072
FXSA20 KWBC 131700
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT THU MAR 13 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN 13 MARCH 2025 AT 13:00 UTC
..CLIMATE/TELECONNECTIONS CONDITIONS
MJO:THE MJO IS CURRENTLY IN PHASE 2. THE ENHANCED CONVECTIVE PHASE
IS CURRENTLY CROSSING AFRICA AND ENTERING THE INDIAN OCEAN BASIN.
THIS PHASE ALSO SHOWS ENHANCED PRECIPITATION OVER THE EASTERN PART
OF BRASIL. THE LARGE SCALE UPPER-LEVEL CONVERGENCE OVER THE
AMERICAS WILL BE INCREASING LIMITING THE COVERAGE OF DEEP
CONVECTION.
ENSO CONDITIONS:LA NINA CONDITIONS ARE PRESENT, A TRANSITION TO
ENSO NEUTRAL IS EXPECTED FROM APRIL TO MAY.
..SYNOPTIC CONDITIONS OVER TROPICAL SOUTH AMERICA
IN ECUADOR AND THE FAR SOUTHWEST OF COLOMBIA, ELEVATED SEA SURFACE
TEMPERATURES (SSTS) OVER THE EAST PACIFIC, THE PACIFIC
INTERTROPICAL CONVERGENCE ZONE (ITCZ), AND WEAK ONSHORE WINDS AT
LOWER ALTITUDES ARE LIKELY TO ENHANCE THE DEVELOPMENT OF SEA
BREEZES. THIS PROCESS WILL FACILITATE THE MOVEMENT OF MOISTURE
INLAND DURING THURSDAY AND FRIDAY, WHICH WILL ENCOURAGE ISOLATED
DIURNAL CONVECTION. THE INCREASED AVAILABILITY OF MOISTURE WILL
FURTHER BOLSTER CONVECTIVE ACTIVITY IN THE REGION, CONTRIBUTING TO
ONGOING ATMOSPHERIC INSTABILITY AND CLOUD FORMATION. ADDITIONALLY,
UPPER-LEVEL DIVERGENCE WILL PROMOTE THE UPWARD MOVEMENT OF AIR,
CREATING IDEAL CONDITIONS FOR THE FORMATION OF CONVECTIVE CLOUDS.
HOWEVER, A SLIGHT REDUCTION IN MOISTURE INFLUX AND RAINFALL IS
EXPECTED BY SATURDAY.
THE FOLLOWING MAXIMA ARE EXPECTED:
COAST OF EACUDOR: A MAXIMA OF 40 - 80MM ON THURSDAY, AND 20 -
45MM ON FRIDAY AND 20 - 35MM ON SATURDAY.
SOUTHWEST COAST OF COLOMBIA: A MAXIMA OF 25 - 50MM ON THURSDAY.
SOUTHERN COLOMBIA AND VENEZUELA: A MAXIMA OF 30 - 60 MM ON FRIDAY
AND SATURDAY.
THE TRANSPORT OF MOISTURE BY TRADE WINDS AROUND THE INTERTROPICAL
CONVERGENCE ZONE (ITCZ) INTO CENTRAL TROPICAL SOUTH AMERICA, ALONG
WITH UPPER-LEVEL DIVERGENCE, WILL CONTINUE FAVORING PRECIPITATION
ALONG THE NORTHERN EXTENSION OF THE NET/ITCZ. TRADE WINDS CARRY
WARM, HUMID AIR FROM THE OCEAN TO THE ITCZ, WHERE IT CONVERGES
AND FAVORS CONVECTIVE CLOUDS DEVELOPMENT AND FAVORS PRECIPITATION
MAXIMA OF THE REGION. IN ADDITION, UPPER-LEVEL DIVERGENCE OVER THE
REGION ENHANCES THIS PROCESS BY PROMOTING UPWARD MOTION.
THEREFORE, THIS INTERACTION WILL SUSTAIN PRECIPITATION ALONG THE
NET/ITCZ, AFFECTING NORTHWESTERN BRASIL AND SOUTHERN VENEZUELA AND
COLOMBIA OVER THE NEXT THREE DAYS.
