Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000
FXSA20 KWBC 041727
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1226 PM EST WED MAR 04 2015

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

MODEL DISCUSSION (VALID FROM MARCH 04 AT 00UTC): CONFIDENCE IN THE
FORECAST IS HIGH THROUGH 96-108 HRS...WITH MODELS MAKING PATTERN
CORRECTIONS ACROSS THE EASTERN PACIFIC DURING THE MEDIUM RANGE
PERIOD. UNCERTAINTY THEN RAPIDLY GROWS THROUGH 132-144 HRS.

DEEP MID LEVEL PERTURBATIONS ARE TO STREAM ACROSS THE EASTERN
PACIFIC INTO THE SOUTHERN CONE OF SOUTH AMERICA...WITH STRONG
PERTURBATION FORECAST TO ENTER SOUTHERN CHILE EARLY IN THE CYCLE.
AN EVEN STRONGER/DEEPER TROUGH IS TO FOLLOW...REACHING THE
SOUTHERN CONE BY 84 HRS...AND ACROSS SOUTHERN CHILE/PATAGONIA IN
ARGENTINA BY 108 HRS. THE DEEP PERTURBATIONS...AS THEY NEAR THE
SOUTHERN CONE...ARE FORECAST TO ESTABLISH A SUBTROPICAL
CONNECTION. INFLOW OF DEEP MOISTURE IS TO THEN SUSTAIN ORGANIZED
CONVECTION ACROSS THE SOUTHERN REGIONS OF CHILE. AT LOW
LEVELS...PROGRESSIVE POLAR FRONTS ARE TO STREAM ACROSS SOUTHERN
CHILE-PATAGONIA ON DAYS 01 AND 03/04. STRONG BOUNDARY LAYER WINDS
ARE TO ACCOMPANY THESE FRONTS...TO ENHANCE TOPOGRAPHICAL FORCING
ACROSS SOUTHERN PORTIONS OF CHILE. IN THIS AREA THE RAINFALL
MAXIMA IS TO PEAK AT 15-25MM/DAY.

NORTHERN SOUTH AMERICA WILL BE UNDER INFLUENCE OF THE SUBTROPICAL
RIDGE...WITH AXIS AT 200 HPA TO ENVELOP AREA TO THE NORTH OF 30S
AND WEST OF 50W...WHILE ANCHORING ON A CLOSED HIGH OVER SOUTHERN
BOLIVIA. AT 250 HPA...AN ANTICYCLONICALLY CURVED SUBTROPICAL JET
MAXIMA BOUNDS THE SOUTHERN FRINGES OF THIS RIDGE...WITH AXIS
ACROSS NORTHERN CHILE-ARGENTINA-RIO DE LA PLATA BASIN/SOUTHERN
STATES OF BRASIL. THE JET ALOFT CONTINUES TO FAVOR AREAS OF UPPER
DIVERGENCE ON THE NORTHERN PROVINCES OF ARGENTINA. THROUGH 72-96
HRS THE JET RELOCATES TO THE EAST...WITH FOCUS OF THE UPPER
DIVERGENCE SHIFTING TO THE SOUTHERN/SOUTHEAST STATES OF BRASIL.
THE STRONG MID/UPPER LEVEL FLOW ACROSS THE NORTHERN ANDES OF CHILE
IS TO FAVOR GENERATION OF LEESIDE PERTURBATIONS ACROSS THE
NORTHERN PROVINCES IN ARGENTINA. THIS IS TO COMBINE WITH THE
OCCASIONAL SHORT WAVE PERTURBATION ON THE NORTHERN STREAM TO
PROVIDE DYNAMICAL SUPPORT TO ORGANIZED DEEP CONVECTION. AT LOW
LEVELS...THE CHACO LOW IS TO FAVOR A MOIST ADVECTIVE PATTERN
ACROSS MATO GROSSO DO SUL IN BRASIL-PARAGUAY TO NORTHERN
ARGENTINA...WITH FLOW/MOISTURE TO CONVERGE INTO A LOW LEVEL TROUGH
OVER MID SECTIONS OF SOUTH AMERICA. THROUGH 72-96 HRS THE TROUGH
IS TO MIGRATE NORTH AND EAST INTO SOUTHEAST BRASIL...WITH A CLOSED
LOW TO FORM OFF THE SOUTHEAST COAST OF BRASIL LATER ON DAY 05.
EARLY IN THE CYCLE THIS IS TO FAVOR SCATTERED DEEP CONVECTION
ACROSS NORTHERN ARGENTINA-PARAGUAY-RIO GRANDE DO SUL IN
BRASIL/URUGUAY...WITH MAXIMA OF 20-30MM. AS THE CONVECTION SHIFTS
NORTH INTO BRASIL...ACTIVITY IS TO GRADUALLY BECOME MORE
ACTIVE/BETTER ORGANIZED...WITH HEAVY CONVECTION TO SUSTAIN
RAINFALL MAXIMA OF 30-60MM IN POTENTIALLY SEVERE CONVECTION.
CONSIDER POTENTIAL OF WATERSPOUTS DEVELOPING ALONG THE COAST OF
SAO PAULO-SANTA CATARINA...WITH RISK OF HAIL ALONG THE SERRA DO
MAR.

EAST OF THE SUBTROPICAL RIDGE...AT 200 HPA...A TROUGH EXTENDS TO
THE NORTHWEST INTO THE NORTHEAST STATES OF BRASIL. THIS IS
INTERACTING WITH THE NEAR EQUATORIAL TROUGH AS THE LATTER MEANDERS
ACROSS THE NORTHERN STATES OF BRASIL TO NORTHERN JUNGLE OF PERU.
ACROSS NORTHWEST BRASIL INTO EASTERN PERU/ECUADOR THIS IS TO FAVOR
ORGANIZED DEEP CONVECTION THROUGH 48-60 HRS...WITH DAILY MAXIMA OF
30-60MM. THROUGH 96-108 HRS THIS DECREASES TO 20-30MM. ACROSS
WESTERN ECUADOR DAILY MAXIMA IS TO RANGE BETWEEN
10-15MM/DAY...WITH A BRIEF SURGE ON DAY 02 WHEN THE MAXIMA IS TO
PEAK AT 15-25MM. ACROSS NORTHEAST BRASIL EXPECTING RAINFALL MAXIMA
OF 15-25MM/DAY...TO INCREASE TO 20-40MM LATER IN THE CYCLE.

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

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.