218  
FXSA20 KWBC 151427  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
927 AM EST FRI DEC 15 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM DEC 15 AT 0000 UTC): AT 200 HPA...A HIGH NEAR  
13S 67W ANCHORS A SHORT WAVE RIDGE OVER THE CONTINENT TO THE NORTH  
OF 30S AND WEST OF 50W. THE RIDGE ALOFT IS VENTING DEEP CONVECTION  
WITH MOST ACTIVE OVER BRASIL TO THE NORTH OF 17S. A SHORT WAVE  
TROUGH TO THE EAST NORTH EXTENDS FROM 33S 35W TO RIO DE  
JANEIRO/SOUTHERN MINAS GERAIS. THIS IS ENHANCING CONVECTION ACROSS  
NORTHERN MINAS GERAIS-BAHIA IN BRASIL.  
 
AT 250 HPA...THE SOUTHERN POLAR LIES ALONG A 153KT MAXIMUM AT 60S  
124W...THEN ALONG 55S 111W...49S 102W...51S 87W...A 149KT MAXIMUM  
AT 51S 74W...47S 55W...SOUTH GEORGIA ISLANDS...57S 28W...EXITING  
AT 50S 12W. THE NORTHERN POLAR LIES ALONG 55S 120W...46S  
100W...46S 85W...A 124KT MAXIMUM AT 44S 74W...EXITING AT 40S 52W.  
THE SUBTROPICAL JET HAS ITS ENTRANCE AT 29S 126W...THEN ALONG 33S  
115W...37S 103W...42S 87W...40S 67W...EXITING AT 34S 57W. A FINGER  
TO THE EAST EXTENDS BETWEEN 32S 52W AND 40S 34W. THE SUBTROPICAL  
JET REFORMS AT 26S 36W...ALONG 30S 29W...29S 19W...EXITING AT 20S  
10W. AT 140 HPA...THE SUBEQUATORIAL JET HAS A FINGER WITH ENTRANCE  
AT 09S 103W...ALONG 09S 95W...EXITING AT 11S 89W. ANOTHER BRANCH  
TO THE NORTH LIES ALONG 03S 110W...05S 100W...EXITING AT 04S 91W.  
 
AT 500 HPA...BUILDING RIDGE ALONG 130W/140W IS INDUCING THE  
NORTHWARD AMPLIFICATION OF A SHORT WAVE TROUGH ON THE SOUTHERN  
STREAM BETWEEN 110W-90W TO 40S. THIS IS FEEDING INTO A BROAD/LOW  
AMPLITUDE TROUGH TO THE EAST THAT EXTENDS OVER THE BELLINGSHAUSEN  
SEA/SOUTHERN CONE OF SOUTH AMERICA. SHORT WAVE RIDGE TO THE NORTH  
EXTENDS OVER NORTHERN CHILE-NORTHERN ARGENTINA TO  
PARAGUAY/SOUTHERN BRASIL...WHERE IT FAVORS A CAP INVERSION. SOUTH  
OF THIS AXIS...SHORT WAVE TROUGH ON THE NORTHERN STREAM EXTENDS  
FROM 43S 45W TO RIO GRANDE DO SUL.  
 
AT LOW LEVELS...A DUAL BARRELED RIDGE DOMINATES THE EASTERN  
PACIFIC...CENTERING ON A 1025 HPA HIGH AT 43S 133W AND A 1025 HPA  
HIGH AT 33S 87W. AN ELONGATED FRONT/NARROW TROUGH SEPARATES THESE  
RIDGES...EXTENDING FROM A 984 HPA LOW AT 53S 44W...THEN ALONG 45S  
49W...44S 58W...A 1002 HPA LOW AT 44S 64W...40S 68W...40S  
73W...42S 77W...A 1006 HPA LOW AT 46S 81W...43S 81W...43S 84W...A  
1002 HPA LOW AT 46S 89W...42S 91W...A 1012 HPA LOW AT 41S  
99W...38S 101W...36S 106W...TO A 1010 HPA LOW AT 35S 110W. ANOTHER  
FRONT TO THE NORTH EXTENDS FROM A 994 HPA LOW AT 50S 37W...ALONG  
45S 36W...A 1002 HPA LOW AT 45S 40W...41S 43W...A 1004 HPA LOW AT  
40S 47W...36S 45W...A 1010 HPA LOW AT 32S 49W...PARANA TO NORTHERN  
ARGENTINA. A RIDGE TO THE SOUTH CENTERS ON A 1013 HPA POLAR HIGH  
AT 34S 62W. OVER THE ATLANTIC BROAD RIDGE TO THE EAST CENTERS ON  
TWO 1025 HPA HIGHS... WITH ONE AT 37S 24W AND THE OTHER AT 33S  
26W. A WANING FRONT TO THE NORTH LIES ALONG A 1020 HPA LOW AT 29S  
11W...27S 15W...26S 20W...23S 31W...TO ESPIRITO SANTO IN BRASIL.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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