..SYNOPTIC CONDITIONS FOR BRASIL
NORTHEASTERN BRASIL: UPPER-LEVEL DIVERGENCE, IN CONJUNCTION WITH
THE TRADE WINDS APPROACHING THE NORTHEAST COAST OF SOUTH AMERICA
FROM GUYANA TO NORTHEASTERN BRASIL, WILL PROMOTE CONVERGENCE ALONG
THE COAST. THIS INSTABILITY IS EXPECTED TO HAVE THE MOST
SIGNIFICANT IMPACT ON NORTHEASTERN BRASIL ON THURSDAY. ON FRIDAY
THESE CONDITIONS WILL CONTINUE TO IMPACT NORTHEASTERN BRASIL, BUT
TO A LESSER EXTENT. ON SATURDAY, THE REGION WILL CONTINUE TO
EXPERIENCE A STEADY INFLUX OF MOISTURE AT LOW LEVELS ASSOCIATED
WITH WEAK TROPICAL PERTURBATIONS. HOWEVER, UPPER-LEVEL CONDITIONS
WILL NOT PROVIDE SUFFICIENT SUPPORT FOR DEEP CONVECTION. AS A
RESULT, EXPECT TO SEE MAINLY STRATIFORM CLOUDS WITH A DECREASE IN
PRECIPITATION MAXIMA THROUGHOUT THE DAY.
SOUTHERN BRASIL: A PERSISTENT AND EXPANSIVE HIGH-PRESSURE SYSTEM
IN THE LOW TO MID TROPOSPHERE CENTERED BETWEEN PANTANAL AND
SOUTHEAST BRASIL WILL PROMOTE MOIST EASTERLY TO NORTHEASTERLY
WINDS IN SOUTHWEST AMAZON AND BOLIVIA, THAT WILL RESULT IN SOME
SHOWERS AROUND THE PERIPHERY OF THE HIGH PRESSURE DURING THE NEXT
THREE DAYS. IN THE SERRA DO MAR, LOCAL EFFECTS SUCH AS SEA
BREEZES, COMBINED WITH AN APPROACHING FRONTAL BOUNDARY, WILL
INCREASE THE LIKELIHOOD OF SHOWERS AND THUNDERSTORMS FROM THURSDAY
(TODAY) THROUGH FRIDAY. EXPECT PERIODS OF RAIN, PARTICULARLY IN
THE AFTERNOONS WHEN CONVECTION IS MOST LIKELY TO OCCUR. THE PEAK
WILL BE ON SATURDAY WITH MAXIMA OF 20 - 35MM.
...SYNOPTIC CONDITIONS FOR BOLIVIA, PARAGUAY, URUGUAY AND
ARGENTINA AND SOUTHERN BRASIL...
FROM THURSDAY THROUGH SATURDAY, A ZONAL UPPER-LEVEL JET WILL BE
POSITIONED OVER NORTHERN ARGENTINA AND SOUTHEASTERN BRASIL. THIS
JET STREAM WILL CONTRIBUTE TO ENHANCED WEATHER ACTIVITY IN THE
REGION. FROM THURSDAY THROUGH SATURDAY, A MID-LEVEL SHORT WAVE
WILL BE MOVING OVER NORTHERN ARGENTINA AND PARAGUAY. THIS SYSTEM
WILL BRING LIMITED POTENTIAL FOR SHOWERS AND LOCALIZED
THUNDERSTOMRS ACROSS PARAGUAY AND THE PARANĂ BASIN IN BRASIL FROM
TODAY (THURSDAY) INTO EARLY SATURDAY. AS THE STRONG SURFACE HIGH
PRESSURE SYSTEM ADVANCES FROM THURSDAY EVENING INTO FRIDAY, DRY
AND STABLE CONDITIONS WILL PREVAIL OVER ARGENTINA, URUGUAY, AND
PARTLY SOUTHEASTERN PARAGUAY. OVERALL, DRIER AIR AT MID LEVELS
WILL BE DOMINANTING ARGENTINA AND CENTRAL PARAGUAY, THEREFORE
CONDITIONS WILL REMAIN MOSTLY STABLE WITH OCCASIONAL CLOUDS AND
ISOLATED SHOWERS POSSIBLE IN THE AFFECTED AREAS.
