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 1559Z Mar 30, 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
1159 AM EDT MON MAR 30 2015

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

MODEL DISCUSSION (VALID FROM MARCH 30 AT 0000 UTC): GOOD AGREEMENT
AMONG GLOBAL MODEL GUIDANCE THROUGH DAY 06. CONFIDENCE IN THE
FORECAST IS HIGH.

BROAD TROUGH ON THE SOUTHERN STREAM IS TO DOMINATE FLOW ACROSS THE
BELLINGSHAUSEN SEA/ANTARCTIC PENINSULA TO THE SOUTHERN CONE OF
SOUTH AMERICA OVER THE NEXT FEW DAYS. PROGRESSIVE SHORT WAVE
PERTURBATIONS ARE TO REVOLVE AROUND THE BROAD TROUGH...THESE ARE
TO STREAM ACROSS SOUTHERN PORTIONS OF CHILE-PATAGONIA IN
ARGENTINA. EARLY IN THE CYCLE A PROGRESSIVE SHORT WAVE TROUGH
STREAMS ACROSS SOUTHERN CHILE...WITH A STRONGER TO FOLLOW BY 54-60
HRS. A THIRD PERTURBATION IS EXPECTED BY 84-96 HRS. AT LOW LEVELS
THIS IS TO SUSTAIN AN ELONGATED POLAR FRONT ACROSS SOUTHERN
PORTIONS OF CHILE...AND A FAIRLY TIGHT PRESSURE GRADIENT.
THIS...IN-TURN...WILL BE CONDUCIVE TO STRONG BELT OF MID LATITUDE
WESTERLIES ACROSS SOUTHERN CHILE-PATAGONIA...WITH 850 HPA WINDS TO
PEAK AT 35-50KTS. THE INFLOW OF SHORT WAVE ENERGY AND STRONG
BOUNDARY LAYER WINDS WILL SUSTAIN SCATTERED SHOWERS...TO FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY. ON DAY 02 THIS INCREASES TO
20-30MM.

SLOWER PERTURBATIONS WILL POPULATE THE NORTHERN STREAM FLOW...WITH
ONE TO PULL ACROSS SOUTHERN BRASIL EARLY IN THE CYCLE AS ANOTHER
ENTERS CENTRAL/NORTHERN CHILE. THE LATTER IS TO ALSO TRACK ACROSS
SOUTHERN BRASIL BY 42/48 HRS...TO THEN DEEPEN AS IT MOVES INTO THE
WESTERN ATLANTIC BY 72-84 HRS. AT LOW LEVELS AN ELONGATED FRONT IS
TO EXTEND ACROSS THE SOUTH ATLANTIC INTO SOUTHERN STATES OF
BRASIL. UNDER INFLUENCE OF SHORT WAVE TROUGH ALOFT A FRONTAL LOW
IS TO DEVELOP OFF THE SOUTHERN COAST OF BRASIL EARLY IN THE CYCLE.
THROUGH 48-72 HRS THIS IS FORECAST TO OCCLUDE AS IT MEANDERS TO
THE EAST-SOUTHEAST. THE OCCLUDING/DEEPENING LOW WILL STRENGTHEN
THE BAROCLINIC BOUNDARY TO THE NORTH. EARLY IN THE CYCLE THIS IS
TO ENHANCE CONVECTION ON THE SOUTHERN STATES OF BRASIL TO FAVOR
MAXIMA OF 25-50MM. THROUGH 36 HRS FOCUS OF THE CONVECTION WILL
SHIFT TO SAO PAULO-RIO DE JANEIRO-MATO GROSSO IN BRASIL...WITH
MAXIMA IN THIS AREA TO PEAK AT 20-30MM/DAY. THIS IS TO PERSIST
THROUGH DAY 05.

AT UPPER LEVELS...THE SUBTROPICAL RIDGE IS TO EXTEND WEST-TO-EAST
ACROSS SOUTHERN PERU/BOLIVIA-SOUTHEAST BRASIL...WHILE ANCHORING ON
A HIGH OVER MINAS GERAIS/NORTHERN SAO PAULO. THIS IS TO STEER THE
AFOREMENTIONED SHORT WAVE PERTURBATIONS ACROSS NORTHERN
CHILE-ARGENTINA-SOUTHERN BRASIL. AS THE PERTURBATIONS PRESS
AGAINST THIS AXIS...AND THE GRADIENT TIGHTENS...A SUBTROPICAL JET
MAXIMA IS TO DEVELOP ACROSS MID SECTIONS OF SOUTH AMERICA. THIS
JET IS TO VENT DEEP CONVECTION ACROSS NORTHERN BOLIVIA-SOUTHERN
PERU-MATO GROSSO-ACRE/RONDONIA IN BRASIL. EARLY IN THE CYCLE
MAXIMA IN THIS AREA IS TO PEAK AT 20-30MM. THROUGH 54-60 HRS THIS
INCREASES TO 25-50MM IN ORGANIZED DEEP CONVECTION. BUT THROUGH
72-96 HRS ACTIVITY IS TO WANE.

NORTH OF THE 200 HPA RIDGE...A TUTT LOW IS TO DOMINATE THE
NORTHEAST STATES OF BRASIL. AS IT MEANDERS TO THE NORTH...THE TUTT
ALOFT IS TO INTERACT WITH THE ITCZ/NEAR EQUATORIAL TROUGH TO
SUSTAIN AREAS OF DEEP CONVECTION. EARLY IN THE CYCLE FOCUS OF THE
ACTIVITY WILL BE NORTHERN PARA-AMAZONAS IN BRASIL TO SOUTHERN
COLOMBIA...WITH MAXIMA TO PEAK AT 35-70MM. THROUGH 48-72 HRS THIS
DECREASES TO 20-30MM...WHILE FOCUS OF THE ACTIVITY SHIFTS TO THE
NORTH COAST OF BRASIL. IN THIS AREA EXPECTING SCATTERED CONVECTION
TO SUSTAIN MAXIMA OF 20-40MM/DAY.

ARREAGA...INAMHI (ECUADOR)
SCHNEIDER...INMET (BRASIL)
DAVISON/GALVEZ...WPC (USA)