Prognostic Meteorological Discussion
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
955 AM EDT THU APR 28 2016

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

SYNOPSIS (VALID FROM APR 28 AT 0000 UTC): AT 200 HPA...HIGH
AMPLITUDE POLAR TROUGH DOMINATES THE WESTERN ATLANTIC AND MID
SECTIONS OF SOUTH AMERICA. THE TROUGH PRESSES AGAINST A WANING
CELL OF THE SUBTROPICAL RIDGE...WITH AXIS CONFINING TO CONTINENTAL
AREA TO THE NORTH OF 10S. UNDER INFLUENCE OF THE POLAR
TROUGH...CONVECTION IS SURGING ACROSS EQUATORIAL SOUTH AMERICA
WHILE CLUSTERING OVER NORTHERN PARA/RORAIMA-AMAZONAS IN BRASIL TO
NORTHERN PERU/EASTERN ECUADOR AND SOUTHERN COLOMBIA. HYDRO
ESTIMATORS SHOW RAIN RATES OF 20-30MM PER HOUR...WITH POTENTIAL
FOR HEAVY RAINFALL AMOUNTS TO AFFECT ECUADOR-COLOMBIA-VENEZUELA.

AT 250 HPA THE SOUTHERN POLAR LIES ALONG 66S 117W...A 150KT
MAXIMUM AT 67S 107W...67S 96W...66S 79W...58S 68W...50S
64W...EXITING AT 49S 58W. IT HAS A FINGER TO THE NORTH WITH
ENTRANCE AT 41S 54W...THEN ALONG 37S 54W...EXITING AT 33S 52W. THE
NORTHERN POLAR HAS ITS ENTRANCE AT 38S 122W...THEN ALONG 31S
117W...A 146KT MAXIMUM AT 33S 106W...A 162KE MAXIMUM AT 36S
97W...EXITING AT 39S 86W. IT REFORMS AT 35S 63W...CROSSING 30S
57W...28S 49W...35S 40W...A 151KT MAXIMUM AT 44S 33W...A 160KT
MAXIMUM AT 48S 23W...A 181KT MAXIMUM AT 49S 13W...AND 179KT
MAXIMUM AT 46S 03W. THE SUBTROPICAL JET LIES ALONG 22S 120W...A
138KT MAXIMUM AT 32S 97W...33S 85W...A 125KT MAXIMUM AT 32S
76W...27S 67W...EXITING AT 23S 59W. THE SUBTROPICAL JET REFORMS AT
21S 54W...THEN ALONG 23S 46W...A 134KT MAXIMUM AT 37S 34W...45S
26W...AND A 153KT MAXIMUM AT 43S 10W.

AT 500 HPA...BROAD TROUGH DOMINATES THE FLOW OVER THE EASTERN
PACIFIC...ENVELOPING AREA BETWEEN 125W-85W AND TO THE NORTH OF
54S. IN A SPLIT FLOW PATTERN A LOW AMPLITUDE RIDGE LIES TO THE
SOUTH...EXTENDING INTO THE POLAR ICE CAP AND THE BELLINGSHAUSEN
SEA. ANOTHER RIDGE EXTENDS ALONG THE COAST OF CHILE. A SHORT WAVE
TROUGH IN THE SOUTHERN STREAM EXTENDS ACROSS THE WEDDELL SEA TO
SOUTHERN PATAGONIA IN ARGENTINA. THIS IS INTERACTING WITH A LONG
WAVE TROUGH IN THE NORTHERN STREAM THAT EXTENDS TO THE NORTHWEST
FROM A CLOSED LOW AT 43S 48W... SOUTHERN STATES OF BRASIL-PARAGUAY
TO BOLIVIA.

AT LOW LEVELS...BROAD TROUGH DOMINATES THE FLOW ACROSS THE EASTERN
PACIFIC...WITH AXIS ANCHORING ON A DEEP 990 HPA LOW AT 42S 102W. A
RIDGE TO THE EAST EXTENDS NORTH TO SOUTH ALONG 80W...WHILE
ANCHORING ON A 1029 HPA HIGH AT 55S 81W AND A 1017 HPA HIGH AT 29S
82W. EAST OF THIS RIDGE...A TROUGH ON THE SOUTHERN STREAM EXTENDS
FROM THE WEDDELL SEA TO CENTRAL PATAGONIA IN ARGENTINA...WHILE
ORIGINATING ON AN OCCLUDING 978 HPA LOW AT 67S 36W. A TROUGH ON
THE NORTHERN STREAM ANCHORS ON A 998 HPA LOW AT 41S 46W...WITH A
POLAR FRONT THAT EXTENDS ALONG A 1002 HPA LOW AT 40S 30W...A 1010
HPA LOW AT 26S 40W...RIO DE JANEIRO/NORTHERN SAO PAULO...TOCANTINS
GOIAS/SOUTHERN PARA TO AMAZONAS IN BRASIL-CENTRAL PERU. THIS
SUSTAINS ORGANIZED DEEP CONVECTION ACROSS NORTHWEST SOUTH AMERICA.
A POLAR RIDGE TO THE SOUTH CENTERS ON A 1025 HPA HIGH AT 30S 64W.

AYALA...DINAC (PARAGUAY)
ENRIQUEZ...DGAC (ECUADOR)
DAVISON/GALVEZ...WPC (USA)
$$





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