149  
FXSA20 KWBC 211343  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
843 AM EST TUE NOV 21 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM NOV 21 AT 0000 UTC): A 200 HPA HIGH NEAR 12S  
62W ANCHORS A RIDGE ACROSS SOUTH AMERICA THAT ENVELOPS CONTINENTAL  
AREA TO THE NORTH OF 20S. THE RIDGE UNDERCUTS A TUTT TO EAST...AS  
THE LATTER CENTERS ON A CLOSED LOW NEAR RECIFE IN NORTHEAST  
BRASIL. RIDGE ALOFT IS VENTING DEEP CONVECTION ACROSS MINAS  
GERAIS-TOCANTINS/GOIAS TO PARA IN BRASIL. IT IS ALSO VENTING  
DIURNAL CONVECTION ACROSS THE PERUVIAN JUNGLE TO EASTERN ECUADOR.  
UNDER INFLUENCE OF THE TROUGH TO THE NORTHEAST...DRY AND STABLE  
CONDITIONS PREVAIL ACROSS THE NORTHEAST STATES OF BRASIL.  
 
THE 250 HPA JET ANALYSIS SHOWS A FINGER OF THE SOUTHERN POLAR  
EXTENDING BETWEEN 67S 83W AND 62S 71W. IT REFORMS AT 43S  
62W...THEN ALONG 41S 60W...40S 52W...A 138KT MAXIMUM AT 40S  
46W...A 124KT MAXIMUM AT 45S 30W...50S 24W...EXITING AT 55S 22W.  
THE NORTHERN POLAR HAS ITS ENTRANCE AT 56S 96W...THEN ALONG 58S  
83W...52S 73W...EXITING AT 41S 73W. IT REFORMS AT 34S 71W...ALONG  
31S 64W...34S 54W...34S 46W...37S 36W...43S 26W...EXITING AT 47S  
17W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 24S 84W...THEN ALONG  
26S 79W...26S 64W...26S 55W...27S 43W...32S 33W...A 130KT MAXIMUM  
AT 36S 25W...37S 11W...A 132KT MAXIMUM AT 36S 07W...AND 31S 00W.  
THE SUBEQUATORIAL JET LIES ALONG 15S 120W...12S 112W...06S  
104W...TO 00N 100W.  
 
AT 500 HPA...A NORTH-TO-SOUTH RIDGE OVER THE EASTERN PACIFIC  
EXTENDS ALONG 90W TO THE POLAR ICECAP. BROAD TROUGH TO THE EAST  
EXTENDS BETWEEN 70W-15W AND TO THE SOUTH OF 30S. THE TROUGH IS  
FOCUSING SHORT WAVE ENERGY ACROSS CENTRAL CHILE TO CENTRAL  
ARGENTINA. THIS IS PROVIDING THE DYNAMICAL SUPPORT TO CONVECTION  
BUILDING ACROSS URUGUAY TO ENTRE RIOS IN ARGENTINA.  
 
AT LOW LEVELS...BROAD RIDGE EXTENDS OVER THE EASTERN PACIFIC WHILE  
CENTERING ON TWO 1033 HPA HIGHS...WITH ONE AT 40S 100W AND THE  
OTHER AT 45S 85W. BROAD TROUGH LIES TO THE EAST...EXTENDING OVER  
THE SOUTHWEST ATLANTIC. POLAR FRONTS REVOLVE AROUND THIS AXIS WITH  
ONE EXTENDING FROM AN OCCLUDED 990 HPA LOW AT 46S 50W...THEN ALONG  
A 986 HPA LOW AT 48S 43W...45S 43W...44S 45W...A 1000 HPA LOW AT  
42S 49W...37S 52W...BUENOS AIRES PROVINCE/LA PAMPA...PATAGONIA TO  
A 994 HPA LOW AT 58S 65W...54S 66W...51S 70W...AND 55S 80W.  
ANOTHER FRONT EXTENDS FROM AN OCCLUDED 974 HPA LOW AT 51S  
29W...ALONG A 972 HPA LOW AT 56S 26W...49S 19W...40S 26W...36S  
33W...33S 43W...RIO GRANDE DO SUL/NORTHERN URUGUAY...ENTRE RIOS TO  
MENDOZA IN ARGENTINA. THESE COMBINE IN SUPPORT OF SCATTERED DEEP  
CONVECTION ACROSS CENTRAL ARGENTINA. AN OLD BOUNDARY TO THE NORTH  
EXTENDS ALONG A 1014 HPA LOW AT 30S 35W...25S 38W...RIO DE  
JANEIRO-MATO GROSSO DO SUL TO SANTA CRUZ IN EASTERN BOLIVIA. THIS  
SUSTAINS SCATTERED DEEP CONVECTION ON THE SOUTHEAST STATES OF  
BRASIL.  
 
OVIEDO...SHN (ARGENTINA)  
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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