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993
FXSA20 KWBC 011520
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1119 AM EDT WED OCT 01 2014

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

MODEL DISCUSSION (VALID FROM OCTOBER 01 AT 00UTC): THE GLOBAL
MODELS AGREE QUITE WELL THROUGH 96-108 HRS...THEN DEVELOP MINOR
TIMING DIFFERENCES LATER IN THE CYCLE. OVERALL CONFIDENCE IN THE
FORECAST IS HIGH.

BUILDING MID LEVEL RIDGE OVER ARGENTINA IS TO SUSTAIN THE
NORTHWARD AMPLIFICATION OF A SHORT WAVE TROUGH OVER THE SOUTH
ATLANTIC...WITH AXIS NORTH ALONG 40W TO 25S EARLY THIS CYCLE.
THROUGH 48 HRS THE TROUGH WILL MOVE TO EXTEND BETWEEN 50W-10W TO
15S...WHERE IT IS TO THEN MEANDER THROUGH 96-108 HRS. AT LOW
LEVELS...BUILDING RIDGE IS TO EXTEND OFF THE COAST OF ARGENTINA.
THIS IS TO SUSTAIN A TIGHT PRESSURE GRADIENT AND STRONG SOUTHERLY
WINDS ACROSS SOUTHERN-SOUTHEAST BRASIL. A POLAR TROUGH LIES TO THE
EAST...WITH FRONT TRAILING ACROSS SOUTHEAST BRASIL-PARAGUAY. FRONT
OVER THE CONTINENT FRONTOLIZES EARLY IN THE CYCLE...WHILE REMNANTS
OVER THE ATLANTIC ARE TO SURGE ACROSS SOUTHEAST BRASIL TO RIO DE
JANEIRO EARLY IN THE CYCLE. THROUGH 48 HRS THE FRONT MOVES NORTH
TO ESPIRITO SANTO... REACHING BAHIA BY 72 HRS. AS THE FRONT SURGES
NORTH IS IT TO THEN TRIGGER A PREFRONTAL SHEAR LINE. THIS IS TO
ENHANCE MOISTURE CONVERGENCE WHILE ALSO TRIGGERING ORGANIZED
CONVECTION. AS THE FRONT MOVES NORTH ACROSS SAO PAULO...IT IS TO
TRIGGER SCATTERED COASTAL CONVECTION WITH ACCUMULATION OF 15-30MM.
OVER MINAS GERAIS-BAHIA-ESPIRITO SANTO IT IS TO THEN FAVOR
RAINFALL AMOUNTS OF 20-40MM BY 48-84 HRS...WHILE OVER
PERNABUCO-TOCANTINS/GOIAS AND PORTIONS OF PARA MOST ACTIVE
CONVECTION IS EXPECTED BY 72-84 HRS.

A DEEP LOW/TROUGH ON THE NORTHERN STREAM LIES OVER THE EASTERN
PACIFIC. THE DEEP MID LEVEL PERTURBATION REACHES CENTRAL CHILE BY
48-60 HRS...AND BY 72-84 HRS IT IS TO SPILL ACROSS THE ANDES INTO
CENTRAL PROVINCES IN ARGENTINA. THE INFLOW OF COLD AIR ALOFT WILL
THEN INDUCE HEIGHT FALLS OF 100-150GPM ACROSS CENTRAL
ARGENTINA-NORTHERN PATAGONIA BY 60-84 HRS. THROUGH 96 HRS A STRONG
CYCLONIC VORTEX IS TO THEN SWING ACROSS BUENOS AIRES PROVINCE/RIO
DE LA PLATA BASIN. THIS PERTURBATION IS TO THEN MEANDER EAST
ACROSS THE SOUTHERN CONE TO THE WESTERN ATLANTIC THROUGH 120-132
HRS. AT LOW LEVELS...THE BROAD RIDGE OVER THE WESTERN ATLANTIC IS
TO SUSTAIN A NORTHERLY JET ACROSS PARAGUAY-ARGENTINA. AS
AFOREMENTIONED FRONT WEAKENS OVER PARAGUAY...A WARM/MOIST
ADVECTIVE PATTERN IS TO ESTABLISH ACROSS MID/SOUTHERN PORTIONS OF
SOUTH AMERICA. THIS...IN COMBINATION WITH COLD ADVECTION
ALOFT...IS TO THEN FAVOR DEEP LAYER CONVECTIVE INSTABILITY FROM
NORTHERN PATAGONIA TO MENDOZA/CORDOBA IN ARGENTINA. AS UPPER
TROUGH SPILLS ACROSS THE ANDES...IT IS TO SUSTAIN CYCLOGENESIS
OVER CENTRAL ARGENTINA...WITH SYSTEM FORECAST TO SLOWLY MOVE EAST
CROSS THE SOUTHERN CONE THROUGH 108-120 HRS. THIS IS TO ALSO
TRIGGER ORGANIZED DEEP CONVECTION ACROSS CENTRAL PROVINCES IN
ARGENTINA...WITH ACCUMULATION OF 25-50MM EXPECTED BETWEEN 72-96
HRS. THIS IS TO GRADUALLY BUILD NORTH ACROSS CORDOBA TO CORRIENTES
IN ARGENTINA THROUGH 108 HRS. UNDER FAVORABLE JET DYNAMICS...THERE
IS A RISK OF SEVERE CONVECTION ON DAY 03.

NORTH OVER THE CONTINENT...AT 200 HPA...THE SUBTROPICAL RIDGE IS
TO EXTEND ACROSS MATO GROSSO-MINAS GERAIS/BAHIA IN BRASIL EARLY IN
THE CYCLE...AS IT IS TO CENTER ON A CLOSED HIGH OVER MINAS GERAIS.
THROUGH 72-96 HRS THE HIGH RELOCATES TO MATO GROSSO/RONDONIA IN
BRASIL. AS IT PULLS AWAY...A TROUGH IS TO THEN AMPLIFY ACROSS
NORTHEAST BRASIL. EARLY IN THE CYCLE THE RIDGE ALOFT IS TO VENT


CONVECTION ACROSS EASTERN-NORTHEASTERN BRASIL...WITH MAXIMA IN
THIS AREA TO PEAK AT 20-40MM BY 48-84 HRS. BY 99-120 HRS FOCUS OF
THE CONVECTION SHIFTS TO PARA-MATO GROSSO-RONDONIA IN BRASIL. ON
THE SIERRA OF PERU...DIURNAL CONVECTION IS TO SUSTAIN RAINFALL
AMOUNTS OF 05-10MM...WHILE OVER NORTHERN PERU/NORTHERN AMAZONAS TO
SOUTHERN COLOMBIA THE MAXIMA PEAKS AT 15-30MM ON DAY 02.
OTHERWISE... EXPECTING ACCUMULATION OF 10-15MM/DAY.

CAROCA...DMC (CHILE)
DAVISON...WPC (USA)
$$






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