SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
959 AM EDT WED MAY 23 2018

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

SYNOPSIS (VALID FROM MAY 23 AT 0000 UTC): AT 200 HPA...FLOW OVER
NORTHERN SOUTH AMERICA DIVERGES BETWEEN A WANING CELL OF THE
SUBTROPICAL RIDGE OVER NORTHERN BRASIL-PERU AND THE SUBEQUATORIAL
RIDGE TO THE NORTH. THE SUBTROPICAL RIDGE LIES JUST SOUTH OF THE
EQUATOR ACROSS NORTHERN BRASIL-PERU...WHILE THE SUBEQUATORIAL
RIDGE EXTENDS ALONG 04N TO THE GUIANAS-VENEZUELA. AS THE FLOW
DIVERGES BETWEEN THESE RIDGES...THIS IS VENTING DIURNAL CONVECTION
ACROSS NORTHERN BRASIL/EQUATORIAL SOUTH AMERICA.

THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR JET FORMING AT
43S 111W ALONG 47S 104W...A 122KT MAXIMA AT 52S 100W...54S
89W...51S 76W...48S 67W...EXITING AT 44S 59W. THE NORTHERN POLAR
EXTENDS ALONG 34S 120W...30S 117W...28S 112W...29S 107W...EXITING
AT 31S 102W. IT REFORMS AT 41S 68W ALONG 36S 59W...31S 55W...30S
49W...A 120KT MAXIMA AT 31S 45W...32S 37W...34S 30W...35S 24W. THE
SUBTROPICAL JET FORMS AT 25S 117W ALONG 26S 107W...28S 100W...32S
89W...33S 81W...32S 70W...29S 61W...26S 55W...24S 48W...25S
41W...28S 34W...30S 24W...31S 17W. THE SUBEQUATORIAL JET EXTENDS
ALONG 20S 120W...19S 113W...21S 102W...A 120KT MAXIMA AT 24S
94W...26S 88W...26S 81W...25S 74W...22S 65W...16S 55W. IT REFORMS
AT 16S 51W ALONG 17S 46W...20S 40W...24S 34W...EXITING AT 25S 24W.

AT 500 HPA...LOW AMPLITUDE RIDGE DOMINATES THE FLOW OVER THE
EASTERN PACIFIC TO THE NORTH OF 50S. THIS IS STEERING SHORT WAVE
PERTURBATIONS ACROSS THE DRAKE PASSAGE/SOUTHERN PORTIONS OF CHILE
TO PATAGONIA IN ARGENTINA. THESE THEN FEED INTO A HIGHER AMPLITUDE
TROUGH TO THE EAST... EXTENDING BETWEEN 60S-35W AND TO THE SOUTH
OF 45S. THIS IS PHASING WITH A NORTHERN STREAM TROUGH THAT EXTENDS
FROM 40S 50W TO THE SOUTHERN STATES OF BRASIL/PARAGUAY.

THE SURFACE ANALYSIS SHOWS A 1002 HPA LOW AT 57S 65W A WEAK FRONT
EXTENDS TO THE NORTH ALONG 48S 55W...A 1010 HPA LOW AT 50S
64W...48S 64W...49S 68W...A 1010 HPA LOW AT 51S 69W...48S
70W...48S 75W. ANOTHER FRONT EXTENDS ALONG 41S 77W...45S 78W... A
1010 HPA LOW AT 46S 81W...45S 83W...45S 88W...A 1002 HPA LOW AT
44S 93W. A 1021HPA HIGH CENTERS AT 41S 73W AND EXTENDS A RIDGE
INTO ANOTHER 1021 HPA HIGH AT 34S 81W...AND ACROSS ARGENTINA INTO
A 1021 HPA HIGH AT 30S 58W...AND INTO ANOTHER 1021 HPA HIGH AT 21S
69W. A 1002 HPA OCCLUDED LOW CENTERS AT 41S 48W AND EXTENDS A
FRONT INTO A 1006 HPA TRIPLE POINT LOW AT 42S 49W...43S 46S...A
1006 HPA LOW AT 38S 42W...35S 42W...31S 44W....27S 49W. A FRONT
EXTENDS ALONG A 1010 HPA LOW AT 37S 38W...32S 39W...INTO 23S 47W.
ANOTHER FRONT EXTENDS ALONG 24S 25W...21S 33W...20S 41W. A SHEAR
LINE EXTENDS ALONG 24S 23W...17S 33W...10S 44W. SCATTERED SHOWERS
WERE OCCURRING IN EASTERN BRASIL.

BALBINO...INMET (BRASIL)
DIAZ...INUMET (URUGUAY)
DAVISON/GALVEZ...WPC (USA)