972  
FXSA20 KWBC 311449  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
949 AM EST WED JAN 31 2018  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM JAN 31 AT 0000 UTC): AT 200 HPA...BROAD CELL  
OF THE SUBTROPICAL RIDGE CONTINUES TO DOMINATE THE FLOW OVER THE  
CONTINENT TO THE NORTH OF 40S...WITH AXIS CENTERING ON A CLOSED  
HIGH OVER MATO GROSSO DO SUL IN BRASIL. THE RIDGE ALOFT IS VENTING  
DEEP CONVECTION ACROSS NORTHWEST ARGENTINA-SOUTHERN BOLIVIA/CHACO  
PARAGUAYO. A NEGATIVELY TILTED TO THE WEST...MEANWHILE...EXTENDS  
ALONG 20S 90W TO NORTHERN PERU. THIS IS VENTING CONVECTION ON THE  
CENTRAL AND SOUTHERN SIERRA. EAST OF THE UPPER LEVEL RIDGE...A  
SHORT WAVE TROUGH EXTENDS ALONG 38S 39W...30S 40W...TO RIO DE  
JANEIRO. ANOTHER TROUGH TO THE NORTH EXTENDS FROM A CLOSED LOW  
NEAR RECIFE...ALONG THE NORTH COAST OF BRASIL TO NORTHERN PARA.  
THESE COMBINE IN SUPPORT OF ORGANIZED DEEP CONVECTION OVER MINAS  
GERAIS-BAHIA.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG  
55S 120W...57S 107W...59S 85W...A 130KT MAXIMUM AT 56S  
81W...EXITING AT 49S 71W. IT REFORMS AT 57S 57W...CROSSING 61S  
45W...A 122KT MAXIMUM AT 57S 31W...EXITING AT 50S 21W. THE  
NORTHERN POLAR LIES ALONG 51S 120W...A 153KT MAXIMUM AT 52S  
112W...53S 87W...45S 75W...44S 58W...A 134KT MAXIMUM AT 48S  
52W...EXITING AT 55S 46W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT  
18S 80W...ALONG 30S 77W...36S 72W...A 139KT MAXIMUM AT 38S  
65W...38S 54W...31S 48W...EXITING AT 24S 44W. IT REFORMS AT 28S  
37W...THEN ALONG 38S 24W...EXITING AT 38S 13W. THE SUBEQUATORIAL  
JET IS ANALYZED AT 150 HPA WITH AXIS ALONG 10S 116W...05S  
95W...00N 83W...EXITING AT 01N 78W. A FINGER TO THE EAST HAS ITS  
ENTRANCE AT 02S 43W...ALONG 06N 40W...EXITING AT 08N 33W.  
 
AT 500 HPA...A SHORT WAVE RIDGE ALONG 85W/90W IS INDUCING THE  
NORTHWARD AMPLIFICATION OF A TROUGH ACROSS THE SOUTHERN CONE TO  
THE SOUTHWEST ATLANTIC...WITH AXIS EXTENDING BETWEEN 75W-50W AND  
TO THE SOUTH OF 40S WHILE CENTERING ON A DEEP LOW NEAR 52S 57W.  
DOWNSTREAM FROM THIS AXIS...A RIDGE EXTENDS BETWEEN 45W-30W AND TO  
THE SOUTH OF 40S. IN A SPLIT FLOW PATTERN...A SHORT WAVE TROUGH TO  
THE NORTH MEANDERS OFF THE SOUTHEAST COAST OF BRASIL WHILE  
CENTERING ON A CLOSED LOW AT 32S 39W. THIS IS PROVIDING DYNAMICAL  
SUPPORT TO ORGANIZED DEEP CONVECTION ACROSS MINAS GERAIS-ESPIRITO  
SANTO AND BAHIA IN BRASIL.  
 
AT LOW LEVELS...A RIDGE ON THE NORTHERN STREAM DOMINATES THE  
NORTHERN STREAM OVER THE EASTERN PACIFIC WHILE ANCHORING ON A  
1025 HPA HIGH AT 34S 113W AND A 1025 HPA HIGH AT 40S 84W. THIS  
FAVORS A TIGHT BELT OF MID LATITUDE WESTERLIES...WITH A  
PROGRESSIVE FRONT EXTENDING FROM AN OCCLUDED 986 HPA LOW AT 59S  
80W...A 986 HPA LOW AT 57S 77W...54S 76W...51S 78W...48S 84W...51S  
92W...56S 97W...TO A 972 HPA LOW AT 58S 100W. ANOTHER FRONT TO THE  
EAST ORIGINATES ON A DEEPENING 966 HPA LOW AT 52S 57W...WITH AXIS  
ALONG A 972 HPA LOW AT 55S 57W....A 980 HPA LOW AT 55S 49W...54S  
47W...A 984 HPA LOW AT 52S 49W...49S 48W...A 1004 HPA LOW AT 45S  
52W...42S 51W...BUENOS AIRES PROVINCE TO MENDOZA. THIS FAVOR  
SCATTERED CONVECTION ACROSS CENTRAL ARGENTINA. A RIDGE TO THE EAST  
CENTERS ON A 1023 HPA HIGH AT 42S 32W. AN OLD/ELONGATED FRONT TO  
THE NORTH EXTENDS ALONG A 1014 HPA LOW AT 35S 26W...33S 27W...33S  
32W...A 1006 HPA LOW AT 30S 37W...27S 36W...RIO DE  
JANEIRO/SOUTHERN MINAS GERAIS...MISIONES/SOUTHEAST PARAGUAY TO  
FORMOSA. THE SOUTH AMERICA CONVERGENCE ZONE EXTENDS FROM THIS  
BOUNDARY ACROSS SOUTHERN MINAS GERAIS-MATO GROSSO DO SUL TO SANTA  
CRUZ IN EASTERN BOLIVIA. ORGANIZED DEEP CONVECTION WAS BUILDING  
ALONG AND NORTH OF THIS FEATURE.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
DAVISON...WPC (USA)  

 
 
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