070  
FXSA20 KWBC 121654  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1153 AM EST TUE DEC 12 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM DEC 12 AT 0000 UTC): NORTH OVER THE  
CONTINENT...AT 200 HPA...ILL ORGANIZED CELL OF THE SUBTROPICAL  
RIDGE EXTENDS TO THE EAST-SOUTHEAST FROM AMAZONAS IN  
BRASIL...ACROSS 10S 50W...INTO THE ATLANTIC ALONG 20S 30W. THE  
RIDGE ALOFT IS VENTING DEEP CONVECTION ALONG THE SACZ OVER  
BRASIL...AS IT EXTENDS FROM MINAS GERAIS TO SOUTHERN AMAZONAS.  
MOST ACTIVE CONVECTION WITH THIS FEATURE WAS BUILDING OVER  
NORTHERN PERU-ECUADOR-SOUTHERN COLOMBIA.  
 
AT 250 HPA...THE SOUTHERN POLAR HAS ITS ENTRANCE AT 53S  
112W...THEN ALONG 54S 91W...53S 72W...55S 54W...A 128KT MAXIMUM AT  
51S 44W...EXITING AT 51S 39W. THE NORTHERN POLAR HAS A FINGER THAT  
EXTENDS BETWEEN 41S 120W AND 43S 102W. IT REFORMS AT 45S  
94W...THEN ALONG 46S 84W...49S 75W...A 133KT MAXIMUM AT 52S  
63W...47S 43W...39S 43W...EXITING AT 33S 41W. IT REFORMS AT 33S  
38W...THEN ALONG 35S 36W...46S 33W...53S 20W...AND 51S 03W. THE  
SUBTROPICAL JET HAS ITS ENTRANCE AT 19S 104W...THEN ALONG 21S  
97W...29S 81W...EXITING AT 29S 70W. IT REFORMS AT 45S 72W...THEN  
ALONG 46S 59W...42S 50W...38S 47W...EXITING AT 31S 45W. THE  
SUBTROPICAL JET REFORMS AT 28S 42W...THEN ALONG 29S 37W...34S  
32W...EXITING AT 37S 29W. IT REFORMS AT 23S 46W...ALONG 25S  
39W...29S 30W...EXITING AT 33S 23W.  
 
AT 500 HPA...IN A TIGHT BELT OF WESTERLIES...PROGRESSIVE SHORT  
WAVE PERTURBATIONS ARE STREAMING ACROSS THE SOUTHEAST  
PACIFIC...WITH ONE ALONG 120W TO 42S AS ANOTHER PULLS ACROSS 95W.  
A THIRD SHORT WAVE TROUGH TO THE EAST ENTERED TIERRA DEL  
FUEGO-SOUTHERN CHILE. ON THE NORTHERN STREAM...A SHORT WAVE TROUGH  
MEANDERS OFF THE CENTRAL COAST OF CHILE WHILE CENTERING ON A  
CLOSED LOW NEAR 33S 83W. SHORT WAVE RIDGE OVER ARGENTINA SEPARATES  
THE LATTER FROM A DEEPER TROUGH TO THE EAST. THE TROUGH EXTENDS  
FROM A CLOSED LOW AT 42S 37W...ALONG 30S 40W...TO SOUTHEAST STATES  
OF BRASIL.  
 
AT LOW LEVELS...A RIDGE ON THE NORTHERN STREAM EXTENDS OVER THE  
EASTERN SOUTH PACIFIC WHILE CENTERING ON TWO 1021 HPA HIGHS...WITH  
ONE AT 35S 101W AND 35S 95W. AN ELONGATED FRONT TO THE SOUTH  
EXTENDS FROM AN OCCLUDED 982 HPA LOW AT 56S 42W...THEN ALONG A 984  
HPA LOW AT 54S 39W...47S 42W...48S 51W...A 992 HPA LOW AT 54S  
62W...49S 68W...41S 91W...41S 103W...AND 38S 113W. OVER THE  
ATLANTIC...AN OCCLUDED 996 HPA LOW AT 30S 38W EXTENDS A FRONT  
ALONG A 990 HPA LOW AT 43S 37W...36S 31W...28S 37W...SAO  
PAULO...25S 50W...A 1008 HPA LOW AT 27S 54W...TO SOUTHEAST  
PARAGUAY. A RIDGE TO THE SOUTH CENTERS ON A 1017 HPA HIGH AT 37S  
54W. AN OLD FRONT TO THE EAST AND NORTH EXTENDS ALONG A 992 HPA  
LOW AT 40S 28W...34S 25W...30S 27W...A 1006 HPA LOW AT 29S  
31W...24S 35W...23S 41W...RIO DE JANEIRO...23S 46W...TO 22S 56W.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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