530  
FXSA20 KWBC 251311  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
911 AM EDT WED OCT 25 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM OCT 25 AT 0000 UTC): AT 200 HPA...A  
NARROW/ELONGATED TROUGH ALONG 77W SEPARATES BROAD RIDGE OVER  
NORTHERN SOUTH AMERICA FROM ANOTHER RIDGE OVER THE EASTERN  
PACIFIC. THE CONTINENTAL RIDGE IS VENTING DEEP CONVECTION ACROSS  
PARA-RORAIMA AND AMAZONAS IN BRASIL. THE TROUGH...MEANWHILE...IS  
VENTING SCATTERED CONVECTION ALONG THE SIERRA OF PERU AND CENTRAL  
JUNGLE.  
 
AT 250 HPA...THE JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH  
ENTRANCE AT 61S 82W...THEN ALONG 52S 74W...51S 55W...A 127KT  
MAXIMUM AT 59S 42W...AND 67S 26W. THE NORTHERN POLAR HAS ITS  
ENTRANCE AT 46S 103W...THEN ALONG 46S 89W...EXITING AT 43S 76W. IT  
REFORMS BETWEEN 36S 52W AND 33S 39W. ANOTHER BRANCH OF THE  
NORTHERN POLAR LIES TO THE EAST WITH ENTRANCE AT 34S 35W...THEN  
ALONG 36S 27W...EXITING AT 41S 19W. A FINGER OF THE SUBTROPICAL  
JET LIES BETWEEN 29S 86W AND 28S 76W. IT REFORMS AT 30S 70W...THEN  
ALONG 30S 63W...32S 53W...29S 44W...EXITING AT 30S 36W. ANOTHER  
BRANCH TO THE NORTH HAS ITS ENTRANCE AT 19S 68W...CROSSING 23S  
58W...23S 44W...30S 28W...37S 14W...AND 37S 04E. A BRANCH OF THE  
SUBEQUATORIAL JET HAS ITS ENTRANCE AT 15S 115W...THEN ALONG 13S  
106W...14S 99W...EXITING AT 14S 93W.  
 
AT 500 HPA...BROAD TROUGH EXTENDS NORTH BETWEEN 80W-50W TO  
30S...WITH AXIS ORIGINATING ON A CLOSED LOW AT 70S 60W. THIS IS  
FOCUSING SHORT WAVE ENERGY ACROSS SOUTHERN/CENTRAL CHILE TO  
ARGENTINA. THE INFLOW OF SHORT WAVE ENERGY TRIGGERED ORGANIZED  
DEEP CONVECTION ACROSS MISIONES IN ARGENTINA/SOUTHEAST PARAGUAY  
AND THE SOUTHERN STATES OF BRASIL. FARTHER EAST...IN A SPLIT FLOW  
PATTERN...THE FLOW DIVIDES BETWEEN A RIDGE ON THE SOUTHERN STREAM  
AND A TROUGH TO THE NORTH. THE RIDGE EXTENDS BETWEEN 35W-10W AND  
TO THE SOUTH OF 50S...WHILE THE TROUGH EXTENDS BETWEEN 45W-20W AS  
IT CENTERS ON A CLOSED LOW NEAR 42S 32W.  
 
AT LOW LEVELS...A RIDGE ON THE NORTHERN STREAM EXTENDS OVER THE  
EASTERN PACIFIC WHILE ANCHORING ON A 1029 HPA HIGH AT 34S 96W.  
BROAD TROUGH LIES TO THE SOUTH...EXTENDING FROM THE ANTARCTIC  
PENINSULA TO THE SOUTHERN CONE WHILE ANCHORING ON AN OCCLUDED 978  
HPA LOW AT 69S 54W. POLAR FRONTS REVOLVE AROUND THIS AXIS...WITH  
ONE EXTENDING FROM A 982 HPA LOW AT 64S 47W...THEN ALONG A 984 HPA  
LOW AT 65S 45W...60S 44W...A 982 HPA LOW AT 62S 52W...55S  
51W...51S 63W...A 1008 HPA LOW AT 50S 70W...46S 67W...TO 42S 69W.  
A SECONDARY FRONT FOLLOWS... EXTENDING ALONG A 1000 HPA LOW AT 49S  
78W...45S 84W...45S 92W...48S 98W...TO A 1006 HPA LOW AT 50S 105W.  
AN ELONGATED FRONT LIES TO THE EAST AND NORTH...WITH AXIS ALONG A  
996 HPA LOW AT 58S 42W...53S 43W...A 1006 HPA LOW AT 52S 49W...49S  
48W...A 1008 HPA LOW AT 47S 52W...40S 55W...BUENOS AIRES PROVINCE  
TO MENDOZA IN ARGENTINA. ALSO OVER THE ATLANTIC...AN OCCLUDED 1006  
HPA LOW AT 41S 31W ANCHORS A BROAD TROUGH ON THE NORTHERN STREAM  
FLOW. THIS EXTENDS A FRONT ALONG A 1022 HPA LOW AT 37S 15W...32S  
20W...29S 25W...A 1022 HPA LOW AT 28S 29W....25S 34W...A 1022 HPA  
LOW AT 24S 38W...RIO DE JANEIRO...SAO PAULO...MISIONES IN  
ARGENTINA TO SALTA. THIS FAVORS SCATTERED DEEP CONVECTION OVER MID  
SECTIONS OF SOUTH AMERICA.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON/GALVEZ...WPC (USA)  

 
 
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