559  
FXSA20 KWBC 011550  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1149 AM EDT WED NOV 01 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
MODEL DISCUSSION (VALID FROM NOV 01 AT 0000 UTC): THE GLOBAL  
MODELS FOLLOW A SIMILAR EVOLUTION THROUGH DAY 06...WITH THE  
ENSEMBLE MEMBERS SUPPORTING THE DETERMINISTIC SOLUTION THROUGH 168  
HRS. AS A RESULT...CONFIDENCE IN THE SHORT AND MEDIUM RANGE  
FORECAST IS HIGH.  
 
DEEP TROUGH OVER THE SOUTH ATLANTIC IS TO MEANDER EAST ACROSS 25W  
LATER TODAY...NEARING 10W LATER ON FRIDAY. AT LOW LEVELS IT  
SUSTAINS AN ELONGATED FRONT THAT IS TO EXTENDS ACROSS THE SOUTH  
ATLANTIC TO SOUTHEAST BRASIL. UNDER INFLUENCE OF A BROAD RIDGE TO  
THE SOUTH THE FRONT MOVES NORTH TO ESPIRITO SANTO/SOUTHERN MINAS  
GERAIS ON THURSDAY...TRAILING ACROSS SAO PAULO TO MATO GROSSO DO  
SUL. AS THE UPPER TROUGH MEANDERS AWAY...AND THE FRONT LOSES ITS  
UPPER LEVEL SUPPORT...THE BOUNDARY IS TO THEN FRONTOLIZE OVER  
BRASIL LATER ON FRIDAY. MEANWHILE...THIS IS TO FAVOR ORGANIZED  
DEEP CONVECTION ACROSS ESPIRITO SANTO-BAHIA AND MINAS  
GERAIS...WITH MAXIMA OF 20-45MM/DAY EXPECTED TODAY AND THURSDAY.  
ON FRIDAY THE MAXIMA IS TO PEAK AT 20-35MM.  
 
A SHORT WAVE RIDGE ALONG THE COAST OF ARGENTINA SEPARATES THE  
ABOVEMENTIONED TROUGH FROM ANOTHER TROUGH OFF THE COAST OF CHILE.  
THE LATTER CENTERS ON A CLOSED LOW JUST WEST OF TEMUCO. THIS IS TO  
REMAIN OFF THE COAST OF CHILE THROUGH THURSDAY MORNING...WITH AXIS  
TO SPILL ACROSS THE ANDES TO CENTRAL ARGENTINA ON THURSDAY. AS IT  
ENTERS CENTRAL ARGENTINA THIS IS TO SUSTAIN HEIGHT FALLS OF  
40-60GPM. ON FRIDAY THE SHORT WAVE TROUGH WILL THEN MOVE OFF THE  
COAST OF ARGENTINA WHILE ALIGNING ALONG 50W. THIS IS TO THEN MERGE  
WITH A DEEPENING TROUGH TO THE SOUTH...TO EVOLVE INTO A BROAD LONG  
WAVE TROUGH OVER THE SOUTH ATLANTIC LATER ON SATURDAY/SUNDAY. ON  
SUNDAY THE DEEP TROUGH IS TO THEN ENVELOP AREA BETWEEN 60W-00W AND  
TO THE SOUTH OF 25S. AT LOW LEVELS THIS SUSTAINS A DEEP OCCLUDED  
TROUGH OFF THE CENTRAL COAST OF CHILE...WHERE IT IS TO MEANDER  
THROUGH THIS EVENING. THIS IS TO MOVE EASTWARD ACROSS CENTRAL  
ARGENTINA/BUENOS AIRES PROVINCE ON THURSDAY. THE ASSOCIATED FRONT  
WILL THEN PUSH EAST AND NORTH ACROSS ARGENTINA...RACING ACROSS LA  
PAMPA TO SOUTHERN CUYO LATER THIS EVENING...AND ACROSS BUENOS  
AIRES PROVINCE-CORDOBA TO MENDOZA ON THURSDAY. ON FRIDAY...FRONTAL  
LOW IS TO RAPIDLY DEEPEN AS IT MEANDERS TO THE EAST-SOUTHEAST  
ACROSS THE WESTERN ATLANTIC. THIS WILL THEN DRIVE THE FRONT  
FARTHER NORTH ACROSS URUGUAY/RIO GRANDE DO SUL TO NORTHERN  
PROVINCES IN ARGENTINA. THIS THEN MEANDERS NORTH ACROSS SAO  
PAULO-MATO GROSSO DO SUL IN BRASIL TO PARAGUAY ON SATURDAY. EARLY  
IN THE PERIOD...THE MEANDERING OCCLUDED LOW IS TO TRIGGER  
SCATTERED CONVECTION ACROSS CENTRAL CHILE WITH ACCUMULATION OF  
10-15MM/DAY ON WEDNESDAY AND THURSDAY. OVER LA PAMPA THE FRONT  
WILL TRIGGER SCATTERED CONVECTION WITH MAXIMA OF 20-40MM ON  
WEDNESDAY-THURSDAY...WHILE OVER URUGUAY-ENTRE RIOS AND CORRIENTES  
IN ARGENTINA THE MAXIMA PEAKS AT 35-70MM ON THURSDAY. ON  
FRIDAY...UNDER FAVORABLE JET DYNAMICS...THIS IS TO TRIGGER AN MCS  
ACROSS PARAGUAY-MISIONES IN ARGENTINA AND SOUTHERN SAO PAULO/SANTA  
CATARINA IN BRASIL...WITH MAXIMA OF 75-125MM IN POTENTIALLY SEVERE  
CONVECTION.  
 
