917  
FXSA20 KWBC 121306  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
905 AM EDT THU OCT 12 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM OCT 12 AT 0000 UTC): AT 200 HPA...A RIDGE  
CENTERS OVER THE AMAZON DELTA AND EXTENDS AN AXIS TO THE SOUTH  
ALONG 60W INTO SOUTHEASTERN BOLIVIA AND MATO GROSSO DO SUL. TO THE  
WEST...A WEAK TROUGH EXTENDS ACROSS CENTRAL PERU INTO SOUTHERN  
COLOMBIA. TO THE EAST...A BROAD TROUGH CENTERS ON A LOT TO THE  
EAST OF SALVADOR DE BAHIA NEAR 12S 33W. THE STRONGEST CONVECTION  
IN TROPICAL SOUTH AMERICA WAS OCCURRING TO THE EAST OF THE TROUGH  
OVER PERU...EXTENDING ACROSS ACRE AND AMAZONAS IN BRASIL.  
 
THE UPPER JET ANALYSIS SHOWS THE SOUTHERN POLAR JET EXTENDING A  
FINGER FROM 60S 115W EXITING AT 59S 86W. IT REFORMS AT 56S 72W  
EXITING AT 53S 58W. ANOTHER BRANCH EXTENDS ALONG 42S 120W...A  
128KT MAXIMA AT 49S 114W...53S 89W...EXITING AT 51S 70W. THE  
NORTHERN POLAR JET EXTENDS ALONG A 142KT MAXIMA AT 40S 120W ALONG  
47S 110W...EXITING AT 47S 98W. IT REFORMS AT 27S 83W ALONG 30S  
74W...A 142KT MAXIMA AT 39S 66W...38S 49W...A 156KT MAXIMA AT 39S  
36W...35S 20W...EXITING AT 25S 19W. THE SUBTROPICAL JET FORMS AT  
22S 82W ALONG 28S 71W...35S 48W...32S 27W...EXITING AT 21S 21W.  
 
AT 500 HPA...A RIDGE CENTERS ON A HIGH AT 35S 102W. TO THE  
EAST...A LOW CENTERS OVER CENTRAL CHILE AT 33S 73W...AND IS  
SHEARING CYCLONIC VORTICITY INTO CENTRAL ARGENTINA. A RIDGE  
CENTERS ON A HIGH OVER SAP PAULO/RIO DE JANEIRO. IN THE SOUTHERN  
STREAM...A LOW CENTERS OVER THE BELLINGSHAUSEN SEA AT 72S 85W.  
THIS IS ASSOCIATED WITH A TIGHT BELT OF WEST-SOUTH WESTERLIES TO  
THE NORTH INTO THE DRAKE PASSAGE. A TROUGH AXIS EXTENDS FROM THIS  
LOW NORTH INTO TIERRA DEL FUEGO.  
 
AT LOW LEVELS...A 974 HPA OCCLUDED LOW 72S 86W. THIS EXTENDS A  
FRONT INTO A TRIPLE POINT LOW OF 980 HPA AT 70S 70W...A 982 HPA  
LOW AT 66S 74W...A 992 HPA LOW AT 60S 74W...55S 72W...52S 83W. A  
982 HPA OCCLUDED LOW AT 63S 56W EXTENDS A FRONT ALONG A 982 TRIPLE  
POINT LOW AT 63S 590W...A 992 HPA LOW AT 56S 49W...A COLD FRONT AT  
50S 52W...47S 63W...AN ILL-DEFINED BOUNDARY ALONG 50S 74W...A 1028  
HPA LOW AT 48S 81W...46S 90W. A 1041 HPA HIGH CENTERS AT 38S  
95W...AND EXTENDS A RIDGE TO THE EAST INTO AYSEN/LOS LAGOS...AND  
INTO A 1029 HPA HIGH AT 40S 62W. A 988 HPA OCCLUDED LOW AT 49S 30W  
EXTENDS A FRONT ALONG42S 33W...389S 43W...37S 53W. A FRONT EXTENDS  
ACROSS A 1014 HPA HIGH AT 36S 31W...31S 41W...29S 50W...A 1006 HPA  
LOW AT 27S 58W...23S 61W...19S 64W. SCATTERED DEEP CONVECTION WAS  
OCCURRING IN SOUTH EASTERN PARAGUAY AND PARANA/SANTA CATARINA IN  
BRASIL.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  

 
 
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