Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center
 
South American Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1515Z Oct 10, 2014)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product


SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1115 AM EDT FRI OCT 10 2014

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

LAST NO AMENDS...NEXT ON TUESDAY OCTOBER 14.

MODEL DISCUSSION (VALID FROM OCTOBER 10 AT 00UTC): THE GLOBAL AND
ENSEMBLE MEMBERS AGREE ON PATTERN EVOLUTION ACROSS THE ENTIRE
DOMAIN THROUGH 144-168 HRS. CONFIDENCE IN THE FORECAST IS HIGH.

AT 500 HPA...A MID LEVEL RIDGE IS TO EXTEND ACROSS THE CONTINENT
BETWEEN 10S-25S...AS IT IS TO CENTER ON A CLOSED HIGH THAT
MEANDERS BETWEEN CHACO PARAGUAYO-EASTERN BOLIVIA. BROAD POLAR
TROUGH LIES TO THE SOUTH...EXTENDING BETWEEN THE
BELLINGSHAUSEN-WEDDELL SEA TO THE SOUTHERN CONE OF SOUTH AMERICA.
AS THE TROUGH PRESSES AGAINST THE RIDGE TO THE NORTH...THIS
SUSTAINS A TIGHT BELT OF MID LATITUDE WESTERLIES ACROSS THE
CONTINENT. EMBEDDED IN THIS FLOW...AT 250 HPA...A SUBTROPICAL JET
MAXIMA IS TO EXTEND ACROSS CENTRAL CHILE/ARGENTINA...WHERE IT IS
TO FAVOR AREAS OF DIVERGENCE ALOFT. AT LOW LEVELS THIS IS TO
SUSTAIN A MEANDERING FRONT ACROSS RIO GRANDE DO SUL IN BRASIL TO
NORTHERN PROVINCES IN ARGENTINA/PARAGUAY...WHERE BOUNDARY IS TO
HOLD DURING THE NEXT FOR DAYS. THIS BOUNDARY WILL BE THE FOCUS OF
MOISTURE CONVERGENCE...SUSTAINING SCATTERED CONVECTION FROM RIO
GRANDE DO SUL TO CORRIENTES IN ARGENTINA. IN THIS AREA...DAILY
MAXIMA IS TO PEAK AT 15-30MM THROUGH 48-60 HRS...AND 15-25MM AT
60-96 HRS.

MODELS THEN FORECAST A PROGRESSIVE MID LEVEL SHORT WAVE TROUGH TO
PULL ACROSS 100W/110W AND TO THE SOUTH OF 50S BY 24 HRS. THROUGH
60-72 HRS IT IS TO THEN PHASE WITH THE TROUGH TO THE EAST...WITH
AXIS TO RAPIDLY AMPLIFY ACROSS THE ANTARCTIC PENINSULA TO THE
SOUTHERN CONE OF SOUTH AMERICA. THROUGH 108-120 HRS THE TROUGH IS
TO THEN PULL ACROSS 40W. AT LOW LEVELS THIS IS TO SUSTAIN GRADUAL
AMPLIFICATION OF SURFACE TROUGH ACROSS THE DRAKE PASSAGE TO THE
SOUTHERN CONE...WITH AXIS TO EXPAND ACROSS PATAGONIA IN ARGENTINA/
SOUTHERN REGIONS OF CHILE BY 72-84 HRS. AN ELONGATED FRONT BOUNDS
THE NORTHERN FRINGES OF THIS TROUGH...WITH AXIS WEST ACROSS THE
SOUTH GEORGIA ISLANDS-SOUTHERN PATAGONIA/CHILE TO THE EASTERN
PACIFIC. THIS BOUNDARY IS TO PERSIST THROUGH AT LEAST 84 HRS...
MEANWHILE ENHANCING COASTAL CONVERGENCE TO THE SOUTH OF PUERTO
MONTT CHILE. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY. FURTHERMORE...A PROGRESSIVE CLIPPER LOW IS TO REVOLVE
AROUND THIS AXIS AND IT IS TO ENTER THE DRAKE PASSAGE BY 72
HRS...DRIVING A PROGRESSIVE FRONT NORTHWARD INTO SOUTHERN
CHILE/PATAGONIA. BUILDING RIDGE TO THE WEST IS TO THEN SUSTAIN A
COLD ADVECTIVE PATTERN...WITH CONDITIONS TO FAVOR SNOW SHOWERS
ACROSS THE SOUTHERN ANDES OF CHILE...AND MIXED PRECIPITATION OVER
TIERRA DEL FUEGO.

A SLOW TO EVOLVE SHORT WAVE TROUGH ON THE NORTHERN STREAM MOVES
ACROSS 100W AND TO THE SOUTH OF 20S BY 72 HRS...NEARING 80W/83W BY
120 HRS. THIS IS TO FOCUS SHORT WAVE ENERGY ACROSS
CENTRAL/SOUTHERN CHILE LATER IN THE CYCLE...WHERE IT IS TO FAVOR
HEIGHT FALLS OF 75-125GPM. AS THE ASSOCIATED TROUGH/FRONT ENTERS
SOUTHERN CHILE LATER IN THE CYCLE IT IS TO TRIGGER SCATTERED RAIN
SHOWERS WITH ACCUMULATION OF 10-15MM...WHILE OVER LA PAMPA IN
ARGENTINA THE MAXIMA IS TO PEAK AT 15-20MM.

AT 200 HPA...OPEN CELL OF THE SUBTROPICAL RIDGE IS TO EXTEND TO
THE SOUTHEAST FROM PERU...ACROSS BOLIVIA-PARAGUAY-SOUTHERN BRASIL
TO THE WESTERN ATLANTIC. AN ELONGATED TROUGH LIES TO THE
NORTH...WITH AXIS NORTHWEST ACROSS ESPIRITO SANTO/MINAS GERAIS IN
BRASIL TO RONDONIA TO THE WEST. THIS RIDGE PATTERN IS TO PERSIST
NEARLY UNCHANGED OVER THE NEXT FOUR TO FIVE DAYS...LIKEWISE FOR
THE UPPER LEVEL TROUGH. AS A RESULT...THE MOST ACTIVE CONVECTION
IS EXPECTED TO THE NORTH OF 10S...WITH MAXIMA OF 20-40MM/DAY
ACROSS SOUTHERN COLOMBIA-NORTHERN PERU/EASTERN ECUADOR TO AMAZONAS
IN BRASIL THROUGH 54-60 HRS...AND 20-30MM/DAY THEREAFTER. OVER
AMAPA-GOIAS-NORTHERN PARA EXPECTING SCATTERED CONVECTION TO FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY...AS TROUGH ALOFT ENHANCES SEA
BREEZE CONVERGENCE/AIR MASS CONVECTION.

CAROCA...DMC (CHILE)
DURAN...SENAHMI (PERU)
GALVEZ...WPC (USA)