102  
FXSA20 KWBC 301623  
PMDSA  
 
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1223 PM EDT MON OCT 30 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
MODEL DISCUSSION (VALID FROM OCT 30 AT 0000 UTC): THE GFS AND THE  
EUROPEAN MODELS FOLLOW A SIMILAR EVOLUTION THROUGH DAY 06. THIS  
SOLUTION IS WELL SUPPORTED BY THE GLOBAL ENSEMBLE MEMBERS. AS A  
RESULT...OUR CONFIDENCE IN THE FORECAST IS HIGH.  
 
A MID LEVEL TROUGH MIGRATES ACROSS PATAGONIA IN ARGENTINA TO THE  
WESTERN ATLANTIC LATER TODAY...WITH AXIS TO ALIGN ALONG 40W TO 20S  
LATER ON TUESDAY. THROUGH THURSDAY EVENING IT IS TO SLOWLY PULL  
ACROSS 20W. AT LOW LEVELS THIS SUSTAINS A POLAR FRONT ACROSS  
SOUTHERN BRASIL-NORTHERN ARGENTINA LATER TODAY. AS IT PUSHES NORTH  
ACROSS PARAGUAY-SOUTHERN BRASIL ON TUESDAY IT IS TO MERGE WITH AN  
OLD BOUNDARY TO THE NORTH. THIS BOUNDARY WILL BE THE FOCUS OF  
ORGANIZED CONVECTION OVER THE NEXT FEW DAYS. ACROSS MATO GROSSO DO  
SUL-SAO PAULO THIS IS TO FAVOR RAINFALL AMOUNTS OF 25-50MM EARLY  
IN THE CYCLE. ON TUESDAY-WEDNESDAY FOCUS OF THE CONVECTION SHIFTS  
TO MINAS GERAIS/RIO DE JANEIRO-ESPIRITO SANTO...WITH MAXIMA OF  
20-30MM. ON WEDNESDAY-THURSDAY...UNDER FAVORABLE JET  
DYNAMICS...THIS INCREASES TO 20-45MM/DAY.  
 
ANOTHER SHORT WAVE TROUGH ON THE NORTHERN STREAM FOLLOWS...WITH  
AXIS TO ANCHOR ON A 500 HPA LOW JUST WEST OF TEMUCO CHILE LATER ON  
TUESDAY EVENING/WEDNESDAY MORNING. THIS IS TO MEANDER OFF THE  
COAST OF CHILE THROUGH WEDNESDAY EVENING. ON THURSDAY IT SPILLS  
ACROSS THE CENTRAL ANDES OF CHILE...TO CONTINUE ACROSS RIO DE LA  
PLATA BASIN TO THE WESTERN ATLANTIC EARLY ON FRIDAY MORNING. AT  
LOW LEVELS THIS WILL SUSTAIN A DEEP OCCLUDED LOW OFF THE CENTRAL  
COAST OF CHILE LATER TODAY/EARLY TUESDAY MORNING. THIS IS TO DRIVE  
A FRONT EAST ACROSS PATAGONIA-LA PAMPA IN ARGENTINA ON  
TUESDAY-WEDNESDAY...MOVING TO THE BUENOS AIRES  
PROVINCE-CORDOBA-MENDOZA IN ARGENTINA ON THURSDAY. AS IT ENTERS  
SOUTHERN CHILE THIS WILL SUSTAIN LIGHT TO MODERATE  
CONVECTION...WITH MAXIMA OF 15-20MM BETWEEN CONCEPCION AND ISLA DE  
CHILOE ON TUESDAY-WEDNESDAY. ON WEDNESDAY THE MAXIMA DECREASES TO  
10-15MM IN POTENTIALLY DEEP CONVECTION. ON THE CENTRAL PROVINCES  
IN ARGENTINA THE MAXIMA IS TO PEAK AT 25-50MM IN POTENTIALLY  
SEVERE CONVECTION BY MIDDAY ON THURSDAY...WITH STABILITY INDICES  
SHOWING POTENTIAL FOR LARGE HAIL TO DEVELOP.  
 
NORTH OVER THE CONTINENT...AT 200 HPA...BROAD CELL OF THE  
SUBTROPICAL RIDGE DOMINATES AREA TO THE NORTH OF 20S...WHILE  
ANCHORING ON A CLOSED HIGH OVER NORTHERN BOLIVIA. THROUGH  
WEDNESDAY EVENING THE HIGH WILL RELOCATE TO MINAS GERAIS/BAHIA IN  
EASTERN BRASIL...WHERE IT IS TO REMAIN THROUGH THE END OF THE  
CYCLE. THE RIDGE ALOFT WILL CONTINUE VENTING DIURNAL CONVECTION  
ACROSS NORTHERN SOUTH AMERICA...WITH MAXIMA OF 20-35MM ACROSS  
TOCANTINS AND GOIAS EARLY IN THE CYCLE. THROUGH WEDNESDAY THIS  
DECREASES TO 15-25MM. HIGHER AMOUNTS ARE EXPECTED OVER AMAZONAS TO  
THE WEST...WHERE THE MAXIMA IS TO PEAK AT 25-50MM THROUGH TUESDAY  
MORNING...AND 15-20MM ON TUESDAY-WEDNESDAY. LATER ON WEDNESDAY  
FOCUS OF THE CONVECTION SHIFTS TO SOUTHERN AMAZONAS-RONDONIA-ACRE  
IN BRASIL TO THE PERUVIAN JUNGLE...WITH MAXIMA OF 20-45MM. THIS  
WEAKENS ON THURSDAY...WITH MAXIMA DECREASING TO 15-25MM.  
 
OVIEDO...SHIN (ARGENTINA)  
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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