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South American Synoptic Discussion
 
(Latest Discussion - Issued 1256Z May 24, 2017)
 
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
856 AM EDT WED MAY 24 2017

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

SYNOPSIS (VALID FROM MAY 24 AT 0000 UTC): AT 200 HPA...A HIGH OVER
NORTHERN AMAZONAS IN BRASIL ANCHORS A BROAD CELL OF THE
SUBTROPICAL RIDGE OVER THE CONTINENT. THE RIDGE EXTENDS FROM
SOUTHERN COLOMBIA/NORTHERN PERU...ACROSS MATO GROSSO-SAO PAULO IN
BRASIL INTO THE WESTERN ATLANTIC ALONG 40S 40W.
THIS...IN-TURN...FAVORS THE NORTHWARD AMPLIFICATION OF A TROUGH TO
THE EAST ALONG 30S 28W...20S 32W...10S 37W...TO THE AMAZON RIVER
DELTA REGION. THE RIDGE ALOFT IS VENTING DIURNAL CONVECTION ACROSS
CENTRAL/WESTERN BRASIL-PERU...BOLIVIA AND ECUADOR. THE
TROUGH...MEANWHILE...WAS ENHANCING COASTAL CONVECTION ACROSS
NORTHEAST BRASIL.

AT 250 HPA...THE SOUTHERN POLAR SPLITS IN TWO BRANCHES...WITH THE
SOUTHERNMOST EXTENDING ALONG 67S 115W...A 149KT MAXIMUM AT 65S
100W...62S 85W...EXITING AT 54S 66W. THE NORTHERNMOST EXTENDS
ALONG A 166KT MAXIMUM AT 64S 120W...A 160KT MAXIMUM A 62S 101W...A
134KT MAXIMUM AT 58S 90W...EXITING AT 50S 83W. IT REFORMS AT 43S
63W... HEN ALONG 48S 50W...50S 34W...54S 19W...AND 61S 14W. THE
NORTHERN POLAR LIES ALONG 59S 120W...59S 105W...47S 87W...42S
82W...34S 86W...EXITING AT 30S 87W. A BRANCH TO THE NORTH HAS ITS
ENTRANCE AT 47S 108W...THEN ALONG 39S 99W...25S 89W...A 126KT
MAXIMUM AT 28S 80W...A 141KT MAXIMUM AT 33S 70W...39S 59W...43S
42W...AND 52S 09W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 22S
98W...THEN ALONG 18S 85W...A 138KT MAXIMUM AT 23S 67W...28S
58W...A 134KT AT 31S 53W...A 135KT MAXIMUM AT 34S 47W...31S
39W...EXITING AT 25S 34W. ANOTHER BRANCH OF THE SUBTROPICAL JET TO
THE NORTH HAS ITS ENTRANCE AT 13S 84W...THEN ALONG 17S 72W...22S
58W...EXITING AT 21S 49W.

AT 500 HPA A LONG WAVE RIDGE OVER THE SOUTH PACIFIC EXTENDS FROM A
CLOSED HIGH AT 24S 109W...ALONG 40S 103W...50S 110W...55S
120W...TO 60S 130W. THE HIGH AMPLITUDE RIDGE IS STEERING SHORT
WAVE PERTURBATIONS ON THE SNR STREAM ACROSS THE BELLINGSHAUSEN SEA
TO THE DRAKE PASSAGE/SOUTHERN CONE OF SOUGH AMERICA. A LONG WAVE
TROUGH TO THE EAST EXTENDS FROM 60S 63W...ACROSS CENTRAL PATAGONIA
IN ARGENTINA...40S 76W...A LOW AT 34S 85W...TO 23S 95W. THE TROUGH
IS FOCUSING SHORT WAVE ENERGY ACROSS CENTRAL REGIONS OF
CHILE...WHERE IT FAVORS SCATTERED CONVECTION AND SNOWFALL ON
ELEVATIONS ABOVE 3000 METERS. IT ALSO SUSTAINS A SERIES OF
CYCLONIC VORTICES THAT ARE TRIGGERING SCATTERED CONVECTION ACROSS
PARAGUAY-SOUTHERN STATES OF BRASIL.

AT LOW LEVELS...BROAD RIDGE OVER THE EASTERN PACIFIC ANCHORS ON A
MASSIVE 1037 HPA HIGH AT 42S 102W. PROGRESSIVE POLAR FRONT TO THE
EAST EXTENDS ALONG A 970 HPA LOW AT 58S 60W...A 970 HPA LOW AT 58S
55W...56S 53W...A 978 HPA LOW AT 55S 57W...50S 63W...47S 72W...A
1010HPA LOW AT 47S 76W...42S 80W...44S 89W...A 1004 HPA LOW AT 60S
96W...AND 71S 107W. THIS FAVORS SCATTERED RAINS ACROSS TIERRA DEL
FUEGO/EXTREME SOUTHERN CHILE. ON THE NORTHERN STREAM...A 1018 HPA
LOW AT 35S 80W EXTENDS A FRONT ALONG 34S 76W...28S 80W...25S
85W...22S 93W...TO 23S 98W. FARTHER EAST...ANOTHER FRONT EXTENDS
ALONG A 1018 HPA LOW AT 41S 53W...41S 56W...A 1014 HPA LOW AT 40S
59W...36S 60W...32S 64W...TO MENDOZA IN ARGENTINA. SOUTH OF THIS
FRONT...A 1017 HPA POLAR HIGH NEAR 39S 67W ANCHORS A RIDGE ACROSS
NORTHERN PATAGONIA TO CENTRAL ARGENTINA. AN ELONGATED FRONT TO THE
NORTH LIES ALONG 42S 27W...39S 33W...38S 36W...A 1026 HPA LOW AT
36S 42W...35S 45W...A 1018 HPA LOW AT 32S 48W...31S 52W...27S
58W...TO 22S 62W. THIS FAVORS ORGANIZED CONVECTION ACROSS SOUTHERN
BRASIL-PARAGUAY. BROAD RIDGE OVER THE ATLANTIC CENTERS ON A 1035
HPA HIGH AT 36S 30W. NORTH OF THIS RIDGE...AN OLD/ELONGATED FRONT
EXTENDS ALONG 13S 16W...13S 23W...14S 30W...TO ESPIRITO SANTO.
THIS SUSTAINS A PREFRONTAL SHEAR LINE ACROSS NORTHEAST
BRASIL...WHERE IT TRIGGERS SCATTERED COASTAL CONVECTION.

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