NEXT MID LEVEL PERTURBATION IS TO LIFT ACROSS THE EASTERN PACIFIC  
TO THE SOUTHERN REGIONS OF CHILE LATER ON FRIDAY. AT LOW LEVELS  
THE TROUGH ALOFT WILL SUSTAIN AN ELONGATED FRONT ACROSS THE SOUTH  
PACIFIC TO SOUTHERN CHILE LATER ON FRIDAY...MOVING INLAND ACROSS  
PATAGONIA IN ARGENTINA ON SATURDAY. AS IT NEARS THE SOUTHERN  
CONE... THE SHORT WAVE TROUGH WILL SUSTAIN A SUBTROPICAL  
CONNECTION. THIS IS TO FEED CONVECTIVE DEVELOPMENT BETWEEN  
CONCEPCION-PUERTO MONTT IN SOUTHERN CHILE TO FAVOR MAXIMA OF  
15-30MM.  
 
NORTH OVER THE CONTINENT...AT 200 HPA...A BROAD CELL OF THE  
SUBTROPICAL RIDGE REMAINS THE DOMINANT FEATURE TO THE NORTH OF  
20S. AN UPPER LEVEL TROUGH BOUNDS THE EASTERN FRINGES OF THE UPPER  
LEVEL RIDGE...EXTENDING ACROSS NORTHEAST BRASIL TO A CLOSED LOW  
NEAR 01S 40W LATER TODAY. UNDER INFLUENCE OF THE RIDGE TO THE  
SOUTH THE LOW IS TO CUT OFF FROM THE FLOW...TO THEN RETROGRESS  
ALONG THE NORTHERN STATES OF BRASIL. THE CLOSE LOW WILL NEAR  
NORTHERN PARA LATER ON FRIDAY/EARLY ON SATURDAY MORNING. BEST  
DIVERGENCE ALOFT IS EXPECTED BETWEEN THIS LOW/TROUGH AND THE RIDGE  
TO THE SOUTH...TO VENT DEEP CONVECTION BETWEEN ESPIRITO  
SANTO/BAHIA IN BRASIL TO PARA/AMAZONAS TO THE WEST. ACROSS MINAS  
GERAIS/BAHIA THIS IS TO FAVOR RAINFALL MAXIMA OF 20-45MM. THROUGH  
SATURDAY...AS THE UPPER LOW STARTS TO WEAKEN...THIS WILL DECREASE  
TO 15-25MM/DAY. THIS IS TO ALSO ENHANCE CONVECTION ACROSS PARA TO  
AMAZONAS IN BRASIL...WITH MAXIMA OF 20-35MM/DAY. THROUGH FRIDAY  
FOCUS OF THE ORGANIZED DEEP CONVECTION SHIFTS TO NORTHWEST  
BRASIL-SOUTHERN COLOMBIA/NORTHERN JUNGLE OF PERU...WITH MAXIMA OF  
20-40MM. ALONG THE PERUVIAN JUNGLE MOST ACTIVE IS EXPECTED FRIDAY  
AND SATURDAY...WITH MAXIMA OF 20-30MM/DAY.  
 
OVIEDO...SHIN (ARGENTINA)  
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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