SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
905 AM EDT MON MAY 13 2013

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

SYNOPSIS (VALID FROM 00 UTC MAY 13): ANALYSIS AT 200 HPA SHOWS A
PERTURBED WESTERLY FLOW PATTERN ACROSS NORTHERN PORTIONS OF THE
DOMAIN...WITH A LOW AMPLITUDE RIDGE OVER BRASIL SEPARATING TWO
TROUGHS...ONE OVER THE EASTERN TROPICAL PACIFIC AND THE OTHER OVER
THE WESTERN ATLANTIC/NORTHEAST BRASIL. AS THE TRADE WINDS
SUBSIDENCE CAP INTENSIFIES OVER THE CONTINENT...DRY AND STABLE
CONDITIONS PREVAIL OVER CENTRAL TO EASTERN BRASIL...WHILE ISOLATED
CONVECTION WAS BUILDING ACROSS SOUTHEAST BRASIL-PARAGUAY-BOLIVIA
TO PERU. MOST ACTIVE CONVECTION IS BUILDING OVER EQUATORIAL
PORTIONS OF SOUTH AMERICA INTO THE GUIANAS-VENEZUELA.

THE JET ANALYSIS AT 250 HPA SHOWS THE SOUTHERN POLAR WITH AXIS
ALONG A 124KT MAXIMUM AT 66S 97W...57S 90W...50S 85W...A 124KT
MAXIMUM AT 46S 72W...45S 65W...47S 51W...48S 46W...SOUTH GEORGIA
ISLANDS...52S 20W...AND 52S 07W. THE NORTHERN POLAR HAS A FINGER
WITH ENTRANCE AT 39S 97W...ALONG 37S 89W...EXITING AT 34S 81W. IT
REFORMS AT 37S 70W...ALONG 38S 59W...41S 49W...45S 41W...EXITING
AT 48S 29W. THE SUBTROPICAL JET HAS ITS ENTRANCE AT 26S
93W...ALONG 25S 82W...24S 73W...EXITING AT 24S 67W. IT HAS A
FINGER TO THE NORTH WITH ENTRANCE AT 18S 68W...ALONG 21S
62W...EXITING AT 23S 53W. THE JET REFORMS AT 30S 51W...ALONG 38S
40W...40S 28W...35S 16W...EXITING AT 28S 10W.

AT 500 HPA...A HIGH AMPLITUDE LONG WAVE PATTERN PREVAILS...WITH A
LONG WAVE RIDGE OVER THE EASTERN PACIFIC EXTENDING NORTH TO SOUTH
ALONG 105W-110W. DOWNSTREAM FROM THIS AXIS...A BROAD TROUGH IS
INITIALIZED BETWEEN 90W-45W AND TO THE SOUTH OF 25S. THE TROUGH
CENTERS ON A CLOSED LOW OVER THE DRAKE PASSAGE. THIS IS FOCUSING
SHORT WAVE ENERGY ACROSS SOUTHERN CHILE TO PATAGONIA IN ARGENTINA.
WEAKER PERTURBATIONS TO THE NORTH ARE STREAMING ACROSS
CENTRAL/NORTHERN CHILE TO ARGENTINA.

THE SURFACE ANALYSIS SHOWS A RIDGE ON THE NORTHERN STREAM OVER THE
FAR EASTERN PACIFIC THAT CENTERS ON A 1029 HPA HIGH AT 41S 92W. A
BROAD TROUGH LIES TO THE EAST...AS IT EXTENDS ACROSS THE DRAKE
PASSAGE TO THE SOUTHERN CONE...WHILE CENTERING IN A DEEP 966 HPA
LOW AT 58S 64W. POLAR FRONTS REVOLVE AROUND THIS AXIS...WITH ONE
ALONG A 992 HPA LOW AT 47S 61W...NORTHERN PATAGONIA...42S 78W...A
1020 HPA LOW AT 45S 84W...AND 45S 91W. A CLIPPER LOW
FOLLOWS...WITH A FRONT ALONG A 996 HPA LOW AT 53S 79W...51S
84W...AND 53S 91W. FARTHER NORTH...AN OLD FRONT LIES ALONG 38S
33W...37S 39W...A 1014 HPA LOW AT 37S 44W...SOUTHERN BRASIL TO
PARAGUAY. ORGANIZED DEEP CONVECTION IS BUILDING TO THE NORTH OVER
PARAGUAY INTO SOUTHERN BRASIL. A RIDGE TO THE SOUTH CENTERS ON A
1017 HPA HIGH AT 35S 54W.

MAQUEDA...DINAC (PARAGUAY)
SILVA DE SOUZA...INMET (BRASIL)
DAVISON...WPC (USA)
GALVEZ...WPC (USA)