Prognostic Meteorological Discussion
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000
FXSA20 KWBC 201308
PMDSA

SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
908 AM EDT WED SEP 20 2017

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

SYNOPSIS (VALID FROM SEP 20 AT 0000 UTC): A 200 HPA HIGH OVER
CENTRAL BOLIVIA EXTENDS A RIDGE TO THE NORTHWEST ACROSS PERU INTO
THE EASTERN TROPICAL PACIFIC. THE HIGH ALSO RIDGES TO THE
SOUTHEAST ACROSS PARAGUAY-URUGUAY TO THE WESTERN ATLANTIC. A
TROUGH TO THE EAST EXTENDS ALONG 40S 37W...30S 40W...SAO PAULO TO
10S 55W. THE RIDGE ALOFT IS VENTING ISOLATED CONVECTION OVER
PARA-AMAZONAS IN BRASIL.

THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH ENTRANCE AT
57S 115W...THEN ALONG 63S 90W...65S 70W...62S 50W...59S 44W...54S
36W...A 143KT MAXIMUM AT 52S 31W...50S 19W...A 156KT MAXIMUM AT
51S 07W. THE NORTHERN POLAR LIES ALONG 34S 120W...35S 115W...A
122KT MAXIMUM AT 38S 108W...41S 100W...EXITING AT 41S 91W. IT
REFORMS AT 39S 73W...THEN ALONG 45S 64W...48S 55W...48S 44W...45S
35W...46S 24W...46S 10W...AND 47S 01W. THE SUBTROPICAL JET HAS ITS
ENTRANCE AT 18S 94W...THEN ALONG 20S 86W...25S 80W...A 134KT
MAXIMUM AT 30S 75W...A 171KT MAXIMUM AT 35S 70W...A 140KT MAXIMUM
AT 40S 59W...39S 50W...34S 47W...29S 47W...23S 50W...19S
52W...EXITING AT 15S 51W. IT REFORMS AT 26S 34W...THEN ALONG 28S
25W...25S 14W...23S 08W...AND 25S 00W.

AT 500 HPA...A LOW AMPLITUDE RIDGE EXTENDS TO THE SOUTHWEST FROM
25S 100W...ALONG 40S 90W...TO 50S 85W. THIS IS INDUCING THE
NORTHWARD AMPLIFICATION OF A TROUGH ALONG THE COAST OF CHILE. THE
TROUGH IS SHEARING SHORT WAVE ENERGY ACROSS THE SOUTHERN/CENTRAL
ANDES INTO ARGENTINA. THIS PROVIDES SUPPORT TO CONVECTION OVER THE
BUENOS AIRES PROVINCE-LA PAMPA IN ARGENTINA. A NORTH-TO-SOUTH
RIDGE TO THE EAST EXTENDS FROM SOUTHERN BRASIL TO THE WEDDELL SEA.

THE SURFACE ANALYSIS SHOWS A 986 HPA OCCLUDED LOW AT 54S 98W
EXTENDING A FRONT ALONG A 984 HPA LOW AT 55S 93W...51S 89W...A 998
HPA LOW AT 48S 92W...43S 93W...A 1012 HPA LOW AT 42S 97W. A 1002
HPA OCCLUDED LOW CENTERS AT 54S 74W. A 1031 HPA HIGH CENTERS AT
30S 92W...AND EXTENDS A RIDGE INTO LOS LAGOS/AYSEN IN CHILE. A
1006 HPA OCCLUDE LOW AT 48S 63W EXTENDS A FRONT ALONG A 1005 HPA
TRIPLE POINT LOW AT 48S 60W...42S 61W...38S 70W...A 1022 HPA LOW
AT 36S 75W...26S 76W...18S 84W.A 1025 HPA HIGH CENTERS AT 39S 43W.
A FRONT EXTENDS ALONG A 1018 HPA LOW AT 42S 24W...38S 29W...A 1026
HPA LOW AT 36S 33W...32S 38W...PORTO ALEGRE IN BRASIL AT 30S 50W.

GONZALEZ...DMC (CHILE)
VANNUCCI...SMN (ARGENTINA)
DAVISON/GALVEZ...WPC (USA)
$$





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