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South American Synoptic Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1324Z Mar 26, 2015)
 
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SOUTH AMERICA SYNOPTIC DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
924 AM EDT THU MAR 26 2015

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

SYNOPSIS (VALID FROM MARCH 25 AT 00UTC): AT 200 HPA...THE
SUBTROPICAL RIDGE IS MUCH BETTER ESTABLISHED NOW CENTERING ON A
CELL OVER NORTHERN MATO GROSSO. THE RIDGE IS VENTILATING
CONVECTION TO THE NORTHEAST ACROSS THE AMAZON DELTA REGION SOUTH
INTO EASTERN PARA/MARANHAO/TOCANTINS AND INTO MATO GROSSO. TO THE
WEST...THE UPPER FLOW IS WEAK OVER THE WESTERN AMAZON BASIN BUT
DEEP-LAYER INSTABILITY IS STILL SUSTAINING DIURNAL THUNDERSTORMS
ALONG A SURFACE TROUGH THAT EXTENDS FROM BOLIVIA INTO THE
PERUVIAN/WESTERN BRASIL AMAZON BASIN. DIURNAL THUNDERSTORMS ARE
ALSO OCCURRING OVER THE ANDES AND MORE SO OVER THE WESTERN SLOPES
OF NORTHERN PERU AND SOUTHERN ECUADOR...AIDED BY A PERSISTENT
DECREASE IN STABILITY DUE TO WARM SSTS.

AT 250 HPA...THE JET ANALYSIS SHOWS THE SOUTHERN POLAR FORMING AT
50S 112W ALONG 59S 98W...67S 84W...55S 42W...57S 24W...EXITING AT
58S 10W. THE NORTHERN POLAR JET FORMS AT 49S 98W ALONG 47S
87W...54S 76W...EXITING AT 49S 72W. IT REFORMS AT 36S 63W ALONG A
124KT MAXIMA AT 36S 54W...EXITING AT 38S 44W. THE SUBTROPICAL JET
FORMS AT 35S 75W ALONG 28S 79W...25S 73W...31S 62W...34S 39W...31S
31W...EXITING AT 26S 27W. A MUCH WEAKER BRANCH FORMS AT 22S 68W
ALONG 29S 56W...EXITING AT 30S 45W.

AT 500 HPA...MID LEVEL ANALYSIS AND IN THE SOUTHERN STREAM A LARGE
TROUGH EXTENDS TO THE WEST OF 110W-100W. A BROAD RIDGE IS
ESTABLISHED TO THE EAST FROM 90W-60W SOUTH INTO THE DRAKE PASSAGE.
SHORT WAVE TROUGHS ARE MOVING IN THE PERIPHERY OF THE
AFOREMENTIONED TROUGH. ONE CENTERS ON A LOW AT 46S 98W AS IT MOVES
TOWARDS THE DRAKE PASSAGE. TO THE NORTHEAST...A TROUGH CENTERS ON
A LOW TO THE SOUTHEAST OF THE BUENOS AIRES PROVINCE AT 41S 53W.
THIS TROUGH IS FOCUSING ITS ENERGY IN THE RIO DE LA PLATA REGION
AND EXTREME SOUTHERN BRASIL. ANOTHER TROUGH CENTERS ON A LOW OFF
THE COAST OF CENTRAL CHILE AT 29S 75W. THIS TROUGH IS SLOWLY
SPILLING OVER THE ANDES...THUS LEADING TO PERSISTENT ADVECTION OF
CYCLONIC VORTICITY NOT ONLY OVER CENTRAL/NORTHERN CHILE BUT INTO
CENTRAL AND NORTHERN ARGENTINA.

AT LOW LEVELS...THE SURFACE ANALYSIS SHOWS A 1025 HPA HIGH AT 55S
60W THAT RIDGES INTO A 1021 HPA HIGH AT 53S 80W. THE 1025 HPA HIGH
HAS ANOTHER RIDGE AXIS INTO CENTRAL ARGENTINA TO A 1021 HPA HIGH
AT 33S 65W. A 1010 HPA OCCLUDED LOW AT 42S 50W EXTENDS A FRONT
ALONG A 1010 HPA LOW AT 41S 44W...33S 47W...CENTRAL RIO GRANDE DO
SUL...CORRIENTES...SANTIAGO DEL ESTERO. SCATTERED STRONG
THUNDERSTORMS WERE OCCURRING ALONG THE FRONT. THE ASSOCIATED
PRE-FRONTAL TROUGH EXTENDS FROM CENTRAL RIO GRANDE DO SUL ALONG26S
58W...21S 62W. THE TAIL OF A WEAKENING FRONT EXTENDS FROM 20S 27W
ALONG 16S 35W INTO SOUTHERN BAHIA.

ARREAGA...INAMHI (ECUADOR)
SCHNEIDER...INMET (BRASIL)
GALVEZ...WPC (USA)