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 1536Z Apr 13, 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
1136 AM EDT MON APR 13 2015

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

MODEL DISCUSSION (VALID FROM APRIL 12 AT 0000 UTC): GLOBAL MODELS
ARE IN EXCELLENT AGREEMENT THROUGH 96-108 HRS...WITH GLOBAL
ENSEMBLE MEMBERS PROVIDING STRONG SUPPORT TO THE DETERMINISTIC
SOLUTION. OUR CONFIDENCE IN THE FORECAST IS HIGH.

A MID LATITUDE TROUGH IN THE SOUTHERN STREAM FLOW IS THE SYSTEM OF
CONCERN...WITH DEEPENING LOW FORECAST TO MEANDER OFF THE SOUTHERN
COAST OF CHILE THROUGH 72-84 HRS. MODELS THEN FORECAST THIS TROUGH
TO SPILL ACROSS THE CENTRAL ANDES INTO CENTRAL ARGENTINA BY 108
HRS. BUILDING SHORT WAVE RIDGE TO THE WEST IS TO THEN INDUCE THE
NORTHWARD AMPLIFICATION OF THIS TROUGH AS IT MEANDERS EAST ACROSS
ARGENTINA TO URUGUAY LATER IN THE CYCLE. AS IT SPILLS ACROSS THE
ANDES A SUBTROPICAL JET MAXIMA IS TO ACCOMPANY THIS TROUGH.
DIVERGENCE ON ITS RIGHT EXIT REGION IS TO VENT ORGANIZED DEEP
CONVECTION OVER CENTRAL ARGENTINA ON DAY 04...WHILE DIVERGENCE ON
ITS LEFT ENTRANCE REGION IS TO VENT DEEP CONVECTION ACROSS
PARAGUAY-CORRIENTES/MISIONES IN ARGENTINA TO SOUTHERN BRASIL ON
DAY 05. AT LOW LEVELS THE TROUGH ALOFT IS TO INTERACT WITH A
MEANDERING FRONT OVER CENTRAL ARGENTINA...TO SUSTAIN CYCLOGENESIS
ALONG THIS BOUNDARY BY 96-108 HRS. THROUGH 120-132 HRS THE LOW IS
TO RAPIDLY OCCLUDE AS IT DEEPENS OFF THE COAST OF URUGUAY. AS THE
LOW DEEPENS...THE SURFACE FRONT IS TO SURGE ACROSS
CENTRAL-NORTHERN ARGENTINA/SOUTHERN STATES OF BRASIL. AHEAD OF
THIS SYSTEM...A MOIST LOW LEVEL NORTHERLY FLOW IS TO ESTABLISH
ACROSS PARAGUAY TO CENTRAL ARGENTINA. THIS IS TO CONVERGE ON THE
CENTRAL PROVINCES IN ARGENTINA WHERE IT IS TO FEED ORGANIZED DEEP
CONVECTION. EARLY IN THE CYCLE SCATTERED CONVECTION OVER CENTRAL
ARGENTINA IS TO RESULT IN DAILY MAXIMA OF 20-30MM. BY 96-108 HRS
THIS IS TO INCREASE TO 50-100MM IN POTENTIALLY SEVERE CONVECTION.
LATER IN THE CYCLE THE FOCUS OF THE HEAVY CONVECTION WILL SHIFT TO
SOUTHERN BRASIL-URUGUAY/MESOPOTAMIA VALLEY IN ARGENTINA AND
PARAGUAY.

NORTH OVER THE CONTINENT...AT 200 HPA...THE UPPER FLOW IS TO
DIVERGE BETWEEN TWO RIDGES...WITH THE SUBTROPICAL RIDGE TO MEANDER
OVER NORTHERN BRASIL AND THE SUBEQUATORIAL RIDGE OVER THE
GUIANAS-VENEZUELA. THIS IS TO VENT ORGANIZED DEEP CONVECTION ALONG
THE NEAR EQUATORIAL TROUGH OVER NORTHERN BRASIL-SOUTHERN
VENEZUELA. IN THIS AREA EXPECTING SCATTERED DEEP CONVECTION OVER
THE NEXT FEW DAY...WITH MAXIMA TO PEAK AT 30-60MM/DAY. THROUGH
72-96 HRS CONVECTION ALONG THE NORTH COAST OF BRASIL DECREASES TO
20-40MM/DAY...WHILE OVER NORTHERN AMAZONAS-RORAIMA TO
COLOMBIA/NORTHERN PERU HEAVY RAINS ARE TO PERSIST. OTHER
CONVECTION IS TO CLUSTER ACROSS WESTERN ECUADOR...WHERE UNDER
FAVORABLE MJO CONDITIONS AND A BRISK WESTERLY FLOW THE DAILY
MAXIMA IS TO PEAK AT 20-45MM OVER THE NEXT TWO TO THREE DAYS.
OTHER TRADE WIND CONVERGENCE IS EXPECTED OVER EASTERN BAHIA IN
BRASIL...WHERE DAILY MAXIMA IS TO PEAK AT 15-25MM/DAY EARLY IN THE
CYCLE. THROUGH 96-120 HRS THIS DECREASES TO 05-10MM/DAY.

SCHNEIDER...INMET (BRASIL)
CALLE...UNALM (PERU)
CHARPENTIER...DMC (CHILE)
DAVISON/GALVEZ...WPC (USA)