Prognostic Meteorological Discussion
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
959 AM EDT WED APR 25 2018

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

SYNOPSIS (VALID FROM APR 25 AT 0000 UTC): AT 200 HPA...A NORTHERN
HEMISPHERE HIGH NEAR 04N 40W EXTENDS A RIDGE WEST ACROSS THE
GUIANAS TO SOUTHERN VENEZUELA. ANOTHER RIDGE TO THE
SOUTH...MEANWHILE...EXTENDS FROM THE CENTRAL TROPICAL ATLANTIC TO
THE NORTHERN STATES OF BRASIL. AN AREA OF UPPER DIFFLUENCE OVER
EQUATORIAL SOUTH AMERICA SEPARATES THESE RIDGES. THIS IS VENTING
DEEP CONVECTION ACROSS THE GUIANAS-PARA-AMAZONAS/RORAIMA IN
BRASIL-PERU-COLOMBIA AND ECUADOR. FARTHER SOUTH...A TROUGH EXTENDS
ALONG 24S 30W...20S 40W TO SOUTHERN MINAS GERAIS. THIS IS
ENHANCING COASTAL CONVECTION BETWEEN BAHIA AND ESPIRITO SANTO.

AT 250 HPA...THE SOUTHERN POLAR EXTENDS ALONG 73S 73W...62S
86W...53S 97W...EXITING AT 48S 98W. IT REFORMS AT 42S 94W...THEN
ACROSS 50S 76W...53S 68W...EXITING AT 53S 46W. IT REFORMS AT 54S
39W...THEN ALONG 51S 24W...AND A 140KT MAXIMUM AT 53S 08W. THE
NORTHERN POLAR HAS ITS ENTRANCE AT 54S 103W...THEN ALONG 41S
102W...39S 93W...EXITING AT 42S 73W. IT REFORMS AT 42S
62W...CROSSING A 122KT MAXIMUM AT 44S 49W...42S 34W...43S
26W...AND 48S 10W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 35S
108W...THEN ALONG 37S 92W...EXITING AT 37S 80W. IT REFORMS AT 21S
82W...CROSSING 31S 72W...37S 57W...36S 46W...EXITING AT 33S 41W.
AT 200 HPA...THE SUBEQUATORIAL JET EXTENDS ALONG 14S 120W...20S
109W...15S 99W...EXITING AT 10S 93W. ANOTHER BRANCH TO THE EAST
HAS ITS ENTRANCE AT 15S 36W...THEN ALONG 19S 20W...AND 19S 05W.

AT 500 HPA...BUILDING RIDGE EXTENDS TO THE SOUTH-SOUTHEAST FROM A
HIGH AT 43S 122W...ALONG 60S 105W...TO THE BELLINGSHAUSEN SEA. A
HIGH AMPLITUDE TROUGH TO THE EAST EXTENDS FROM THE ANTARCTIC
PENINSULA...ALONG 60S 80W...55S 90W...40S 100W...TO 36S 05W. THIS
IS FOCUSING SHORT WAVE ENERGY AND DEEP SUBTROPICAL MOISTURE ACROSS
THE SOUTHERN REGIONS OF CHILE. IT IS ALSO STEERING A PROGRESSIVE
SHOR WAVE TROUGH ACROSS LA PAMPA/CENTRAL PROVINCES IN ARGENTINA.
THIS PROVIDES DYNAMICAL SUPPORT TO CONVECTION OVER THE BUENOS
AIRES PROVINCE.

AT LOW LEVELS...A RIDGE OVER THE PACIFIC ANCHORS ON A 1033 HPA
HIGH AT 47S 117W. BROAD TROUGH TO THE EAST EXTENDS ACROSS THE
DRAKE PASSAGE TO THE SOUTHERN CONE OF SOUTH AMERICA. POLAR FRONT
REVOLVING AROUND THIS AXIS EXTENDS FROM AN OCCLUDED 994 HPA LOW AT
60S 57W...ALONG 61S 61W...A 994 HPA LOW AT 61S 52W...58S 49W...55S
58W...A 998 HPA LOW AT 57S 67W...TIERRA DEL FUEGO...41S 79W...A
998 HPA LOW AT 47S 84W...TO 42S 89W. THIS IS PHASING WITH A FRONT
TO THE NORTH THAT EXTENDS ALONG A 998 HPA LOW AT 41S 87W...40S
87W...39S 89W...A 1004 HPA LOW AT 37S 93W...34S 95W...AND 32S
105W. A RIDGE TO THE NORTH CENTERS ON THREE 1021 HPA HIGHS...WITH
ONE AT 26S 101W...ANOTHER AT 30S 82W...AND A THIRD AT 40S 73W.
ANOTHER RIDGE OVER THE ATLANTIC CENTERS ON THREE 1025 HPA
HIGHS...WITH ONE AT 43S 56W...ANOTHER AT 42S 50W...AND A THIRD AT
43S 42W. A FRONT TO THE NORTH LIES ALONG A 994 HPA LOW AT 49S
09W...45S 17W...A 1006 HPA LOW AT 43S 21W...41S 26W...40S 30W...A
1018 HPA LOW AT 39S 33W...37S 36W...35S 45W... SOUTHERN URUGUAY TO
A 1010 HPA LOW AT 33S 65W. THIS TRIGGERED SCATTERED CONVECTION
ACROSS THE BUENOS AIRES PROVINCE. FARTHER NORTH...A RIDGE ON THE
NORTHERN STREAM CENTERS ON A 1029 HPA HIGH AT 31S 21W. AN OLD
FRONT BOUNDS THE NORTHERN FRINGES OF THIS RIDGE...EXTENDING ALONG
18S 10W...TO 19S 34W.

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





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