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 1614Z Aug 15, 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
1214 PM EDT FRI AUG 15 2014

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

MODEL DISCUSSION (VALID FROM AUGUST 15 AT 00UTC): MINOR
CORRECTIONS TO THE PREVIOUS FORECAST PACKAGE AS GLOBAL MODELS
REMAIN IN GOOD AGREEMENT ON LONG WAVE PATTERN EVOLUTION ACROSS THE
DOMAIN. CONSISTENT WITH PREVIOUS FORECASTS...THE EUROPEAN...GFS
AND GLOBAL ENSEMBLE MEMBERS CONTINUE TO FORECAST A HIGHLY
AMPLIFIED SINUSOIDAL WAVE PATTERN TO ESTABLISH ACROSS SOUTH
AMERICA THROUGH 72-96 HRS. AS THE PATTERN EVOLVES...A LONG WAVE
RIDGE IS TO ESTABLISH A FOOTHOLD ACROSS CHILE/ARGENTINA. THIS
RIDGE IS THEN EXPECTED TO PERSIST THROUGH DAY 08-09...MEANWHILE
SUSTAINING UNSEASONABLY WARM TEMPERATURES ACROSS CENTRAL/SOUTHERN
PORTIONS OF SOUTH AMERICA. THE ABOVE NORMAL TEMPERATURES...AS THEY
COMBINE WITH LOW MOISTURE CONTENT ACROSS ARGENTINA...WILL LIKELY
FAVOR FIRE WEATHER CONDITIONS DURING THE LATER PART OF THE
FORECAST.

UNDER INFLUENCE OF A RIDGE OVER THE FAR WESTERN ATLANTIC...A
MID/UPPER LEVEL TROUGH EXTENDS NORTH ACROSS THE CENTRAL ATLANTIC.
THROUGH 24 HRS THE TROUGH IS TO MIGRATE EAST ACROSS 20W TO
20S...WITH AXIS TO THEN SLOWLY WEAKEN AS SHORT WAVE ENERGY SHEARS
TO THE EAST-SOUTHEAST THROUGH 120-132 HRS. AT LOW LEVELS...THE
TROUGH ALOFT SUSTAINS AN ELONGATED FRONT ACROSS THE SOUTH ATLANTIC
TO RIO DE JANEIRO-MATO GROSSO-NORTHERN BOLIVIA. FRONTAL
BOUNDARY...AS IT LOSES UPPER LEVEL SUPPORT...IS TO RETROGRESS
ACROSS THE SOUTHERN STATES OF BRASIL TO PARAGUAY BY 36-48
HRS...WHERE IT IS TO REMAIN THROUGH 84-96 HRS. AS IT
RETROGRESSES...THE FRONT WILL INTERACT WITH AN UPPER LEVEL SHORT
WAVE TROUGH. THIS IS TO PULL ACROSS NORTHERN ARGENTINA TO PARAGUAY
BY 48-54 HRS...MOVING ACROSS PARAGUAY TO SOUTHERN BRASIL BY 60-72
HRS. AS THEY INTERACT...THIS IS TO TRIGGER SCATTERED DEEP
CONVECTION...WITH MAXIMA OF 15-25MM EXPECTED THROUGH 48-60
HRS...AND 10-15MM AT 60-84 HRS.

OVER THE PACIFIC...MEANWHILE...A TROUGH IS TO EXTEND TO THE
NORTHWEST FROM A DEEP LOW OVER THE BELLINGSHAUSEN SEA...ALONG 50S
100W TO 30S 110W. THROUGH 60-72 HRS THE TROUGH IS TO SPLIT IN
TWO...WITH SOUTHERN HALF TO PULL ACROSS THE ANTARCTIC PENINSULA/
DRAKE PASSAGE TO THE SOUTH ATLANTIC. THE NORTHERN HALF...
MEANWHILE...EVOLVES INTO A BROAD TROUGH ON THE NORTHERN STREAM...
WITH AXIS TO ENVELOP AREA BETWEEN 120W-75W AND TO THE SOUTH OF
15S. MEANWHILE...AS THE NORTHERN STREAM TROUGH DEEPENS TO THE
WEST...THIS IS TO THEN INDUCE THE SOUTHWARD AMPLIFICATION OF A
RIDGE ACROSS THE FAR EASTERN PACIFIC/CHILE TO ARGENTINA. THE RIDGE
REACHES MAXIMUM AMPLITUDE BY 96-120 HRS. EARLY IN THE CYCLE...THE
LONG WAVE TROUGH IS TO FOCUS SUBTROPICAL MOISTURE/SHORT WAVE
ENERGY ACROSS SOUTHERN CHILE TO PATAGONIA IN ARGENTINA.
THIS...HOWEVER...IS TO SUBSIDE THROUGH 72-84 HRS AS MID LEVEL
RIDGE BUILDS SOUTH ACROSS CHILE/ ARGENTINA. INFLOW OF
SUBTROPICAL/SHORT WAVE ENERGY IS TO MEANWHILE FEED CONVECTIVE
DEVELOPMENT ACROSS SOUTHERN CHILE...WITH MAXIMA OF 20-40MM.
THROUGH 72-84 HRS THIS DECREASES TO 15-20MM... WITH LESSER AMOUNTS
LATER IN THE CYCLE. OVER ARGENTINA...THE BUILDING MID LEVEL RIDGE
WILL SUSTAIN A STRONG SUBSIDENCE CAP...WITH GLOBAL MODEL GUIDANCE
SHOWING DAILY MAXIMA ACROSS NORTHWEST PROVINCES PEAKING AROUND
27-33C...WHILE ON THE RIO DE LA PLATA BASIN TEMPERATURES ARE
LIKELY TO REACH 24-28C.

NORTH OVER THE CONTINENT...AT 200 HPA...WEAK CELL OF THE
SUBTROPICAL RIDGE IS TO CONFINE TO EQUATORIAL SOUTH AMERICA.
THROUGH 72-96 HRS THE RIDGE IS FORECAST TO WEAKEN AS A SHORT WAVE
TROUGH AMPLIFIES ACROSS CENTRAL BRASIL. AS THE RIDGE
WEAKENS...CONVECTION ACROSS EQUATORIAL SOUTH AMERICA IS TO
WEAKEN/BECOME MORE SPARSE. INITIALLY EXPECTING RAINFALL AMOUNTS OF
10-15MM/DAY IN SCATTERED CONVECTION. THROUGH DAY 04/05 THIS WILL
DECREASE TO 05-10MM...WITH MOST ACTIVE NORTH OF THE EQUATOR. OVER
EASTERN BRASIL...TRADE WIND CONVERGENCE IS TO SUSTAIN COASTAL
CONVECTION BETWEEN RIO DE JANEIRO/EASTERN BAHIA...WITH MAXIMA IN
THIS AREA TO PEAK AT 15-25MM OVER THE NEXT THREE DAYS. THIS THEN
DECREASES TO 05-10MM/DAY.

JALFIN...SMN (ARGENTINA)
CAROCA...DMC (CHILE)
GALVEZ...WPC (USA)
DAVISON...WPC (USA)