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 1723Z Jan 26, 2015)
 
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
1223 PM EST MON JAN 26 2015

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

MODEL DISCUSSION (VALID FROM JANUARY 26 AT 00UTC): GLOBAL MODELS
ARE IN GENERAL AGREEMENT...WITH THE MEAN OF THE GLOBAL ENSEMBLES
PROVIDING GOOD SUPPORT TO THE DETERMINISTIC MODELS. CONFIDENCE IN
THE FORECAST IS HIGH.

AT 500 HPA...SHORT WAVE TROUGH ENTER SOUTHERN CHILE EARLY IN THE
CYCLE...AND THROUGH 42-48 HRS IT WILL PULL ACROSS PATAGONIA IN
ARGENTINA TO THE WESTERN ATLANTIC. THIS IS TO THEN FOLLOW A RAPID
RATE OF INTENSIFICATION THROUGH 84-96 HRS...WHEN IT IS TO EVOLVE
INTO A BROAD TROUGH BETWEEN 60W-20W TO 28S. AT LOW LEVELS THIS
SUSTAINS A PROGRESSIVE FRONT THAT ENTERS SOUTHERN CHILE EARLY IN
THE CYCLE...THEN QUICKLY P8ULLS ACROSS LA PAMPA TO THE CENTRAL
PROVINCES IN ARGENTINA/RIO DE LA PLATA BASIN BY 48 HRS. FRONT IS
TO THEN MOVE NORTH ACROSS URUGUAY/RIO GRANDE DO SUL IN
BRASIL-CORDOBA TO MENDOZA IN ARGENTINA...WHERE IT IS TO REMAIN
THROUGH 96-120 HRS. AS IT ENTERS SOUTHERN CHILE IT IS TO FAVOR
SCATTERED CONVECTION WITH ACCUMULATION OF 10-15MM. HIGHER AMOUNTS
ARE EXPECTED OVER CENTRAL ARGENTINA...WHERE IN PREFRONTAL
CONVECTION EXPECTING MAXIMA OF 25-50MM. AS IT PULLS NORTH INTO
CENTRAL/NORTHERN PROVINCES OF ARGENTINA-RIO DE LA PLATA
BASIN/URUGUAY IT IS TO CONTINUE FAVORING SCATTERED DEEP CONVECTION
WITH RAINFALL MAXIMA OF 20-45MM/DAY. THROUGH 72-96 HRS THIS IS TO
GRADUALLY EXPAND NORTH WHILE CLUSTERING OVER PARAGUAY-MISIONES IN
ARGENTINA-PARANA/SANTA CATARINA IN SOUTHERN BRASIL.

NEXT...A LONG WAVE TROUGH IS TO MOVE TO THE EASTERN PACIFIC
THROUGH 72-84 HRS...WITH AXIS TO ENVELOP AREA BETWEEN 120W-65W AND
TO THE SOUTH OF 50S. AS IT APPROACHES THE CONTINENT...THE DEEP
TROUGH IS TO FOCUS SHORT WAVE ENERGY ACROSS SOUTHERN PORTIONS OF
CHILE TO PATAGONIA IN ARGENTINA. AN INDUCED RIDGE IS TO BUILD TO
THE EAST...WITH AXIS TO EXTEND SOUTH FROM THE SOUTHERN CONE TO THE
DRAKE PASSAGE/ANTARCTIC PENINSULA. AT LOW LEVELS THIS IS TO
SUSTAIN A BROAD TROUGH ACROSS THE SOUTHEAST PACIFIC LATER ON DAY
03...WHERE IT IS TO GENERALLY PERSIST THROUGH DAY 05. POLAR FRONTS
ARE TO REVOLVE AROUND THIS AXIS...TO STREAM ACROSS SOUTHERN CHILE
TO THE ANTARCTIC PENINSULA. THESE ARE TO GENERALLY FAVOR LIGHT
RAINFALL AMOUNTS AS THEY STRIKE THE SOUTHERN CONE OF SOUTH AMERICA.

AT 200 HPA...A WEAK CELL OF THE SUBTROPICAL RIDGE IS INITIALIZED
OVER PERU-BOLIVIA-MATO GROSSO IN BRASIL. THROUGH 72-96 HRS THE
HIGH/RIDGE IS TO BECOME BETTER ORGANIZED...ANCHORING ON A CLOSED
HIGH OVER NORTHERN CHILE WHILE EXPANDING ACROSS PERU-WESTERN
BRASIL TO NORTHERN ARGENTINA/CHILE AND PARAGUAY. AS THE RIDGE
BUILDS...A LOW/TROUGH OVER THE TROPICAL ATLANTIC IS TO RETROGRESS
TO NORTHEAST BRASIL...TO ENTER NORTHEAST BRASIL LATER ON DAY 03
WHILE THE TROUGH EXPANDS INLAND ACROSS EQUATORIAL SOUTH AMERICA.
AS THE UPPER PATTERN EVOLVES...A CONVERGENT/SUBSIDENT PATTERN IS
TO ESTABLISH ACROSS BRASIL TO THE EAST OF 60W AND NORTH OF 20S.
EARLY IN THE CYCLE EXPECTING SCATTERED CONVECTION IN THIS AREA TO
RESULT IN RAINFALL AMOUNTS OF 15-20MM/DAY. BUT THIS DECREASES TO
TRACE AMOUNTS THROUGH 96 HRS. ACROSS SOUTHERN PERU-NORTHERN
BOLIVIA...RIDGE ALOFT IS TO INITIALLY FAVOR RAINFALL AMOUNTS OF
35-70MM. THROUGH 60-72 HRS IT DECREASES TO 20-35MM WHILE BUILDING
EAST AND NORTH ACROSS ACRE-AMAZONAS IN BRASIL TO NORTHERN
PERU/SOUTHERN COLOMBIA.

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