411  
FXSA20 KWBC 311252  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
851 AM EDT TUE OCT 31 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM OCT 31 AT 0000 UTC): AT 200 HPA...A HIGH NEAR  
10S 55W ANCHORS A RIDGE OVER THE CONTINENT TO THE NORTH OF 23S. AN  
INDUCED TROUGH TO THE EAST AND NORTH EXTENDS ALONG 19S 30W...08S  
40W...TO THE GUIANAS. THE RIDGE ALOFT IS VENTING ORGANIZED DEEP  
CONVECTION ACROSS BRASIL TO THE NORTH OF 10S...WHILE ACROSS  
PERU-ECUADOR IT FAVORS ISOLATED TO SCATTERED CONVECTION.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH ENTRANCE AT  
52S 118W...THEN ALONG 59S 101W...EXITING AT 59S 79W. IT REFORMS AT  
50S 48W...ALONG A 121KT MAXIMUM AT 53S 43W...56S 28W...EXITING AT  
53S 15W. THE NORTHERN POLAR HAS ITS ENTRANCE AT 41S 101W...THEN  
ALONG 37S 94W...EXITING AT 35S 85W. IT REFORMS AT 38S 80W...ALONG  
44S 70W...40S 64W...EXITING AT 36S 60W. IT REFORMS AT 40S  
48W...ALONG 48S 43W...51S 26W...EXITING AT 40S 19W. THE  
SUBTROPICAL JET HAS ITS ENTRANCE AT 18S 96W...ALONG 22S 87W...24S  
75W...A 150KT MAXIMUM AT 28S 57W...29S 47W...32S 36W...28S  
22W...EXITING AT 27S 11W.  
 
AT 500 HPA...A SKEWED RIDGE EXTENDS FROM 28S 114W...ALONG 40S  
110W...50S 100W TO THE DRAKE PASSAGE. THE RIDGE UNDERCUTS A TROUGH  
TO THE EAST. THE TROUGH EXTENDS BETWEEN 100W-77W AND TO THE SOUTH  
OF 20S...CENTERING ON A CLOSED LOW AT 42S 86W. AND INDUCED RIDGE  
ALONG 70W SEPARATES THE LATTER FROM ANOTHER TROUGH TO THE EAST.  
THE TROUGH EXTENDS FROM THE SOUTH GEORGIA ISLANDS...ALONG 50S  
55W...A LOW AT 46S 57W...URUGUAY TO SOUTHEAST PARAGUAY. A HIGHER  
AMPLITUDE RIDGE TO THE EAST EXTENDS FROM 25S 33W...ALONG 40S  
30W...TO 60S 25W.  
 
AT LOW LEVELS...PROGRESSIVE POLAR TROUGH ON THE SOUTHERN STREAM  
DOMINATES THE WEDDELL SEA-ANTARCTIC PENINSULA WHILE CENTERING ON  
AN OCCLUDED 970 HPA LOW AT 69S 54W. THIS EXTENDS A FRONT ALONG A  
970 HPA LOW AT 70S 49W...A 970 HPA LOW AT 66S 48W...59S 59W...58S  
69W...60S 78W...TO A 992 HPA LOW AT 63S 93W. RIDGE TO THE NORTH  
CENTERS ON A 1025 HPA HIGH AT 48S 100W. EAST OF THIS RIDGE...AN  
OCCLUDED 998 HPA LOW AT 42S 84W EXTENDS A FRONT ALONG A 1004 HPA  
LOW AT 44S 79W...41S 76W...38S 78W...A 1012 HPA LOW AT 36S  
83W...33S 88W...TO 33S 95W. THIS FAVORS MODERATE INTERMITTENT  
SHOWERS ACROSS SOUTHERN CHILE. FARTHER EAST...AN OCCLUDED 998 HPA  
ANCHORS A TROUGH OFF THE COAST OF PATAGONIA....WITH A POLAR FRONT  
EXTENDING FROM AN OCCLUDED 992 HPA LOW AT 55S 44W...A 988 HPA LOW  
AT 58S 37W...56S 33W...53S 36W...A 996 HPA LOW AT 52S 42W...49S  
41W...45S 43W...A 1004 HPA LOW AT 42S 47W...35S 48W...RIO GRANDE  
DO SUL...MISIONES-CORRIENTES TO TUCUMAN/SANTIAGO DEL ESTERO IN  
NORTHWEST ARGENTINA. A POLAR HIGH TO THE SOUTH CENTERS ON A 1017  
HPA HIGH AT 35S 61W. FARTHER EAST...BROAD RIDGE ON THE SOUTHERN  
STREAM EXTENDS OVER THE CENTRAL ATLANTIC WHILE CENTERING ON A 1025  
HPA HIGH AT 40S 28W. EAST AND NORTH OF THIS RIDGE...A POLAR FRONT  
EXTENDS ALONG A 1008 HPA LOW AT 34S 08W...28S 12W...25S 20W...A  
1014 HPA LOW AT 25S 27W...23S 30W...24S 34W...A 1006 HPA LOW AT  
24S 42W...RIO DE JANEIRO/SOUTHERN MINAS GERAIS...MATO GROSSO DO  
SUL TO CHACO PARAGUAYO. THIS SUSTAINS SCATTERED DEEP CONVECTION.  
 
OVIEDO...SHIN (ARGENTINA)  
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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