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South American Synoptic Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1448Z Dec 13, 2017)
 
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
948 AM EST WED DEC 13 2017

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

SYNOPSIS (VALID FROM DEC 13 AT 0000 UTC): AT 200 HPA...A HIGH OVER
SOUTHERN PARA IN BRASIL EXTENDS A RIDGE TO THE SOUTH-SOUTHWEST
ACROSS BOLIVIA TO NORTHERN ARGENTINA...AND WEST ACROSS PERU. A
SHORT WAVE TROUGH TO THE EAST EXTENDS FROM SOUTHERN BRASIL TO MATO
GROSSO. THE RIDGE ALOFT IS VENTING DEEP CONVECTION ALONG THE SACZ
OVER NORTHERN BRASIL.

AT 250 HPA...THE SOUTHERN POLAR LIES ALONG 55S 120W...51S
110W...EXITING AT 52S 98W. IT REFORMS AT 53S 100W...THEN ALONG 57S
79W...58S 64W...54S 54W...51S 44W...51S 32W...A 120KT MAXIMUM AT
54S 20W...AND 57S 11W. THE NORTHERN POLAR HAS IT ENTRANCE AT 45S
120W...THEN ALONG 46S 113W...A 150KT MAXIMUM AT 45S 102W...EXITING
AT 44S 88W. IT REFORMS AT 46S 66W...THEN ALONG 47S 57W...A 134KT
MAXIMUM AT 48S 42W...46S 36W...37S 34W...35S 29W...43S 23W...47S
24W...AND 54S 05W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 26S
86W...CROSSING 31S 74W...EXITING AT 37S 64W. IT REFORMS AT 21S
45W...THEN ALONG 27S 33W...A 131KT MAXIMUM AT 35S 24W...41S
19W...EXITING AT 45S 11W. THE SUBEQUATORIAL JET TO THE NORTH HAS A
FINGER WITH ENTRANCE AT 14S 106W...AND EXITING AT 13S 90W. ANOTHER
FINGER TO THE NORTH LIES ALONG 04S 110W...08S 100W...EXITING AT
06S 88W.

AT 500 HPA...IN A TIGHT BELT OF MID LATITUDE WESTERLIES...A
PROGRESSIVE SHORT WAVE TROUGHS ARE STREAMING ACROSS THE SOUTHEAST
PACIFIC...WITH ONE ALONG 109W AND TO THE SOUTH OF 47S...WHILE
ANOTHER EXTENDS ALONG 95W TO 40S. ON THE NORTHERN STREAM...A
TROUGH EXTENDS TO THE NORTHWEST FROM CENTRAL CHILE TO 13S 100W.
THIS IS FOCUSING SHORT WAVE ENERGY ACROSS CENTRAL CHILE TO CENTRAL
ARGENTINA...WHERE IT PROVIDES DYNAMICAL SUPPORT TO SCATTERED DEEP
CONVECTION. FARTHER EAST...OVER THE SOUTH ATLANTIC...A SHORT WAVE
TROUGH ON THE SOUTHERN STREAM BOUNDS BETWEEN 50W-10W AND TO THE
SOUTH OF 47S...WHILE A SHORT WAVE TROUGH TO THE NORTH EXTENDS FROM
A CLOSED LOW AT 42S 29W...ALONG 34S 30W...TO 29S 35W.

AT LOW LEVELS...BROAD TROUGH ON THE SOUTHERN STREAM DOMINATES THE
SOUTHEAST PACIFIC...WITH A POLAR FRONT EXTENDING FROM AN OCCLUDED
964 HPA LOW AT 63S 90W...THEN ALONG A 974 HPA LOW AT 63S 76W...57S
77W...55S 83W...A 990 HPA LOW AT 53S 92W...TO 47S 95W. AN
ELONGATED FRONT TO THE NORTH EXTENDS FROM A 982 HPA LOW AT 56S
26W...53S 31W...A 986HPA LOW AT 51S 36W...46S 38W...45S 43W...A
1006 HPA LOW AT 45S 48W...41S 56W...LA PAMPA-PATAGONIA IN
ARGENTINA...A 1008 HPA LOW AT 47S 69W...42S 72W...42S 77W...46S
84W...A 1004 HPA LOW AT 47S 91W...43S 97W...AND 41S 104W. A POLAR
1015 HPA HIGH AT 45S 61W ANCHORS A RIDGE OFF THE COAST OF
PATAGONIA...WHILE A 1023 HPA HIGH AT 33S 93W ANCHORS A RIDGE ON
THE NORTHERN STREAM OVER THE EASTERN PACIFIC. OVER THE
ATLANTIC...ON THE NORTHERN STREAM...A 1021 HPA HIGH AT 29S 42W
ANCHORS A RIDGE OVER THE WESTERN ATLANTIC AND OFF THE SOUTH COAST
OF BRASIL. EAST AND NORTH OF THE LATTER...A POLAR FRONT EXTENDS
FROM A 976 HPA LOW AT 40S 30W...A 998 HPA LOW AT 46S 29W...39S
21W...33S 23W...29S 26W...A 1014 HPA LOW AT 27S 28W...22S
31W...21S 35W...TO SOUTHERN MINAS GERAIS. AN OLD BOUNDARY TO THE
NORTH...MEANWHILE...LIES ALONG A 1002 HPA LOW AT 44S 18W...36S
16W...32S 19W...A 1014 HPA LOW AT 27S 25W...21S 30W...19S 33W...TO
ESPIRITO SANTO IN BRASIL.

OVIEDO...SHN (ARGENTINA)
POMIER...SENAMHI (BOLIVIA)
RIVAS...SENAMHI (PERU)
GALVEZ...WPC (USA)