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 1609Z Apr 09, 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
1209 PM EDT WED APR 09 2014

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

MODEL DISCUSSION (VALID FROM 09 APRIL 00UTC): THE GLOBAL MODELS
ONCE AGAIN FAILED TO REACH A CONSENSUS ON HOW THE MEDIUM RANGE
PATTERN IS GOING TO EVOLVE...WITH THE EUROPEAN MODEL STILL
FAVORING A SLOWER/DEEPER TROUGH TO STREAM ACROSS ARGENTINA THAN
WHAT THE GFS AND MAJORITY OF GLOBAL ENSEMBLES SUGGEST. ALTHOUGH
DEEPER AND SLOWER THAN THE GFS...THE UKMET MADE SOME PATTERN
ADJUSTMENTS...AND IT IS NOW TRENDING TOWARDS THE WEAKER GFS
SOLUTION. NOTE THAT OUR FORECAST CHARTS ARE BIASED TOWARDS THE GFS
SOLUTION AS SUPPORTED BY THE GLOBAL ENSEMBLE MEMBERS.

AT MID LEVELS...BROAD TROUGH IS TO EXTEND INTO THE SOUTHERN CONE
OF SOUTH AMERICA EARLY IN THE CYCLE. THROUGH 36 HRS THE TROUGH IS
TO PULL ACROSS THE DRAKE PASSAGE-PATAGONIA IN ARGENTINA/SOUTHERN
CHILE TO THE EASTERN PACIFIC. AS IT PULLS ACROSS THE SOUTHERN
CONE...THIS IS TO THEN SHEAR A SHORT WAVE TROUGH OFF THE NORTHERN
COAST OF CHILE...WHILE MAIN BODY OF THE TROUGH IS TO SLOWLY PULL
TO THE EAST-SOUTHEAST. AT LOW LEVELS THE ASSOCIATED FRONT MOVES
NORTH ACROSS LA PAMPA-MENDOZA...WITH BOUNDARY TO FRONTOLIZE AS IT
NEARS RIO DE LA PLATA BASIN THROUGH 48 HRS. OVER SOUTHERN CHILE
THIS IS TO MEANWHILE FAVOR SCATTERED CONVECTION WITH ACCUMULATION
OF 05-10MM.

AS THE AFOREMENTIONED TROUGH ENTERS THE SOUTHERN CONE...IT IS TO
THEN INTERACT WITH A SHORT WAVE TROUGH TO THE NORTH. THE MID LEVEL
VORTEX CENTERS OFF THE COAST OF ARGENTINA. THROUGH 48-72 HRS IT IS
TO GRADUALLY SHEAR ACROSS THE SOUTH GEORGIA ISLANDS WHILE YIELDING
TO THE DEEPER TROUGH TO THE WEST. AT LOW LEVELS THIS SUSTAINS A
DEEP OCCLUDED LOW OVER THE WESTERN ATLANTIC AND A POLAR FRONT
ACROSS SOUTHERN BRASIL TO NORTHERN PROVINCES IN ARGENTINA. FRONT
IS FORECAST TO REMAIN NEARLY STATIONARY THROUGH 48-72 HRS.

THE MEANDERING FRONT IS TO THEN INTERACT WITH THE SHORT WAVE
TROUGH FORMING OFF THE NORTHERN COAST OF CHILE. THROUGH 60-72 HRS
THE MID LEVEL TROUGH IS TO SLOWLY SPILL ACROSS THE NORTHERN
ANDES... MEANWHILE SHEARING SHORT WAVE ENERGY ACROSS NORTHERN
ARGENTINA-PARAGUAY/SOUTHERN BRASIL. A SUBTROPICAL JET MAXIMA IS TO
ACCOMPANY THIS TROUGH AS IT PULLS ACROSS CHILE/ARGENTINA...WITH
DIVERGENCE ON ITS LEFT ENTRANCE REGION TO VENT CONVECTION ACROSS
MID SECTIONS OF SOUTH AMERICA. INFLOW OF SHORT WAVE ENERGY WILL
SUSTAIN A SURGE IN CONVECTION ACROSS PARAGUAY-SOUTHERN
BRASIL...WITH MAXIMA OF 35-70MM EXPECTED THROUGH 36 HRS...AND
50-100MM AT 60-84 HRS. THROUGH 84-96 HRS THIS WILL DECREASE TO
15-20MM.

NEXT MID LEVEL TROUGH IS TO ENTER SOUTHERN CHILE BY 60 HRS...AND
ACROSS PATAGONIA-CENTRAL ARGENTINA BY 66-7 HRS. THE TROUGH IS TO
THEN SLOWLY PULL TO THE EAST-SOUTHWEST WHILE TRAILING TO THE
NORTHERN PROVINCES IN ARGENTINA. AT LOW LEVELS THIS WILL SUSTAIN A
DEEP FRONTAL LOW OVER SOUTHERN CHILE BY 42-48 HRS...WHERE IT IS TO
TRIGGER MODERATE CONVECTION WITH ACCUMULATION OF 15-20MM. THE
FRONT THEN MOVES NORTH ACROSS BUENOS AIRES PROVINCE-CENTRAL
ARGENTINA BY 72 HRS. A BUILDING POLAR RIDGE OVER ARGENTINA IS TO
THEN DISPLACE THIS FRONT EAST TO THE WESTERN ATLANTIC WHILE ALSO
FAVORING A SOUTHERLY WIND SURGE ACROSS PARAGUAY TO EASTERN
BOLIVIA. AS THE WINDS SURGE ACROSS PARAGUAY THIS IS TO THEN FAVOR
ORGANIZED DEEP CONVECTION ACROSS MATO GROSSO-RONDONIA IN
BRASIL-PARAGUAY/CENTRAL-SOUTHERN PERU. BY 84-106 HRS EXPECTING
ACCUMULATION OF 35-70MM. BUT AS IT SPREADS ACROSS AMAZONAS IN
BRASIL TO CENTRAL/NORTHERN PERU THIS IS TO THEN TRIGGER MODERATE
TO HEAVY RAINFALL AMOUNTS WITH ACCUMULATION OF 30-60MM.

NORTH OVER THE CONTINENT...AT 200 HPA...THE SUBTROPICAL RIDGE WILL
CONFINE TO AREA NORTH OF 25S. A MEANDERING HIGH OVER MATO
GROSSO-EASTERN BOLIVIA IS TO ANCHOR THIS RIDGE OVER THE NEXT FEW
DAYS. IN INTERACTION WITH THE SUBEQUATORIAL RIDGE TO THE NORTH
THIS IS TO VENT DEEP CONVECTION ACROSS NORTHEAST BRASIL...WHERE WE
EXPECT RAINFALL AMOUNTS OF 20-35MM/DAY. ACROSS NORTHWEST BRASIL
EXPECTING ACCUMULATION OF 15-30MM. ON THE SOUTHERN SIERRA OF PERU
AND THE ALTIPLANO OF BOLIVIA EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY. THROUGH 72-96 HRS FOCUS OF THE CONVECTION SHIFTS TO
NORTHERN BOLIVIA-SOUTHERN PERU AS THE STRONG SOUTHERLY WINDS
TRIGGER ORGANIZED DEEP CONVECTION.

ITA...SENAMHI (PERU)
FERNANDES...INMET (BRASIL)
DAVISON...WPC (USA)