550  
FXSA20 KWBC 051405  
PMDSA  
 
SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
904 AM EST TUE DEC 05 2017  
 
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/  
 
SYNOPSIS (VALID FROM DEC 04 AT 0000 UTC): AT 200 HPA...A CLOSED  
HIGH NEAR 17S 57W ANCHORS A RIDGE THAT EXTENDS OVER THE CONTINENT  
TO THE NORTH OF 35S. AN ELONGATED TROUGH BOUNDS THE NORTHERN  
FRINGES OF THIS RIDGE...WITH AXIS NORTHWEST ALONG 10S 30W...AMAZON  
RIVER DELTA REGION TO THE SOUTHERN GUIANAS. THE RIDGE ALOFT IS  
VENTING DEEP CONVECTION OVER THE CONTINENT BETWEEN 23S-05S...WITH  
MOST INTENSE CLUSTERING BETWEEN MATO GROSSO DO SUL IN BRASIL AND  
CENTRAL BOLIVIA. THE TROUGH TO THE NORTH...MEANWHILE...FAVORS AN  
UPPER CONVERGENT PATTERN THAT IS INHIBITING DEVELOPMENT ACROSS  
NORTHEAST BRASIL... NORTHERN PARA AND RORAIMA.  
 
THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG  
54S 120W...55S 101W...58S 82W...A 139KT MAXIMUM AT 58S  
73W...EXITING AT 56S 55W. IT REFORMS AT 53S 36W...ALONG 46S  
32W...EXITING AT 42S 27W. THE NORTHERN POLAR LIES ALONG A 145KT  
MAXIMUM AT 50S 120W...50S 106W...54S 75W...EXITING AT 50S 51W. THE  
SUBTROPICAL JET HAS ITS ENTRANCE AT 25S 75W...THEN ALONG 33S  
61W...A 132KT MAXIMUM AT 31S 41W...EXITING AT 30S 30W. THE  
SUBEQUATORIAL JET LIES ALONG 09S 115W...10S 102W...EXITING AT 08S  
88W. ANOTHER BRANCH TO THE NORTH EXTENDS ALONG 00S 108W...00S  
93W...EXITING AT 02N 85W.  
 
AT 500 HPA...A BROAD TROUGH ON THE SOUTHERN STREAM DOMINATES THE  
FLOW OVER THE SOUTHEAST PACIFIC TO THE SOUTH OF 45S...WITH AXIS  
CENTERING ON A CLOSED LOW AT 68S 105W. IN A TIGHT BELT OF MID  
LEVEL WESTERLIES...PROGRESSIVE SHORT WAVE PERTURBATIONS ARE  
STREAMING TOWARDS TIERRA DEL FUEGO/DRAKE PASSAGE. IN THIS PATTERN  
A FAIRLY STRONG SHORT WAVE TROUGH EXTENDS BETWEEN 100WW-110W AND  
TO THE SOUTH OF 45S. ANOTHER SHORT WAVE TROUGH TO THE EAST EXTENDS  
FROM THE ANTARCTIC PENINSULA...ACROSS THE MALVINAS/FALKLAND  
ISLANDS...TO 45S 60W. A SKEWED RIDGE TO THE EAST EXTENDS FROM 43S  
50W...ALONG 50S 45W...60S 43W...TO THE WEDDELL SEA.  
THIS...IN-TURN...FAVORS THE NORTHWARD AMPLIFICATION OF A TROUGH  
BETWEEN 40W-15W TO 27S. SHORT WAVE TROUGH ON THE NORTHERN  
STREAM...MEANWHILE...TRAILS OFF THE CENTRAL/NORTHERN COAST OF  
CHILE...WITH AXIS EXTENDING TO THE NORTHWEST FROM A CLOSED LOW AT  
37S 76W...ALONG 28S 80W...TO 20S 88W.  
 
A LOW LEVELS...BROAD RIDGE ON THE NORTHERN STREAM DOMINATES THE  
EASTERN PACIFIC WHILE CENTERING ON A CLOSED 1029 HPA HIGH AT 36S  
102W. BROAD TROUGH TO THE SOUTH ANCHORS ON A 950 HPA LOW AT 68S  
111W.THIS SUSTAINS A POLAR FRONT THAT EXTENDS FROM AN OCCLUDED 974  
HPA LOW AT 63S 58W...ALONG A 982 HPA LOW AT 61S 51W...53S  
53W...49S 61W...A 1006 HPA LOW AT 47S 67W... NORTHERN  
PATAGONIA...40S 72W...35S 86W AND 35S 94W. ANOTHER RIDGE LIES TO  
THE EAST...DOMINATING CENTRAL ARGENTINA WHILE CENTERING ON A 1023  
HPA HIGH AT 40S 49W. AN ELONGATED FRONT TO THE EAST AND NORTH  
EXTENDS ALONG A 992 HPA LOW AT 43S 19W...35S 22W...31S 35W...A  
1014 HPA LOW AT 31S 45W...27S 46W...SAO  
PAULO...MISIONES/CORRIENTES TO TOCUMAN IN ARGENTINA. ANOTHER FRONT  
LIES ALONG A 1014 HPA LOW AT 30S 18W...27S 20W...26S 24W...24S  
31W...TO RIO DE JANEIRO.  
 
OVIEDO...SHN (ARGENTINA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  

 
 
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