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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1634Z Jun 03, 2020)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1234 PM EDT WED JUN 03 2020

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

FORECAST DISCUSSION FROM JUNE 03/16UTC: A MID/UPPER LEVEL RIDGE
OVER THE EASTERN PACIFIC IS STEERING A CLOSED LOW AND ASSOCIATED
SHORT WAVE TROUGH NORTH ALONG THE CENTRAL COAST OF CHILE...WITH
SYSTEM TO BRIEFLY STALL AS IT NEARS LA SERENA CHILE LATER THIS
EVENING. LATER ON THURSDAY...AS THE RIDGE TO THE WEST COLLAPSES
AND A DEEPENING MID LEVEL TROUGH BECOMES THE DOMINANT SYNOPTIC
FEATURE OVER THE EASTERN PACIFIC...THE CLOSED LOW IS FORECAST TO
JUMP ACROSS THE NORTHERN ANDES OF CHILE TO THE NORTHWEST PROVINCES
IN ARGENTINA. CONSISTENT WITH PREVIOUS FORECAST...THE CLOSED LOW
IS TO THEN TRACK TO THE EAST-SOUTHEAST ACROSS NORTHERN ARGENTINA
TO SOUTHERN BRASIL/URUGUAY THROUGH FRIDAY EVENING...WEAKENING AS
IT DRIFTS ACROSS SOUTHERN BRASIL TO THE WESTERN ATLANTIC ON
SATURDAY-SUNDAY. MEANWHILE...AT 250 HPA...A POLAR JET MAXIMA IS TO
ACCOMPANY THIS LOW/TROUGH AS IT TRACKS ACROSS NORTHERN
ARGENTINA-SOUTHERN BRASIL...FAVORING AN UPPER DIVERGENT PATTERN
THAT IS TO VENT ORGANIZED DEEP CONVECTION ON THURSDAY-FRIDAY. AT
LOW LEVELS...THE MID LEVEL LOW SUSTAINS A WANING SURFACE FRONT
THAT LIFTS ACROSS THE BUENOS AIRES PROVINCE TO MENDOZA IN
ARGENTINA LATER TODAY...MEANWHILE TRIGGERING LIGHT/LOCALLY
MODERATE CONVECTION ACROSS CENTRAL CHILE AND MENDOZA/NORTHWEST
ARGENTINA. THE MID LEVEL LOW IS TO ALSO INTERACT WITH A MEANDERING
FRONT TO THE NORTH...SUSTAINING CYCLOGENESIS OVER PARAGUAY EARLY
IN THE CYCLE. ON THURSDAY TO FRIDAY...UNDER FAVORABLE JET
DYNAMICS...THE FRONTAL LOW IS FORECAST TO DEEPEN AS IT OCCLUDES
ACROSS URUGUAY TO ENTRE RIOS/CORRIENTES IN ARGENTINA. THE
DEEPENING LOW WILL THEN DRIVE THE FRONT NORTH ACROSS SOUTHEASTERN
BRASIL-MATO GROSSO TO CENTRAL BOLIVIA ON SATURDAY-SUNDAY. OVER
PARAGUAY-MISIONES IN ARGENTINA THE DEEPENING LOW WILL INITIALLY
FAVOR MODERATE TO HEAVY CONVECTION WITH MAXIMA OF 15-30MM. AS THE
LOW DEEPENS ON THURSDAY-FRIDAY...CONVECTION IS TO INTENSIFY...WITH
MAXIMA ACROSS PARAGUAY-SOUTHERN BRASIL PEAKING AT 40-80MM IN
POTENTIALLY SEVERE CONVECTION. ON FRIDAY-SATURDAY ACTIVITY ACROSS
SOUTHERN-SOUTHEAST BRASIL WANES...WITH MAXIMA PEAKING AT
20-40MM...WHILE OVER URUGUAY/ENTRE RIOS THE MAXIMA INCREASES TO
30-60MM AS MOISTURE WRAPS AROUND THE OCCLUDING LOW AND AN ECHO
TRAINING PATTERN SETTLES.

