Prognostic Meteorological Discussion
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
854 AM EDT FRI SEP 22 2017

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

SYNOPSIS (VALID FROM SEP 22 AT 0000 UTC): NORTH OVER THE
CONTINENT...AT 200 HPA...A SHORT WAVE RIDGE EXTENDS ACROSS
PARA-AMAZONAS IN BRASIL TO PERU/NORTHERN BOLIVIA. A TUTT LOW TO
THE EAST CENTERS NEAR 18S 49W. THE TUTT LOW IS ENHANCING
CONVECTIVE INSTABILITY ACROSS TOCANTINS-GOIAS-BAHIA-MINAS GERAIS
IN BRASIL...FAVORING ELEVATED CONVECTION. OTHER ACTIVITY TO THE
WEST WAS BUILDING ACROSS PARA-AMAZONAS-RONDONIA-ACRE...WITH
ACTIVITY CLUSTERING ACROSS SOUTHERN COLOMBIA-NORTHERN JUNGLE OF
PERU TO EASTERN ECUADOR.

AT 250 HPA...THE JET ANALYSIS SHOWS A FINGER OF THE SOUTHERN POLAR
WITH ENTRANCE AT 40S 109W...THEN ALONG 45S 101W...EXITING AT 47S
89W. IT REFORMS AT 52S 76W...THEN ALONG 51S 60W...50S
46W...EXITING AT 50S 34W. THE NORTHERN POLAR LIES ALONG 32S
120W...34S 110W...39S 100W...A 134KT MAXIMUM AT 42S 95W...41S
85W...EXITING AT 37S 75W. IT REFORMS AT 39S 57W...THEN ALONG A
154KT MAXIMUM AT 44S 36W...43S 29W...A 134KT MAXIMUM AT 45S
23W...48S 14W...45S 05W...EXITING AT 39S 01W. THE SUBTROPICAL JET
HAS ITS ENTRANCE AT 20S 84W...THEN ALONG 23S 74W...30S 61W...36S
50W...37S 40W...32S 30W...EXITING AT 24S 28W. A BRANCH TO THE
NORTH ROUNDS AN UPPER LEVEL TROUGH...WHILE EXTENDING FROM 22S
50W...ALONG 15S 53W...11S 49W...14S 46W...EXITING AT 19S 44W.

AT 500 HPA...A PROGRESSIVE TROUGH OVER THE SOUTH PACIFIC EXTENDS
BETWEEN 120W-105W TO 25S. AN INDUCED RIDGE TO THE EAST EXTENDS
ALONG 90W TO 50S. THIS FAVORS A TIGHT BELT OF MID/UPPER LATITUDE
EASTERLIES...WITH PROGRESSIVE SHORT WAVE PERTURBATIONS STREAMING
ACROSS THE DRAKE PASSAGE/TIERRA DEL FUEGO. A MID LEVEL SHORT WAVE
TROUGH IS STREAMING ACROSS SOUTHERN CHILE TO PATAGONIA IN
ARGENTINA AS ANOTHER TROUGH TO THE NORTH PULLS ACROSS THE BUENOS
AIRES PROVINCE TO ENTRE RIOS/URUGUAY. FARTHER EAST...OVER THE
SOUTH ATLANTIC...A SHORT WAVE TROUGH EXTENDS BETWEEN 35W-15W TO
40S.

AT LOW LEVELS...A DEEP OCCLUDED LOW OVER THE WEDDELL SEA EXTENDS A
FRONT FROM A 948 HPA LOW AT 75S 42W...THEN ALONG A 938 HPA LOW AT
74S 42W...69S 33W...A 962 HPA LOW AT 67S 36W...61S 44W...A 982 HPA
LOW AT 60S 61W...53S 73W...54S 88W...A 990 HPA LOW AT 56S 97W...A
994 HPA LOW AT 51S 103W...AND A 998 HPA LOW AT 46S 108W. THIS
SUSTAINS LIGHT CONVECTION OVER TIERRA DEL FUEGO. ANOTHER FRONT TO
THE NORTH EXTENDS FROM A 974 HPA LOW AT 61S 41W...THEN 52S
46W...49S 56W...A 1002 HPA LOW AT 51S 67W...43S 70W...A 1018 HPA
LOW AT 44S 76W...37S 80W...39S 89W...AND A 1014 HPA LOW AT 39S
100W. A RIDGE TO THE NORTH DOMINATES THE FLOW OVER THE EASTERN
PACIFIC WHILE CENTERING ON A 1031 HPA HIGH AT 32S 87W. FARTHER
EAST...OVER THE ATLANTIC...AN ELONGATED FRONT EXTENDS FROM A 962
HPA LOW AT 54S 24W...THEN 46S 19W...38S 28W...35S 43W...A 1016 HPA
LOW AT 33S 51W...30S 52W...A 1014 HPA LOW AT 29S 55W...22S
56W...TO 18S 61W. A POLAR RIDGE TO THE SOUTH CENTERS ON TWO 1025
HPA HIGHS...WITH ONE AT 40S 50W AND THE OTHER AT 30S 63W. BROAD
RIDGE ON THE NORTHERN STREAM EXTENDS OVER THE ATLANTIC...WHILE
CENTERING ON A 1031 HPA HIGH AT 30S 25W AND A 1029 HPA HIGH AT 37S
10W.

GONZALEZ...DMC (CHILE)
VANNUCCI...SMN (ARGENTINA)
DAVISON/GALVEZ...WPC (USA)
$$




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