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South American Synoptic Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1506Z Dec 11, 2017)
 
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1006 AM EST MON DEC 11 2017

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

SYNOPSIS (VALID FROM DEC 11 AT 0000 UTC): AT 200 HPA...A ROBUST
SUBTROPICAL RIDGE/BOLIVIAN HIGH CENTERS OVER MATO GROSSO IN
BRASIL. THE HIGH IS VENTILATING CONVECTION ACROSS MOST OF TROPICAL
SOUTH AMERICA...BUT ESPECIALLY IN EASTERN BRASIL...WHERE
DEEP-LAYER INSTABILITY REMAINS IN PLACE. STRONGEST CONVECTION IS
ORGANIZING IN ASSOCIATION WITH LOW-LEVEL TROUGHS ACROSS
CENTRAL/EASTERN BRASIL...AND INTO MATO GROSSO DO SUL/PANTANAL.
ALSO...SHORT-LIVED DIURNAL CONVECTION IS OCCURRING IN THE PERUVIAN
AND BOLIVIAN ANDES.

THE 250 HPA JET ANALYSIS SHOWS THE SOUTHERN POLAR JET FORMING AT
49S 105W ALONG 55S 89W...A 176KT MAXIMA AT 55S 70W...53S 57W...38S
49W...EXITING AT 37S 44W. IT REFORMS AT 40S 42W...EXITING AT 49S
37W. THE NORTHERN POLAR FORMS AT 39S 118W ALONG 43S 101W...51S
77W...48S 65W...37S 59W...EXITING AT 30S 50W. THE SUBTROPICAL JET
FORMS AT 15S 113W...18S 108W...23S 102W...EXITING AT 26S 79W. IT
REFORMS AT 24S 54W ALONG 23S 50W...24S 39W...EXITING AT 26S 36W. A
SUBEQUATORIAL JET EXTENDS ALONG 03S 110W...EXITING AT 05S 92W.

AT 500 HPA...A BROAD SOUTHERN STREAM LOW CENTERS AT 68S 08W OVER
THE BELLINGSHAUSEN SEA. THIS LOW EXTENDS AN AXIS TO THE EAST INTO
THE DRAKE PASSAGE. TO THE NORTH...A TIGHT BELT OF WESTERLIES
EXTENDS ALONG 50S-55S AND IS FAVORING WINDY CONDITIONS IN TIERRA
DEL FUEGO. TO THE EAST...OVER THE ATLANTIC...A LARGE AND DEEP
TROUGH EXTENDS A MERIDIONAL AXIS ALONG 45W-50W NORTH INTO 20S. IN
THE NORTHERN STREAM...A RIDGE EXTENDS FROM A HIGH OFF THE COAST OF
CENTRAL PERU INTO MOST OF CHILE AND WESTERN ARGENTINA SOUTH INTO
48S. THIS IS SUSTAINING WARM CONDITIONS IN MOST OF
CHILE...ARGENTINA...PARAGUAY AND URUGUAY.

AT LOW LEVELS...A 962 HPA LOW CENTERS AT 61S 73W AND EXTENDS A
FRONT INTO A 986 HPA TRIPLE POINT LOW AT 58S 60W...53S 61W...51S
76W...46S 93W. A 1025 HPA HIGH CENTERS AT 39S 89W. A 1000 HPA LOW
CENTERS AT 37S 73W. TO THE EAST...A 1017 HPA POLAR HIGH CENTERS AT
41S 63W. A 988 HPA OCCLUDED LOW AT 49S 44W EXTENDS A FRONT ALONG A
990 HPA LOW AT 51S 43W...45S 38W...39S 42W...A 998 HPA LOW AT 37S
44W...31S 47W...30S 54W...A 1006 HPA LOW AT 32S 57W...32S 67W. THE
SOUTH ATLANTIC CONVERGENCE ZONE HAS FORMED AND EXTENDS FROM 27S
34W ALONG 20S 34W...17S 40W...A 1008 HPA LOW AT 15S 60W...14S 69W.
STRONG CONVECTION WAS OCCURRING ALONG AND TO THE NORTH OF THE
SACZ.

OVIEDO...SHN (ARGENTINA)
POMIER...SENAMHI (BOLIVIA)
RIVAS...SENAMHI (PERU)
GALVEZ...WPC (USA)