/SOUTHERN BRASIL. AT LOW LEVELS A SURFACE FRONT IS
TO MEANDER TO THE NORTHWEST ACROSS URUGUAY-NORTHERN ARGENTINA
EARLY IN THE CYCLE. AS THE MID LEVEL TROUGH INTERACTS WITH THIS
SYSTEM A FRONTAL LOW IS TO DEVELOP OVER URUGUAY/RIO GRANDE DO SUL.
THIS IS TO INTENSIFY WHILE MEANDERING EAST INTO THE SOUTH
ATLANTIC. AS THE LOW DEEPENS THE SURFACE FRONT IS TO MIGRATE
ACROSS SOUTHERN BRASIL-PARAGUAY BY 42-48 HRS...INTO SAO
PAULO-PARAGUAY BY 72-84 HRS. INFLOW OF SHORT WAVE ENERGY AND
FAVORABLE UPPER DYNAMICS ARE TO TRIGGER A MESO SCALE CONVECTIVE
SYSTEM ACROSS SOUTHEAST PARAGUAY-MESOPOTAMIA VALLEY IN
ARGENTINA-URUGUAY...WITH MAXIMA IN THIS AREA TO PEAK AT 35-70MM
THROUGH 36 HRS. AS THE FRONT MOVES TO SOUTHERN BRASIL THIS
DECREASES TO 20-35MM...WHILE ALONG THE TAIL END OVER PARAGUAY
EXPECTING 15-25MM.

CONSISTENT WITH PREVIOUS FORECASTS...A BROAD TROUGH CONTINUES TO
DOMINATE THE FLOW ACROSS THE ANTARCTIC PENINSULA/WEDDELL
SEA-SOUTHERN CONE OF SOUTH AMERICA. THROUGH 72 HRS THE TROUGH IS
TO MIGRATE ACROSS 40W...AND BY 120 HRS IT IS TO PULL ACROSS 00W.
AT LOW LEVELS THIS IS TO SUSTAIN A BROAD TROUGH ACROSS THE DRAKE
PASSAGE TO SOUTHERN CHILE/ARGENTINA OVER THE NEXT 48-60 HRS. AS IT
MEANDERS OVER THE CONTINENT...POLAR FRONTS ARE TO REVOLVE AROUND
THIS AXIS. IN A COLD ADVECTIVE PATTERN CONDITIONS WILL REMAIN
FAVORABLE FOR ORGANIZED SNOWFALL AMOUNTS ACROSS EXTREME SOUTHERN
PORTIONS OF CHILE/TIERRA DEL FUEGO...WITH MAXIMA IN THIS AREA
EXPECTED TO PEAK AT 05-10CM THROUGH 36-42 HRS.

BUILDING RIDGE TO THE WEST IS TO THEN STEER A MID LEVEL TROUGH
ACROSS SOUTHERN CHILE BY 60-66 HRS...INTO PATAGONIA IN ARGENTINA
BY 72 HRS. AS IT MIGRATES ACROSS THE SOUTHERN CONE THE SHORT WAVE
TROUGH IS TO THEN PHASE WITH A CLIPPER LOW ENTERING THE DRAKE
PASSAGE. THROUGH 96-120 HRS THESE ARE TO THEN COMBINE INTO A HIGH
AMPLITUDE LONG WAVE TROUGH OVER THE WESTERN ATLANTIC-MID SECTIONS
OF SOUTH AMERICA. THIS EVOLUTION IS WELL SUPPORTED BY THE GLOBAL
ENSEMBLES AND DETERMINISTIC MODELS. AT LOW LEVELS THIS IS TO
SUSTAIN A FRONTAL TROUGH OVER SOUTHERN CHILE/PATAGONIA IN
ARGENTINA BY 66-78 HRS. THIS DEEPENS OVER THE WESTERN ATLANTIC
THROUGH 108-120 HRS...WHILE OVER THE CONTINENT A POLAR RIDGE IS TO
BUILD ACROSS ARGENTINA. THIS IS TO ANCHOR ON A 1027-1031 HPA HIGH
NEAR CORDOBA IN ARGENTINA. AS THE LOW DEEPENS THE SURFACE FRONT
ACCELERATES ACROSS PATAGONIA-SOUTHERN CHILE THROUGH 72-84
HRS...INTO THE BUENOS AIRES PROVINCE-MENDOZA IN ARGENTINA BY 96
HRS. BY 108-120 HRS THE FRONT WILL SURGE ACROSS SOUTHERN
BRASIL-PARAGUAY WHERE IT IS TO MERGE WITH/REPLACE THE OLD FRONTAL
BOUNDARY TO THE NORTH. AS THE FRONT ENTERS SOUTHERN CHILE THIS IS
TO TRIGGER SCATTERED CONVECTION WITH ACCUMULATION OF 05-10MM.
ACROSS ARGENTINA-RIO DE LA PLATA BASIN THIS IS TO ONLY FAVOR LIGHT
CONVECTION...WITH MOST INTENSE TO CLUSTER ON THE SOUTHERN STATES
OF BRASIL AND PORTIONS OF PARAGUAY LATER ON DAY 04...WHEN THE
MAXIMA IS TO PEAK AT 30-60MM. UNDER INFLUENCE OF A LOW LEVEL JET
OVER NORTHERN ARGENTINA/PARAGUAY THE FOCUS OF THE ORGANIZED DEEP
CONVECTION WILL SHIFT TO THE WEST AND NORTH ACROSS BOLIVIA TO
SOUTHERN PERU LATER IN THE CYCLE. MOST INTENSE IS TO AFFECT
CENTRAL-NORTHERN BOLIVIA-RONDONIA IN BRASIL WITH MAXIMA IN THIS
AREA TO PEAK AT 75-125MM...WHILE OVER CENTRAL JUNGLE OF PERU THE
MAXIMA IS TO PEAK AT 25-50MM.

AT 200 HPA A RIDGE IS INITIALIZED OVER THE EASTERN TROPICAL
PACIFIC...WITH AXIS ANCHORING ON A CLOSED HIGH JUST WEST OF
ECUADOR. THROUGH 72-96 HRS THE HIGH/RIDGE MOVES INLAND ACROSS PERU
TO WESTERN BRASIL. A TROUGH TO THE EAST IS TO INITIALLY EXTEND
ACROSS SAO PAULO TO MATO GROSSO IN BRASIL. THIS TROUGH MOVES EAST
TO CENTRAL/NORTHEASTERN BRASIL BY 72-96 HRS. TROUGH ALOFT IS TO
ENHANCE DIURNAL CONVECTION ACROSS EQUATORIAL SOUTH AMERICA...WITH
CONVECTION OVER NORTHERN AMAZONAS IN BRASIL-SOUTHERN
COLOMBIA/NORTHERN JUNGLE OF PERU FORECAST TO PEAK AT 10-15MM/DAY.
ON THE AMAZON DELTA AND NORTH COAST OF BRASIL THE DAILY MAXIMA IS
TO PEAK AT 05-10MM. HIGHER AMOUNTS...HOWEVER...ARE EXPECTED
BETWEEN RECIFE-SALVADOR DE BAHIA IN BRASIL...WHERE TRADE WIND
CONVERGENCE IS TO SUSTAIN RAINFALL MAXIMA OF 15-30MM OVER THE NEXT
COUPLE OF DAYS. THROUGH 72-96 HRS...HOWEVER...THIS DECREASES TO
05-10MM.

CHARPENTIER...DMC (CHILE)
CISNEROS...UNALM (PERU)
ROMERO...DMC (CHILE)
DAVISON...WPC (USA)
$$




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