220  
FXSA20 KWBC 021607  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1207 PM EDT THU NOV 02 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
MODEL DISCUSSION (VALID FROM NOV 02 AT 0000 UTC): THE GLOBAL MODEL  
GUIDANCE AGREE ON ENVIRONMENTAL CONDITIONS BECOMING HIGHLY  
FAVORABLE FOR AN MCS TO DEVELOP ON MID SECTIONS OF SOUTH AMERICA  
EARLY ON SATURDAY MORNING. THIS IS TO SUSTAIN HEAVY RAINFALL  
AMOUNTS...WITH SOME OF THE ENSEMBLE MEMBERS SHOWING LOCALIZED  
MAXIMA OF 200MM. THIS IS TO ALSO TRIGGER SEVERE  
THUNDERSTORMS...WITH LARGE HAIL HIGHLY PROBABLE.  
 
CONSISTENT WITH PREVIOUS FORECASTS...A TROUGH OVER THE WESTERN  
ATLANTIC IS TO MEANDER EAST ACROSS 20W LATER TODAY...NEARING 10W  
ON FRIDAY. THE UPPER TROUGH SUSTAINS A SURFACE FRONT THAT EXTENDS  
TO THE WEST-NORTHWEST ACROSS THE SOUTH ATLANTIC TO ESPIRITO  
SANTO/SOUTHERN MINAS GERAIS TO MATO GROSSO DO SUL IN BRASIL. AS  
THE UPPER LEVEL TROUGH MEANDERS AWAY...THE SURFACE FRONT WILL  
GRADUALLY LOSE ITS UPPER LEVEL SUPPORT...AND EARLY ON SATURDAY IT  
IS TO FRONTOLIZE OVER THE CONTINENT. OVER THE NEXT COUPLE OF DAYS  
THIS IS TO FAVOR MODERATE CONVECTION ACROSS ESPIRITO SANTO-MINAS  
GERAIS TO BAHIA IN NORTHEAST BRASIL...WITH RAINFALL MAXIMA OF  
20-40MM/DAY. AS THE FRONT WEAKENS THIS DECREASES TO 15-25MM/DAY ON  
SATURDAY TO SUNDAY.  
 
A SHORT WAVE TROUGH FOLLOWS...WITH MID LEVEL AXIS TO MOVE ACROSS  
CENTRAL CHILE TO CENTRAL ARGENTINA LATER TODAY...MEANWHILE  
FAVORING HEIGHT FALLS OF 50-70GPM. THIS IS TO CONTINUE EAST ACROSS  
50W LATER ON FRIDAY. ON SATURDAY-SUNDAY THIS IS TO THEN MERGE WITH  
A DEEPENING TROUGH TO THE SOUTH...TO EVOLVE INTO A BROAD LONG WAVE  
TROUGH OVER THE SOUTH ATLANTIC. ON SUNDAY THE DEEP TROUGH IS TO  
THEN ENVELOP AREA BETWEEN 60W-20W AND TO THE SOUTH OF 25S. AT LOW  
LEVELS THE ASSOCIATED SURFACE FRONT MOVES ACROSS CENTRAL PROVINCES  
IN ARGENTINA TO THE BUENOS AIRES PROVINCE/ENTRE RIOS LATER THIS  
AFTERNOON. BUILDING POLAR RIDGE WILL THEN DISPLACE THE FRONT NORTH  
ACROSS URUGUAY TO RIO GRANDE DO SUL TO NORTHERN ARGENTINA ON  
FRIDAY... MOVING ACROSS SAO PAULO TO PARAGUAY ON SATURDAY. ACROSS  
URUGUAY-MESOPOTAMIA VALLEY IN ARGENTINA THE FRONT IS TO SUSTAIN  
HEAVY RAINFALL PRODUCING SEVERE THUNDERSTORMS...WITH MAXIMA OF  
35-70MM. ACROSS PARAGUAY-PARANA IN BRASIL THIS IS TO SUSTAIN A  
MESO SCALE CONVECTIVE SYSTEM (MCS) THAT IS TO SUSTAIN SEVERE  
CONVECTION AND RAINFALL MAXIMA OF 75-150MM DURING THE MORNING  
HOURS ON SATURDAY. AS PREVIOUSLY INDICATED LOCALLY HIGHER AMOUNTS  
ARE HIGHLY PROBABLE. ON SATURDAY THE MAXIMA ACROSS PARAGUAY  
DECREASES TO 30-60MM...WHILE OVER THE SOUTHERN STATES OF BRASIL IT  
WILL PEAK AT 20-30MM.  
 
THE MODELS THEN FORECAST A LOWER AMPLITUDE TROUGH TO ENTER THE  
SOUTHERN/CENTRAL REGIONS OF CHILE LATER ON FRIDAY/SATURDAY  
MORNING. THIS IS TO THEN QUICKLY MOVE ACROSS CENTRAL ARGENTINA  
LATER IN THE DAY. 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-CENTRAL ARGENTINA ON  
SATURDAY-SUNDAY. 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 15-20MM...WHILE OVER NORTHERN  
PATAGONIA/LA PAMPA THIS IS TO TRIGGER RAINFALL AMOUNTS OF  
00-05MM/DAY.  
 
NORTH OVER THE CONTINENT...AT 200 HPA...UPPER LEVEL RIDGE IS TO  
EXTEND EAST TO WEST ACROSS NORTHERN SOUTH AMERICA...WHILE  
CONFINING TO AREA BETWEEN 10S-20S. A TROUGH TO THE NORTH IS TO  
RETROGRESS ACROSS THE NORTHEAST STATES OF BRASIL TO NORTHERN PARA  
LATER ON FRIDAY. THIS IS TO THEN REMAIN NEARLY STATIONARY THROUGH  
THE WEEKEND TO EARLY NEXT WEEK. 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...SHN (ARGENTINA)  
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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