079
FXSA20 KWBC 212011
PMDSA
SOUTH AMERICA FORECAST DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
311 PM EST TUE JAN 21 2025
GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/
SOUTH AMERICAN FORECAST BULLETIN FOR 21 JAN 2025 AT 2000 UTC:
THIS WEEK...THE MADDEN-JULIAN OSCILLATION (MJO) IS PRESENTING
CONVERGENT OVER THE SOUTH AMERICAN CONTINENT AND IT IS EXPECTED TO
REMAIN IN THIS PHASE OVER THE NEXT SEVERAL DAYS. WITH THE PRESENCE
OF THE CONVERGENT PHASE OF THE MJO...EXPECT PRECIPITATION TO BE
AFFECTED BY BECOMING ISOLATED AND MAXIMA COULD SEE A DECREASE IF
THE CONDITIONS ARE NOT FAVORABLE FOR DEEP CONVECTION.
ON TUESDAY...THE CENTER OF THE BOLIVIAN HIGH IS EXPECTED JUST WEST
OF PERU AND NORTH CHILE OVER THE PACIFIC OCEAN...WHERE IT WILL
EXTEND INTO PERU...BOLIVIA...WEST BRASIL...AND NORTH PARAGUAY. TO
THE EAST...AN UPPER LEVEL TROUGH EXTENDS OVER EAST BRASIL AND
EXPECTED TO RETROGRADE FURTHER WEST INTO EAST-CENTRAL BRASIL BY
TUESDAY EVENING. THIS INTERACTION BETWEEN THE TWO UPPER LEVEL
SYSTEMS WILL ENHANCE DEEP CONVECTION IN EAST PERU...WEST
BRASIL...AND IN NORTH BOLIVIA. WITH LOWER LEVEL CONVERGENCE
EXPECTED ALONG THE ANDES MOUNTAINS AND IN NORTH PARA-BRASIL. THE
REGIONS OF CENTRAL BOLIVIA AND NORTH PARA CAN EXPECT MAXIMA OF
30-60MM...WHILE SOUTH PERU CAN EXPECT MAXIMA OF 20-45MM. LOCALIZED
HIGHER AMOUNTS ARE POSSIBLE. ELSEWHERE IN WEST BRASIL...EAST
BOLIVIA...AND PORTIONS OF THE GUIANAS CAN EXPECT GENERALIZED
MAXIMA OF 20-35MM. ON WEDNESDAY...THE UPPER LEVEL TROUGH IN BRASIL
CONTINUES TO RETROGRADE INTO CENTRAL BRASIL...INTERACTING WITH THE
BOLIVIAN HIGH IN SIMILAR LOCATIONS FROM THE DAY BEFORE. THE UPPER
LEVEL DIFFLUENCE IS EXPECTED OVER THE NORTH AND WEST REGIONS OF
THE CONTINENT...CONTINUING TO FAVOR DEEP CONVECTION FROM WEDNESDAY
INTO THURSDAY. THE UPPER TROUGH IS BEGINNING TO CLOSE OFF AND
GENERATE A WEAK UPPER JET OVER MINAS GERAIS AND GOIAS BY WEDNESDAY
EVENING. DUE TO THE LOW AMOUNT OF AVAILABLE MOISTURE IN THE
SOUTHERN REGIONS OF BRASIL...PRECIPITATION TOTALS ARE EXPECTED TO
REMAIN BELOW 25MM FROM SOUTH TOCANTINS THROUGH MINAS GERAIS.
