601  
FXSA20 KWBC 271316  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
916 AM EDT FRI OCT 27 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM OCT 27 AT 0000 UTC): BROAD CELL OF THE  
SUBTROPICAL RIDGE DOMINATES CONTINENTAL AREA TO THE NORTH OF 20S  
WHILE ANCHORING ON A CLOSED HIGH OVER AMAZONAS IN BRASIL. THE  
RIDGE ALOFT VENTS ORGANIZED DEEP CONVECTION ACROSS NORTHWEST SOUTH  
AMERICA...WITH MOST INTENSE OVER PARA-AMAZONAS-RORAIMA IN BRASIL.  
OTHER CONVECTIONS CLUSTERED ACROSS EASTERN ECUADOR AND THE  
PERUVIAN JUNGLE.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR JET FORMING AT  
56S 40W ALONG 57S 27W...61S 17W. THE NORTHERN POLAR JET FORMS AT  
55S 108W ALONG 48S 103W...44S 97W...45S 85W...45S 77W...41S 70W.IT  
REFORMS AT 40S 61W ALONG 42S 53W...A 120KT MAXIMA AT 41S  
43W...EXITING AT 42S 32W. THE SUBTROPICAL EXTENDS A FINGER FROM  
36S 55W ALONG 38S 44W...EXITING AT 36S 33W. ANOTHER BRANCH FORMS  
AT 27S 87W ALONG 30S 77W...30S 65W...EXITING AT 30S 58W. ANOTHER  
BRANCH FORMS AT 17S 89W ALONG 23S 81W...A 123KT MAXIMA AT 26S  
71W...24S 62W...EXITING AT 22S 57W.  
 
AT 500 HPA...A RIDGE EXTENDS SOUTH ALONG 110W TO THE POLAR ICECAP.  
THIS...IN-TURN...SUSTAINS THE NORTHWARD AMPLIFICATION OF A TROUGH  
ALONG 90W/95W TO 38S. IN A SINUSOIDAL PATTERN...A LOWER AMPLITUDE  
RIDGE TO THE EAST EXTENDS SOUTH ALONG 80W. DOWNSTREAM FROM THIS  
FEATURE...A SHORT WAVE TROUGH IS STREAMING ACROSS PATAGONIA-CUYO  
IN ARGENTINA. THIS FAVORS SQUALLY WEATHER ACROSS CENTRAL PROVINCES  
IN ARGENTINA-MISIONES/URUGUAY. ANOTHER SHORT WAVE TROUGH TO THE  
EAST EXTENDS ACROSS URUGUAY/SOUTHERN BRASIL TO PARAGUAY. THIS  
TRIGGERED DEEP CONVECTION ACROSS SOUTHERN/SOUTHEAST BRASIL.  
 
THE SURFACE ANALYSIS SHOWS A FRONT EXTENDING ALONG 44S 65W INTO A  
1006 HPA LOW AT 50S 68W...44S 69W...44S 75W...50S 78W...A 998 HPA  
LOW AT 52S 86W...47S 83W...41S 92W. A 1017 HPA HIGH CENTERS AT 43S  
57W. OVER THE PACIFIC A 1029 HPA HIGH CENTERS AT 34S 97W. STRONG  
CONVECTION WAS OCCURRING IN CENTRAL ARGENTINA. A FRONT EXTENDS  
ALONG A 1012 HPA LOW AT 41S 40W...37S 47W...A 1012 HPA LOW AT 36S  
52W...33S 55W...34S 60W...32S 67W. A FRONT EXTENDS ALONG A 1020  
HPA LOW AT 20S 36W...28S 30W...29S 44W...27S 48W...23S 51W...23S  
56W...22S 60W. SCATTERED RAINFALL OBSERVATIONS WERE BEING REPORTED  
IN EASTERN PARAGUAY AND SOUTHERN BRASIL.  
 
VANNUCCI...SMN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON/GALVEZ...WPC (USA)  

 
 
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