Prognostic Meteorological Discussion
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
856 AM EDT TUE MAY 30 2017

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

SYNOPSIS (VALID FROM MAY 30 AT 0000 UTC): THE 200 HPA ANALYSIS
SHOWS A BROAD CELL OF THE SUBTROPICAL RIDGE OVER THE CONTINENT
WITH AXIS ENVELOPING AREA NORTH OF 25S. THE RIDGE ANCHORS ON A
CLOSED HIGH NEAR 10S 35W. A CELL OF THE SUBEQUATORIAL RIDGE TO THE
NORTH LIES WEST ACROSS COLOMBIA-VENEZUELA-THE GUIANAS. UPPER FLOW
DIVERGES BETWEEN THESE RIDGE...RESULTING IN AN AREA OF ENHANCED
CONVECTION ACROSS EQUATORIAL SOUTH AMERICA. MOST ACTIVE IS
CLUSTERING OVER BRASIL NORTH OF 05S.

THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR WITH AXIS ALONG
41S 120W...43S 110W...EXITING AT 46S 98W. IT REFORMS AT 46S
89W...THEN ALONG A 135KT MAXIMUM A 49S 80W...53S 72W...EXITING AT
57S 57W. IT REFORMS AT 43S 45W...THEN ALONG 44S 31W...43S 19W...A
129KT MAXIMUM AT 44S 09W...AND 46S 01W. THE NORTHERN POLAR LIES
ALONG 37S 120W...40S 109W...40S 96W...45S 82W...EXITING AT 48S
71W. IT REFORMS BETWEEN 48S 59W AND 40S 60W. IT REFORMS AT 37S
54W...THEN ALONG 37S 46W...39S 34W...39S 24W...EXITING AT 38S 14W.
THE SUBTROPICAL JET LIES ALONG 33S 110W...36S 99W...A 129KT
MAXIMUM AT 38S 94W...37S 82W...31S 78W...EXITING AT 26S 78W. IT
REFORMS AT 27S 71W...THEN ALONG 31S 62W...34S 51W...EXITING AT 33S
36W. ANOTHER BRANCH OF THE SUBTROPICAL HAS ITS ENTRANCE AT 15S
78W...THEN ALONG 20S 72W...A 130KT MAXIMUM AT 23S 67W...27S
58W...A 135KT MAXIMUM AT 28S 46W...27S 39W...EXITING AT 25S 32W.

AT 500 HPA...BROAD TROUGH DOMINATES THE FLOW OVER THE SOUTHEAST
PACIFIC...ENVELOPING AREA TO THE SOUTH OF 30S. THIS IS FOCUSING
SHORT WAVE VORTICES ACROSS SOUTHERN CHILE/DRAKE PASSAGE. IT IS
ALSO PRESSING AGAINST A SKEWED RIDGE TO THE NORTH THAT EXTENDS
FROM 24S 100W...ALONG 37S 80W...PATAGONIA IN ARGENTINA...THE
MALVINAS/ FALKLAND ISLANDS TO THE ANTARCTIC PENINSULA/WEDDELL SEA.
THE RIDGE UNDERCUTS A TROUGH TO THE NORTH...WITH THE LATTER
MEANDERING OFF THE CENTRAL/NORTHERN COAST OF CHILE WHILE ANCHORING
ON A CLOSED LOW WEST OF LA SERENA. THE TROUGH IS FOCUSING SHORT
WAVE ENERGY ACROSS NORTHERN CHILE/SOUTHERN BOLIVIA INTO THE
NORTHERN PROVINCES IN ARGENTINA. ALSO ON THE NORTHERN
STREAM...OVER THE ATLANTIC...A SHORT WAVE TROUGH MEANDERS OFF THE
COAST OF ARGENTINA WHILE CENTERING ON A LOW NEAR 44S 56W.

AT LOW LEVELS THE SURFACE ANALYSIS SHOWS A BROAD TROUGH OVER THE
SOUTHEAST PACIFIC WITH POLAR FRONTS REVOLVING AROUND THIS AXIS.
ONE EXTENDS ALONG A 990 HPA LOW AT 63S 68W...60S 67W...A 994 HPA
LOW AT 58S 70W...55S 67W...A 1014 HPA LOW AT 51S 70W...48S
69W...45S 73W...45S 80W...A 1010 HPA LOW AT 44S 89W...40S 87W...A
1014 HPA LOW AT 39S 91W...34S 93W...31S 99W...AND 28S 105W. OVER
THE ATLANTIC...AN ELONGATED FRONT LIES ALONG A 1018 HPA LOW AT 43S
47W...38S 51W...BUENOS AIRES PROVINCE TO CENTRAL CUYO IN
ARGENTINA. POLAR RIDGE TO THE SOUTH ANCHORS ON A 1029 HPA HIGH AT
40S 68W. FARTHER NORTH...AN OCCLUDED 1010 HPA LOW T 33S 42W
EXTENDS A FRONT ALONG A 1016 HPA LOW AT 34S 37W...32S 37W...A 1014
HPA LOW AT 31S 40W...28S 43W...A 1018 HPA LOW AT 28S 48W...26S
50W...A 1020 HPA LOW AT 27S 54W...URUGUAY TO SOUTHEAST BOLIVIA.
THIS FAVORS SCATTERED RAINFALL ACROSS PARAGUAY/NORTHERN ARGENTINA
WITH EMBEDDED DEEP CONVECTION OVER MISIONES IN ARGENTINA. A
TRAILING FRONT ON THE NORTHERN STREAM EXTENDS FROM A 1022 HPA LOW
AT 29S 72W...THEN ALONG 26S 72W...23S 78W...22S 83W...TO 23S 90W.

ABDEMUR...FAA (ARGENTINA)
ESPINOLA...DNM (PARAGUAY)
DAVISON...WPC (USA)
$$





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