720  
FXSA20 KWBC 181450  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
949 AM EST THU JAN 18 2018  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM JAN 18 AT 0000 UTC): THE 200 HPA ANALYSIS  
SHOWS BROAD CELL OF THE SUBTROPICAL RIDGE DOMINATING AREA TO THE  
NORTH OF 30S WHILE CENTERING ON A CLOSED HIGH OVER EL CHACO  
PARAGUAYO. THE RIDGE UNDERCUTS A TROUGH TO THE NORTH THAT EXTENDS  
OVER PARA-NORTHEAST STATES OF BRASIL WHILE CENTERING ON A CLOSED  
LOW AT 09S 53W. THE TROUGH IS ENHANCING CONVECTION ALONG THE NEAR  
EQUATORIAL TROUGH OVER NORTHERN PARA-AMAPA IN BRASIL...WHILE THE  
RIDGE IS VENTING CONVECTION ACROSS SOUTHERN  
BRASIL-PARAGUAY-BOLIVIA TO SOUTHERN PERU.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG  
51S 120W...A 159KT MAXIMUM AT 53S 107W...56S 96W...EXITING AT 60S  
89W. IT REFORMS AT 63S 80W...THEN ALONG 59S 69W...EXITING AT 53S  
62W. THE NORTHERN POLAR LIES ALONG 47S 120W...A 145KT MAXIMUM AT  
48S 113W...50S 99W...54S 88W...57S 78W...51S 70W...48S  
64W...EXITING AT 50S 52W. THE NORTHERN POLAR REFORMS AT 49S  
46W...THEN ALONG 51S 34W...53S 23W...EXITING AT 47S 15W. A BRANCH  
TO THE NORTH HAST ITS ENTRANCE AT 40S 56W...THEN ALONG A 120KT  
MAXIMUM AT 43S 46W...EXITING AT 43S 31W. THE SUBTROPICAL JET HAS  
ITS ENTRANCE AT 29S 92W...ALONG 30S 72W... SOUTHERN URUGUAY...38S  
41W...38S 29W...37S 19W...AND 40S 03E. A FINGER OF THE SUBTROPICAL  
JET LIES TO THE NORTH...WITH AXIS BETWEEN 18S 44W AND 09S 56W.  
 
AT 500 HPA...BROAD TROUGH ON THE SOUTHERN STREAM EXTENDS OVER THE  
SOUTH PACIFIC WHILE ENVELOPING AREA BETWEEN 140W-90W AND TO THE  
SOUTH OF 45S. THIS IS PRESSING AGAINST A RIDGE TO THE EAST THAT  
EXTENDS FROM THE SOUTH COAST OF CHILE TO THE BELLINGSHAUSEN  
SEA/ANTARCTIC PENINSULA. DOWNSTREAM FROM THE RIDGE...ANOTHER  
TROUGH EXTENDS BETWEEN 70W-30W AND TO THE SOUTH OF 43S. THIS IS  
PHASING WITH A SHORT WAVE TROUGH TO THE NORTH THAT EXTENDS OVER  
THE RIO DE LA PLATA BASIN.  
 
AT LOW LEVELS...A RIDGE ON THE NORTHERN STREAM CENTERS ON A 1027  
HPA HIGH AT 36S 91W. AN ELONGATED FRONT TO THE SOUTH EXTENDS FROM  
A 998 HPA LOW AT 53S 60W...49S 58W...46S 60W...A 1002 HPA LOW AT  
46S 65W...PUERTO MADRID... NORTHERN PATAGONIA-TEMUCO CHILE...39S  
74W...46S 78W...59S 81W...A 958 HPA LOW AT 62S 88W...60S 84W...55S  
83W...A 986 HPA LOW AT 55S 90W...52S 89W...50S 91W...A 998 HPA LOW  
AT 50S 95W...47S 98W...AND 45S 104W. THIS SUSTAINS SCATTERED  
RAINFALL ACROSS SOUTHERN REGIONS OF CHILE. FARTHER EAST...ANOTHER  
FRONT EXTENDS FROM A 970 HPA LOW AT 61S 32W...ALONG A 982 HPA LOW  
AT 58S 27W...54S 27W...50S 34W...A 1002 HPA LOW AT 52S 40W...50S  
40W...A 1002 HPA LOW AT 47S 49W...44S 49W...A 1006 HPA LOW AT 42S  
56W...BUENOS AIRES PROVINCE TO CENTRAL CUYO. THIS SUSTAINS  
SCATTERED DEEP CONVECTION ACROSS CENTRAL ARGENTINA. A RIDGE TO THE  
NORTH CENTERS ON A 1025 HPA HIGH AT 40S 25W. AN ELONGATED FRONT OT  
HE NORTH LIES ALONG 33S 20W...31S 31W...TO URUGUAY/ENTRE RIOS IN  
ARGENTINA. CONVECTION IS CLUSTERING TO THE NORTH ACROSS  
PARAGUAY/NORTHERN ARGENTINA TO SOUTHERN BRASIL.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
DAVISON...WPC (USA)  

 
 
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