020  
FXSA20 KWBC 281424  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
923 AM EST THU DEC 28 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM DEC 29 AT 0000 UTC): AT 200 HPA...A CELL OF  
THE SUBTROPICAL RIDGE TRAVERSES THE CONTINENT FROM WEST-TO-EST  
ALONG 20S WHILE CENTERING ON A CLOSED HIGH NEAR 18S 70W AND 20S  
55W. A TROUGH TO THE NORTH CENTERS ON A CUT OFF LOW NEAR 05S  
50W...WHILE EXTENDING A SHORT WAVE TROUGH TO THE ILHA DE MARAJO.  
THE TROUGH...IN INTERACTION WITH THE RIDGE TO THE SOUTH...VENTS  
DEEP CONVECTION ACROSS TOCANTINS-GOIAS TO PARA IN BRASIL. THE  
RIDGE IS ALSO VENTING DEEP CONVECTION ALONG THE SIERRA OF PERU AND  
THE ALTIPLANO OF BOLIVIA.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG  
53S 120W...49S 116W...46S 107W...A 134KT MAXIMUM AT 46S 100W...51S  
84W...EXITING AT 54S 62W. IT HAS A FINGER TO THE EAST THAT EXTENDS  
BETWEEN 54S 51W AND 50S 32W. THE NORTHERN POLAR HAS ITS ENTRANCE  
AT 42S 120W...THEN ALONG 43S 99W...44S 87W...A 126KT MAXIMUM AT  
46S 74W...48S 59W...EXITING AT 45S 41W. THE SUBTROPICAL JET HAS  
ITS ENTRANCE AT 36S 118W...THEN ALONG 38S 101W...40S 86W...44S  
72W... EXITING AT 44S 55W. IT REFORMS TO THE NORTH NEAR 28S  
75W...ALONG 29S 61W...EXITING AT 31S 40W. AT 175 HPA...THE  
SUBEQUATORIAL JET LIES ALONG 09S 116W...EXITING AT 10S 95W. A  
FINGER TO THE NORTH LIES ALONG 03S 110W...EXITING AT 03S 96W.  
FARTHER EAST...A FINGER OF THE SUBEQUATORIAL JET EXTENDS BETWEEN  
21S 31W AND 13S 39W.  
 
AT 500 HPA...A RIDGE IS BUILDING BETWEEN 130W-150W TO 70S.  
THIS...IN-TURN...IS INDUCING THE NORTHWARD AMPLIFICATION OF A  
TROUGH BETWEEN 120W-80W TO 30S. AS IT DEEPENS...THE TROUGH IS  
FOCUSING SHORT WAVE ENERGY AND SUBTROPICAL MOISTURE ACROSS THE  
SOUTHERN REGIONS OF CHILE. DOWNSTREAM FROM THIS TROUGH...A RIDGE  
LIES ALONG 60W TO THE ANTARCTIC PENINSULA. A SHORT WAVE TO THE  
NORTH IS STREAMING ACROSS CENTRAL ARGENTINA TO THE BUENOS AIRES  
PROVINCE. FARTHER EAST...A BROAD/LOW AMPLITUDE TROUGH EXTENDS  
BETWEEN 45W-00W TO 30S. SHORT WAVE PERTURBATIONS CONTINUE TO  
REVOLVE AROUND THIS AXIS.  
 
AT LOW LEVELS...BROAD RIDGE ON THE NORTHERN STREAM CENTERS ON A  
1021 HPA HIGH AT 29S 87W. SOUTH OF THIS AXIS...A TROUGH DOMINATES  
THE SOUTHEAST PACIFIC. POLAR FRONTS REVOLVE AROUND THIS  
AXIS...WITH ONE EXTENDING FROM AN OCCLUDED 964 HPA LOW AT 56S  
93W...THEN ALONG A 966 HPA LOW AT 56S 90W...49S 91W...45S  
98W...AND 42S 110W. ANOTHER FRONT TO THE NORTH EXTENDS ALONG A 988  
HPA LOW AT 51S 56W...48S 57W...48S 60W...A 994 HPA LOW AT 50S  
63W...46S 64W...44S 68W...A 1010 HPA LOW AT 43S 77W...39S  
83W...36S 92W...A 1010 HPA LOW AT 37S 98W...AND 34S 101W. OVER THE  
ATLANTIC...A RIDGE ANCHORS ON TWO HIGHS...A 1019 HPA AT 33S 38W  
AND A 1013 HPA HIGH AT 40S 48W. AN ELONGATED FRONT SEPARATES THESE  
HIGHS...AS IT EXTENDS ALONG 43S 21W...38S 34W...37S 46W...TO  
NORTHERN PATAGONIA/LA PAMPA IN ARGENTINA. ANOTHER FRONT LIES ALONG  
30S 12W...26S 22W...25S 29W...A 1014 HPA LOW AT 27S 33W...25S  
38W...25S 43W...RIO GRANDE DO SUL...URUGUAY TO CORDOBA IN  
ARGENTINA.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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