Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2
000
FXSA20 KWBC 251517
PMDSA

SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1117 AM EDT WED MAY 25 2016

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

MODEL DISCUSSION (VALID FROM MAY 25 AT 0000 UTC): CONFIDENCE IN
THE FORECAST REMAINS HIGH THROUGH 120 HRS...WITH GLOBAL MODELS AND
ENSEMBLE MEMBERS FOLLOWING A SIMILAR EVOLUTION.

MID LEVEL FLOW ACROSS THE EASTERN PACIFIC SPLITS BETWEEN A RIDGE
ON THE SOUTHERN STREAM AND A TROUGH TO THE NORTH. THE RIDGE IS TO
INITIALLY ANCHOR ON A CLOSED HIGH OVER TIERRA DEL FUEGO...THAT
MOVES TO THE MALVINAS/FALKLAND ISLANDS BY 54/60 HRS. BY 72-96 HRS
IT IS TO SETTLE ALONG 50W TO THE WEDDELL SEA/ANTARCTIC
PENINSULA...WHERE IT IS TO THEN HOLD THROUGH THE END OF THE CYCLE.
AT LOW LEVELS THIS WILL ANCHOR A RIDGE OVER PATAGONIA/WESTERN
ATLANTIC THROUGH 48-60 HRS. THIS...IN-TURN...WILL SUSTAIN A MOIST
EASTERLY FLOW ACROSS LA PAMPA TO NORTHERN PATAGONIA. AS THE
PARCELLS ADIABATICALLY LIFT...THIS IS TO THEN FAVOR GENERATION OF
SCATTERED CONVECTION ALONG THE EASTERN SLOPES OF THE ANDES ACROSS
NORTHERN PATAGONIA. IN THIS AREA WE NOW EXPECT MAXIMA OF
15-20MM...WITH MODELS PROJECTING LOCALLY HIGHER AMOUNTS DUE TO
STRONG TOPOGRAPHICAL FORCING.

THE MID LEVEL TROUGH TO THE NORTH...MEANWHILE...IS TO MEANDER OVER
SOUTHERN-CENTRAL CHILE THROUGH 36-48 HRS...THEN SLOWLY PULL ACROSS
THE ANDES INTO ARGENTINA BY 48-60 HRS. AS IT PULLS ACROSS
ARGENTINA TO PARAGUAY THIS WILL SUSTAIN FRONTOGENESIS...WITH
BOUNDARY TO GRADUALLY STRENGTHEN THROUGH 84-96 HRS. AS IT BECOMES
BETTER ORGANIZED THIS WILL TRIGGER MODERATE CONVECTION WITH
ACCUMULATION OF 20-45MM/DAY...TO AFFECT PARAGUAY BY 48-60 HRS AND
MATO GROSSO DO SUL-SOUTHERN BRASIL BY 72 HRS. BY 96-108 HRS
CONVECTION WILL INCREASE TO 25-50MM/DAY WITH LOCALLY HIGHER
AMOUNTS HIGHLY LIKELY.

FURTHERMORE...UNDER THE INFLUENCE OF THE SOUTHERN STREAM RIDGE...A
POLAR TROUGH IN THE SOUTHERN STREAM FLOW CONTINUES TO AMPLIFY
ACROSS THE SOUTH ATLANTIC. THROUGH 48-60 HRS THE TROUGH IS TO
REACH MAXIMUM AMPLITUDE AS IT IS TO EXTEND BETWEEN 50W-00W AND TO
THE SOUTH OF 30S. AT LOW LEVELS THIS WILL SUSTAIN A FRONT ACROSS
NORTHERN PATAGONIA/LA PAMPA IN ARGENTINA. THIS IS TO MEANDER NORTH
ACROSS THE BUENOS AIRES PROVINCE TO RIO DE LA PLATA BASIN BY 48
HRS...AND NORTH INTO URUGUAY/ENTRE RIOS IN ARGENTINA BY 72 HRS.
THIS IS TO THEN INTERACT WITH DEEPENING TROUGH OVER
PARAGUAY/SOUTHERN BRASIL. AS IT MEANDERS NORTH...THE FRONT WILL
TRIGGER COASTAL CONVECTION WITH ACCUMULATION OF 00-05MM/DAY.

ANOTHER FRONT LIES TO THE NORTH...WITH AXIS WEST-NORTHWEST ACROSS
ESPIRITO SANTO-MINAS GERAIS. THE FRONT SUSTAINS A PREFRONTAL SHEAR
LINE ACROSS EASTERN BAHIA...WHERE IT IS TO REMAIN OVER THE NEXT
FEW DAYS. THIS WILL BE THE FOCUS OF LOW LEVEL MOISTURE
CONVERGENCE...WITH MODELS PROJECTING MODERATE AMOUNTS OVER THE
NEXT FEW DAYS WITH DAILY MAXIMA PEAKING AROUND 15-30MM. THROUGH 96
HRS THIS IS TO DECREASE TO 10-15MM/DAY.

AT 200 HPA...A RIDGE BUILDS OVER THE EASTERN TROPICAL PACIFIC
THROUGH 48-72 HRS. AS THE RIDGE INTENSIFIES IT IS TO THEN SUSTAIN
THE NORTHWARD AMPLIFICATION OF A TROUGH ACROSS THE PERUVIAN JUNGLE
TO SOUTHERN COLOMBIA. THE AMPLIFYING TROUGH IS TO THEN FAVOR AN
INCREASE IN DIURNAL CONVECTION ACROSS AMAZONAS IN BRASIL...SRN
COLOMBIA AND NORTHERN PERU...WHERE THE MAXIMA PEAKS AT 20-30MM BY
60-108 HRS. OTHERWISE...LIGHT TO MODERATE CONVECTION IS TO BUILD
ACROSS NORTHERN BRASIL IN A DIURNAL PATTERN THAT WILL SUSTAIN
RAINFALL AMOUNTS OF 10-15MM/DAY.

ENRIQUEZ...DGAC (ECUADOR)
AYALA...DINAC (PARAGUAY)
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.