432  
FXSA20 KWBC 231340  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
939 AM EDT MON OCT 23 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM OCT 23 AT 0000 UTC): AT 200 HPA...A HIGH NEAR  
03S 100W ANCHORS A RIDGE OVER THE EASTERN TROPICAL PACIFIC.  
THIS...IN-TURN...IS INDUCING THE NORTHWARD AMPLIFICATION OF A  
TROUGH ALONG THE COAST OF PERU. THE TROUGH IS ENHANCING DIURNAL  
CONVECTION ALONG THE SIERRA AND JUNGLE OF PERU...AMAZONAS/ACRE IN  
WESTERN BRASIL AND NORTHERN BOLIVIA...WHERE MOISTURE IS BEING  
INGESTED FROM THE PERUVIAN/ECUADORIAN AMAZON. FARTHER  
EAST...BROAD/OPEN RIDGE EXTENDS ACROSS MID-SECTIONS OF THE  
CONTINENT. THIS IS VENTILATING CONVECTION ALONG ITS SOUTHERN  
PERIPHERY IN THE AMAZON OF PERU...ACRE...RONDONIA...EASTERN  
BOLIVIA AND MATO GROSSO.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG  
65S 120W...A 138KT MAXIMUM AT 53S 102W...49S 89W...A 146KT MAXIMUM  
AT 52S 74W...EXITING AT 59S 62W. IT REFORMS AT 60S 54W...ALONG 60S  
43W...EXITING AT 54S 29W. THE NORTHERN POLAR HAS ITS ENTRANCE AT  
36S 102W...THEN ALONG 38S 90W...EXITING AT 38S 75W. IT REFORMS AT  
33S 53W...ALONG 33S 45W...40S 39W...45S 25W...AND A 194KT MAXIMUM  
AT 44S 06W. THE SUBTROPICAL JET LIES ALONG 18S 120W...23S  
110W...31S 98W...32S 88W...32S 73W...EXITING AT 25S 60W. IT  
REFORMS AT 23S 58W...THEN ALONG 27S 50W...A 157KT MAXIMUM AT 32S  
42W...A 155KT MAXIMUM AT 40S 28W...40S 10W...AND 34S 03E. THE  
SUBEQUATORIAL JET LIES ALONG 11S 116W...15S 110W...17S 100W...14S  
90W...EXITING AT 07S 85W.  
 
THE 500 HPA ANALYSIS SHOWS A LARGE TROUGH IN THE SOUTHERN STREAM  
CENTERING ON A LOW AT 59S 85W. THIS TROUGH IS FOCUSING ITS ENERGY  
ON THE DRAKE PASSAGE. TO THE EAST...A RIDGE EXTENDS ALONG 50W FROM  
48S INTO THE WEDDELL SEA AT 75S. IN THE NORTHERN STREAM...A RIDGE  
EXTENDS FROM NORTHERN CHILE ACROSS CENTRAL ARGENTINA INTO 50S 50W.  
A LOW CENTERS TO ITS NORTHEAST AT 38S 42W. THIS LOW EXTENDS AN  
AXIS TO THE NORTHEAST INTO RIO GRANDE DO SUL-PARAGUAY.  
 
THE SURFACE ANALYSIS SHOWS A BROAD TROUGH ON THE SOUTHERN STREAM  
DOMINATING THE FLOW OVER THE SOUTHEAST PACIFIC/SOUTHERN CONE OF  
SOUTH AMERICA...ANCHORING ON A 960 HPA LOW AT 60S 82W. POLAR  
FRONTS REVOLVE AROUND THIS AXIS...WITH ONE EXTENDING ALONG A 970  
HPA LOW AT 63S 69W...61S 64W...A 976 HPA LOW AT 58S 66W...53S  
64W...A 988 HPA LOW AT 51S 68W...47S 74W...A 1000 HPA LOW AT 47S  
80W...43S 84W...43S 91W...TO A 1012 HPA LOW AT 43S 96W. ANOTHER  
FRONT EXTENDS ALONG A 992 HPA LOW AT 61S 52W...57S 50W...A 992 HPA  
LOW AT 54S 58W...50S 58W...47S 62W...A 1004 HPA LOW AT 45S  
67W...40S 71W...A 1010 HPA LOW AT 42S 77W...37S 82W...A 1018 HPA  
LOW AT 36S 87W...AND 32S 92W. OVER THE ATLANTIC...BROAD TROUGH ON  
THE NORTHERN STREAM ANCHORS ON AN OCCLUDED 998 HPA LOW AT 36S 45.  
THIS EXTENDS A FRONT ALONG A 1004 HPA LOW AT 38S 28W...36S  
24W...34S 28W...A 1008 HPA LOW AT 34S 32W...30S 34W...28S 39W...A  
1014 HPA LOW AT 27S 43W...SAO PAULO...23S 47W...A 1014 HPA LOW AT  
24S 52W...TO CHACO PARAGUAY. SCATTERED DEEP CONVECTION IS BUILDING  
AHEAD OF THIS FRONT ON THE SOUTHEAST-CENTRAL STATES OF BRASIL. A  
RIDGE TO THE SOUTH CENTERS ON A 1023 HPA HIGH OVER URUGUAY AND A  
1025 HPA HIGH AT 49S 37W.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON/GALVEZ...WPC (USA)  

 
 
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