BY SATURDAY, A WEAK UPPER-LEVEL TROUGH AND A SHORT WAVE AT
MID-LEVELS WILL MOVE ACROSS ARGENTINA, INTERACTING WITH A SURFACE
LOW PRESSURE SYSTEM. THIS COMBINATION WILL CREATE A LINE OF
CONVERGENCE OVER CENTRAL ARGENTINA WITH A MAXIMA OF 15 - 20MM,
PRIMARILY AFFECTING THE SOUTHERN CUYO AND NORTHERN PATAGONIA. THE
SEA BREEZE WILL ENHANCE MOISTURE CONVERGENCE OVER THE NORTHERN
PATAGONIA COAST, PROMOTING INCREASED CONVECTION AND HIGHER
PRECIPITATION RATES. EXPECT SCATTERED SHOWERS AND THUNDERSTORMS,
PARTICULARLY IN THE AFTERNOON AND EVENING HOURS, WITH THE
POTENTIAL FOR LOCALIZED HEAVY RAINFALL RATES AND SLIGHT RISK OF
SEVERE WEATHER.
IN BOLIVIA AND PERU, EASTERLY WINDS AT BOTH THE LOW AND UPPER
LEVELS WILL ENHANCE MOISTURE INFLUX FROM THE INTERIOR OF THE
CONTINENT. FURTHER THE BOLIVIAN HIGH WILL BE PROMOTING UPWARD
MOTION OVER THE NORTHERN BOLIVIA AND EASTERN PERU. IN THE
ALTIPLANO AND SOUTHERN PERU DIURNAL CONVETION WILL BE ENHANCE DUE
TO AN UPPER TROUGH AND JET DYNAMIC APPROACHING FROM THE SOUTHWEST,
FAVORING PRECIPIATION MAXIMA OVER THE NEXT THREE DAYS. OVERALL,
CONDITIONS WILL BE WARMER AND MORE HUMID AS MOISTURE CONTINUES TO
FLOW INTO THE AREA FOR FRIDAY AND SATURDAY.
..SYNOPTIC CONDITIONS FOR CHILE
AS THE SURFACE HIGH-PRESSURE SYSTEM (SOUTH PACIFIC ANTICYCLONE)
ADVANCES TOWARD CHILE, STABLE CONDITIONS ARE ANTICIPATED OVER
CENTRAL AND SOUTHERN CHILE OVER THE NEXT THREE DAYS. THIS
STABILITY IS LINKED TO SUBSIDENCE CAUSED BY THE HIGH-PRESSURE
SYSTEM, WHICH SUPPRESSES VERTICAL MOTION AND RESTRICTS CLOUD
FORMATION. IN THE SOUTHERN AND AUSTRAL REGIONS, CONDITIONS WILL
ALSO REMAIN PREDOMINANTLY STABLE, WITH THE PRESENCE OF STRATIFORM
CLOUDS. BY FRIDAY, AN UPPER-LEVEL JET IS EXPECTED TO MOVE INTO THE
ZONA AUSTRAL, AIDING IN THE DEVELOPMENT OF STRATIFORM RAIN.
HOWEVER, LOW-LEVEL MOISTURE ADVECTION IS ANTICIPATED TO BE
LIMITED, WHICH MAY RESTRICT THE INTENSITY OF PRECIPITATION. A
MAXIMA OF 15 - 20MM ON THURSDAY AND MAXIMA OF 15MM ON FRIDAY AND
SATURDAY. OVERALL, EXPECT MOSTLY DRY AND STABLE WEATHER CONDITIONS
ACROSS THESE REGIONS, WITH SOME LIGHT RAIN POSSIBLE IN THE SOUTH
BY THE END OF THE WEEK.
FOR MORE QPF GRAPHICAL INFORMATION:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/INTERNATIONAL/SAM_DAY1-3.SHTML
LEDESMA...(WPC)
GALVEZ...(WPC)
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page