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South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1616Z Dec 08, 2014)
 
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SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1116 AM EST MON DEC 08 2014

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

MODEL DISCUSSION (VALID FROM DECEMBER 08 AT 00UTC): THE GLOBAL
MODELS ARE IN EXCELLENT AGREEMENT...CONVERGING ON SIMILAR SOLUTION
THROUGH DAY 07. OUR CONFIDENCE IN THE FORECAST IS HIGH.

AT MID LEVELS...A SHORT WAVE TROUGH IS TO ENTER THE SOUTHERN CONE
OF SOUTH AMERICA THROUGH 30-36 HRS...THEN TO MOVE OFF THE COAST OF
PATAGONIA BY 48 HRS. THROUGH 96 HRS THE TROUGH IS TO SLOWLY PULL
ACROSS 20W/25W WHILE REMAINING TO THE SOUTH OF 35S. AT LOW LEVELS
THE ASSOCIATED FRONT ENTERS SOUTHERN CHILE/PATAGONIA IN ARGENTINA
EARLY IN THE CYCLE. BUILDING POLAR RIDGE IS TO THEN DISPLACE THIS
BOUNDARY NORTH ACROSS THE BUENOS AIRES PROVINCE TO MENDOZA IN
ARGENTINA BY 48 HRS...REACHING SOUTHERN BRASIL-NORTHERN PROVINCES
IN ARGENTINA BY 72 HRS. FRONT IS TO THEN REMAIN NEARLY STATIONARY
THROUGH 120-132 HRS. OVER SOUTHERN CHILE THIS IS TO TRIGGER
SCATTERED CONVECTION WITH ACCUMULATION OF 10-15MM. AS IT SURGES
ACROSS THE CENTRAL-NORTHERN PROVINCES IN ARGENTINA EXPECTING
MAXIMA OF 20-45MM IN POTENTIALLY SEVERE CONVECTION BY 36-72 HRS.

MID/UPPER LEVEL RIDGE IS TO THEN BUILD ACROSS THE EASTERN PACIFIC.
THROUGH 72-96 HRS THE RIDGE BUILDS SOUTH ALONG 80W/90W TO THE
ANTARCTIC ICECAP. AT LOW LEVELS THIS IS TO SUSTAIN A BROAD RIDGE
OVER THE SOUTHEAST PACIFIC/OFF THE COAST OF CHILE...WITH HIGH TO
BUILD FROM A 1029 HPA HIGH EARLY IN THE CYCLE TO A 1033 HPA HIGH
LATER IN THE PERIOD. BUILDING RIDGE IS TO THEN SUSTAIN A TIGHT
BELT OF MID/UPPER LATITUDE WESTERLIES ACROSS THE SOUTH
PACIFIC/DRAKE PASSAGE. PROGRESSIVE POLAR FRONTS ARE TO EMBED IN
THIS FLOW...BUT THEY ARE FORECAST TO CONFINE TO EXTREME SOUTHERN
CHILE/PATAGONIA IN ARGENTINA. IN THIS AREA EXPECTING LIGHT
CONVECTION TO SUSTAIN RAINFALL AMOUNTS OF 00-05MM/DAY.

NORTH OVER THE CONTINENT...AT 200 HPA...THE BOLIVIA HIGH IS TO
REMAIN WEST OF ITS CLIMATOLOGICAL POSITION...WITH CLOSED HIGH TO
CENTER OFF THE SOUTH COAST OF PERU EARLY IN THE CYCLE. THROUGH
48-72 HRS IT IS TO MEANDER WEST NEAR 10S 90W. MEANWHILE...THE HIGH
IS TO EXTEND A RIDGE TO THE EAST-SOUTHEAST ACROSS NORTHERN
CHILE/PARAGUAY-SOUTHERN STATES OF BRASIL. AS THE RIDGE HOLDS TO
THE WEST...A TROUGH IS TO EXTEND OVER THE CONTINENT...WITH AXIS
NORTHWEST ACROSS THE SOUTHERN STATES OF BRASIL TO AMAZONAS TO THE
NORTHWEST. THIS PATTERN IS TO HOLD OVER THE NEXT THREE DAYS.
ACROSS MATO GROSSO-MINAS GERAIS-NORTHERN SAO PAULO THE TROUGH
ALOFT IS TO ENHANCE DIURNAL CONVECTION...TO FAVOR ORGANIZED DEEP
CONVECTION THROUGH 36 HRS... WITH RAINFALL MAXIMA OF 30-60MM. THIS
THEN DECREASES TO 20-30MM/DAY WHILE SPREADING WEST AND NORTH
ACROSS PARA TO AMAZONAS TO THE WEST. OTHER CONVECTION IS TO
CLUSTER ALONG THE SOUTHERN JUNGLE OF PERU/ACRE IN BRASIL-NORTHERN
BOLIVIA...WITH MAXIMA OF 20-45MM EXPECTED THROUGH 36 HRS...AND
20-35MM AT 48-72 HRS. 

ARREAGA...INAMHI (ECUADOR)
DURAN...SENAHMI (PERU)
DAVISON...WPC (USA)