997  
FXSA20 KWBC 181307  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
907 AM EDT WED OCT 18 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM OCT 18 AT 0000 UTC): AT 200 HPA...A RIDGE  
CONTINUES EXTENDING FROM GUYANA/RORAIMA SOUTH INTO WESTERN MATO  
GROSSO/RONDONIA ALONG 60W. ISOLATED TO SCATTERED DIURNAL  
CONVECTION IS OCCURRING IN AMAZONAS-BRASIL AND RONDONIA.  
ALSO...ENHANCED CONVECTION IS OCCURRING IN SOUTHEASTERN PERU UNDER  
THE INFLUENCE FROM AN UPPER TROUGH APPROACHING FROM THE WEST.  
 
THE UPPER JET ANALYSIS SHOWS THE SOUTHERN POLAR JET FORMING AT 57S  
47W ALONG 58S 30W...A 132KT MAXIMA AT 55S 18W...50S 09W. THE  
NORTHERN POLAR FORMS A FINGER AT 45S 100W EXITING AT 43S 88W. IT  
REFORMS AT 46S 68W ALONG 52S 47W...52S 19W...EXITING AT 40S 06W.  
ANOTHER BRANCH FORMS AT 39S 109W ALONG 41S 97W...EXITING AT 38S  
87W. IT REFORMS AT 33S 79W ALONG 40S 68W EXITING AT 45S 56W. THE  
SUBTROPICAL JET EXTENDS ALONG A 124KT MAXIMA AT 26S 118W...25S  
110W...EXITING AT 22S 102W. IT REFORMS AT 23S 81W...ALONG 27S  
69W...33S 58W...41S 49W...A 143KT MAXIMA AT 44S 40W...EXITING AT  
40S 29W.  
 
AT 500 HPA...A LOW CENTERS OVER THE WESTERN ANTARCTIC PENINSULA AT  
69S 70W. THIS TROUGH IS BROAD AND EXTENDS TO THE NORTH INTO 50S  
AND FROM 90W TO 50W. A SHORT WAVE AXIS EXTENDS OFF THE COAST OF  
CHILE ALONG 45S 75W...NORTH INTO 38S 80W...TO 25S 83W. THIS IS  
FOCUSING CYCLONIC VORTICITY ADVECTION INTO LOS LAGOS AND AYSEN IN  
CHILE. A SHORT WAVE TROUGH EXTENDS OFF THE COAST OF THE RIO DE LA  
PLATA.  
 
AT LOW LEVELS...A 980 HPA OCCLUDED LOW CENTERS AT 63S 66W. A 986  
HPA OCCLUDED LOW CENTERS AT 56S 60W. A 1006 HPA OCCLUDED LOW  
CENTERS AT 49S 78W. A FRONT EXTENDS ALONG A 1000 HPA LOW AT 48S  
46W...43S 52W...41S 61W...A 1006 HPA LOW AT 43S 66W...38S 70W...A  
1014 HPA LOW AT 38S 72W...32S 78W...28S 88W. A SHORT FRONTAL  
SYSTEM EXTENDS FROM 29S 49W ALONG A 1014 HPA LOW AT 32S 52W...29S  
57W...29S 64W. STRONG CONVECTION WAS OCCURRING IN URUGUAY AND  
ENTRE RIOS IN ARGENTINA. OVER THE ATLANTIC...A 1033 HPA HIGH  
CENTERS AT 33S 25W. TO THE NORTH...AN ILL-DEFINED FRONT EXTENDS  
ALONG 24S 29W...22S 43W.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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