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South American Forecast Discussion
 
(Latest Discussion - Issued 1720Z Feb 18, 2020)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1220 PM EST TUE FEB 18 2020

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

FORECAST DISCUSSION FROM FEBRUARY 18/1700UTC: MID LEVEL TROUGH ON
THE NORTHERN STREAM MEANDERS OVER THE WESTERN ATLANTIC OFF THE
SOUTH COAST OF BRASIL-BUENOS AIRES PROVINCE IN ARGENTINA...WHILE A
DEEPENING TROUGH EXTENDS OVER THE SOUTHERN CONE. UNDER INFLUENCE
OF A BUILDING RIDGE TO THE WEST...THE LATTER IS TO RAPIDLY
INTENSIFY WHILE AMPLIFYING NORTH ACROSS URUGUAY/SOUTHERN STATES OF
BRASIL TO CENTRAL SOUTH AMERICA...WHILE THE FORMER WEAKENS AS IT
SHEARS TO THE SOUTHEAST. THE DEEPENING TROUGH REACHES MAXIMUM
AMPLITUDE ON THURSDAY TO FRIDAY...THEN GRADUALLY WEAKENS DURING
THE WEEKEND WHEN IT STARTS TO PULL TO THE EAST-SOUTHEAST. AT LOW
LEVELS...AN OCCLUDING LOW TO THE EAST-SOUTHEAST OF URUGUAY EXTENDS
A FRONT ACROSS SOUTHERN BRASIL TO NORTHERN ARGENTINA. ANOTHER
FRONT LIES TO THE SOUTH OVER PATAGONIA IN ARGENTINA/SOUTHERN
REGIONS OF CHILE...WITH AXIS ORIGINATING ON AN OCCLUDING LOW OVER
THE DRAKE PASSAGE. THE FORMER IS TO REMAIN NEARLY STATIONARY
DURING THE NEXT COUPLE OF DAYS...WHILE THE LATTER RACES NORTH
ACROSS ARGENTINA AS A RIDGE BUILDS TO THE SOUTH OVER PATAGONIA-LA
PAMPA. THROUGH THURSDAY IT IS TO THEN REPLACE THE OLD FRONT TO THE
NORTH.

MEANWHILE...EXPECTING SCATTERED DEEP CONVECTION ACROSS SOUTHERN
BRASIL-CORRIENTES/MISIONES IN ARGENTINA TO CHACO TO RESULT IN
MAXIMA OF 30-60MM. ON WEDNESDAY THIS DECREASES TO 20-45MM/DAY
WHILE BUILDING NORTH ACROSS SOUTHERN BRASIL TO SOUTHEAST
PARAGUAY/CORRIENTES. HIGHER AMOUNTS ARE EXPECTED TO THE WEST...TO
CLUSTER OVER SOUTHERN BOLIVIA AS ENHANCED BY A SOUTHERLY LOW LEVEL
JET. IN THIS AREA ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE
FOR AN MCS TO DEVELOP...TO SUSTAIN MAXIMA OF 75-125MM THROUGH
WEDNESDAY MORNING...WHILE ON WEDNESDAY TO THURSDAY THE MAXIMA
INCREASES TO 75-150MM. ON THURSDAY CONVECTION IS TO SPREAD ACROSS
CENTRAL BOLIVIA...TO ALSO SUSTAIN MAXIMA OF 75-125MM. OVER ACRE IN
BRASIL-SOUTHERN PERU EXPECTING MAXIMA OF 50-100MM ON
FRIDAY-SATURDAY...WITH SIMILAR AMOUNTS OVER CENTRAL JUNGLE OF PERU
EARLY DURING THE WEEKEND.

NORTH OVER THE CONTINENT...BROAD UPPER LEVEL RIDGE WILL DOMINATE
CENTRAL SOUTH AMERICA OVER THE NEXT FEW DAYS...WITH AXIS TO CENTER
ON A CLOSED HIGH OVER MATO GROSSO DO SUL IN BRASIL. LATER IN THE
WEEK...AS CONVECTION OVER NORTHERN BOLIVIA-SOUTHERN PERU
INTENSIFIES...THE HIGH MEANDERS WEST...WITH CLOSED HIGH RELOCATING
ACROSS SOUTHERN BOLIVIA TO NORTHERN CHILE. THE EVOLVING UPPER
LEVEL RIDGE PATTERN IS TO VENT DEEP CONVECTION ACROSS
ECUADOR...WITH ACTIVITY CLUSTERING ALONG THE WESTERN SLOPES OF THE
ANDES TO INCREASES TO 25-50MM ON WEDNESDAY. THROUGH FRIDAY PEAK IN
CONVECTION SHIFTS TO THE EASTERN SLOPES...WITH MAXIMA OF 35-70MM
ON THE CENTRAL-SOUTHERN SIERRA OF PERU INITIALLY EXPECTING MAXIMA
OF 15-20MM. ON WEDNESDAY-THURSDAY THIS DECREASES TO
05-10MM...WHILE ON FRIDAY ACTIVITY SURGES AS THE HIGH RELOCATES
ACROSS MIDSECTIONS OF SOUTH AMERICA.

EAST OF THIS RIDGE...A TUTT EXTENDS FROM THE ATLANTIC TO A TUTT
LOW OVER NORTHEAST BRASIL. THE UPPER LEVEL LOW MEANDERS INLAND
INTO NORTHEAST BRASIL ON WEDNESDAY...TO THEN GRADUALLY WEAKEN
WHILE MEANDER FARTHER TO THE WEST. THIS IS TO ENHANCE CONVECTION
ACROSS PARA-AMAZON RIVER DELTA REGION IN BRASIL. IN THIS AREA
MAXIMA INCREASES FROM 20-45MM/PER EARLY IN THE CYCLE TO
35-70MM/DAY ON WEDNESDAY-THURSDAY. BUT AS THE UPPER TROUGH
WEAKENS...THIS WILL ALSO WANE.

MENDOZA...SENAMHI (BOLIVIA)
GONZALEZ...DINAC (PARAGUAY)
DAVISON...WPC (USA)