229  
FXSA20 KWBC 301405  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
905 AM EST THU NOV 30 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM NOV 30 AT 0000 UTC): AT 200 HPA...BROAD CELL  
OF THE SUBTROPICAL RIDGE DOMINATES THE FLOW OVER THE CONTINENT TO  
THE NORTH OF 30S...WHILE ANCHORING ON A CLOSED HIGH NEAR 13S 64W.  
THIS IS VENTING SCATTERED DEEP CONVECTION ACROSS BRASIL TO THE  
NORTH OF 10S...WHILE ALSO PROVIDING THE VENTILATION ALOFT TO AN  
MCS OVER PARAGUAY.  
 
THE 250 HPA ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG 55S  
120W...57S 98W...EXITING AT 51S 88W. IT REFORMS AT 53S 67W...ALONG  
57S 54W...A 129KT MAXIMUM AT 59S 40W...EXITING AT 53S 23W. THE  
NORTHERN POLAR HAS ITS ENTRANCE AT 48S 125W...THEN ALONG 50S  
110W...EXITING AT 46S 98W. THE JET REFORMS AT 48S 66W...ACROSS THE  
MALVINAS/FALKLAND ISLANDS...55S 51W...50S 28W...45S 31W...EXITING  
AT 42S 37W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 36S  
90W...ALONG 37S 84W...39S 73W...EXITING AT 37S 67W. IT REFORMS AT  
32S 52W...ALONG A 120KT MAXIMUM AT 25S 47W...EXITING AT 21S 37W.  
ANOTHER BRANCH OF THE SUBTROPICAL LIES TO THE NORTH WITH ENTRANCE  
AT 26S 73W...ALONG 26S 61W...21S 47W...EXITING AT 16S 40W. THE  
SUBEQUATORIAL JET LIES ALONG 10S 116W...11S 107W...EXITING AT 11S  
100W. ANOTHER FINGER TO THE NORTH LIES ALONG 02S 110W...EXITING AT  
00N 103W.  
 
AT 500 HPA...A LOW AMPLITUDE RIDGE EXTENDS OVER THE PACIFIC ALONG  
100W TO 60S. A TROUGH TO THE EAST...MEANWHILE...EXTENDS FROM A LOW  
OVER THE BELLINGSHAUSEN SEA...ALONG 60S 84W...50S 85W...40S  
87W...TO 30S 90W. A SHORT WAVE TROUGH ON THE NORTHERN STREAM IS  
MOVING ACROSS CENTRAL ARGENTINA. THIS IS PRESSING AGAINST A SKEWED  
RIDGE TO THE EAST...AS THE LATTER EXTENDS FROM THE RIO DE LA PLATA  
BASIN/URUGUAY...ALONG 45S 50W...40S 50W...TO THE SOUTH GEORGIA  
ISLANDS. THE RIDGE UNDERCUTS A TROUGH OVER THE ATLANTIC THAT  
EXTENDS TO THE NORTHWEST FROM A LOW AT 45S 25W...ALONG 35S  
40W...TO THE SOUTHERN STATES OF BRASIL.  
 
AT LOW LEVELS...PROGRESSIVE FRONT ON THE SOUTHERN STREAM EXTENDS  
FROM AN OCCLUDED 970 HPA LOW AT 65S 77W...THEN ALONG A 966 HPA LOW  
AT 69S 75W....66S 70W...62S 69W...A 986 HPA LOW AT 59S 74W...57S  
73W...55S 75W...A 1000 HPA LOW AT 53S 80W...47S 82W...TO 42S 90W.  
AN ELONGATED FRONT TO THE EAST AND NORTH EXTENDS FROM AN OCCLUDED  
962 HPA LOW AT 68S 48W...THEN ALONG A 990 HPA LOW AT 61S 31W...57S  
36W...55S 40W...A 1006 HPA LOW AT 56S 48W...52S 49W...51S 52W...A  
1008 HPA LOW AT 49S 57W...44S 59W... NORTHERN PATAGONIA...A 1014  
HPA LOW AT 46S 70W...40S 77W...35S 86W...33S 94W...AND 30S 105W. A  
1015 HPA HIGH AT 47S 64W ANCHORS A RIDGE OFF THE COAST OF  
PATAGONIA. FARTHER NORTH...ANOTHER FRONT EXTENDS ALONG A 1010 HPA  
LOW AT 40S 21W...34S 22W...28S 28W...A 1014 HPA LOW AT 25S  
33W...23S 33W...RIO DE JANEIRO/SOUTHERN MINAS GERAIS...SOUTHEAST  
PARAGUAY TO CHACO ARGENTINO. THIS FAVORS ORGANIZED DEEP CONVECTION  
ACROSS CENTRAL SOUTH AMERICA. A RIDGE TO THE SOUTH CENTERS ON A  
1021 HPA HIGH AT 36S 41W.  
 
OVIEDO...SHN (ARGENTINA)  
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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