THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


SOUTH AMERICAN MODEL DISCUSSION




SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1152 AM EST THU FEB 26 2015

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

MODEL DISCUSSION (VALID FROM FEBRUARY 26 AT 00UTC): AMPLIFYING
MID/UPPER LEVEL TROUGH IS TO DOMINATE FLOW OVER THE WESTERN
ATLANTIC OVER THE NEXT COUPLE OF DAYS...WITH AXIS TO ENVELOP AREA
BETWEEN 50W-20W AND TO THE SOUTH OF 25S. THE TROUGH REACHES
MAXIMUM AMPLITUDE BY 48-60 HRS...THEN STARTS TO MIGRATE TO THE
EAST-SOUTHEAST...ACCELERATING ACROSS 20W BY 72 HRS AND NEARING 00W
BY 120 HRS. AT LOW LEVELS...THE ASSOCIATED FRONT MOVES NORTH
ACROSS RIO DE LA PLATA BASIN/CENTRAL ARGENTINA EARLY IN THE
CYCLE...INTO THE SOUTHERN STATES OF BRASIL-NORTHERN ARGENTINA BY
48-60 HRS. IT IS TO THEN REMAIN NEARLY STATIONARY THROUGH 84-96
HRS. AS IT SURGES NORTH...THIS IS TO TRIGGER SCATTERED DEEP
CONVECTION ACROSS URUGUAY-ENTRE RIOS IN ARGENTINA-RIO GRANDE DO
SUL BRASIL...WITH MAXIMA OF 25-50MM. THROUGH 48-60 HRS MAXIMA
DECREASES TO 20-40MM. OTHER CONVECTION IS EXPECTED TO THE
NORTH...WITH AMPLIFYING MID/UPPER LEVEL TROUGH TO ENHANCE
CONVECTIVE DEVELOPMENT ACROSS SOUTHEAST BRASIL. OVER SAO PAULO-RIO
DE JANEIRO-ESPIRITO SANTO AND SOUTHEAST MINAS GERAIS THIS IS TO
SUSTAIN AN INCREASE IN CONVECTION THROUGH 72-84 HRS...WHEN MAXIMA
IS TO PEAK AT 20-40MM. DUE TO STRONG TOPOGRAPHICAL FORCING LOCALLY
HIGHER AMOUNTS ARE HIGHLY LIKELY.

THE NEXT MID/UPPER LEVEL LONG WAVE TROUGH MOVES ACROSS THE EASTERN
PACIFIC THROUGH 24-48 HRS. THIS IS TO NEAR TO SOUTH COAST OF CHILE
BY 84 HRS...AND THEN INLAND ACROSS THE SOUTHERN CONE INTO
ARGENTINA BY 108-120 HRS. AS THE HIGH AMPLITUDE/LONG WAVE TROUGH
NEARS THE CONTINENT THIS IS TO FOCUS SUBTROPICAL MOISTURE INTO
SOUTHERN PORTIONS OF CHILE. AT LOW LEVELS THIS IS TO SUSTAIN A
BROAD TROUGH ON THE SOUTHERN STREAM FLOW...FORECAST TO EXTEND
NORTHWARD ACROSS THE BELLINGSHAUSEN SEA/SOUTHEAST PACIFIC TO THE
SOUTHERN CONE OF SOUTH AMERICA. ASSOCIATED SURFACE FRONT IS TO
STRETCH ACROSS THE DRAKE PASSAGE/TIERRA DEL FUEGO BY 48-72 HRS. IT
THEN MOVES NORTH INTO PATAGONIA-SOUTHERN CHILE BY 72-96 HRS. AS
THE PRESSURE GRADIENT TIGHTENS...STRONG BOUNDARY LAYER WINDS ARE
TO ACCOMPANY THIS BOUNDARY...WITH WINDS FORECAST TO PEAK AT
35-45KT. THE INFLOW OF SUBTROPICAL MOISTURE IS TO SUSTAIN
MODERATE...LOCALLY HEAVY CONVECTION...WITH MAXIMA TO PEAK AT
15-20MM.

ON THE NORTHERN STREAM...A MID LEVEL LOW AND ASSOCIATED SHORT WAVE
TROUGH ARE TO MEANDER OFF THE COAST OF CHILE THROUGH 60-72 HRS. IT
IS TO THEN RAPIDLY SHEAR EASTWARD ACROSS THE ANDES INTO CENTRAL
ARGENTINA AS THE LONG WAVE TROUGH NEARS THE SOUTHERN PORTIONS OF
CHILE. INFLOW OF SHORT WAVE ENERGY IS TO TRIGGER SCATTERED
CONVECTION ALONG THE CENTRAL ANDES...WITH ACCUMULATION OF 05-10MM
EXPECTED ON DAYS 02-03. THIS IS TO THEN INTERACT WITH THE THERMAL
LOW OVER ARGENTINA TO SUSTAIN AN INCREASE IN CONVECTION ACROSS THE
NORTHERN PROVINCES IN ARGENTINA TO NORTHERN URUGUAY/SOUTHERN
STATES OF BRASIL. IN THIS AREA EXPECTING DEEP CONVECTION TO
SUSTAIN RAINFALL MAXIMA OF 30-60MM IN POTENTIALLY SEVERE
CONVECTION.

NORTH OVER THE CONTINENT...AT 200 HPA...DISORGANIZED SUBTROPICAL
RIDGE PATTERN IS TO DOMINATE PERU-WESTERN BRASIL-BOLIVIA EARLY IN
THE CYCLE. THROUGH 72-96 HRS THE HIGH/RIDGE PATTERN IS TO
GRADUALLY STRENGTHEN...BUILDING EASTWARD ACROSS BRASIL. AS THE
RIDGE BECOMES BETTER ORGANIZED DIURNAL/TROPICAL CONVECTION OVER
NORTHERN PORTIONS OF THE CONTINENT IS TO ALSO BECOME MORE ACTIVE.
MOST ACTIVE CONVECTION...HOWEVER...IS EXPECTED TO THE NORTH ALONG
THE NEAR EQUATORIAL TROUGH OVER NORTHERN BRASIL-PERU/EASTERN
ECUADOR...WITH MAXIMA OF 25-50MM EXPECTED THROUGH 36 HRS...AND
20-40MM/DAY THEREAFTER. ACROSS NORTHEAST BRASIL SCATTERED
CONVECTION IS TO SUSTAIN MAXIMA OF 15-20MM/DAY. THROUGH 72-96 HRS
THIS INCREASES TO 20-30MM/DAY AS AN UPPER LEVEL TROUGH MEANDERS
WEST ALONG THE NORTH COAST OF BRASIL.

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





Last Updated: 1152 AM EST THU FEB 26 2015