UPSTREAM OVER THE EASTERN PACIFIC...A BROAD MID/UPPER LEVEL TROUGH
IS TO STREAM ACROSS THE SOUTHEAST PACIFIC TO THE DRAKE
PASSAGE/SOUTHERN CONE LATER THIS EVENING/EARLY ON THURSDAY
MORNING. AS IT PRESSES AGAINST A MID LEVEL RIDGE TO THE
NORTH...THIS IS TO FOCUS SUBTROPICAL MOISTURE AND SHORT WAVE
ENERGY ACROSS THE SOUTHERN REGIONS OF CHILE/PATAGONIA IN
ARGENTINA. AS SHORT WAVE ENERGY STREAMS TO THE SOUTH...THIS WILL
THEN FAVOR THE RAPID EROSION OF THE MID LEVEL RIDGE PATTERN. THIS
SETS THE STAGE FOR A HIGH AMPLITUDE/LONG WAVE TROUGH TO AMPLIFY
ACROSS THE EASTERN PACIFIC BETWEEN 80W-90W TO 20S LATER ON FRIDAY.
SHORT WAVE PERTURBATIONS REVOLVING AROUND THE LONG WAVE AXIS ARE
TO THEN STREAM ACROSS SOUTHERN CHILE/PATAGONIA IN ARGENTINA...WITH
FAIRLY STRONG MID LEVEL VORTEX EXPECTED EARLY ON SATURDAY MORNING
AND ANOTHER ON SUNDAY-MONDAY. AT LOW LEVELS...A BROAD POLAR TROUGH
IS TO MOVE TO THE SOUTHEAST PACIFIC/BELLINGSHAUSEN SEA DURING THE
DAY TODAY...WITH AXIS TO QUICKLY EXPAND ACROSS THE SOUTHERN CONE
WHILE MOVING EAST ACROSS THE ANTARCTIC PENINSULA TO THE WEDDELL
SEA ON THURSDAY. STRONG BOUNDARY LAYER WINDS ARE TO ACCOMPANY THE
DEEPENING SURFACE TROUGH...WITH WINDS ACROSS SOUTHERN CHILE/TIERRA
DEL FUEGO-PATAGONIA IN ARGENTINA TO PEAK AT 35-50KT DURING THE
NEXT FIVE DAYS. THIS WILL ENHANCE LOW LEVEL MOISTURE TRANSPORT AND
CONVERGENCE ON THE SOUTHERN REGIONS OF CHILE...WHILE ADIABATICALLY
ASCENDING ACROSS THE SOUTHERN ANDES. THE MOST ACTIVE CONVECTION
WITH THIS FEATURE IS EXPECTED BETWEEN PUERTO MONTT AND ISLA DE
CHILOE IN SOUTHERN CHILE...WITH MAXIMA OF 15-30MM EXPECTED ON
WEDNESDAY-THURSDAY...INCREASING TO 20-40MM/DAY ON
THURSDAY-SATURDAY. FURTHERMORE...THE INFLOW OF COLD AIR ALOFT
WOULD LIKELY FAVOR ISOLATED THUNDERSTORMS OVER SOUTHERN CHILE
SATURDAY MORNING AND AGAIN ON SUNDAY-MONDAY MORNING.

NORTH OVER THE CONTINENT...AT 200 HPA...A BROAD CELL OF THE
SUBTROPICAL RIDGE ENVELOPS CONTINENTAL AREA TO THE NORTH OF 20S.
EMBEDDED IN THIS AXIS...A CLOSE HIGH WILL ROLL ACROSS NORTHEAST
BRASIL EARLY IN THE CYCLE...TO CONTINUE ACROSS CENTRAL TO WESTERN
BRASIL/NORTHERN BOLIVIA DURING THE WEEKEND.
AS THE RIDGE HOLDS TO THE NORTH...A SUBTROPICAL JET IS TO BOUND
THE SOUTHERN FRINGES OF THIS RIDGE DURING THE NEXT THREE DAYS...TO
ALSO FAVOR A DIVERGENT PATTERN ALOFT THAT IS TO VENT THE
AFOREMENTIONED CONVECTION OVER PARAGUAY-SOUTHERN BRASIL. THE RIDGE
ALOFT IS TO ALSO VENT CONVECTION ACROSS EQUATORIAL SOUTH
AMERICA...WITH MOST INTENSE AS TROPICAL WAVE STREAMING TO THE
NORTH INTERACT WITH THE NEAR EQUATORIAL TROUGH. ACROSS AMAZONAS IN
BRASIL-SOUTHERN COLOMBIA/NORTHERN PERU-EASTERN ECUADOR THIS IS TO
FAVOR SEVERAL DAYS OF SCATTERED DEEP CONVECTION WITH MAXIMA IN
THIS AREA PEAKING AROUND 20-40MM/DAY. THIS...HOWEVER...IS TO SURGE
ON THURSDAY-FRIDAY WHEN THE MAXIMA INCREASES TO 30-60MM. OTHER
CONVECTION IS TO CLUSTER ACROSS AMAPA IN BRASIL/NORTHERN PARA TO
THE SOUTHERN GUIANAS...WITH MAXIMA OF 15-30MM EXPECTED OVER THE
NEXT FEW DAYS.

DAVISON...WPC (USA)
GALVEZ...WPC (USA)