074  
FXSA20 KWBC 051714  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1214 PM EST MON FEB 05 2018  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
MODEL DISCUSSION (VALID FROM FEB 05 AT 0000 UTC): THE GLOBAL  
MODELS ARE IN GOOD AGREEMENT...FOLLOWING A SIMILAR EVOLUTION  
THROUGH THE END OF THE WEEK. THIS FORECAST IS WELL SUPPORTED BY  
THE GLOBAL ENSEMBLE MEMBERS.  
 
OVER THE EASTERN PACIFIC...AT 500 HPA...A PROGRESSIVE SHORT WAVE  
TROUGH IS TO STREAM ACROSS THE SOUTHERN REGIONS OF CHILE ON  
TUESDAY MORNING. LATER IN THE DAY IT WILL MOVE ACROSS PATAGONIA IN  
ARGENTINA TO THE WESTERN ATLANTIC...AND THROUGH WEDNESDAY EVENING  
IT IS TO THEN MERGE INTO A BROAD LONG WAVE TROUGH TO THE SOUTH. AT  
LOW LEVELS THIS INTERACTS WITH AN ELONGATED FRONT IN SUPPORT OF A  
FRONTAL LOW. THE LOW REACHES SOUTHERN CHILE ON TUESDAY  
MORNING...CROSSING PATAGONIA ON TUESDAY AFTERNOON. THIS WILL THEN  
DRIVE THE FRONT NORTH ACROSS LA PAMPA TO SOUTHERN CUYO IN  
ARGENTINA. AS IT ENTERS SOUTHERN CHILE THIS IS TO SUSTAIN  
SCATTERED CONVECTION WITH MAXIMA OF 15-20MM. OVER LA  
PAMPA-SOUTHERN CUYO EXPECTING LESSER AMOUNTS...WITH ACCUMULATION  
OF 05-10MM/DAY ON BOTH TUESDAY AND WEDNESDAY.  
 
A DEEPER MID/UPPER LEVEL TROUGH LIES TO THE SOUTH...DOMINATING THE  
FLOW OVER THE SOUTHEAST PACIFIC/BELLINGSHAUSEN SEA. THE DEEP  
TROUGH IS TO MEANDER OVER THE SOUTHEAST PACIFIC DURING THE NEXT  
48-60 HRS. LATER ON WEDNESDAY IT IS TO THEN MEANDER ACROSS THE  
ANTARCTIC PENINSULA TO THE WEDDELL SEA...AND NORTH ACROSS SOUTHERN  
CHILE TO PATAGONIA IN ARGENTINA...MEANWHILE FOCUSING SHORT WAVE  
ENERGY ON CONTINENTAL AREA TO THE SOUTH OF 40S. ON THURSDAY...AS A  
RIDGE BUILDS ALONG 90W/100W TO THE POLAR ICECAP...THIS IS TO  
INDUCE THE NORTHWARD AMPLIFICATION OF THIS TROUGH TO THE CENTRAL  
PROVINCES IN ARGENTINA...WHERE IT IS TO REMAIN THROUGH FRIDAY  
EVENING. AT LOW LEVELS THE TROUGH ALOFT WILL SUSTAIN A FRONT THAT  
MEANDERS ACROSS SOUTHERN CHILE-TIERRA DEL FUEGO DURING THE NEXT  
THREE DAYS. ON THURSDAY...BUILDING RIDGE OVER THE SOUTHEAST  
PACIFIC WILL THEN FAVOR A STRONG SOUTHERLY JET ACROSS PATAGONIA TO  
CENTRAL ARGENTINA. THIS IS TO DISPLACE THE FRONT NORTH ACROSS LA  
PAMPA/BUENOS AIRES PROVINCE TO THE RIO DE LA PLATA BASIN LATER ON  
FRIDAY. AS IT MEANDERS OVER TIERRA DEL FUEGO THE FRONT IS TO FAVOR  
LIGHT CONVECTION WITH ACCUMULATION OF 05-10MM/DAY DURING THE NEXT  
THREE DAYS. OVER LA PAMPA-BUENOS AIRES PROVINCE THIS INCREASES TO  
15-25MM ON THURSDAY...WHILE ON FRIDAY THE MAXIMA OVER  
URUGUAY-ENTRE RIOS IN ARGENTINA THE MAXIMA WILL PEAK AT  
20-40MM...WITH LOCALLY HIGHER AMOUNTS HIGHLY PROBABLE.  
 
AT 200 HPA...A HIGH OVER NORTHERN CHILE-SOUTHERN BOLIVIA ANCHORS A  
CELL OF THE SUBTROPICAL RIDGE THAT EXTENDS NORTH-TO-SOUTH OVER THE  
CONTINENT TO THE WEST OF 60W. THE RIDGE...AS IT HOLDS TO THE  
WEST...SUSTAINS THE NORTHWARD AMPLIFICATION OF A TROUGH ACROSS  
SOUTHEAST BRASIL. THIS PATTERN HOLDS DURING THE NEXT 48-72 HRS. AS  
IT HOLDS...IT IS TO FAVOR AN UPPER DIVERGENT PATTERN ACROSS THE  
NORTHEAST STATES OF BRASIL. THIS IS TO THEN VENT DEEP CONVECTION  
ALONG THE SOUTH AMERICA CONVERGENCE ZONE (SACZ) AND THE NEAR  
EQUATORIAL TROUGH TO THE NORTH. OVER BAHIA-TOCANTINS/GOIAS THIS IS  
TO INITIALLY FAVOR RAINFALL MAXIMA OF 75-150MM. THROUGH WEDNESDAY  
THIS DECREASES TO 40-80MM AS THE SACZ WEAKENS. THIS IS TO ALSO  
FAVOR MODERATE TO HEAVY CONVECTION ACROSS PARA/AMAZONAS IN BRASIL  
TO CENTRAL-NORTHERN JUNGLE OF PERU...WITH MAXIMA OF 35-70MM ON  
MONDAY-TO-TUESDAY...AND 25-50MM/DAY ON TUESDAY AND WEDNESDAY.  
THROUGH THE END OF THE WEEK THIS WILL DECREASE TO 15-20MM/DAY.  
 
THE RIDGE ALOFT IS TO ALSO VENT CONVECTION ALONG THE  
CENTRAL-NORTHERN ANDES OF ARGENTINA. EARLY IN THE CYCLE THIS IS TO  
PEAK AT 05-10MM/DAY...WHILE ON TUESDAY THE MAXIMA INCREASES TO  
15-20MM. ACROSS THE ALTIPLANO OF BOLIVIA CONVECTION INTENSIFIES ON  
TUESDAY-WEDNESDAY...WITH GDI SHOWING POTENTIAL FOR MODERATE TO  
HEAVY RAINFALL AMOUNTS...WITH MAXIMA OF 15-30MM.  
THIS...HOWEVER...WILL BE SHORT LIVED...WITH MAXIMA ON THURSDAY  
DECREASING TO 05-10MM.  
 
BALBINO...INMET (BRASIL)  
POMIER...SENAMHI (BOLIVIA)  
DAVISON...WPC (USA)  

 
 
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