842
FXSA20 KWBC 121823
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 PM EDT WED MAR 12 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN 12 MARCH 2025 AT 14:00 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.
ENSO CONDITIONS:
LA NINA CONDITIONS ARE PRESENT, A TRANSITION TO ENSO NEUTRAL IS
EXPECTED FROM APRIL TO MAY.
..SYNOPTIC CONDITIONS OVER TROPICAL SOUTH AMERICA
A REGION OF PARTICULAR INTEREST IS ECUADOR AND THE FAR SOUTHWEST
OF COLOMBIA, WHERE WARM SEA SURFACE TEMPERATURES (SSTS), THE
PACIFIC INTERTROPICAL CONVERGENCE ZONE (ITCZ) AND WEAK ONSHORE
FLOW AT THE LOWER LEVELS ALONG THE PACIFIC ITCZ WILL LIKELY
ENHANCE THE SEA BREEZE DEVELOPMENT, WHICH HELPS TRANSPORT MOISTURE
INLAND DURING THE DAY ON THURSDAY AND FRIDAY, TO CONTINUE DRIVING
ISOLATED DIURNAL CONVECTION. THIS INCREASED MOISTURE SUPPLY
FURTHER SUPPORTS CONVECTIVE ACTIVITY OVER ECUADOR AND SOUTHWEST
COLOMBIA, CONTRIBUTING TO SUSTAINED ATMOSPHERIC INSTABILITY AND
CLOUD FORMATION IN THE REGION. THIS CONVECTION IS FURTHER
SUPPORTED BY UPPER-LEVEL DIVERGENCE, WHICH FACILITATES THE UPWARD
MOTION OF AIR, CREATING FAVORABLE CONDITIONS FOR THE DEVELOPMENT
OF CONVECTIVE CLOUDS.
THE TRANSPORT OF MOISTURE BY TRADE WINDS AROUND THE INTERTROPICAL
CONVERGENCE ZONE (ITCZ) INTO THE CENTRAL REGION OF TROPICAL SOUTH
AMERICA, COMBINED WITH UPPER-LEVEL DIVERGENCE, PLAYS A CRITICAL
ROLE IN ENHANCING PRECIPITATION ALONG THE NORTHERN EXTENSION OF
THE NET/ITCZ. THE TRADE WINDS CARRY WARM, MOIST AIR FROM THE OCEAN
SURFACE TOWARD THE ITCZ, WHERE IT CONVERGES, RISES, AND COOLS,
LEADING TO CONDENSATION AND CLOUD FORMATION. UPPER-LEVEL
DIVERGENCE FURTHER SUPPORTS THIS PROCESS BY CREATING A FAVORABLE
ENVIRONMENT FOR UPWARD MOTION. THIS DYNAMIC INTERACTION BETWEEN
MOISTURE TRANSPORT, LOWER LEVEL CONVERGENCE, AND UPPER-LEVEL
DIVERGENCE WILL CONTINUE SUSTAINING PRECIPITATION ALONG THE NET/
ITCZ, IMPACTING NORTHWESTERN BRASIL, AS WELL AS THE SOUTHERN
PARTS OF VENEZUELA COLOMBIA.
THE UPPER-LEVEL DIVERGENCE, COMBINED WITH THE TRADE WINDS AS THEY
APPROACH THE NORTHERN COAST OF SOUTH AMERICA, FROM GUYANA TO
NORTHEASTERN BRASIL, WILL FACILITATE CONVERGENCE ALONG THE COAST.
THIS INSTABILITY IS LIKELY TO LEAD TO THE FORMATION OF CONVECTIVE
CLOUDS. FURTHERMORE, THE INTERACTION WITH THE SEA BREEZE MAY
ENHANCE THE DEVELOPMENT OF THESE CONVECTIVE CLOUDS DURING THE NEXT
3 DAYS. THESE SYSTEMS CAN SPREAD WIDELY AND MOVE INLAND INTO THE
CONTINENT.
...SYNOPTIC CONDITIONS FOR BRASILâ€
A PERSISTENT AND EXPANSIVE SURFACE HIGH-PRESSURE SYSTEM CENTERED
AT PANTANAL AND MATO GROSSO IN BRASIL WILL PROMOTE MOIST EASTERLY
TO, NORTHEASTERLY WINDS, THAT WILL RESULT IN A NARROW COASTAL
BAND OF CLOUD COVER AROUND THE PERIPHERY OF THE HIGH PRESSURE IN
THE NORTHWESTERN REGION OF BRASIL DURING THE EVENING THROUGHOUT
THE UPCOMING FORECAST CYCLE.
...SYNOPTIC CONDITIONS FOR BOLIVIA, PARAGUAY, URUGUAY AND
ARGENTINA...
