818  
FXSA20 KWBC 011435  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
935 AM EST FRI DEC 01 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM DEC 01 AT 0000 UTC): AT 200 HPA... NORTHERN  
SOUTH AMERICA IS UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE THAT  
EXTENDS OVER THE CONTINENT TO THE NORTH OF 30S...WITH AXIS  
CENTERING ON A HIGH THAT MEANDERS BETWEEN RONDONIA IN BRASIL AND  
NORTHERN BOLIVIA. THE RIDGE ALOFT IS VENTING DEEP CONVECTION  
ACROSS THE CENTRAL STATES OF BRASIL...WITH MOST INTENSE AFFECTING  
MINAS GERAIS-TOCANTINS AND GOIAS. OTHER CONVECTION TO THE SOUTH  
ASSOCIATES WITH AN MCS THAT AFFECTED MATO GROSSO DO SUL IN BRASIL  
AND CENTRAL BOLIVIA. ACROSS PERU...DEEP CONVECTION IS CLUSTERING  
ALONG THE SIERRA.  
 
AT 250 HPA...THE SOUTHERN POLAR EXTENDS ALONG 55S 120W...A 131KT  
MAXIMUM AT 56S 115W...56S 104W...A 128KT MAXIMUM AT 56S 95W...59S  
80W...EXITING AT 58S 65W. IT REFORMS AT 57S 53W...THEN ALONG 60S  
39W...57S 25W...EXITING AT 54S 17W. THE NORTHERN POLAR LIES ALONG  
40S 120W...45S 109W...48S 100W...EXITING AT 49S 88W. IT REFORMS  
BETWEEN 39S 71W AND 46S 58W. ANOTHER BRANCH OF THE NORTHERN POLAR  
HAS ITS ENTRANCE AT 48S 53W...THEN ALONG 53S 40W...49S 26W...  
EXITING AT 45S 23W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 24S  
85W...THEN ALONG 28S 71W...EXITING AT 26S 58W. IT REFORMS AT 26S  
53W...ALONG A 125KT MAXIMUM AT 23S 41W...23S 33W...EXITING AT 22S  
26W. THE SUBEQUATORIAL JET LIES ALONG 10S 116W...13S  
110W...EXITING AT 15S 104W. ANOTHER FINGER TO THE NORTH LIES ALONG  
02S 107W... EXITING AT 02S 100W.  
 
AT 500 HPA...BROAD/LOW AMPLITUDE TROUGH ON THE SOUTHERN STREAM  
FLOW DOMINATES THE SOUTHEAST PACIFIC. EMBEDDED IN THIS FLOW A  
SHORT WAVE TROUGH IS STREAMING ALONG 95W AND TO THE SOUTH OF 50S.  
A SKEWED RIDGE TO THE NORTH...MEANWHILE...EXTENDS FROM 30S  
110W...ALONG 40S 95W...TO 45S 90W. FARTHER EAST...A TROUGH EXTENDS  
FROM 60S 55W...ACROSS PATAGONIA IN ARGENTINA...40S 75W...30S 85W  
TO 27S 90W. OVER THE WESTERN ATLANTIC...IN A SPLIT FLOW  
PATTERN...THE FLOW DIVIDES BETWEEN A RIDGE ON THE SOUTHERN STREAM  
AND A SHORT WAVE TROUGH TO THE NORTH. THE RIDGE EXTENDS SOUTH OF  
40S AND BETWEEN 50W-25W. THE TROUGH...MEANWHILE...EXTENDS BETWEEN  
50S 30W AND TO THE SOUTH OF 20S...WHILE CENTERING ON A CLOSED LOW  
AT 33S 42W.  
 
AT LOW LEVELS...A RIDGE ON THE NORTHERN STREAM CENTERS ON A 1031  
HPA HIGH AT 38S 97W. BROAD TROUGH LIES TO THE SOUTH...DOMINATING  
THE SOUTHEAST PACIFIC WHILE CENTERING ON AN OCCLUDED 962 HPA LOW  
AT 67S 97W. POLAR FRONTS EMBED IN THIS FLOW...WITH ONE EXTENDING  
FROM AN OCCLUDED 978 HPA LOW AT 67S 75W...THEN ALONG A 988 HPA LOW  
AT 62S 74W...58S 77W...55S 85W...56S 90W...A 1000 HPA LOW AT 55S  
97W...53S 99W...TO 50S 103W. FARTHER EAST...AN ELONGATED FRONT  
EXTENDS ALONG A 994 HPA LOW AT 63S 27W...61S 32W...61S 40W...A 996  
HPA LOW AT 62S 50W...50S 49W...A 1010 HPA LOW AT 54S 60W...48S  
60W...TO NORTHERN PATAGONIA. ANOTHER FRONT TO THE EAST EXTENDS  
FROM AN OCCLUDED 1006 HPA LOW AT 53S 48W...ALONG A 1008 HPA LOW AT  
55S 45W...52S 44W...50S 49W...A 1010 HPA LOW AT 48S 51W...44S  
54W...41S 58W...A 1010 HPA LOW AT 40S 61W...TO SOUTHERN CUYO. THIS  
SUSTAINS SCATTERED DEEP CONVECTION ALONG THE LEE OF THE ANDES OVER  
CENTRAL ARGENTINA. A RIDGE TO THE EAST CENTERS ON A 1025 HPA HIGH  
AT 42S 33W. AN ELONGATED FRONT LIES TO THE EAST AND NORTH...WITH  
AXIS ALONG A 1018 HPA LOW AT 37S 16W...33S 17W...31S 21W...A 1018  
HPA LOW AT 30S 25W...28S 26W...28S 28W...A 1014 HPA LOW AT 29S  
33W...24S 35W...23S 39W...RIO DE JANEIRO-MATO GROSSO DO SUL TO  
SOUTHEAST PARAGUAY. ORGANIZED DEEP CONVECTION WAS BUILDING ACROSS  
SOUTHEAST BRASIL.  
 
OVIEDO...SHN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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