311  
FXSA20 KWBC 291420  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
920 AM EST MON JAN 29 2018  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM JAN 29 AT 0000 UTC): AT 200 HPA...BROAD RIDGE  
DOMINATES CONTINENTAL AREA TO THE NORTH OF 35S...WITH AXIS  
ANCHORING ON A CLOSED HIGH OVER CHACO ARGENTINO. THE RIDGE ALOFT  
IS VENTING DEEP CONVECTION ACROSS SAO PAULO-MATO GROSSO/MATO  
GROSSO DO SUL...BOLIVIA AND SOUTHERN PERU. A NEGATIVELY TILTED  
TROUGH TO THE WEST EXTENDS ALONG 20S 94W...10S 83W...TO NORTHERN  
PERU. ANOTHER TROUGH TO THE EAST...MEANWHILE...EXTENDS ALONG 20S  
30W...06S 40W TO AMAPA/SOUTHERN GUIANAS.  
 
AT 250 HPA...THE SOUTHERN POLAR LIES ALONG A 130KT MAXIMUM AT 55S  
121W...51S 104W...54S 87W...A 125KT MAXIMUM AT 57S 70W...EXITING  
AT 53S 60W. THE NORTHERN POLAR LIES ALONG 51S 120W...A 133KT  
MAXIMUM AT 48S 111W...47S 100W...A 134KT MAXIMUM AT 51S 87W...51S  
69W...EXITING AT 44S 48W. IT REFORMS AT 45S 45W...ALONG 55S  
31W...50S 11W...AND 47S 00W. THE SUBTROPICAL JET HAS ITS ENTRANCE  
AT 23S 79W...ALONG 33S 72W...34S 59W...32S 44W...EXITING AT 25S  
36W. A FINGER OF THE SUBEQUATORIAL JET LIES ALONG 14S 120W...13S  
107W...EXITING AT 12S 95W. ANOTHER BRANCH TO THE NORTH LIES ALONG  
09S 115W...03S 94W...AND 03N 80W. THE JET REFORMS TO THE EAST NEAR  
18S 36W...ALONG 14S 39W...11S 42W...EXITING AT 07S 44W.  
 
AT 500 HPA...BROAD/LOW AMPLITUDE TROUGH ON THE SOUTHERN STREAM  
EXTENDS BETWEEN 110W-80W AND TO THE SOUTH OF 40S...FOCUSING ITS  
SHORT WAVE ENERGY ACROSS EXTREME SOUTHERN PORTIONS OF CHILE. A  
NEGATIVELY TILTED TROUGH TO THE EAST EXTENDS FROM THE DRAKE  
PASSAGE...ALONG 50S 50W...40S 48W...TO URUGUAY. THIS IS PRESSING  
AGAINST AN INDUCED RIDGE THAT EXTENDS ALONG 40S 20W...50S 30W...TO  
THE SOUTH GEORGIA ISLANDS.  
 
AT LOW LEVELS...THE SURFACE ANALYSIS SHOWS A RIDGE ON THE NORTHERN  
STREAM THAT ANCHORS ON TWO 1025 HPA HIGHS...WITH ONE AT 34S 110W  
AND THE OTHER AT 34S 103W. BROAD/LOW AMPLITUDE TROUGH LIES TO THE  
SOUTH...CENTERING ON A 962 HPA LOW AT 67S 96W. AN ELONGATED FRONT  
REVOLVES AROUND THIS AXIS...EXTENDING FROM A 978 HPA LOW AT 61S  
65W...A 986 HPA LOW AT 61S 52W...59S 51W...A 988 HPA LOW AT 55S  
56W...50S 56W...48S 66W...A 998 HPA LOW AT 51S 70W...48S 70W...48S  
75W...52S 79W...A 976 HPA LOW AT 55S 83W...52S 82W...48S 87W...A  
1008 HPA LOW AT 46S 96W...43S 98W...AND 40S 107W. ANOTHER FRONT  
OVER THE ATLANTIC EXTENDS FROM AN OCCLUDED 990 HPA LOW AT 54S  
39W...ALONG A 990 HPA LOW AT 55S 36W...53S 34W...51S 38W...A 990  
HPA LOW AT 51S 42W...49S 41W...A 998 HPA LOW AT 46S 44W...44S  
43W...39S 46W...URUGUAY-ENTRE RIOS ARGENTINA. A POLAR RIDGE TO THE  
SOUTH CENTERS ON A 1013 HPA HIGH AT 37S 56W. FARTHER NORTH...AN  
ELONGATED FRONT EXTENDS ALONG A 1014 HPA LOW AT 30S 23W...26S  
26W...26S 32W...A 1010 HPA LOW AT 28S 37W...26S 40W...31S 45W...A  
1006 HPA LOW AT 35S 49W...RIO GRANDE DO SUL...CORRIENTES TO CHACO  
ARGENTINO. ORGANIZED DEEP CONVECTION IS CLUSTERING TO THE NORTH  
ACROSS PARAGUAY TO SOUTHERN BRASIL.  
 
OVIEDO...SHN (ARGENTINA)  
POMIER...SENAMHI (BOLIVIA)  
DAVISON...WPC (USA)  

 
 
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