643  
FXSA20 KWBC 191351  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
850 AM EST TUE DEC 19 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM DEC 19 AT 0000 UTC): AT 200 HPA...A HIGH NEAR  
18S 60W ANCHORS A RIDGE THAT EXTENDS OVER THE CONTINENT BETWEEN  
10S AND 40S. A TROUGH TO THE EAST AND NORTH OF THIS  
RIDGE...MEANWHILE... EXTENDS FROM A CLOSED LOW AT 19S 34W...ACROSS  
NORTHEAST BRASIL TO PARA. THE TROUGH IS ENHANCING CONVECTION ALONG  
THE NORTH COAST OF BRASIL BETWEEN ILHA DE MARAJO AND PERNAMBUCO.  
THE RIDGE ALOFT IS VENTING ORGANIZED CONVECTION ACROSS  
ACRE-RONDONIA-AMAZONAS IN BRASIL TO CENTRAL/SOUTHERN JUNGLE OF  
PERU.  
 
THE 250 HPA ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG A  
151KT MAXIMUM AT 55S 120W...46S 109W...A 120KT MAXIMUM AT 51S  
97W...56S 83W...53S 58W...51S 45W...EXITING AT 50S 32W. THE  
NORTHERN POLAR HAS ITS ENTRANCE AT 47S 120W...THEN ALONG 43S  
108W...49S 90W...51S 74W...47S 52W...45S 35W...45S 26W...AND 55S  
07W. A FINGER OF THE NORTHERN POLAR TO THE NORTH EXTENDS BETWEEN  
37S 105W AND 38S 85W. AN ANTICYCLONICALLY CURVED BRANCH OF THE  
SUBTROPICAL RIDGE HAS ITS ENTRANCE AT 29S 76W...ALONG A 124KT  
MAXIMUM AT 35S 63W...35S 56W...EXITING AT 26S 43W. AT 150  
HPA...THE SUBEQUATORIAL JET LIES ALONG 09S 116W...12S  
107W...EXITING AT 12S 99W.  
 
AT 500 HPA...A TROUGH EXTENDS BETWEEN 120W-90W TO 35S. EAST OF  
THIS AXIS...IN TIGHT BELT OF MID LATITUDE WESTERLIES...PROGRESSIVE  
SHORT WAVE PERTURBATIONS ARE STREAMING ACROSS THE EASTERN  
PACIFIC-SOUTHERN CONE OF SOUTH AMERICA. IN THIS PATTERN A SHORT  
WAVE TROUGH CENTERS ON A CYCLONIC MAXIMA AT 42S 90W...WHILE A  
SHORT WAVE TROUGH TO THE EAST IS SPILLING ACROSS THE CENTRAL ANDES  
OF CHILE TO CUYO IN ARGENTINA. FARTHER EAST...OVER THE SOUTH  
ATLANTIC...A BROAD/LOW AMPLITUDE TROUGH EXTENDS BETWEEN 50W-15W  
AND TO THE SOUTH OF 40S...WHILE CENTERING ON A CLOSED LOW AT 66S  
31W.  
 
AT LOW LEVELS...BROAD TROUGH ON THE SOUTHERN STREAM DOMINATES THE  
SOUTHEAST PACIFIC WHILE CENTERING ON AN OCCLUDED 966 HPA LOW AT  
64S 100W. POLAR FRONT TO THE NORTH EXTENDS FROM AN OCCLUDED 976  
HPA LOW AT 55S 101W...THEN ALONG A 970 HPA LOW AT 58S 96W...57S  
88W...54S 88W...A 980 HPA LOW AT 54S 94W...47S 98W...43S  
105W...AND 40S 116W. ANOTHER FRONT TO THE NORTH EXTENDS ALONG A  
1006 HPA LOW AT 46S 87W...42S 85W...39S 88W...A 1014 HPA LOW AT  
40S 93W...37S 92W...35S 97W...A 1014 HPA LOW AT 37S 104W...34S  
103W...AND 30S 109W. A RIDGE TO THE NORTH CENTERS ON TWO CLOSED  
HIGHS...A 1021 HPA HIGH AT 30S 99W AND A 1023 HPA HIGH AT 35S 84W.  
OVER THE ATLANTIC...A LOW AMPLITUDE TROUGH DOMINATES WHILE  
CENTERING ON AN OCCLUDED 958 HPA LOW AT 66S 30W. A POLAR FRONT  
STREAMING TO THE NORTH EXTENDS FROM AN OCCLUDED 988 HPA LOW AT 54S  
40W...A 986 HPA LOW AT 55S 38W...51S 37W...48S 40W...A 1006 HPA  
LOW AT 49S 44W...47S 49W...48S 62W...TO SOUTHERN PATAGONIA. A  
RIDGE TO THE NORTH CENTERS ON A 1025 HPA HIGH AT 38S 42W. AN  
ELONGATED FRONT TO THE EAST AND NORTH OF THIS AXIS EXTENDS ALONG A  
986 HPA LOW AT 52S 17W...13S 19W...37S 25W...32S 37W...A 1018 HPA  
LOW AT 30S 42W...27S 43W...SRN BRASIL TO NORTHERN ARGENTINA.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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