INTERACTIONS WITH A STATIONARY FRONT IN SAO PAULO WILL FAVOR
MAXIMA OF 20-35MM. IN THE SOUTH GUIANAS INTO NORTH
PARA/AMAZONAS-BRASIL EXPECT MAXIMA OF 30-60MM. SIMILAR AMOUNTS ARE
EXPECTED IN CENTRAL BOLIVIA ON WEDNESDAY. FROM NORTH BRASIL TO
MATO GROSSO EXPECT MAXIMA OF 20-45MM. ON THURSDAY...MODEL GUIDANCE
IS NOT VERY CONSISTENT WITH PRECIPITATION OVER THE EASTERN
PORTIONS OF BRASIL...HOWEVER THEY DO SIGNAL A DECREASE OVER THE
NORTHERN REGION OF THE CONTINENT AS THE UPPER TROUGH CONTINUES TO
RETROGRADE WESTWARD AN THE DIVERGENCE IN THE REGION IS NOT AS
PROMINENT. MAXIMA OF 20-45MM ARE EXPECTED FROM SOUTH PERU INTO
CENTRAL BOLIVIA. THE ALTIPLANO IN WEST BOLIVIA CAN EXPECT MAXIMA
OF 15-30MM...WHILE MAXIMA OF 20-35MM ARE EXPECTED IN CENTRAL PERU.
TO THE NORTH...INTERACTIONS WITH THE ITCZ AND THE UPPER LEVEL
DIVERGENCE WILL FAVOR MAXIMA OF 20-45MM IN AMAZONAS-BRASIL AND
NORTHEAST PARA-BRASIL.
IN THE SOUTHERN REGION OF THE CONTINENT...THE UPPER LEVEL TROUGHS
ARE REMAINING SOUTHWARD BUT INTERACTING WITH THE UPPER LEVEL
BOLIVIAN HIGH IN THE CENTRAL PORTION OF THE CONTINENT. THIS WILL
FAVOR SHORTWAVE TROUGHS OVER THE NEXT SEVERAL DAYS...WHICH WILL
ENHANCE THE SEVERITY IN THE REGION FROM WEDNESDAY THROUGH FRIDAY
EARLY MORNING. FURTHER SOUTH...FRONTAL BOUNDARIES ARE ENTERING
SOUTHERN CHILE...INCREASING THE AVAILABLE MOISTURE IN THE COUNTRY.
ON TUESDAY...EXPECT MAXIMA OF 15-25MM IN THE AUSTRAL REGION. ON
WEDNESDAY...EXPECT THE HIGHER VALUES WITH MAXIMA OF 20-35MM IN THE
AUSTRAL REGION OF CHILE...AND MAXIMA OF 15-20MM IN LOS RIOS TO LOS
LAGOS-CHILE. ON THURSDAY...THE AUSTRAL REGION CAN EXPECT MAXIMA
BELOW 15MM. TO THE CENTRAL PORTION OF THE CONTINENT..A SERIES OF
SHORTWAVE TROUGHS WILL FAVOR DISTURBANCES IN THE LOWER
LEVEL...WHICH WILL INTERACT WITH THE ADVECTION OF MOIST AIR FROM
THE NORTH OVER THE NEXT SEVERAL DAYS. BY THURSDAY...THE SALLJ IS
EXPECTED IN BOLIVIA...ENHANCING THE TRANSPORT OF MOISTURE INTO
NORTH ARGENTINA AND PARAGUAY. ON TUESDAY...NO SIGNIFICANT RAINFALL
IS EXPECTED IN NORTH ARGENTINA AND PARAGUAY. ON WEDNESDAY...A
TROUGHING IN THE LOWER LEVELS WILL TRIGGER DEEP
CONVECTION...ENHANCED BY A SHORT WAVE TROUGH IN THE MID TO UPPER
LEVELS IN NORTHERN ARGENTINA...WHERE EXPECT MAXIMA OF 30-60MM IN
THE CHACO REGION. A SLIGHT RISK OF SEVERE WEATHER IS EXPECTED IN
SOUTH PARAGUAY WITH A MAXIMA OF 15MM. ON THURSDAY...INCREASED
AMOUNTS OF MOISTURE AND AN INCREASE IN INSTABILITY OVER SOUTH
PARAGUAY INTO NORTH ARGENTINA WILL FAVOR MAXIMA OF 30-60MM. A
MODERATE RISK OF SEVERE WEATHER IS EXPECTED IN BUENOS AIRES AS
ANOTHER SHORTWAVE TROUGH PROPAGATES OVER THE REGION IN THE MID TO
UPPER LEVELS. HOWEVER...EXPECT MAXIMA BELOW 15MM.
CASTELLANOS...(WPC)
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