840  
FXSA20 KWBC 121433  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
933 AM EST FRI JAN 12 2018  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM JAN 12 AT 0000 UTC): A 200 HPA CELL OF THE  
SUBTROPICAL RIDGE DOMINATES CONTINENTAL AREA TO THE NORTH OF 35S  
AND WEST OF 57W...WITH AXIS ANCHORING ON A CLOSED HIGH AT 17S 65W.  
THIS IS STEERING A SHORT WAVE TROUGH ACROSS LA PAMPA-BUENOS AIRES  
PROVINCE IN ARGENTINA...WHERE IT TRIGGERED SCATTERED DEEP  
CONVECTION. ANOTHER SHORT WAVE TROUGH TO THE EAST EXTENDS FROM  
SOUTHERN BRASIL TO MATO GROSSO DO SUL. FARTHER NORTH...A CLOSED  
LOW AT 11S 42W EXTENDS A TROUGH TO THE GUIANAS. MOST ACTIVE  
CONVECTION IS BUILDING BETWEEN THIS TROUGH AND THE RIDGE TO THE  
WEST...CLUSTERING OVER TOCANTINS-GOIAS AND MATO GROSSO IN BRASIL.  
 
AT 250 HPA...THE SOUTHERN POLAR HAS ITS ENTRANCE AT 60S  
110W...THEN ALONG 57S 100W...50S 94W...EXITING AT 48S 90W. IT  
REFORMS AT 49S 82W...ALONG 54S 74W...60S 66W...A 124KT MAXIMUM AT  
61S 48W...55S 29W...46S 21W...43S 12W...AND 47S 01W. THE NORTHERN  
POLAR HAS ITS ENTRANCE AT 50S 100W...THEN ALONG 44S 92W...44S  
85W...A 140KT MAXIMUM AT 45S 80W...A 147KT MAXIMUM AT 50S  
74W...EXITING AT 57S 61W. A FINGER TO THE EAST EXTENDS BETWEEN 52S  
37W AND 41S 23W. THE SUBTROPICAL JET LIES ALONG 32S 120W...33S  
107W...36S 99W...41S 84W...45S 75W...EXITING AT 47S 63W. A FINGER  
TO THE NORTH EXTENDS BETWEEN 30S 83W AND 23S 82W. IT REFORMS AT  
23S 77W...EXITING AT 30S 74W. ANOTHER FINGER TO THE EAST EXTENDS  
BETWEEN 33S 68W AND 33S 62W.  
 
AT 500 HPA...A RIDGE IS BUILDING ALONG 110W TO 60S.  
THIS...IN-TURN...IS INDUCING THE NORTHWARD AMPLIFICATION OF A  
TROUGH BETWEEN 95W-65W AND TO THE SOUTH OF 38S. THE TROUGH IS  
FOCUSING SHORT WAVE ENERGY ACROSS SOUTHERN CHILE TO SOUTHERN  
PATAGONIA/TIERRA DEL FUEGO. A BROAD/LOW AMPLITUDE RIDGE LIES TO  
THE EAST...EXTENDING BETWEEN 65W-35W AND TO THE SOUTH OF 40S.  
DOWNSTREAM FROM THIS RIDGE A TROUGH EXTENDS BETWEEN 30W-10E AND TO  
THE SOUTH OF 30S.  
 
AT LOW LEVELS...A RIDGE OVER THE EASTERN PACIFIC ANCHORS ON TWO  
CLOSED HIGHS...A 1027 HPA HIGH AT 40S 104W AND A 1023 HPA HIGH AT  
29S 94W. BROAD TROUGH TO THE EAST-SOUTHEAST SUSTAINS A POLAR  
FRONT THAT ORIGINATES ON A 980 HPA LOW AT 59S 71W...ALONG A 978  
HPA LOW AT 58S 68W...56S 66W...A 986 HPA LOW AT 55S 69W...SOUTHERN  
PATAGONIA... A 998 HPA LOW AT 49S 73W...45S 75W...35S 87W...AND A  
1018 HPA LOW AT 28S 110W. AN ELONGATED FRONT OVER THE ATLANTIC  
EXTENDS ALONG 35S 15W...35S 30W...37S 40W...43S 43W...A 1010 HPA  
LOW AT 50S 46W...46S 46W...A 1006 HPA LOW AT 46S 55W...TO LA  
PAMPA. THIS FAVORS SCATTERED CONVECTION ACROSS CENTRAL ARGENTINA.  
A RIDGE TO THE NORTH CENTERS ON TWO 1021 HPA HIGHS...WITH ONE AT  
41S 37W AND THE OTHER AT 32S 36W. AN OLD/WANING FRONT LIES FARTHER  
TO THE NORTH...WITH AXIS ALONG 28S 06W...26S 19W...23S 28W...TO  
26S 43W.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
DAVISON...WPC (USA)  

 
 
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