IN THE UPPER LEVELS, THERE IS A TROUGH WITH ITS AXIS JUST EAST OF
SOUTHERN SOUTH AMERICA, ITS BASE BEING OVER CENTRAL ARGENTINA
PROPAGATING SLIGHTLY TO THE NORTH AND EXITING SOUTH AMERICA FROM
TODAY (WEDNESDAY) INTO THURSDAY MORNING.
IN THE MID LEVELS, THE OVERALL PATTERNS ARE FORECAST TO BE SIMILAR
TO THE UPPER LEVELS, MEANING THAT THE TROUGHS AND RIDGES, AS WELL
AS THE HIGH PRESSURE OVER NORTHERN SOUTH AMERICA ARE FAIRLY
VERTICALLY STACKED. THIS PATTERN WILL ALSO PROVIDE A MID-LEVEL JET
IN THE SOUTHERN PERIPHERY OF THE HIGH PRESSURE, WHICH WILL PROVIDE
VENTILATION ALONG A LOW-LEVEL TROUGH, ENHANCING SHOWER AND
THUNDERSTORM POTENTIAL FROM SOUTHERN BOLIVIA THROUGH PARAGUAY AND
INTO SOUTHEAST BRASIL, MAINLY TODAY (WEDNESDAY) INTO EARLY
THURSDAY. EASTERLY WINDS AT THE MID AND UPPER LEVELS WILL
ENHANCE MOISTURE INFLUX FROM THE INTERIOR OF THE CONTINENT NEAR
THE ALTIPLANO SURFACE.
THE UPPER AND MID-LEVEL TROUGH WILL ALSO BE A CONTRIBUTOR TO THE
ENHANCED SHOWER AND THUNDERSTORM POTENTIAL OVER NORTHERN ARGENTINA
INTO URUGUAY AND EXTREME SOUTHEAST BRASIL. A STATIONARY FRONT
OVER THE REGION NORTHERN ARGENTINA AND SOUTHERN BRASIL IS EXPECTED
TO DISSIPATE BY TONIGHT (WEDNESDAY NIGHT) . SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG THE FRONTAL BOUNDARY,
MAINLY AFFECTING NORTHWEST ARGENTINA AND PARAGUAY (THE CHACO
REGION) THIS AFTERNOON AND DRYING OUT BY THURSDAY.
THE NORTHERN REGION OF URUGUAY AND SOUTHEASTERN BRAZIL WILL ALSO
EXPERIENCE ELEVATED TEMPERATURES ON WEDNESDAY ALONG THE COAST DUE
TO THE DEVELOPMENT OF A FRONTAL BOUNDARY TO THE EAST.
ADDITIONALLY, LOCAL EFFECTS, SUCH AS SEA BREEZES, WILL ENHANCE THE
LIKELIHOOD OF SHOWERS AND THUNDERSTORMS ON THAT DAY. AFTER THAT,
DRIER CONDITIONS AND A MORE STABLE ATMOSPHERE IS EXPECTED IN
THOSE REGIONS FROM THURSDAY INTO FRIDAY
AS THE STRONG SURFACE HIGH PRESSURE SYSTEM ADVANCES FROM THURSDAY
EVENING INTO FRIDAY, DRY AND STABLE CONDITIONS WILL PREVAIL OVER
ARGENTINA, URUGUAY, AND PARAGUAY.
..SYNOPTIC CONDITIONS FOR CHILE
AS THE HIGH-PRESSURE SYSTEM ADVANCES TOWARD CHILE AND ARGENTINA,
PREDOMINANTLY STABLE CONDITIONS ARE EXPECTED OVER THE NORTE GRANDE
AND NORTE CHICO REGIONS, AS WELL AS THE CENTRAL ZONE FROM TODAY
(WEDNESDAY) INTO FRIDAY. THE STABLE CONDITIONS IN THE NORTHERN AND
CENTRAL ZONES ARE ASSOCIATED WITH SUBSIDENCE INDUCED BY THE
HIGH-PRESSURE SYSTEM, WHICH SUPPRESSES VERTICAL MOTION AND LIMITS
CLOUD DEVELOPMENT. IN THE SOUTHERN AND AUSTRAL REGIONS, CONDITIONS
WILL ALSO REMAIN MOSTLY STABLE, WITH THE DEVELOPMENT OF STRATIFORM
CLOUDS. AN UPPER LEVEL JET WILL MOVE INTO ZONA AUSTRAL FROM
TODAY (WEDNESDAY) INTO THURSDAY MORNING AND IT WILL SUPPORT THE
DEVELOPMENT OF STRATIFORM RAIN, ALTHOUGH LOW-LEVEL MOISTURE
ADVECTION IS EXPECTED TO BE LIMITED.
FOR MORE QPF GRAPHICAL INFORMATION:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/INTERNATIONAL/SAM_DAY1-3.SHTML
LEDESMA...(WPC)
ALAMO...(WPC)
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